NAVFAC Dm7-02 (Foundations and Earth Structures) Complete Manual
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An Annotated Reproduction of
NAVFAC Design Manual 7.2 Foundations and Earth Structures PLEASE NOTE This is the second volume of an extraordinary document, published in 1982, that is now considerably out‐of‐date and is no longer a sanctioned publication of the US Government. NAVFAC DM 7.2 is provided here as a reference because of the incredible density of highly practical geotechnical design guidance it contains. It is also of significant historical interest, and when combined with DM 7.1, it represents perhaps THE principle compendium of geotechnical knowledge used by designers between 1982 and around the turn of the century. The importance of the Federal labs (particularly FHWA, Bureau of Reclamation, Army and Navy labs) in pushing the practice of geotechnical engineering forward between 1930 and around the time of the publication of this manual cannot be overstated, and this manual is a testament to that heritage. Thus, you are holding in your hands (or in your computer memory) a great reference for preliminary design guidance and a knowledge artifact that will be recognized by nearly every senior practicing geotechnical engineer. This copy of NAVFAC DM 7.2 (1982) has been updated to comply in spirit with NAVFAC DM 7.02 (1986). DM 7.02 was actually a very minor update of DM 7.2 made mostly to correct some out‐of‐date numbers that referenced relatively obscure Federal publications. This reproduction has considerable advantages over the widely‐distributed and much‐appreciated PDF version that has been floating around the net. That version was hosted at Vulcan Hammer’s site (many thanks!) for years. The asterisks and parentheses that were the artifact of an early PDF conversion have been replaced in this version with the lines originally intended. Further, Greek symbols and the size of the figures are as per the original paper publication of 1982 rather than the shrunken versions. The resulting file size is much bigger, of course, but I believe the improved quality is worth it. Enjoy this historic document, but please use it with caution. J Ledlie Klosky
ABSTRACT Design guidance i s presented for use by experienced engineers. The c o n t e n t s include: excavations; compaction, earthwork, and hydraulic f i l l s ; a n a l y s i s of walls and retaining structures; shallow foundations; and deep foundations.
For sale by the Superintendent of Documents, U.S. Government Printing Of6e.e Washington. D.C. 20402
FOREWORD This design manual for Foundations and Earth Structures is one of a series that has been developed from an extensive re-evaluation of the relevant , Foundations, and Earth Structures, NAVFAC D W 7 portions of Soil ~echanics of March 1971, from surveys of available new materials and construction methods, and from selection of the best design practices of the Naval Facilities Engineering Command, other Government agencies, and private industry. This manual includes a modernization of the former criteria and the maximum use of national professional society, association and institute codes. Deviations from these criteria should not be ma$e without the prior approval of the Naval Facilities Engineering Command Headquarters (NAVFAC HQ)
.
Design cannot remain static any more than can the naval functions it serves, or the technologies it uses. Accordingly, this design manual, Foundations and Earth Structures, NAVFAC DM-7.2, along with the companion manuals, Soil Mechanics NAVFAC DM-7.1 and Soil Dynamics, Deep Stabilization, and Special Soil Geotechnical Construction, NAVFAC DM-7.3, cancel and supersede Mechanics. Foundations. and Earth Structures. NAVFAC DM-7 of March 1971 in its entirety, and all changes issued.
!;zot",~:A
CEC, U. S. Navy 'Commander \ Naval Facilities Engineering Command
This Page Intentionally Left Blank
PREFAC This manual c o v e r s t h e a p p l i c a t i o n of b a s i c e n g i n e e r i n g p r i n c i p l e s of s o i l mechanics i n t h e d e s i g n of f o u n d a t i o n s and e a r t h s t r u c t u r e s f o r naval s h o r e f a c i l i t i e s . Companion manuals (NAVFAC DM-7.1 and DM-7.3) cover t h e p r i n c i p l e s of s o i l mechanics and s p e c i a l a s p e c t s of g e o t e c h n i c a l e n g i n e e r i n g . These c r i t e r i a , t o g e t h e r w i t h t h e d e f i n i t i v e d e s i g n s and g u i d e l i n e s p e c i f i c a t i o n s of t h e Naval F a c i l i t i e s Engineering Command, c o n s t i t u t e t h e Command's d e s i g n guidance. These s t a n d a r d s a r e based on f u n c t i o n a l r e q u i r e m e n t s , e n g i n e e r i n g judgment, knowledge of m a t e r i a l s and equipment, and t h e e x p e r i e n c e g a i n e d by t h e Naval F a c i l i t i e s Engineering Command and o t h e r commands and bureaus of t h e Navy i n t h e d e s i g n , c o n s t r u c t i o n , o p e r a t i o n , and maintenance of n a v a l shore f a c i l i t i e s . The d e s i g n manual s e r i e s p r e s e n t s c r i t e r i a t h a t s h a l l be used i n t h e d e s i g n of f a c i l i t i e s under t h e cognizance of t h e Naval F a c i l i t i e s Engineering Command. The d i r e c t i o n and s t a n d a r d s f o r procedures, methods, d i m e n s i o n s , m a t e r i a l s , l o a d s and s t r e s s e s w i l l be included. Design manuals a r e n o t t e x t books, but a r e f o r t h e use of experienced a r c h i t e c t s and e n g i n e e r s . Many c r i t e r i a and s t a n d a r d s appearing i n t e c h n i c a l t e x t s i s s u e d by Government a g e n c i e s , p r o f e s s i o n a l a r c h i t e c t u r a l and e n g i n e e r i n g groups, and t r a d e a n d i n d u s t r y groups a r e s u i t a b l e f o r , and have been made i n t e g r a l p a r t s o f , t h i s s e r i e s . The l a t e s t e d i t i o n of e a c h p u b l i c a t i o n s o u r c e s h a l l be used. B i b l i o g r a p h i e s of p u b l i c a t i o n s c o n t a i n i n g background i n f o r m a t i o n and a d d i t i o n a l r e a d i n g on t h e v a r i o u s s u b j e c t s a r e i n c l u d e d i n t h e manuals. T h i s m a t e r i a l , however, i s n o t a p a r t of t h e c r i t e r i a , nor i s a r e a d i n g of t h e s e s o u r c e s n e c e s s a r y f o r t h e u s e of t h e c r i t e r i a p r e s e n t e d i n t h e manuals. To avoid d u p l i c a t i o n and t o f a c i l i t a t e f u t u r e r e v i s i o n s , c r i t e r i a a r e p r e s e n t e d o n l y once i n t h i s s e r i e s a s f a r a s p o s s i b l e . C r i t e r i a having g e n e r a l a p p l i c a t i o n s appear i n t h e b a s i c manuals numbered DM-1 t h r o u g h DM-10 (numbers DM-1 1 through DM-20 were unassigned i n t h e o r i g i n a l i s s u e s ) . Manuals numbered DM-21 and above c o n t a i n c r i t e r i a t h a t u s u a l l y a r e a p p l i c a b l e o n l y t o t h e s p e c i f i c f a c i l i t y c l a s s covered by each manual. When c r i t e r i a f o r o n e f a c i l i t y a l s o have an a p p l i c a t i o n i n a n o t h e r f a c i l i t y c l a s s , . t h e b a s i c r u l e has been t o p r e s e n t s u c h c r i t e r i a i n t h e b a s i c , o r l o w e s t numbered, manual and c i t e i t by r e f e r e n c e where r e q u i r e d i n l a t e r manuals. The s p e c i f i c d e s i g n manuals (DM-21 and above), w i t h b u t t h r e e e x c e p t i o n s , l i s t d e s i g n c r i t e r i a f o r s p e c i f i c f a c i l i t i e s i n t h e o r d e r of t h e c a t e g o r y codes. The e x c e p t i o n s a r e :
(1) Drydocking F a c i l i t i e s , NAVFAC DM-29, Codes 213 and 223.
which i n c l u d e s both Category
( 2 ) C r i t e r i a f o r f a c i l i t y c l a s s 800, U t i l i t i e s and Ground Improvements, which have been included i n t h e b a s i c manuals on mechanical, e l e c t r i c a l , and c i v i l e n g i n e e r i n g .
( 3 ) Weight Handling Equipment and S e r v i c e C r a f t , NAVFAC DM-38,
which i n c l u d e s t h e d e s i g n c r i t e r i a f o r t h e s e f a c i l i t i e s under t h e cognizance of t h e Naval F a c i l i t i e s Engineering Command t h a t a r e n o t c l a s s i f i e d a s r e a l property. These i n c l u d e weight and l i n e h a n d l i n g equipment, d r e d g e s , yard c r a f t , and p i l e d r i v i n g equipment.
F o r t h e e f f e c t i v e u s e of t h e s e c r i t e r i a , t h e d e s i g n e r must have a c c e s s t o :
(1) The b a s i c and s p e c i f i c d e s i g n manuals a p p l i c a b l e t o t h e p r o j e c t . See l i s t on page ix. ( 2 ) Published c r i t e r i a sources.
( 3 ) Applicable d e f i n i t i v e d e s i g n s , D e f i n i t i v e Designs f o r Naval Shore F a c i l i t i e s , NAVFAC P-272.
( 4 ) Command g u i d e l i n e s p e c i f i c a t i o n s .
LIST OF DESIGN MANUALS BASIC MANUALS
I
UUL
of Date
Title
I Number
NAVFAC DM-1 .................................................. NAVFAC DM-5 ............................................. NAVFAC DM-9 ...................................... NAVFAC DM-10 ........................... DM-6 ................................... NAVFAC NAVFAC DM-4 ........................................ NAVFAC DM-7.2 .............................. NAVFAC DM-8 ................................... ........................................ NAVFAC DM-3 NAVFAC DM-7.3 ........................... NAVFAC DM-7.1 ................................................ ........................................ NAVFAC DM-2
Architecture Civil Engineering Cold Regions Engineering Cost Data for Military Construction Drawings and Specifications Electrical Engineering Foundations and Earth Structures Fire Protection Engineering Mechanical Engineering Soil Dynamics. Deep Stabilization and Special Geotechnical Construction Soil Mechanics Structural Engineering
SPECIFIC MANUALS
..................................... NAVFAC NAVFAC DM-3 4 ............................................ DM-21 ...... NAVFAC DM-23 .......................................... NAVFAC DM-37 ......................................... NAVFAC DM-29 ................................................ NAVFAC DM-35 ................................. NAVFAC DM-26 ............................... NAVFAC DM-33 ................................... NAVFAC DM-24 ...................... NAVFAC DM-22 ........................................ NAVFAC NAVFAC DM-28 ......................................... DM-30 .................... NAVFAC DM-31 ............................................. NAVFAC DM-32 ........................................... NAVFAC DM-27 ................................................. NAVFAC DM-36 ............................. NAVFAC DM-25 ................... NAVFAC DM-38
Administrative Facilities Airfield Pavements Communications. Navigational Aids. and Airfield Lighting Community Facilities Drydocking Facilities Family Housing Harbor and Coastal Facilities Hospital and Medical Facilities Land Operational Facilities Liquid Fueling and Dispensing Facilities Maintenance Facilities Production Facilities Research. Development. and Test Facilities Supply Facilities Training Facilities Troop Housing Waterfront Operational Facilities Weight Handling Equipment and Service Craft INDEX MANUAL
..........................................
Cumulative Index
NAVFAC DM-50
CONTENTS
.
CHAPTER 1 Section Section Section Section Section Section Section
... .. .
1 2 3 4 5 6 7
.
Introduction........................................7. Open Cuts...........................................7. Trenching .........................................7. Braced Excavations..................................7. Rock Brcavation.....................................7. Groundwater Control.................................7. Excavation Stabilization. Monitoring. and Safety
.
CHAPTER 2 Section Secfion Section Section Section Section
..
1 2 3
4 5 6
.. ..
.
.. .. 5.
1 2 3 4
COMPACTION. EARTHWORK. AND HYDRAULIC FILLS
... 4. 5. 6. 7. 8. 1 2 3
2-37 2-38 7. 2-45 2-50 2-52 -54
..............
.
ANALYSIS OF WALLS AND RETAINING STRUCTURES
Introduction.......................................7. Computation of Wall Pressures Rigid Retaining Walls Design of Flexible Walls ............................7. Cofferdams..........................................7.
....................... ...............................
CHAPTER 4 Section Section Section Section Section Section Section Section
2-1 2-1 2-2 2-13 2-19 2-27 7. 2-27
....
Introduction. ......................................7. Embankment Cross-Section Design.....................7. Compaction Requirements and Procedures Embankment Compaction Control.......................7. Borrow Excavation...................................7. Hydraulic and Underwater Fills ......................7.2
CHAPTER 3 Section Section Section Section Section
EXCAVATIONS
.
2-59
7. 2-59 7. 2-82
2-85 2-116
SHALLOW FOUNDATIONS 2-129 ........................... 2-129 ................ 2-146 ................. 2-150 ...................... 2-159 2-159 ......................
Introduction........................................7. Bearing Capacity Analysis Spread Footing Design Considerations Mat and Continuous Beam Foundations Foundations on Engineered Fill Foundations on Expansive Soils Foundation Waterproofing............................7. . Uplift Resistance...................................7.
7. 7. 7. 7. 7.
2-163 2-169
Page
. DEEP FOUNDATIONS I n t r o d u c t i o n ........................................7.2.177 Foundation Types and D e s i g n Criteria ................7 -2-178 Bearing Capacity and S e t t l e m e n t . . . . . . . . . . . . . . . . . . . . 7 . 2-191 P i l e I n s t a l l a t i o n and Load T e s t s .................... 7 0 2-213 D i s t r i b u t i o n o f Loads on P i l e Groups ................7 . 2-230 Deep Foundations o n Rock ............................7.2-232 L a t e r a l Load Capacity ...............................7 -2-234 CHAPTER 5
Section Section Section Section Section Section Section
1 2 3 4 5 6 7
... .. .
.
..............BIBLIOGRAPHY ..............
1
.............................7.2- A-1 GLOSSARY*. ........................................................... m7.2- G-1 SYMBOLS.*............~~.~~~..... -7-2-s-1 .. 1 APPENDIX A
- Listing
o f Computer Programs
..moo
INDEX***.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . o
....................ooe~.-.~
FIGURES Figure
Title
Page
CHAPTER 1
.......................................... ................................................ ........................................... ..................................................... .............................................. ............................. ............................... ... ..........................
S l i d i n g Trench Shield 7. 2-7 Skeleton Shoring 7. 2-10 Close (Tight) Sheeting 7. 2-11 BOX Shoring 7. 2-12 Telescopic Shoring 7. 2-12 Support System - Walled Excavation 7. 2-15 General Guidance f o r Underpinning 7. 2-20 R i p p a b i l i t y of Subsurface M a t e r i a l s Related t o Longitudinal Seismic Velocity f o r a Heavy Duty Ripper (Tractor-Mounted) .7.2-22 Suggested Guide f o r Ease of Excavation 7. 2-23 Cube Root Scaling Versus Maximum P a r t i c l e Velocity ..............7.2-24 Guideline f o r Assessing P o t e n t i a l f o r Damage Induced by B l a s t i n g Vibration t o R e s i d e n t i a l s t r u c t u r e Founded on Dense S o i l o r ~ o c k 7. 2-25 Guide f o r P r e d i c t i n g Human Response t o Vibrations and 7. 2-26 Blasting Effects Methods of Construction Dewatering .7. 2-31 Limits of Dewatering Methods Applicable t o D i f f e r e n t S o i l s 7. 2-33
............................................ .............................................. ............................ ......
CHAPTER 2 1
Resistance of E a r t h D m Bnbankment M a t e r i a l s t o Piping and Cracking
......................................................
7. 2-42
CHAPTER 3
....................... ............................................. . ............................................. ................................................ ....................... .................... ......................... ............................... ........................ ............. ............ ......................................
E f f e c t of W a l l Movement on Wall P r e s s u r e s Computation of Simple Active and Passive P r e s s u r e s ..............7. Active and Passive C o e f f i c i e n t s . Sloping B a c k f i l l (Granular S o i l s ) P o s i t i o n of F a i l u r e Surface f o r Active and Passive Wedges (Granular S o i l s ) Active and Passive C o e f f i c i e n t s with W a l l F r i c t i o n (Sloping Wall) Active and Passive C o e f f i c i e n t s with W a l l F r i c t i o n ( Sloping B a c k f i l l ) Computation of General Active P r e s s u r e s C o e f f i c i e n t s KA and Kp f o r Walls with Sloping Wall and F r i c t i o n . and Sloping B a c k f i l l Computation of General Passive P r e s s u r e s E f f e c t of Groundwater Conditions on Wall Pressures Horizontal P r e s s u r e s on Rigid Wall from Surface Load L a t e r a l P r e s s u r e on a n Unyielding Wall Due t o Uniform Rectangular Surface Load
7. 2-60 2-62
- 7 2-64 .7. 2-65 7. 2-66
.7. 2-67 7. 2-68
7. 2-69 7. 2-71 .7. 2-72 7. 2-74 7. 2-75
Figure
Title
Page
CHAPTER 3 (continued)
............. ............... .... ......
Horizontal P r e s s u r e on Walls from Compaction E f f o r t 7. 2-77 Values of F f o r Determination of Dynamic L a t e r a l Pressure Coefficients ..............................................7. 2-79 Example C a l c u l a t i o n s f o r Dynamic Loading on Walls 7. 2-80 Design C r i t e r i a f o r Rigid Retaining Walls .7 . 2-83 Design Loads f o r Low Retaining Walls ( S t r a i g h t Slope B a c k f i l l ) ..7. 2-86 Design Loads f o r Low Retaining Walls (Broken Slope B a c k f i l l ) 7. 2-87 Design C r i t e r i a f o r Anchored Bulkhead ( F r e e E a r t h Support) 7. 2-88 Reduction i n Bending Moments i n Anchored Bulkhead from Wall F l e x i b i l i t y ...................................................7. 2-89 Design C r i t e r i a f o r Deadman Anchorage 7.2-91 Example of Analysis of Anchored Bulkhead .7........ 2-93 Sand Dike Scheme f o r C o n t r o l l i n g Active P r e s s u r e 7. 2-94 Analysis f o r C a n t i l e v e r Wall ....................................7. 2-95 C a n t i l e v e r S t e e l Sheet P i l e Wall i n Homogeneous Granular S o i l 7. 2-97 C a n t i l e v e r S t e e l Sheet P i l e Wall i n Cohesive S o i l with Granular B a c k f i l l .............................................7. 2-98 Pressure D i s t r i b u t i o n f o r Brace Loads i n I n t e r n a l l y Braced F l e x i b l e Walls ................................................7. 2-100 Design C r i t e r i a f o r Braced F l e x i b l e Walls 7. 2-102 S t a b i l i t y of Base f o r Braced Cut ................7 . 2-104 P r e s s u r e D i s t r i b u t i o n f o r Tied-Back W a l l s 7. 2-105 Example of Analysis of P r e s s u r e s on F l e x i b l e Wall of Narrow Cut i n Clay - Undrained Conditions ..............7. 2-107 Example of Excavation i n Stages .................................7. 2-108 Culmann Method f o r Determining Passive R e s i s t a n c e of Earth Berm (Granular S o i l ) ..........................................7. 2-113 Passive Pressure D i s t r i b u t i o n f o r S o l d i e r P i l e s .................7. 2-114 Gabion Wall ...........................7. 2-115 Reinforced E a r t h ................................................7. 2-117 Design C r i t e r i a f o r Crib and Bin Walls ..........................7. 2-118 Design C r i t e r i a f o r C e l l u l a r Cofferdams ............. 7. 2-119
....
........................... ................ ...
....................... .......................
CHAPTER 4 Ultimate Bearing Capacity of Shallow Footings w i t h Concentric b a d s ............ 7 2-131 Ultimate Bearing Capacity with Groundwater E f f e c t ...............7. 2-132 Ultimate Bearing Capacity of Continuous Footings w i t h I n c l i n e d . 2-133 Load ............................7 E c c e n t r i c a l l y Loaded Footings ................7. 2-134 U l t i m a t e Bearing Capacity f o r Shallow Footing Placed on o r Near a Slope ................. 7 2-135 Bearing Capacity Factors f o r Shallow Footing Placed on o r Near a Slope ..................................................7. 2-136 Ultimate Bearing Capacity of Two Layer Cohesive S o i l (@PO) 7. 2-137 Examples of Computation of Allowable Bearing Capacity Shallow Footings on Cohesive.7....S i.l..s... ...o.... 2-139
...
......
Figure
Page
Title CHAPTER 4 (continued)
.................................... ............................................. ... ............................................ ................................................... ................................................... ..... ......................... ................... ....................... ......................................................... .................
Examples of Computation of Allowable Bearing Capacity Shallow Footings on Granular S o i l s Allowable Bearing P r e s s u r e f o r Sand from S t a t i c Cone Penetration Tests Example of Proportioning Footing S i z e t o Equalize Settlements Computation of Shear. Moment. and Deflection. B e r m s on E l a s t i c Foundation Functions f o r Shear. Moment. and Deflection. Beams on Elastic 'Foundations Functions f o r Shear. Moment. and Deflections. Mats on Elastic Foundations Limits of Compaction Beneath Square and Continuous Footings Construction Details f o r Swelling S o i l s Typical Foundation Drainage and Waterproofing Capacity of Anchor Rods i n Fractured Rock Resistance of Footings and Anchorages t o Combined T r a n s i e n t Loads Tower Guy Anchorage i n S o i l by Concrete Deadman
7. 2-140
7. 2-147 7. 2-148 7. 2-153
7. 2-154
7. 2-157 7. 2-160 7. 2-162 7. 2-167 7. 2-170 7. 2-171 7. 2-172
CHAPTER 5
......... ......................................................... ....................................... ......................... ................................ ................. .......... ................... ..................... . ........ . ........................... ..........
7. 2-193 Load Carrying Capacity of Single P i l e i n Granular S o i l s U l t i m a t e h a d Capacity of S i n g l e P i l e o r P i e r i n Cohesive Soils 7. 2-196 Bearing Capacity of P i l e Groups i n Cohesive S o i l s ............ 2-206 ..A Settlement of P i l e Groups 7. 2-210 P r i n c i p l e s of Operation of P i l e Drivers 7. 2-222 I n t e r p r e t a t i o n of P i l e Load Test 7. 2-229 h a d Test Analysis Where Downdrag A c t s on P i l e s 7. 2-231 Example Problem Batter P i l e Group a s Guy Anchorage -7. 2-233 C o e f f i c i e n t of Variation of Subgrade Reaction 7. 2-236 Design Procedure f o r L a t e r a l l y Loaded P i l e s 7. 2-237 Influence Values f o r P i l e with Applied L a t e r a l Load and F l e x i b l e Cap o r Hinged End Condition) 7. 2-238 Moment (Case I Influence Values f o r L a t e r a l l y U a d e d P i l e (Case I1 Fixed 7. 2-239 Against R o t a t i o n a t Ground Surface) Slope C o e f f i c i e n t f o r P i l e with L a t e r a l Load o r Moment 7. 2-240
TABLES Table
Page
Title CHAPTER 1
1 2 3 4 5
6 7
Factors Controlling Stability of Sloped Cut in Some Problem Soils Factors Controlling Excavation Stability OSHA Requirements (Minimum) for Trench Shoring Types of Walls ..................................................7. Factors Involved in Choice of a Support System For a Deep Excavation (> 20 feet) Design Considerations for Braced and Tieback Walls Methods of Groundwater Control
................................................. ........................ .................. ........................................ .............. ..................................
7 . 2-3 7.2-4 7.2-8 2-14
7 . 2-16 7 . 2-17 7 . 2-28
CHAPTER 2 1 2 3 4 5 6
... 2-39 ................ 7.2-40 ....................................... 7 . 2-44 ....................................... ..7. 2-46 ................................. ............................7.2-48 7 . 2-55
Typical Properties of Compacted Soils ........................7. Relative Desirability of Soils as Compacted Fill Clay Dispersion Potential Compaction Requirements Compaction Equipment and Methods Methods of Fill Placement Underwater CHAPTER 3
1
Friction Factors and Adhesion for Dissimilar Materials
..........7 . 2-63
CHAPTER 4 1 2 3 4 5
Presumptive Values of Allowable Bearing Pressure for Spread Foundations Selection of Allowable Bearing Pressures for Spread Foundations Definitions and Procedures. Analysis of Beams on Elastic Foundation Definitions and Procedures. Mats on Elastic Foundations Requirements for Foundation Waterproofing and Dampproofing
................................................... ................................................... .................................................... ......... ......
7 . 2-142 7 . 2-144
7 . 2-151 7 . 2-155 7.2-164
CHAPTER 5 1 2 3 4
Design Criteria for Bearing Piles...............................7. Characteristics of Common ExcavatedIDrilled Foundations Design Parameters for Side Friction for Drilled Piers in Cohesive Soils Application of Pile Driving Resistance Formulas
2-179 7 . 2-184
......... ................................................ .................
7 . 2-198 7 . 2-203
Table
Title
Page
CHAPTEK 5 ( c o n t i n u e d ) 5
6 7 8 9 10
Typical Values of C o e f f i c i e n t Cp f o r E s t i m a t i n g S e t t l e m e n t of a S i n g l e P i l e ..............................................7. General Criteria f o r I n s t a l l a t i o n of P i l e Foundations Supplementary Procedures and Appurtenances Used i n P i l e Driving Impact and V i b r a t o r y Pile-Driver Data Treatment of F i e l d Problems Encountered During P i l e D r i v i n g D r i l l e d P i e r s : C o n s t r u c t i o n Problems.
2-208 ........... 7. 2-214 ...................................................... 7.2-218 ........................... 7. 2-219 ..... 7. 2-226 ..........................7. 2-227
ACKNOWLEDGEMENTS Acknowledgement
Figure or Table Figure 13, Chapter 1
Mazurkiewicz, D.K., Design and Construction of Dry Docks, Trans Tech Publications, Rockport, MA., 1980.
Figure 1, Chapter 2
Sherard, J.L., Influence of Soil Properties and Construction Methods on the Performance of Homogeneous Earth Dams, Technical Memorandum 645, U.S. Department of the Interior, Bureau of Reclamation. ~~~~~
Figures 5, 6 7, Chapter 3
-
&
Caquot, A., and Kerisel, J., Tables for the Calculation of Passive Pressure, Active Pressure and Bearing Capacity of Foundations, Gauthier-Villars, Paris.
Figure 16 & 17 Chapter 3
Terzaghi, K. and Peck, R.B., Soil Mechanics in Engineering Practice, John Wiley & Sons, Inc., New York, NY.
Figures 23, 24 & 25, Chapter 3
U.S. Steel, Sheet Piling Design Manual, July, 1975.
Figure 36, Chapter 3
Portland Cement Association, Concrete Crib Retaining Walls, Concrete Information No. St. 46, Chicago, IL., May, 1952.
Figures 10 & 11, Chapter 4
Hetenyi, M., Beams on Elastic Foundation, The University of Michigan Press, Ann Arbor, MI.
Figure 14, Chapter 4
Parcher, J.V., and Means, R.E., Soil Mechanics and Foundations, Charles E. Merril Publishing Company, Columbus, OH., 1968.
Figw-e 2, C1' 3cl8.i?r 5 ( d.;p f panel , rignt)
Skempton, A.W., The Bearing Capacity of Clays, Proceedings, Building Research Congress, London, 1951.
This Page Intentionally Left Blank
CHAPTER 1. S e c t i o n 1.
EXCAVATIONS INTRODUCTION
SCOPE. This chapter covers t h e methods of e v a l u a t i n g t h e s t a b i l i t y of 1. There a r e two b a s i c types of excavations: ( a ) shallow and deep excavations. "open excavations" where s t a b i l i t y i s achieved by providing s t a b l e s i d e slopes, and (b) "braced excavations" where v e r t i c a l o r sloped s i d e s a r e maint a i n e d w i t h p r o t e c t i v e s t r u c t u r a l systems t h a t can be r e s t r a i n e d l a t e r a l l y by i n t e r n a l o r e x t e r n a l s t r u c t u r a l elements. Guidance on performance monitoring i s given i n DM-7.1, Chapter 2.
2. METHODOLOGY. I n s e l e c t i n g and designing t h e excavation system, t h e p r i mary c o n t r o l l i n g f a c t o r s w i l l include: ( a ) s o i l type and s o i l s t r e n g t h parameters; (b) groundwater c o n d i t i o n s ; ( c ) s l o p e p r o t e c t i o n ; (d) s i d e and bottom s t a b i l i t y ; and ( e ) v e r t i c a l and l a t e r a l movements of a d j a c e n t a r e a s , and e f f e c t s on e x i s t i n g s t r u c t u r e s .
3. RELATED CRITERIA. lowing source :
For a d d i t i o n a l c r i t e r i a on excavations, s e e t h e f o l -
Subject
Source
Dewatering and Groundwater Control of Deep Excavations....NAVFAC S e c t i o n 2.
1.
P-418
OPEN CUTS
SLOPED CUTS.
a. General. The depth and slope of an excavation, and groundwater cond i t i o n s c o n t r o l t h e o v e r a l l s t a b i l i t y and movements of open excavations. I n granular s o i l s , i n s t a b i l i t y u s u a l l y does not extend s i g n i f i c a n t l y below t h e excavation provided seepage f o r c e s a r e c o n t r o l l e d . I n rock, s t a b i l i t y i s c o n t r o l l e d by depths and slopes of excavation, p a r t i c u l a r j o i n t p a t t e r n s , i n s i t u s t r e s s e s , and groundwater conditions. I n cohesive s o i l s , i n s t a b i l i t y t y p i c a l l y involves s i d e slopes but may a l s o i n c l u d e m a t e r i a l s w e l l below t h e base of t h e excavation. I n s t a b i l i t y below t h e base of excavation, o f t e n r e f e r r e d t o as bottom heave, i s a f f e c t e d by s o i l type and s t r e n g t h , d e p t h of c u t , s i d e s l o p e and/or berm geometry, groundwater c o n d i t i o n s , and construct i o h procedures. Methods f o r c o n t r o l l i n g bottom heave a r e given i n DM-7.1, Chapter 6.
b. Evaluation. Methods described i n DM-7.1, Chapter 7 may be used t o evaluate t h e s t a b i l i t y of open excavations i n s o i l s where behavior of such s o i l s can be reasonably determined by f i e l d i n v e s t i g a t i o n , l a b o r a t o r y testi n g , and a n a l y s i s . In c e r t a i n geologic formations ( s t i f f c l a y s , s h a l e s , s e n s i t i v e c l a y s , c l a y t i l l s , e t c . ) s t a b i l i t y i s c o n t r o l l e d by c o n s t r u c t i o n procedures, s i d e e f f e c t s during and a f t e r excavation, and i n h e r e n t geologic planes of weaknesses. Table 1 (modified from Reference 1, E f f e c t s of Cons t r u c t i o n on Geotechnical Engineering, by Clough and Davidson) p r e s e n t s a
summary of t h e primary f a c t o r s c o n t r o l l i n g e x c a v a t i o n s l o p e s i n some problem s o i l s . Table 2 (modified from Reference 1 and Reference 2, S o i l s and Geology, Procedures f o r Foundation Design of B u i l d i n g s and Other S t r u c t u r e s , Departments of Army and A i r Force) summarizes measures t h a t can be used f o r e x c a v a t i o n p r o t e c t i o n f o r b o t h c o n v e n t i o n a l and problem s o i l s . 2. VERTICAL CUTS. Many c u t s i n c l a y s w i l l s t a n d w i t h v e r t i c a l s l o p e s f o r a period of time b e f o r e f a i l u r e occurs. However, changes i n t h e s h e a r s t r e n g t h of t h e c l a y w i t h time and s t r e s s r e l e a s e r e s u l t i n g from t h e e x c a v a t i o n c a n l e a d t o p r o g r e s s i v e d e t e r i o r a t i o n i n s t a b i l i t y . This p r o c e s s c a n be r a p i d i n s t i f f , h i g h l y f i s s u r e d c l a y s , b u t r e l a t i v e l y slow i n s o f t e r c l a y s . (See DM-7.1, Chapter 7 f o r c r i t i c a l h e i g h t s f o r v e r t i c a l c u t s i n c o h e s i v e s o i l s . ) For c u t s i n hard unweathered r o c k , s t a b i l i t y i s m o s t l y c o n t r o l l e d by s t r e n g t h along bedding p l a n e s , groundwater c o n d i t i o n , and o t h e r f a c t o r s ( s e e DM-7.1, Chapter 6 and Reference 3 , S t a b i l i t y of S t e e p S l o p e s on Hard Unweathered ~ o c k , by Terzaghi f o r d e t a i l e d d i s c u s s i o n on t h e e f f e c t s of r o c k d i s c o n t i n u i t i e s ) . Cuts i n rock can s t a n d v e r t i c a l without b o l t i n g o r anchoring depending on r o c k q u a l i t y and j o i n t p a t t e r n .
Section 3.
TRENCHING
1. SITE EXPLORATION. I n d i v i d u a l t r e n c h i n g p r o j e c t s f r e q u e n t l y extend o v e r long d i s t a n c e s . A n e x p l o r a t i o n program should be performed t o d e f i n e t h e s o i l and groundwater c o n d i t i o n s over t h e f u l l e x t e n t of t h e p r o j e c t , so t h a t t h e d e s i g n of t h e s h o r i n g system can be a d j u s t e d t o s a t i s f y t h e v a r y i n g s i t e cond it ions.
2. TRENCH STABILITY. P r i n c i p a l f a c t o r s i n f l u e n c i n g t r e n c h s t a b i l i t y a r e t h e l a t e r a l e a r t h p r e s s u r e s on t h e w a l l s u p p o r t system, bottom heave, and t h e p r e s s u r e and e r o s i v e e f f e c t s of i n f i l t r a t i n g groundwater ( s e e Chapter 3 and DM-7.1, Chapter 6 ) . E x t e r n a l f a c t o r s which i n f l u e n c e t r e n c h s t a b i l i t y include : a. S u r f a c e Surcharge. The a p p l i c a t i o n of any a d d i t i o n a l l o a d between t h e edge of t h e e x c a v a t i o n and t h e i n t e r s e c t i o n of t h e ground s u r f a c e w i t h t h e p o s s i b l e f a i l u r e plane must be considered i n t h e s t a b i i i t y a n a l y s e s f o r t h e excavation. b. V i b r a t i o n Loads. The e f f e c t s of v i b r a t i n g machinery, b l a s t i n g o r o t h e r dynamic l o a d s i n t h e v i c i n i t y of t h e e x c a v a t i o n must be considered. The e f f e c t s of v i b r a t i o n s a r e cumu1ati;e over p e r i o d s of time and can be p a r t i c u l a r l y dangerous i n b r i t t l e m a t e r i a l s such a s c l a y e y sand o r g r a v e l . c. Groundwater Seepage. Improperly dewatered t r e n c h e s i n g r a n u l a r s o i l s c a n r e s u l t i n q u i c k c o n d i t i o n s and a complete l o s s of s o i l s t r e n g t h o r bottom heave. (See DM-7.1, Chapter 6.) d. S u r f a c e Water Flow. T h i s c a n r e s u l t i n i n c r e a s e d l o a d s on t h e w a l l s u p p o r t system and r e d u c t i o n of t h e s h e a r s t r e n g t h of t h e s o i l . S i t e d r a i n a g e should be designed t o d i v e r t water away from trenches.
TABLE 1 Factors C o n t r o l l i n g S t a b i l i t y of Sloped Cut i n Some Problem S o i l s
2
SOIL TYPE
i
PRIMARY CONSIDERATIONS FOR SLOPE DESIGN
S t i f f - f i s s u r e d Clays and Shales
F i e l d shear r e s i s t a n c e may be l e s s than suggested by Slope f a i l u r e s may occur progresl a b o r a t o r y tests. s i v e l y and s h e a r s t r e n g t h s reduced t o r e s i d u a l v a l u e s compatible with r e l a t i v e l y l a r g e deformations. Some c a s e h i s t o r i e s suggest t h a t t h e long-term performance i s c o n t r o l l e d by t h e r e s i d u a l f r i c t i o n a n g l e which f o r The most r e l i a b l e some s h a l e s may be a s low a s 12'. design procedure would involve t h e use of l o c a l experience and recorded observations.
Loess and Other Collapsible S o i l s
Strong p o t e n t i a l f o r c o l l a p s e and e r o s i o n of r e l a t i v e l y d r y m a t e r i a l upon wetting. Slopes i n l o e s s a r e f r e q u e n t l y more s t a b l e when c u t v e r t i c a l t o p r e v e n t i n f i l t r a t i o n . Benches a t i n t e r v a l s can be used t o reduce e f f e c t i v e s l o p e angles. Evaluate p o t e n t i a l f o r c o l l a p s e a s described i n DM 7.1, Chapter 1. (See DM-7.3, Chapter 3 f o r f u r t h e r guidance.)
Residual S o i l s
S i g n i f i c a n t l o c a l v a r i a t i o n s i n p r o p e r t i e s can be expected depending on t h e w a t h e r i n g p r o f i l e from p a r e n t rock. Guidance based on recorded o b s e r v a t i o n provides prudent b a s i s f o r design.
S e n s i t i v e Clays
Considerable l o s s of s t r e n g t h upon remolding g e n e r a t e d by n a t u r a l o r man-made d i s t u r b a n c e . Use a n a l y s e s based on unconsolidated undrained tests o r f i e l d vane tests.
Talus
Talus i s c h a r a c t e r i z e d by l o o s e a g g r e g a t i o n of rock t h a t accumulates a t t h e f o o t of rock c l i f f s . Stable s l o p e s a r e commonly between 1-114 t o 1-314 h o r i z o n t a l t o 1 vertical. I n s t a b i l i t y i s a s s o c i a t e d with abundance of water, mostly when snow i s melting.
Loose Sands
May s e t t l e under b l a s t i n g v i b r a t i o n , o r l i q u i f y , s e t t l e , and l o s e s t r e n g t h i f s a t u r a t e d . Also prone t o e r o s i o n and piping.
TABLE 2 F a c t o r s C o n t r o l l i n g Excavation S t a b i l i t y
4
Construction Activity
Comments
Objectives
Dewatering
To prevent b o i l i n g , s o f t e n i n g , o r heave i n e x c a v a t i o n bottom, reduce l a t e r a l p r e s s u r e s on s h e e t i n g , reduce seepage press u r e s on f a c e of open c u t , e l i m i n a t e p i p i n g of f i n e s through s h e e t i n g .
I n v e s t i g a t e s o i l c o m p r e s s i b i l i t y and e f f e c t of dewatering on s e t t l e m e n t of nearby s t r u c t u r e s ; c o n s i d e r r e c h a r g i n g o r s l u r r y w a l l c u t o f f . Examine f o r presence of lower a q u i f e r and need t o dewater. I n s t a l l piezometer i f needed. Consider e f f e c t s of dewatering i n c a v i t y - l a d e n l i m e s t o n e . Dewater i n advance of excavation.
Excavation and Grading
Pipe t r e n c h i n g , basement e x c a v a t i o n , s i t e grading.
Analyze s a f e s l o p e s ( s e e DM-7.1, Chapter 7 ) o r b r a c i n g requirement ( s e e Chapter 3 ) , e f f e c t s of s t r e s s r e d u c t i o n on overc o n s o l i d a t e d , s o f t o r s w e l l i n g s o i l s and shales Consider hor i zont a 1 and v e r t ic a l movements i n a d j a c e n t a r e a s due t o e x c a v a t i o n and e f f e c t on nearby s t r u c t u r e s . Keep equipment and s t o c k p i l e s a s a f e d i s t a n c e from t o p of excavation.
.
Excavation Wall C o n s t r u c t i o n
>
To s u p p o r t v e r t i c a l e x c a v a t i o n walls, t o s t a b i l i z e trenching i n l i m i t e d space.
See Chapter 3 f o r w a l l design. Reduce e a r t h movements and b r a c i n g s t r e s s e s , where n e c e s s a r y , by i n s t a l l i n g l a g g i n g on f r o n t f l a n g e of s o l d i e r p i l e . Cons i d e r e f f e c t of v i b r a t i o n s due t o d r i v i n g s h e e t p i l e s o r s o l d i e r p i l e s . Cons i d e r dewatering r e q u i r e m e n t s a s w e l l a s wall s t a b i l i t y i n calculating sheeting depth. Movement monitoring may be warranted.
TABLE 2 (continued) Factors C o n t r o l l i n g Excavation S t a b i l i t y
Construction A c t i v i t y
Comments
Objectives
Blasting
To remove o r t o f a c i l i t a t e t h e removal of rock i n the excavation.
Consider e f f e c t of v i b r a t i o n s on s e t t l e ment o r damage t o a d j a c e n t a r e a s . Design and monitor o r r e q u i r e t h e c o n t r a c t o r t o design and monitor b l a s t i n g i n c r i t i c a l a r e a s ; r e q u i r e a pre-construction survey of nearby s t r u c t u r e s .
Anchor o r S t r u t I n s t a l l a t i o n , Wedging of S t r u t s , Pre-stressing Ties
To o b t a i n support system s t i f f n e s s and i n t e r a c t i o n .
Major excavations r e q u i r e c a r e f u l i n s t a l l a t i o n and monitoring, e.g., c a s e anchor h o l e s i n c o l l a p s i b l e s o i l s ; measure stress i n ties and s t r u t s ; wedging, e t c .
--
-
3. SUPPORT SYSTEMS. lows :
Excavation s u p p o r t systems commonly used a r e a s f o l -
a. Trench S h i e l d . A r i g i d p r e f a b r i c a t e d s t e e l u n i t used i n l i e u o f s h o r i n g , which e x t e n d s from t h e bottom of t h e e x c a v a t i o n t o w i t h i n a few f e e t of t h e t o p of t h e c u t . Pipes a r e l a i d w i t h i n t h e s h i e l d , which i s p u l l e d ahead, a s t r e n c h i n g proceeds, a s i l l u s t r a t e d i n F i g u r e 1 (from Reference 4 , Cave-In! by P e t e r s e n ) . T y p i c a l l y , t h i s system i s u s e f u l i n l o o s e g r a n u l a r o r s o f t cohesive s o i l s where e x c a v a t i o n d e p t h does n o t exceed 1 2 f e e t . S p e c i a l s h i e l d s have been used t o d e p t h s of 30 f e e t . b. Trench Timber Shoring. Table 3 i l l u s t r a t e s t h e Occup&tional S a f e t y and H e a l t h A c t ' s minimum requirements f o r t r e n c h shoring. Braces and s h o r i n g of t r e n c h a r e c a r r i e d a l o n g w i t h t h e excavation.. Braces and d i a g o n a l s h o r e s of timber should n o t be s u b j e c t e d t o compressive s t r e s s e s i n e x c e s s o f :
where :
L = unsupported l e n g t h ( i n c h e s ) D = l e a s t s i d e of t h e timber ( i n c h e s )
S = a l l o w a b l e compressive s t r e s s i n pounds per s q u a r e i n c h of c r o s s s e c t i o n Maximum R a t i o
LID=
50
( 1 ) S k e l e t o n Shoring. Used i n s o i l s where cave-ins a r e expected. A p p l i c a b l e t o most s o i l s t o d e p t h up t o 20 f e e t . See F i g u r e 2 (from Refere n c e 4 ) f o r i l l u s t r a t i o n and guidance f o r s k e l e t o n shoring. S t r u c t u r a l components should be designed t o s a f e l y w i t h s t a n d e a r t h p r e s s u r e s .
( 2 ) Close ( T i g h t ) Sheeting. Used i n g r a n u l a r o r o t h e r running s o i l s , compared t o s k e l e t o n s h o r i n g , i t i s a p p l i c a b l e t o g r e a t e r depths. S e e i l l u s t r a t i o n i n F i g u r e 3 (from Reference 4). ( 3 ) Box Shoring. Applicable t o t r e n c h i n g i n any s o i l . Depth l i m i t ed by s t r u c t u r a l s t r e n g t h and s i z e of timber. Usually l i m i t e d t o 40 f e e t . See i l l u s t r a t i o n i n F i g u r e 4 (from Reference 4 ) . ( 4 ) T e l e s c o p i c Shoring. Used f o r e x c e s s i v e l y deep t r e n c h e s . i l l u s t r a t i o n i n F i g u r e 5 (Reference 4).
See
c. S t e e l S h e e t i n g and Bracing. S t e e l s h e e t i n g and b r a c i n g can be used i n l i e u of timber shoring. S t r u c t u r a l members should s a f e l y w i t h s t a n d water and l a t e r a l e a r t h S t e e l s h e e t i n g w i t h timber wales and s t r u t s have a l s o been used.
-
TABLE 3 C6HA Requirents (Minjmum) hr Trench Sbring J
Size a d Spacirg of Menbers cross &aces1
Stringers
Uprights
Maxinnm Spacing
Width of Trench i d or Condition f i i m u n Depth of K Dimmion of Earth Trench
Maxhuu Minimun Dimension Spacing
Inches
Feet
Inches
Feet
Hard, canpact
3x4 or 2x6
6
Likely to crack
3x4 or 2x6
3
4x6
4
Soft, s d y , or filled
3x4 or 2xfj
Close
4 x 6
Hydrostatic pressure
3x4 o r 2x6
Close sheeting
3x4 or 2x6
Likely to crack Soft , s a d y or f illed
Feet
5 to 10
MPcirmm Spcing
11 t o 15 Hard
Hydrostatic pressure
IbriVertical zontal
Upto 4 t o 6 7 t o 9 feet 3 feet feet
lot012 13to15 feet feet
Incks Inches I n c k s
Inches
Incks
Feet
Feet
......... ........ 2 x 6
4 x 4
4x6
6 x 5
6 x 8
4
6
2x6
4 x 4
4 x 6
6 x 6
6 x 8
4
6
4
4 x 4
4x6
6x6
6 x 8
8 x 8
4
6
6 x 8
4
4 x 4
4 x 6
6 x 6
6 x 8
8 x 8
4
6
4
4x6
4
4 x 4
4x6
6 x 6
6 x 8
8 x 8
4
6
3x4 or 2x6
2
4x 6
4
4 x 4
4x6
6 x 6
6 x 8
8 x 8
3x4 or 2x6
Close skting
4 x 6
4
4x6
6 x 6
6 x 8
8 x 8
8x10
4
6
3x6
Close sheeting
8 x 10
4
4 x 6
6 x 6
6 x 8
8 x 8
8x10
4
6
sktirlg
v
Trench jacks may be used i n lieu of, or i n canbination d t h , cross braces. Where desirable, steel s k t piling a d bracirg of equal strength may be substituted for mod.
6
-
Requirements f o r S k e l e t o n S h o r i n g
TRENCH
UPRIGHTS
-s
s m
Size
brizontal SPC~%
Size
Vert id Spacis
Size
brizontal Spacis
Up t o 42" 4' t o 10'
2" x 6"
3' cc
2" x 6"
(a)
2"x61'(b)
6'c-c
Over 42"
4' t o 10'
2" x 6"
3' c-c
4" x 6"
4' c-c
4" x 6"(b)
6' c c
Up t o 42"
10' t o 15'
2" x 6"
3' c-c
2" x 6"
(c)
2" x 6"(d)
6' crc
Up t o 42"
Over 15'
2" x 6"
(XEE
4"x12"
4"x12"
6' c c
Width
Ikpth
4'cc
NOlES: CLOSE: Close u p r i g h t s up t i g h t . Center-to-Center c-c: ( a ) Minimum: Two s t r i n g e r s , one on top and one on bottom. ( b ) Minimum: Two s t r u t s t o 7' depth and t h r e e t o 10'. ( c ) Minimum: Three s t r i n g e r s , placed top, bottom and center. (d) Minimum: Three s t r u t s t o 13' depth and four t o 15'.
FIGURE 2 Skeleton Shoring 7.2-10
Requirements f o r Close S h e e t i n g r
Ibrizuntal
-
Width
Depth
Size
SIRUrS
sTmmRs
m G I . r J s
mENQI
s@%
size
Vertical s@%
Ibrinmtal
Size
s@%
Up t o 42" 4' to 10'
2" x 6"
UDSE
4"x6"
(a)
4" x 6"
6' c-c
4' t o 10'
2" x 6"
UDSE
Vx6'
(a)
4" x 6"
6' cc
O\Rr 42"
/
7
Up t o 42" 10' t o 15' 2" x 6"
UX33
4"x6"
2" x 6"
UDSE
4"x12"
Up to 42"
Over 15'
(b)
4'-
Vx6"
6' c c
4"x12"
6' e c
N(7IES: -
CLOSE: Close uprights up tight. Center-toanter c-c: ( a ) Minimum: Two s t r i n g e r s , one on top and one on bottom. (b) Minimum: Two s t r u t s t o 7' depth and three t o 10'. ( c ) Minimum: Three stringers, placed top, bottom and center. (d) Minimum: Three s t r u t s t o 13' depth and four t o 15'.
FIGURE 3 Close ( T i g h t ) Sheeting
FIGURE 4 Box Shoring
FIGURE 5 Telescopic Shoring
Section 4. 1. WALL selection Figure 6. Reference
BRACED EXCAVATIONS
TYPES. Commonly used wall types and l i m i t a t i o n s t o be c o n s i d e r e d i n a r e given i n Table 4. Schematics of support systems a r e shoyn on A d e s c r i p t i o n of w a l l types l i s t e d i n Table 4 is presented i n 5, L a t e r a l Support Systems and Underpinning, by Goldberg, e t al.
2. SELECTION OF SUPPORT SYSTEM. F a c t o r s t o be considered i n s e l e c t i n g types of support systems a r e given i n Table 5. ,
3. EARTH PRESSURES. The tm l i m i t i n g pressures which may act on the w a l l a r e t h e s t a t e s of a c t i v e pressure and passive pressure. D e f i n i t i o n s and methods f o r computing e a r t h pressures a r e presented i n Chapter 3. For most p r a c t i c a l c a s e s , c r i t e r i a f o r e a r t h p r e s s u r e s do not e x a c t l y conform t o t h e s t a t e of a c t i v e , passive o r a t rest pressure. Actual e a r t h p r e s s u r e depends on w a l l deformation and t h i s i n t u r n depends on s e v e r a l f a c t o r s . Among t h e p r i n c i p a l f a c t o r s a r e : (1) s t i f f n e s s of w a l l and support systems; (2) s t a b i l i t y of t h e excavation; and (3) depth of excavation and w a l l deflection. The e f f e c t s of w a l l d e f l e c t i o n on p r e s s u r e d i s t r i b u t i o n , and d i f f e r e n c e s between s t r u t l o a d s computed from a c t i v e e a r t h pressure theory and those a c t u a l l y measured f o r deep excavation i n s o f t c l a y , a r e i l l u s t r a t e d i n Reference 6 , s t a b i l i t y of ~ l e x i b l eS t r u c t u r e s by Bjerrum, e t a l . A s many d i f f e r e n t v a r i a b l e s a f f e c t p r e s s u r e s a c t i n g on w a l l s , many types of a n a l y s e s a r e a v a i l a b l e f o r s p e c i a l s i t u a t i o n s . ( D e t a i l s concerning t h e s e a r e given i n Reference 7, Braced Excavation by Lambe.) Examples of e a r t h p r e s s u r e computations are given i n Chapter 3. 4. OTHER DESIGN AND CONSTRUCTION CONSIDERATIONS. Several f a c t o r s o t h e r t h a n e a r t h p r e s s u r e s a f f e c t t h e s e l e c t i o n , d e s i g n and t h e performance of braced excavations. See Table 6 f o r a summary of t h e s e f a c t o r s .
LATERAL MOVEMENTS. For w e l l constructed s t r u t t e d excavations i n d e n s e 5. sands and till, maximum l a t e r a l w a l l movements a r e o f t e n less than 0.2% of In excavation depth. L a t e r a l movements a r e u s u a l l y less f o r t i e d back w a l l s . s t i f f f i s s u r e d c l a y s , l a t e r a l movements may reach 0.5% o r higher depending on q u a l i t y of c o n s t r u c t i o n . In s o f t c l a y s , a major p o r t i o n of movement o c c u r s below excavation bottom. L a t e r a l movement may be i n t h e range of 0.5% t o 2% of excavation depth, depending on the f a c t o r of s a f e t y a g a i n s t b o t t a n i n s t a b i l i t y . Higher movements a r e a s s o c i a t e d w i t h lesser f a c t o r s of s a f e t y . SOIL SETTLEMENTS BEHIND WALLS. Reference 8, Deep Excavations and Tunnel6. i n g i n S o f t Ground by Peck, provides guidance based on e m p i r i c a l o b s e r v a t i o n of s e t t l e m e n t behind wall. Settlements up t o about 1%of t h e e x c a v a t i o n d e p t h have been measured behind w e l l c o n s t r u c t e d w a l l s f o r c u t s i n sand and i n medium s t i f f c l a y s . In s o f t e r c l a y s , t h i s may be a s high a s 2% and c o n s i d e r a b l y more i n very s o f t clays. ,
TABLE 4 Types of Walls
Name
Typical E I Values P e r Foot ( k s f ) 900
-
90,000
S o l d i e r P i l e and Lagging
2,000
-
120,000
Cas t-in-place o r Pre-cast Conc r e t e Slurry Wall (diaphragm w a l l s , s e e DM7.3, Chapter 3 )
288,000
-
2,300,000
(1)
S t e e l Sheeting
(2)
(3)
Comments
-
-
-
-
(4)
Cylinder P i l e Wall
115,000
-
1,000,000
-
-
Can be impervious Easy t o h a n d l e and c o n s t r u c t Easy t o handle and c o n s t r u c t Permits drainage Can be d r i v e n o r augered Can be impervious Relatively high s t i f f n e s s Can be p a r t of permanent structure Can be p r e s t r e s s e d R e l a t i v e l y less l a t e r a l w a l l movement pe mi t t ed compared t o ( 1 ) and ( 2 ) High i n i t i a l c o s t Specialty contractor required t o construct Very l a r g e and heavy w a l l must be used f o r deep systems Permits y i e l d i n g of subs o i l s , but precast concrete u s u a l l y shows l e s s y i e l d i n g than s t e e l sheeting o r s o l d i e r p i l e procedures. Secant p i l e s impervious Relatively high s t i f f n e s s Highly s p e c i a l i z e d equipment n o t needed f o r t a n g e n t p i l e s S l u r r y n o t needed
A. CANTILEVER WALL
B. CROSS-LOT BRACED WALL
F;DUNDATION SLAB C. RAKER SYSTEM
D. ANCHOR OR TIEBKK WALL
E. EARTH BERM SUPPORT
FIGURE 6 Support S y s t e m Walled Excavation
-
TABLE 5 F a c t o r s Involved i n Choice of A Support System For A Deep Excavation (> 20 f e e t )
Requirements
Lends I t s e l f t o Use Of
Comment s
-
1.
Open excavation area
Tiebacks o r r a k e r s o r c a n t i l e v e r w a l l s (shallow excavation)
2.
Low i n i t i a l c o s t
Soldier p i l e o r s h e e t p i l e walls; combined s o i l slope with wall
3.
Use a s p a r t of permanent structure
Diaphragm ( s e e DM 7.3 Chapter 3 ) o r c y l i n d e r p i l e walls
Diaphragm w a l l most common a s permanent w a l l .
4.
Deep, s o f t c l a y subsurface conditions
Strutted o r raker supported diaphragm o r cylinder p i l e walls
Tieback c a p a c i t y n o t adequate i n s o f t c l a y s .
5.
Dense, g r a v e l l y sand o r c l a y subsoils
S o l d i e r p i l e , diaphragm o r cylinder p i l e
6.
Deep, overconsolidated clays
S t r u t s , long t i e b a c k s o r combination t i e b a c k s and struts.
High i n s i t u l a t e r a l stresses a r e relieved i n overconsolidated s o i l s . L a t e r a l movements may b e l a r g e and extend deep i n t o soil.
7.
Avoid dewatering
Diaphragm w a l l s , p o s s i b l y sheetpile walls i n soft subsoils
S o l d i e r p i l e wall i s pervious.
8.
Minimize movements
High preloads on s t i f f s t r u t t e d o r tied-back w a l l
Analyze f o r s t a b i l i t y o f bottom of excavation.
9.
Wide excavation ( g r e a t e r than 65 f e e t wide)
Tiebacks o r r a k e r s
Tiebacks p r e f e r a b l e except i n very s o f t c l a y subsoils.
10.
Narrow excavat i o n ( l e s s than 65 f e e t wide)
Crosslot s t r u t s
S t r u t s more economical but t i e b a c k s s t i l l may be p r e f e r r e d t o keep excav a t i o n open.
-
S h e e t p i l e s may l o s e i n t e r l o c k on hard d r i v i n g .
TABLE 6 Design C o n s i d e r a t i o n s f o r Braced and Tieback Walls
Design F a c t o r
?
Comments
1.
Water Loads
Often g r e a t e r t h a n e a r t h l o a d on impervious wall. Recommended piezometers d u r i n g c o n s t r u c t i o n t o monitor water l e v e l s . Should c o n s i d e r p o s s i b l e lower water p r e s s u r e s a s a r e s u l t of seepage through o r under w a l l . Dewatering can be used t o reduce water l o a d s . Seepage under w a l l r e d u c e s passive r e s i s t a n c e .
2.
Stability
Consider p o s s i b l e i n s t a b i l i t y i n any berm o r exposed slope. S l i d i n g potent i a l beneath t h e w a l l o r behind t i e b a c k s should be e v a l u a t e d . Deep s e a t e d b e a r i n g f a i l u r e under weight of s u p p o r t e d s o i l t o be checked i n weak s o i l s . S t a b i l i t y should c o n s i d e r weight of s u r c h a r g e o r t h e weight of o t h e r f a c i l i t i e s i n c l o s e proximity t o e x c a v a t i o n .
3.
Piping
Loss of ground caused by h i g h groundwater t a b l e and s i l t y and f i n e sand s o i l s . D i f f i c u l t i e s occur due t o flow b e n e a t h w a l l , through bad j o i n t s i n w a l l s , o r through unsealed s h e e t p i l e h a n d l i n g h o l e s . Dewatering may b e required.
4.
Movements
Movements can be minimized through use of s t i f f w a l l supported by preloaded t i e b a c k o r braced system.
5.
Dewatering
6.
Surcharge
C o n s t r u c t i o n m a t e r i a l s u s u a l l y s t o r e d n e a r w a l l systems. always be made f o r surcharge.
7.
P r e s t r e s s i n g of t i e backs o r s t r u t s
Useful t o remove s l a c k from system and minimize s o i l movements.
-
recharge
Dewatering r e d u c e s l o a d s on w a l l systems and minimizes p o s s i b l e l o s s of ground due t o piping. May cause s e t t l e m e n t s and w i l l t h e n need t o r e c h a r g e o u t s i d e of s u p p o r t system. Allowance should
d
TABLE 6 (continued) Design Considerations f o r Braced and Tieback Walls
Comments
Design F a c t o r
8.
Construction Sequence
The amount of wall movement i s dependent on t h e depth of excavation. The amount of load on t h e t i e backs i s dependent on t h e amount of w a l l movement which occurs b e f o r e t h e y a r e i n s t a l l e d . Movements of wall should be checked a t every major c o n s t r u c t i o n stage. Upper s t r u t s should be i n s t a l l e d early.
9,
Temperature
S t r u t s s u b j e c t t o load f l u c t u a t i o n due t o temperature l o a d s ; may b e important f o r long s t r u t s .
10.
Frost Penetration
I n very c o l d c l i m a t e s , f r o s t p e n e t r a t i o n can cause s i g n i f i c a n t loading on wall system. Design of upper p o r t i o n of system should be conservative. Anchors may have t o be heated. Freezing temperatures a l s o can cause blockage of flow and t h u s unexpected buildup of water pressure.
11.
Earthquakes
Seismic l o a d s may be induted during earthquake,
12.
F a c t o r s of S a f e t y
See DM-7.3,
Chapter 1.
Suggested Minimum Design Factor of S a f e t y f o r Overall S t a b i l i t y I
Item
Permanent
Temporary
E a r t h Berms Cut Slopes Bottom heave above foundation level General s t a b i l i t y Bottan heave a t foundation level
2.0 1.5 1.5
1.5 1.3 1.5
1.5 2.0
1.3 1.5
Note:
These v a l u e s a r e suggested g u i d e l i n e s only. f a c t o r depends on p r o j e c t requirements.
Design s a f e t y
7. PROTECTION OF ADJACENT STRUCTURES. E v a l u a t e t h e e f f e c t s of b r a c e d excav a t i o n s on a d j a c e n t s t r u c t u r e s t o determine whether e x i s t i n g b u i l d i n g foundat i o n s a r e t o be p r o t e c t e d . See DM-7.3, Chapters 2 and 3 on s t a b i l i z i n g found a t i o n s o i l s and methods of underpinning. F i g u r e 7 (modified from R e f e r e n c e 9, Damage t o B r i c k Bearing Wall ~ t r u c t u ; e s ~ a i s e dby Adjacent Braced C u t s and Tunnels. bv O'Rourke. e t a l . ) i l l u s t r a t e s a r e a s behind a braced w a i l where underpinning i s o r may be r e q u i r e d . s
.
F a c t o r s i n f l u e n c i n g t h e type of b r a c i n g used and t h e need f o r u n d e r p i n n i n g include : ( a ) L a t e r a l d i s t a n c e of e x i s t i n g s t r u c t u r e from t h e braced e x c a v a t i o n . E m p i r i c a l o b s e r v a t i o n s on t h i s can be found i n Reference 8. ( b ) Lowering groundwater can cause s o i l c o n s o l i d a t i o n and s e t t l e m e n t of structures. ( c ) Dewatering should be p r o p e r l y c o n t r o l l e d t o e n s u r e t h e r e i s n o removal of f o u n d a t i o n s o i l s o u t s i d e t h e e x c a v a t i o n . ( d ) T o l e r a n c e of s t r u c t u r e s t o movement. See DM-7.1, Chapter 5 f o r e v a l u a t i o n of t o l e r a n c e of s t r u c t u r e t o v e r t i c a l movements. V e r t i c a l and l a t e r a l movements produce h o r i z o n t a l s t r a i n s i n s t r u c t u r e . Guidance o n p e r m i s s i b l e h o r i z o n t a l s t r a i n s f o r s t r u c t u r e s i s g i v e n i n Reference 9. S e c t i o n 5.
ROCK EXCAVATION
1. OBJECTIVE. Primary o b j e c t i v e i s t o conduct work i n such a manner t h a t a s t a b l e e x c a v a t i o n w i l l be maintained and t h a t rock o u t s i d e t h e e x c a v a t i o n prism w i l l n o t be a d v e r s e l y d i s t u r b e d . 2. PRELIMINARY CONSIDERATIONS. Rock e x c a v a t i o n planning must be b a s e d o n d e t a i l e d g e o l o g i c a l d a t a a t t h e s i t e . To t h e e x t e n t p o s s i b l e , s t r u c t u r e s t o be c o n s t r u c t e d i n rock should be o r i e n t e d f a v o r a b l y w i t h t h e g e o l o g i c a l s e t ting. For example, t u n n e l s should be a l i g n e d w i t h a x i s p e r p e n d i c u l a r t o t h e s t r i k e of f a u l t s o r major f r a c t u r e s . Downslope d i p of d i s c o n t i n u i t i e s i n t o a n open c u t should be avoided. I n g e n e r a l , f a c t o r s t h a t must be c o n s i d e r e d i n p l a n n i n g , d e s i g n i n g and cons t r u c t i n g a r o c k e x c a v a t i o n a r e a s follows: ( 1 ) presence of s t r i k e , d i p o f f a u l t s , f o l d s , f r a c t u r e s , and o t h e r d i s c o n t i n u i t i e s ; ( 2 ) i n s i t u stresses; ( 3 ) groundwater c o n d i t i o n s ; ( 4 ) n a t u r e of m a t e r i a l f i l l i n g j o i n t s ; (5) d e p t h and s l o p e of c u t ; ( 6 ) s t r e s s e s and d i r e c t i o n of p o t e n t i a l s l i d i n g s u r f a c e s ; ( 7 ) dynamic l o a d i n g , i f any; ( 8 ) d e s i g n l i f e of c u t a s compared t o w e a t h e r i n g o r d e t e r i o r a t i o n r a t e of r o c k f a c e ; ( 9 ) r i p p a b i l i t y a n d / o r t h e need f o r b l a s t i n g ; and (10) e f f e c t of e x c a v a t i o n a n d / o r b l a s t i n g on a d j a c e n t s t r u c t u r e s . The i n f l u e n c e of most of t h e s e f a c t o r s on e x c a v a t i o n s i n rock i s similar t o t h a t of e x c a v a t i o n s i n s o i l , s e e DM-7.1, Chapter 7.
\
\
\
\
TIGHTLY BRACED/ T I E EXCAVATION WALL
BASE OF STABLE AND DEWATORED EXCAVATION
ZONE A: FOUNDATIONS WITHIN T H I S ZONE GENERALLY REQUIRE UNDERPINNING.
ZONE B: FOUNDATIONS WITHIN T H I S ZONE GENERALLY MAY NOT REQUIRE UNDERPINNING DEPENDING ON TYPE OF STRUCTURE AND LOADING CONDITIONS. ZONE C: UNDERPINNING I F USED MUST BE FOUNDED I N T H I S ZONE TO APPROPRIATE DEPTHS ESTABLISHED BY EXPLORATION AND ANALYSIS. Note:
A d d i t i o n a l d e t a i l s on underpinning m a y be found i n DM-7.3, FIGURE 7 G e n e r a l G u i d a n c e for U n d e r p i n n i n g
C h a p t e r 3.
3. RIPPABILITY. Excavation e a s e o r r i p p a b i l i t y can be a s s e s s e d a p p r o x i m a t e l y from f i e l d o b s e r v a t i o n i n s i m i l a r m a t e r i a l s o r by u s i n g s e i s m i c v e l o c i t y , f r a c t u r e s p a c i n g , o r p o i n t l o a d s t r e n g t h index. F i g u r e 8 (from R e f e r e n c e 10, Handbook of Ripping, by C a t e r p i l l a r T r a c t o r Co.) shows an example of charts f o r heavy d u t y r i p p e r performance ( r i p p e r mounted on t r a c k e d b u l l d o z e r ) as r e l a t e d t o s e i s m i c wave v e l o c i t y . Charts s i m i l a r t o Figure 8 a r e a v a i l a b l e from v a r i o u s equipment manufacturers. F i g u r e 8 i s f o r guidance and r e s t r i c t e d i n a p p l i c a b i l i t y t o l a r g e t r a c t o r s h e a v i e r t h a n 50 t o n s w i t h engine h o r s e p o w e r g r e a t e r than 350 Hp. Ripper performance i s a l s o r e l a t e d t o c o n f i g u r a t i o n of r i p p e r t e e t h , equipment c o n d i t i o n and s i z e , and f r a c t u r e o r i e n t a t i o n . Another t e c h n i q u e of r e l a t i n g p h y s i c a l p r o p e r t i e s of r o c k t o e x c a v a t i o n e a s e i s shown on F i g u r e 9 (from Reference 11, Logging t h e Mechanical C h a r a c t e r of Rock, by F r a n k l i n , e t a l . ) where f r a c t u r e frequency ( o r s p a c i n g ) i s p l o t t e d a g a i n s t t h e p o i n t l o a d s t r e n g t h index c o r r e c t e d t o a r e f e r e n c e d i a m e t e r of 50 mm. (See Reference 12, The Point-Load S t r e n g t h T e s t , by Broch and F r a n k l i n . ) A t h i r d and u s e f u l technique i s e x p l o r a t i o n t r e n c h i n g i n which t h e d e p t h o f u n r i p p a b l e r o c k can be e s t a b l i s h e d by d i g g i n g t e s t t r e n c h e s i n rock u s i n g r i p p e r s ( o r o t h e r e x c a v a t i o n equipment) a n t i c i p a t e d t o be used f o r t h e project. The s i z e and shape of t h e a r e a t o be excavated i s a s i g n i f i c a n t f a c t o r i n determining t h e need f o r b l a s t i n g , o r t h e equipment needed t o remove t h e rock.
4.
BLASTING. Of major concern i s t h e i n f l u e n c e of t h e b l a s t i n g on a d j a c e n t s t r u c t u r e s . The maximum p a r t i c l e v e l o c i t y ( t h e l o n g i t u d i n a l v e l o c i t y o f a p a r t i c l e i n t h e d i r e c t i o n of t h e wave t h a t i s g e n e r a t e d by t h e b l a s t ) i s accepted a s a c r i t e r i o n f o r e v a l u a t i n g t h e p o t e n t i a l f o r s t r u c t u r a l damage induced by b l a s t i n g v i b r a t i o n . The c r i t i c a l l e v e l of t h e p a r t i c l e v e l o c i t y depends on t h e frequency c h a r a c t e r i s t i c s of t h e s t r u c t u r e , frequency of ground and rock motion, n a t u r e of t h e overburden, and c a p a b i l i t y of t h e s t r u c t u r e t o withstand dynamic s t r e s s . F i g u r e 10 can be used f o r e s t i m a t i n g t h e maximum p a r t i c l e v e l o c i t y , which can then be used i n F i g u r e 11 (from R e f e r e n c e 1 3 , B l a s t i n g V i b r a t i o n s and T h e i r E f f e c t s on S t r u c t u r e s , by Bureau of M i n e s ) t o e s t i m a t e p o t e n t i a l damage t o r e s i d e n t i a l s t r u c t u r e s . Guidance f o r human response t o b l a s t i n g v i b r a t i o n s i s g i v e n i n Figure 12 (from Reference 1 4 , ~ n g i n e d r i n gof Rock B l a s t i n g on C i v i l P r o j e c t s , by Hendron). Once i t has been determined t h a t b l a s t i n g i s r e q u i r e d , a p r e - b l a s t i n g s u r v e y should be performed. As a minimum, t h i s should i n c l u d e : ( a ) e x a m i n a t i o n of t h e s i t e ; ( b ) d e t a i l e d examination and perhaps photographic r e c o r d s o f a d j a c e n t s t r u c t u r e s ; and ( c ) e s t a b l i s h m e n t of h o r i z o n t a l and v e r t i c a l s u r v e y cont r o l points. I n a d d i t i o n , t h e p o s s i b i l i t y of v i b r a t i o n monitoring s h o u l d b e c o n s i d e r e d , and monitoring s t a t i o n s and s c h e d u l e s should be e s t a b l i s h e d . During c o n s t r u c t i o n , d e t a i l e d r e c o r d s should be k e p t o f : ( a ) charge w e i g h t , ( b ) l o c a t i o n of b l a s t p o i n t and d i s t a n c e from e x i s t i n g s t r u c t u r e s , ( c ) d e l a y s , and ( d ) r e s p o n s e a s i n d i c a t e d by v i b r a t i o n monitoring. For s a f e t y , s m a l l c h a r g e s should be used i n i t i a l l y t o e s t a b l i s h a s i t e s p e c i f i c r e l a t i o n s h i p between c h a r g e weight, d i s t a n c e , and response.
,
TOPS01L CLAY GLACIAL TILL IGNEOUS ROCKS
I
--.---a
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a*
-
SEDl MENTARY ROCKS
CONGWMERATE
METAMORPHIC ROCKS
RIPPABLE MARGINAL NON-RIPPABLE
--------
0
1
2 3
4
5
6
7 8 9
1011 1 2 1 3 1 4 1 5 1 6
LONGITUDINAL VELOCITY IN FT. PER SEC. (THOUSANDS)
FIGURE 8 Rippability of Subsurface Materials Related to Longitudinal Seismic Velocity for a Heavy Duty Ripper (Tractor-Mounted)
A
W
LL
*
POINT LOAD STRENGTH 1, (50)TONSIFT
*
POINT LOAD STRENGTH CORRECTED TO A REFERENCE DIAMETER OF 5 0 MM.
FIGURE 9 suggested Guide for Ease of Excavation
I
2
3
5
0 2 0 3 0 5070100 R/(w)I)S, FT./LR@
7
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SCALED RANGE
EXAMPLE :
Weight of Explosive Charge = 8 l b s . = W Distance from Blast Point = 100 f t. = R
~ / ( w i 1 / 3 = 50 Peak Vr = 0.5 i n / s e c from chart L
FIGURE 10 Cube Root Scaling Versus Maximum P a r t i c l e Velocity
f
10.0
-
9.0-
--
MAJOR DAMAGE (FALL OF PLASTER, 8.0 SERIOUS CRACKING)
-
cj W
q z 1
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-
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4.03.0
-
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0
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0
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,
FIGURE 11 Guideline f o r Assessing P o t e n t i a l f o r Damage Induced by B l a s t i n g V i b r a t i o n t o R e s i d e n t i a l S t r u c t u r e Founded on Dense S o i l o r Rock
4
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1
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DAMAGE 4.0
4O .
CAUTION
CAUTION
2.o
2.0 SEVERE
n
d
1.2 1.0
-
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-
DISTURBING
-I
-
SEVERE.
k
COMPLAINTS LIKELY
04
0
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W
4
-
0
k 0
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-
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-
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0.06
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L
TRANSIENT MOTION. NO SOWD EFFECTS. lMPARTIAL OBSERVER.
. A
0.01 BLAST1NG VIBRATIONS ACOOMe#NIED BY SOUND EFFECTS. B lASEO OBSERVER.
FIGURE 12 Guide for Predicting Human Response t o Vibrations and Blasting E f f e c t s
S e c t i o n 6.
GROUNDWATER CONTROL
1. APPLICATION. Excavations below t h e groundwater t a b l e r e q u i r e groundw a t e r c o n t r o l t o permit c o n s t r u c t i o n i n t h e d r y and m a i n t a i n t h e s t a b i l i t y of e x c a v a t i o n base and s i d e s . T h i s i s accomplished by c o n t r o l l i n g s e e p a g e i n t o t h e e x c a v a t i o n and c o n t r o l l i n g a r t e s i a n water p r e s s u r e s below t h e b o t t o m of t h e excavation. 2. METHOD. See Table 7 (modified from Reference 15, C o n t r o l of Groundwater by Water Lowering, by Cashman and H a r r i s ) f o r methods of c o n t r o l l i n g groundw a t e r , t h e i r a p p l i c a b i l i t y- ,- and l i m i t a t i o n s . W e l l p o i n t s , deep w e l l s , a n d sumps a r e most- commonly used. F i g u r e s 13(A) (from- ~ e f e r e n c e and 1 3 ( ~ ) (from Reference 16, Design and C o n s t r u c t i o n of Dry Docks, by Mazurkiewbcz) show a dewatering system u s i n g deep w e l l s , and a two s t a g e w e l l p o i n t system. F i g u r e s 13(C) and 13(D) (from Reference 16) shows d e t a i l s of a w e l l p o i n t system, and a deep w e l l w i t h e l e c t r i c submersible pump. See F i g u r e 1 4 (from Reference 2 ) f o r a p p l i c a b l e limits of dewatering methods.
i)
3. DESIGN PROCEDURE. See DM-7.1, Chapter 6 f o r d e s c r i p t i o n of d e s i g n . p r o c e d u r e s f o r groundwater c o n t r o l . For a d d i t i o n a l guidance on groundwater c o n t r o l s e e NAVFAC P-418. S e c t i o n 7.
EXCAVATION STABILIZATION, MONITORING, AND SAFETY
1. STABILIZATION. During t h e planning and d e s i g n s t a g e , i f a n a l y s e s i n d i c a t e p o t e n t i a l s l o p e i n s t a b i l i t y , means f o r s l o p e s t a b i l i z a t i o n o r r e t e n t i o n should be c o n s i d e r e d . Some methods f o r c o n s i d e r a t i o n are g i v e n i n C h a p t e r 3. On o c c a s i o n , t h e complexity of a s i t u a t i o n may d i c t a t e u s i n g v e r y s p e c i a l i z e d s t a b i l i z a t i o n methods. These may i n c l u d e g r o u t i n g and i n j e c t i o n , g r o u n d f r e e z i n g , deep d r a i n a g e and s t a b i l i z a t i o n , such as vacuum w e l l s o r e l e c t r o osmosis ( s e e DM-7.3, Chapter 2 ) , and diaphragm w a l l s ( s e e DM-7.3, C h a p t e r 3 ) .
2. MONITORING. During e x c a v a t i o n , p o t e n t i a l bottom heave, l a t e r a l w a l l o r s l o p e movement, and s e t t l e m e n t of a r e a s behind t h e w a l l o r s l o p e s h o u l d b e i n s p e c t e d c a r e f u l l y and monitored i f c r i t i c a l . Monitoring can be a c c o m p l i s h e d by c o n v e n t i o n a l s u r v e y t e c h n i q u e s , o r by more s o p h i s t i c a t e d means s u c h as heave p o i n t s , s e t t l e m e n t p l a t e s , extensometers o r i n c l i n o m e t e r s , and a v a r i e t y of o t h e r d e v i c e s . See DM-7.1, Chapter 2. 3. SAFETY. D e t a i l e d s a f e t y requirements vary from p r o j e c t t o p r o j e c t . As a g u i d e , s a f e t y requirements a r e s p e c i f i e d by OSHA, see Reference 17, P u b l i c Law 91-596. A summary of t h e 1980 requirements follows: a.
OSHA Rules.
( 1 ) Banks more t h a n 4 f e e t high s h a l l be shored o r sloped t o t h e a n g l e of r e p o s e where a danger of s l i d e s o r cave-ins e x i s t s a s a r e s u l t of excavation.
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TABLE 7 ( c o n t i n u e d ) Methods of Groundwater C o n t r o l
Method
5.
Sheet p i l i n g c u t off
Soils Suitable For Treatment A l l t y p e s of s o i l ( e x c e p t b o u l d e r beds). Tongue and groove wood sheeting u t i l i z e d f o r shallow excavations i n s o f t and medium s o i l s .
Uses P r a c t i c a 1l y unr es t r i c t e d use.
Comments Well-understood method u s i n g readily available plant. Rapid i n s t a l l a t i o n . Steel can be i n c o r p o r a t e d i n perman e n t works o r r e c o v e r e d . Sump pumping may be r e q u i r e d . E s t i m a t e seepage flow based on 0.01 gpmlsq f t of w a l l per f o o t of d i f f e r e n t i a l head. Decrease i n t e r l o c k l e a k a g e by f i l l i n g i n t e r l o c k w i t h sawd u s t , b e n t o n i t e , cement grout, o r similar materials.
-
-
6.
Slurry trench cuto f f ( s e e DM-7.3, Chapter 3 and DM-7.1, Chapter 6 )
7.
Freezing ( s e e DM-7.3, Chapter 2 ) a.
Ammonium/brine refrigerator
S i l t s , sands, gravels, and c o b b l e s .
P r a c t i c a l l y unres t r i c t e d . Extensive c u r t a i n w a l l s around open e x c a v a t i o n s .
Rapidly i n s t a l l e d . Can b e keyed i n t o impermeable s t r a t a such a s c l a y s o r s o f t shales. May be i m p r a c t i c a l t o key int o h a r d o r i r r e g u l a r bedrock s u r f a c e s , o r i n open g r a v e l s .
A l l t y p e s of s a t u r a t e d s o i l s and rock.
Formation of i c e i n the voids stops water.
Treatment e f f e c t i v e from working s u r f a c e outwards. Better f o r l a r g e a p p l i c a t i o n s
of long d u r a t i o n .
Treatment
takes longer t i m e t o develops.
TABLE 7 (continued) Methods of Groundwater Control
Method b.
8.
Liquid n i t r o gen r e f r i g e r ant
Soils Suitable For Treatment
,
Uses
Comments
A l l types of s a t u r a t e d s o i l s and rock.
Formation of ice i n the voids stops water.
B e t t e r f o r small a p p l i c a t i o n s of s h o r t d u r a t i o n where quick Liquid f r e e z i n g i s required. n i t r o g e n i s expensive. Requires s t r i c t s i t e c o n t r o l . Some ground heave occurs.
A l l s o i l types including those c o n t a i n i n g boulders.
Deep basements, underground construction, shafts.
Can be designed t o form p a r t of a permanent foundation. Particularly efficient for c i r c u l a r excavations. Can be keyed i n t o rock. Minimum v i b r a t i o n and noise. Can be used i n r e s t r i c t e d space. Can be put down v e r y c l o s e t o e x i s t i n g foundation.
A l l s o i l types but p e n e t r a t i o n through b o u l d e r s may be d i f f i c u l t and c o s t l y
Deep basements, underground construction, shafts.
A r a p i d l y i n s t a l l e d , form of diaphragm wall. Can be keyed i n t o impermeable s t r a t a such a s clays o r s o f t shales.
Diaphragm structural walls a.
Diaphragm walls (struct u r a l conc r e t e ) (see DM-7.3, C h a p ter 3 )
b. Contiguous bored p i l e walls o r impervious w a l l of mixed i n place p i l e s
FIRST STAGE GROUND
__---FINE SILTY SAND
------__
------------. . .
NOTE: PUMPING FROM FIRST- STAGE SYSTEM LOWERS WATER TABLE APPROXIMATELY 15 FEET WHICH WILL PERMIT EXCAVATION FOR INSTALLATIONOFSECOND-STACiE SYSTEM. DEWATERING USING TWO STAGE WELLPOINT SYSTEM WATER LEVEL AFTER FIRST S T A G E @ m M OFEXCAVATION @WATER LEVEL AFTER SECOND STAGE
@
+
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+ 22
22
4. CLAY 5. DEEP WELLS 6. ARTESIAN WATER PRESSURE REDUCED TO -36 FEET (HORIZONTAL SCALE/VERTlCAL SCALE = 2/51 7 DOWNWARD PRESSURE (TCTAL WEIGHT OFSOIL) DEWATERING SYSTEM OF A DRY DOCK PIT
I. PI EZOMETER 2. GROUNDWATER LEVEL 3. SAND
@ COMBlNE WELLPOINT AND DEEPWELL SYSTEM FIGURE 13 Methods of Construction Dewatering
r
WATER TABLE
GRAVEL FILTER
JETTING HOLES (C) DETAILS OF W E W T !WSfW
I. PERFORATED WELL LINER 2. DELIVERY PIPE 3 FILTER MEMA 4. ELECTRIC SUBMERSIBLE PUMP (Dl DETAILS OF DEEP WELL WITH SUBMERSIBLE PUMP
FIGURE 13 (continued) Methods of Construction Dewatering
( 2 ) S i d e s of t r e n c h e s i n u n s t a b l e o r s o f t m a t e r i a l , 4 f e e t o r more i n d e p t h , s h a l l be s h o r e d , s h e e t e d , b r a c e d , s l o p e d , o r o t h e r w i s e s u p p o r t e d by ineans of sufficient s t r e n g t h t o p r o t e c t t h e employee working w i t h i n them. ( 3 ) S i d e s of t r e n c h e s i n hard o r compact s o i l , i n c l u d i n g embankments, s h a l l be shored o r o t h e r w i s e s u p p o r t e d when t h e t r e n c h i s more t h a n 4 f e e t i n d e p t h and 8 f e e t o r more i n l e n g t h . I n l i e u of s h o r i n g , t h e s i d e s of t h e t r e n c h above t h e & f o o t l e v e l may be sloped t o p r e c l u d e c o l l a p s e , b u t s h a l l n o t be s t e e p e r than a 1-foot r i s e t o each 112-foot h o r i z o n t a l . When t h e o u t s i d e diameter of a pipe i s g r e a t e r t h a n 6 f e e t , a bench of 4-foot minimum s h a l l be provided a t t h e t o e of t h e sloped p o r t i o n . ( 4 ) M a t e r i a l s used f o r s h e e t i n g and s h e e t p i l i n g , b r a c i n g , s h o r i n g , and underpinning s h a l l be i n good s e r v i c e a b l e c o n d i t i o n . Timbers used s h a l l be sound and f r e e from l a r g e o r l o o s e k n o t s , and s h a l l be designed and i n s t a l l e d so a s t o be e f f e c t i v e t o t h e bottom of t h e e x c a v a t i o n . ( 5 ) A d d i t i o n a l p r e c a u t i o n s by way of s h o r i n g and b r a c i n g s h a l l . b e t a k e n t o p r e v e n t s l i d e s o r cave-ins when ( a ) e x c a v a t i o n s o r t r e n c h e s a r e made i n l o c a t i o n s a d j a c e n t t o b a c k f i l l e d e x c a v a t i o n s ; o r ( b ) where e x c a v a t i o n s a r e s u b j e c t e d t o v i b r a t i o n s from r a i l r o a d o r highway t r a f f i c , o p e r a t i o n of machinery, o r any o t h e r source.
( 6 ) Employees e n t e r i n g bell-bottom p i e r h o l e s s h a l l be p r o t e c t e d by t h e i n s t a l l a t i o n of a removable-type c a s i n g of s u f f i c i e n t s t r e n g t h t o r e s i s t s h i f t i n g of t h e surrounding e a r t h . Such temporary p r o t e c t i o n s h a l l be provided f o r t h e f u l l d e p t h of t h a t p a r t of each p i e r h o l e which i s above t h e b e l l . A l i f e l i n e , s u i t a b l e f o r i n s t a n t r e s c u e and s e c u r e l y f a s t e n e d t o t h e s h a f t s , s h a l l be provided. This l i f e l i n e s h a l l be i n d i v i d u a l l y manned and s e p a r a t e from any l i n e used t o remove m a t e r i a l s excavated from t h e b e l l f o o t i n g . ( 7 ) Minimum requirements f o r t r e n c h t i m b e r i n g s h a l l be i n a c c o r d a n c e w i t h Table 3.
(8) Where employees a r e r e q u i r e d t o be i n t r e n c h e s 3 f e e t deep o r more, l a d d e r s s h a l l be provided which extend from t h e f l o o r of t h e t r e n c h e x c a v a t i o n t o a t l e a s t 3 f e e t above t h e t o p of t h e e x c a v a t i o n . They s h a l l be l o c a t e d t o provide means of e x i t without more t h a n 2 5 f e e t of l a t e r a l t r a v e l . (9) excavation.
Bracing o r shoring of t r e n c h e s s h a l l be c a r r i e d a l o n g w i t h t h e
( 1 0 ) Cross b r a c e s o r t r e n c h jacks s h a l l be placed i n t r u e h o r i z o n t a l p o s i t i o n , spaced v e r t i c a l l y , and secured t o prevent s l i d i n g , f a l l i n g , o r k i c k outs. ( 1 1 ) P o r t a b l e t r e n c h boxes o r s l i d i n g t r e n c h s h i e l d s may be used f o r t h e p r o t e c t i o n of employees only. Trench boxes o r s h i e l d s s h a l l be d e s i g n e d , c o n s t r u c t e d , and maintained t o meet a c c e p t a b l e e n g i n e e r i n g s t a n d a r d s . ( 1 2 ) B a c k f i l l i n g and removal of t r e n c h s u p p o r t s s h a l l p r o g r e s s t o g e t h e r from t h e bottom of t h e trench. J a c k s o r b r a c e s s h a l l be r e l e a s e d s l o w l y , and i n u n s t a b l e s o i l , r o p e s s h a l l be used t o p u l l o u t t h e j a c k s o r b r a c e s from above a f t e r employees have c l e a r e d t h e t r e n c h .
REFERENCES
1.
Clough, G.W. and Davidson, R.R., E f f e c t s of Construction on Geotechnical Engineering, S p e c i a l t y Session No. 3, R e l a t i o n s h i p Between Design and Construction i n S o i l Engineering, Ninth I n t e r n a t i o n a l Conference on S o i l Mechanics and Foundation Engineering, Tokyo, 1977.
2.
Departments of t h e Army and the Air Force, S o i l s and Geology, Procedures f o r Foundation Design of Buildings and Other S t r u c t u r e s (Except Hydraulic S t r u c t u r e s ) , TM 5/818-1/AFM 88-3, Chapter 7, 1979. Washington, D.C.,
3.
Terzaghi, K., S t a b i l i t y of Steep Slopes on Hard Unweathered Rock, Norwegian Geotechnical I n s t i t u t e , P u b l i c a t i o n No. 50, 1963.
4.
Cave-In!, Roads and Engineering Construction, November Petersen, E.V., 1963, December 1963, January 1964.
5.
L a t e r a l Support Goldberg, D.T., Jaworkski, W.E., and Gordon, M.D., Systems and Underpinning, Vol. 11, Design Fundamentals, Vol. 111. Construction Methods, Federal Highway Administration, Report Nos. FWA-RD-75-129, 130, 1976.
S t a b i l i t y of F l e x i b l e 6. Bjerrum, L., Clausen, J.F. and Duncan, J.M., S t r u c t u r e s , General Report, Proceedings, F i f t h I n t e r n a t i o n a l European Conference on S o i l Mechanics and Foundation Engineering, Vol. 11, 1977'. 7.
Lambe, T.W., Braced Excavation, 1970 S p e c i a l t y Conference, L a t e r a l S t r e s s e s i n t h e Ground and Design of Earth R e t a i n i n g S t r u c t u r e s , J u n e 22-24, Cornell University, ASCE, 1971.
8.
Deep Excavations and Tunneling i n S o f t Ground, Proceedings, Peck, R.B., Seventh I n t e r n a t i o n a l Conference on S o i l Mechanics and Foundation Engin e e r i n g , State-of-the-Art Vol. 1, 1969.
9.
O'Rourke, T.P., Cording, E.J. and Boscardin, M., Damage t o Brick Bearing Wall S t r u c t u r e s Caused by Adjacent Braced Cuts and Tunnels, Large Ground Movements, John Wiley & Sons, 1977.
10.
C a t e r p i l l a r T r a c t o r Co., Handbook of Ripping, F i f t h E d i t i o n , P e o r i a , IL., 1975.
11.
F r a n k l i n , J.A., Broch, E. and Walton, G., Logging t h e Mechanical Character of Rock, Transactions, I n s t i t u t i o n of Mining and Metallurgy, January 1971.
12.
Broch, E. and Franklin, J.A., The Point-load S t r e n g t h T e s t , I n t e r n a t i o n a l J o u r n a l Rock Mechanics and Mining Science, Vol. 9 , 1972.
13.
Bureau of Mines, B l a s t i n g Vibrations and Their E f f e c t on S t r u c t u r e s , United S t a t e s Department of t h e I n t e r i o r , 1971.
14.
Hendron, A.J., Engineering of Rock Blasting on Civil Projects, Rock Excavation Seminar Lectures, ASCE, New York, October, 1976.
15.
Cashman, P.M. and Harris, E.T., Control of Groundwater by Water Lowering, Conference on Ground Engineering, Institute of Civil Engineers, London, 1970.
16.
Mazurkiewicz, B.K., Design and Construction of Dry Docks, Trans Tech Publications, Rockport, MA, 1980.
17.
Public Law 91-596 (Williams-Steiger Act), Occupational Safety and Health Act (OSHA) of 1970, Dec. 29, 1970.
18
Naval Facilities Command P-Publication, P-418, Dewatering and Groundwater Control.
CHAPTER 2.
COMPACTION, EARTHWORK, AND HYDRAULIC FILLS S e c t i o n 1.
INTRODUCTION
1. SCOPE. T h i s c h a p t e r concerns d e s i g n and c o n s t r u c t i o n of compacted f i l l s and performance of compacted m a t e r i a l s . Compaction r e q u i r e m e n t s a r e g i v e n f o r v a r i o u s a p p l i c a t i o n s and equipment. Earthwork c o n t r o l procedures and a n a l y s i s of c o n t r o l t e s t d a t a a r e d i s c u s s e d . Guidance on h y d r a u l i c f i l l s i s a l s o included. 2. RELATED CRITERIA. For a d d i t i o n a l c r i t e r i a concerned w i t h compaction and earthwork o p e r a t i o n s , c o n s u l t t h e following s o u r c e s : Subject
Pavements...............................................NAVFAC S o i l Conservation.......................................NAVFAC F l e x i b l e Pavement Design f o r Airfield...................NAVFAC Dredging Types of Dredging Equipment.............................NA
...............................................F
Source DM-5.4 DM-5.11 DM-21.3 A DM-26 DM-38
PURPOSE OF COMPACTION. (1) (2) (3) (4) (5)
Reduce m a t e r i a l c o m p r e s s i b i l i t y . Increase material strength. Reduce p e r m e a b i l i t y . C o n t r o l expansion. Control f r o s t s u s c e p t i b i l i t y .
4. APPLICATIONS. The p r i n c i p a l u s e s of compacted f i l l i n c l u d e s u p p o r t o f s t r u c t u r e s o r pavements, embankments f o r water r e t e n t i o n o r f o r l i n i n g r e s e r v o i r s and c a n a l s , and b a c k f i l l surrounding s t r u c t u r e s o r b u r i e d u t i l i t i e s . TYPES OF FILL. a. C o n t r o l l e d Compacted F i l l s . P r o p e r l y placed compacted f i l l w i l l b e more r i g i d and uniform and have g r e a t e r s t r e n g t h t h a n most n a t u r a l s o i l s . b. H y d r a u l i c F i l l s . Hydraulic f i l l s cannot be compacted d u r i n g placement and t h e r e f o r e i t i s important t h a t t h e s o u r c e m a t e r i a l s be s e l e c t e d c a r e fully. c. U n c o n t r o l l e d F i l l s . These c o n s i s t of s o i l s o r i n d u s t r i a l and domest i c wastes, s u c h a s a s h e s , s l a g , chemical w a s t e s , b u i l d i n g r u b b l e , and r e f u s e . Use of a s h , s l a g , and chemical waste i s s t r i n g e n t l y c o n t r o l l e d and c u r r e n t Environmental P r o t e c t i o n Agency o r o t h e r a p p r o p r i a t e r e g u l a t i o n s must be considered.
Section 2.
EMBANKMENT CROSS-SECTION DESIGN
1. INFLUENCE OF MATERIAL TYPE. Table 1 lists some typical properties of compacted soils which may be used for preliminary analysis. For final analysis engineering property tests are necessary. a. Utilization. See Table 2 for relative desirability of various soil types in earth fill dams, canals, roadways and foundations. Although practically any nonorganic insoluble soil may be incorporated in an embankment when modern compaction equipment and control standards are employed, the following soils may be difficult to use economically: ( 1 ) Fine-grained soils may have insufficient shear strength or excessive compressibility.
(2) Clays of medium to high plasticity may expand if placed under low confining pressures and/or at low moisture contents. See DM-7.1, Chapter 1 for identification of soils susceptible to volume expansion. (3) Plastic soils with high natural moisture are difficult to process for proper moisture for compaction. (4)
Stratified soils may require extensive mixing of borrow.
2. EMBANKMENTS ON STABLE FOUNDATION. The side slopes of fills not subjected to seepage forces ordinarily vary between 1 on 1-1/2 and 1 on 3. The geometry of the slope and berms are governed by requirements for erosion control and maintenance. See DM-7.1, Chapter 7 for procedures to calculate stability of embankments.
3. EMBANKMENTS ON WEAK FOUNDATIONS. Weak foundation soils may require partial or complete removal, flattening of embankment slopes, or densification. Analyze cross-section stability by methods of DM-7.1, Chapter 7. See DM-7.3, Chapter 2 for methods of deep stabilization, and Chapter 3 for special problem soils. 4.
EMBANKMENT SETTLEMENT. Settlement of an embankment is caused by foundation consolidation, consolidation of the embankment material itself, and secondary compression in the embankment after its completion. a. Foundation Settlement. See DM-7.1, Chapter 5 for procedures to decrease foundation settlement or to accelerate consolidation. See DM-7.3, Chapter 1 for guidance on settlement potential under seismic conditions. b. Embankment Consolidation. Significant excess pore pressures can develop during construction of fills exceeding about 80 feet in height or for lower fills of plastic materials placed wet of optimum moisture. ~issi~ation of these excess pore pressures after construction results in settlement. For earth dams and other high fills where settlement is critical, construction pore pressures should be monitored by the methods of DM-7.1, Chapter 2.
LABIZ 1 Typical P r o p e r t i e s of Compacted S o i l s Typical Value of Compresaion
croup Symbol
S o i l Type
Ranpe of Maximu Dry Unit Weight, pcf
Range of Optimum PIolature, Parcant
At 1.4 tmf (20 p s i )
At 3.6 taf (50 pmi)
Typical StrenRth Characterimtics Cohesion (an c w patted) paf
Cohesion (maturated) paf
0 ( I f f a c t iva Streaa Envelop. Dcgreaa)
Tao 9
Typical Coefficient of P e r m e r billty ' ft./min.
Range of CBR Valuam
Range of Subgr.de Hodulum k l b l c u in.
Percent of Original Height
-
CU
Well graded clean gravelm. gravel-nand mixtures.
125
CP
Poorly graded clean gravels. gravel-sand mix
115
CH
S i l t y gravels, poorly graded gravel-sand-silt.
CC
Clayey gravela. poorly graded gravel-aand-clay.
SU
Well graded clean aands, gravelly aands.
SP
Poorly graded clean mandm. sand-gravel mlx.
SH
S i l t y sands. poorly graded sand-silt mix.
110
Sand~iltclaymixuith a l i g h t l y p l a s t i c fines.
110-130
SC
Clayey aandm, poorly graded sand-clay-mix.
105
HI.
Inorganic a i l t a and clayey ailts.
SH-SC
PIL-CL
Mixture of inorganic a i l t and clay.
CL
Inorganic claya of la, t o medium p l a s t i c i t y .
OL
Organic s i l t a and m i l t claya. l w plasticity.
W
Inorganic clayey s i l t s . elastic silts.
Cll
Inorganic clays of high plasticity
OH
Organic clays and s i l t y clays
135
- 125 120 - 135 115 - 130 110 - 130 100 - 120 -
125
- 125 95 - 120 100 - 120 95 - 120 80 - 100 70 - 95 75 - 105 65 - 100
-8 14 - 11 12
-8
0.5
1.1
14
-9
0.7
1.6
..... .....
16
-9
0.6
1.2
0
0
38
0.79
>lo-3
21
-
12
0.8
1.4
0
0
37
0.74
>lo-3
16
- I1
0.8
1.6
1050
420
34
0.67
5 x >lO-5
15-11
0.8
1.4
I050
300
33
0.66
2 x >lo-(
- 80 30 - 60 20 - 60 20 - 40 20 - 40 10 - 40 10 - 40 5 - 30
5x>10-7
5-20
11
0.3
0.6
0
0
>38
>0.79
0.4
0.9
0
0
>37
>0.74
10-1
..... .....
>34
>0.67
>lo-(
>31
>0.60
>lo-?
19
- 11
1.1
2.2
1550
2 30
31
0.60
24
-
12
0.9
1.7
1400
190
32
0.62
22
-
12
1.0
2.2
1350
460
32
0.62
1.3
2.5
1800
270
28
0.54
- 12 33 - 21 40 - 24
.....
...............
2.0
3.8
1500
4 20
25
0.47
36
-
2.6
3.9
2150
230
19
0.35
45
- 21 .....
24
19
.....
.
..........
..... .....
5 x
>10-5 5 x >LO-7 >lo-7
.......... 5 x >lo-7 >10-7
..........
40
15 o r lema
A l l propertiea a r e For condition of "Standard Proctor" mximun
15 o r lea. 5 or less 10 o r lemm 15 o r Isam 5 o r leas
3.
Compresaion values a r e f o r v e r t i c a l loading with complete l a t e r a l con€inement.
4.
0)indicate.
deosity, except v r l w a of k and CBR which a r e f o r "modified Proctor. maximum dmsity. 2.
Typical mtength characteriaticm a r e f o r e f f e c t i v e atrength envelopes and a r e obtained from USBR data.
100-300 100
- 200
.....
Notes: 1.
- 500 250 - 400 100 - 400 100 - 300 200 - 300 200 - 300 100 - 300 100 - 300 300
t h a t typical property i s greater than the value mhovn. (..)i n d i c a t e s insufficient data available f o r an estimate.
- 200 50 - 100 50 - 100 50 - 150 25 - 100 50
TABLE 2 R e l a t i v e D e s i r a b i l i t y of S o i l s a s Compacted F i l l
--
-- - ---
RELATIVE DESIRABILITY FOR VARIOUS USES (No. 1 i s Considered t h e Best. No. 14 Least D e s i r a b l e )
Rolled E a r t h F i l l Dams
Canal S e c t i o n s
Foundations
Roadways Fills
Group Symbol
S o i l Type
2
m
2 e 85
0
0 c U
rl ,-,
.,
u
w c
g
:2
c m 0 u
Url
U c U m m m u u
1
ms n u
I: LI w
mO :
U4 . . 10 o
x u
e
0
C
m
* U wDL
u C
2
%5 I 0r 1 O
,2
2
r(
U
%
m
WU x r l
a
4 3
.A
U
*m
U
El
m
s
GW
Well graded g r a v e l s , gravelsand m i x t u r e s , l i t t l e o r no fines
-
-
1
1
-
-
1
1
1
3
GP
Poorly-graded g r a v e l s , gravel-sand mixtures, l i t t l e o r no f i n e s
-
-
2
2
-
-
3
3
3
-
GM
S i l t y g r a v e l s , poorly graded g r a v e l - s a n d - s i l t mixtures
2
4
-
4
4
4
4
9
5
CC
Clayey g r a v e l s , poorly graded gravel-sand-clay mixtures
1
I
-
3
I
2
6
5
5
1
SW
Well-graded sands, g r a v e l l y s a n d s , l i t t l e o r no f i n e s
-
-
6
-
-
2
2
2
4
SP
Poorly-graded sands, g r a v e l l y s a n d s , l i t t l e o r no f i n e s
-
-
7
-
-
5
6
4
-
5
3
7
6
10
6
4
8
7
6
2
6 erosion critical
6
9
10
11
-
3
5
10
9
7
7
7
7
11
11
12
-
8
12
12
13
-
9
13
13
8
-
10
14
14
14
-
St4
5
3 if gravelly 4 if gravelly
-
if gravelly
S i l t y sands, poorly graded s a n d - s i l t mixtures
4
Clayey sands, poorly graded sand-clay mixtures
3
2
-
5
6
6
-
-
5
3
-
9
Organic S i l t s and o r g a n i c s i l t - c l a y s of low p l a s t i c i t y
8
8
-
-
MN
Inorganic s i l t s , micaceous o r diatomaceous f ~ n esandy o r s i l t y soils, elastic s i l t s
9
9
-
CH
I n o r g a n i c c l a y s of high plasticity, f a t clays
7
7
-
10
OH
Organic c l a y s of medium high plasticity
10
10
-
8-vol change critical
-
-
SC
ML
CL
OL
Inorganic s i l t s and very f i n e sands, rock f l o u r , s i l t y o r clayey f i n e sands with s l i g h t plasticity I n o r g a n i c c l a y s of low t o medium p l a s t i c i t y , g r a v e l l y c l a y s , sandy c l a y s , s i l t y clays, lean c l a y s
-
1
8 if gravelly
erosion critical
2
erosion critical
-
Not a p p r o p r l a c e f o r t h i s type of use.
-
c. Secondary Compression. Even f o r well-compacted embankments, seconda r y compression and s h e a r s t r a i n c a n cause s l i g h t s e t t l e m e n t s a f t e r complet i o n . Normally t h i s i s o n l y of s i g n i f i c a n c e i n h i g h embankments, and c a n amount t o between 0.1 and 0.2 p e r c e n t of f i l l h e i g h t i n t h r e e t o f o u r y e a r s o r between 0.3 and 0.6 p e r c e n t i n 15 t o 20 y e a r s . The l a r g e r v a l u e s a r e f o r fine-grained p l a s t i c s o i l s .
5. EARTH DAM EMBANKMENTS. E v a l u a t e s t a b i l i t y a t t h r e e c r i t i c a l stages; t h e end of c o n s t r u c t i o n s t a g e , s t e a d y s t a t e seepage s t a g e , and r a p i d drawdown s t a g e . See DM-7.1, Chapter 7 f o r pore p r e s s u r e d i s t r i b u t i o n a t t h e s e s t a g e s . Seismic f o r c e s must be included i n t h e e v a l u a t i o n . Requirements f o r s e e p a g e c u t o f f . and s t a b i l i t y d i c t a t e d e s i g n of c r o s s s e c t i o n and u t i l i z a t i o n o f borrow materials. a. Seepage Control. Normally t h e earthwork of an e a r t h dam i s zoned w i t h t h e l e a s t p e r v i o u s , f i n e - g r a i n e d s o i l s i n t h e c e n t r a l zone and c o a r s e s t , most s t a b l e m a t e r i a l i n t h e s h e l l . Analyze seepage by t h e methods of DM-7.1, Chapter 6. ( 1 ) Cutoff Trench. Consider t h e p r a c t i c a b i l i t y of a p o s i t i v e c u t o f f t r e n c h e x t e n d i n g t o impervious s t r a t a b e n e a t h t h e embankment and i n t o t h e abutments. ( 2 ) I n t e r c e p t i n g Seepage. For a p r o p e r l y designed and c o n s t r u c t e d zoned e a r t h dam, t h e r e i s l i t t l e danger from seepage through t h e embankment. Drainage d e s i g n g e n e r a l l y i s d i c t a t e d by n e c e s s i t y f o r i n t e r c e p t i n g s e e p a g e through t h e f o u n d a t i o n o r abutments. Downstream seepage c o n d i t i o n s a r e more c r i t i c a l f o r homogeneous f i l l s . See DM-7.1, Chapter 6 f o r d r a i n a g e a n d f i l t e r requirements. b. P i p i n g and Cracking. A g r e a t danger t o e a r t h dams, p a r t i c u l a r l y t h o s e of zoned c o n s t r u c t i o n , i s t h e t h r e a t of c r a c k i n g and piping. Serious c r a c k i n g may r e s u l t from t e n s i o n zones caused by d i f f e r e n c e s i n s t r e s s - s t r a i n p r o p e r t i e s of zoned m a t e r i a l . See F i g u r e 1 (Reference 1, I n f l u e n c e of S o i l P r o p e r t i e s and C o n s t r u c t i o n Methods on t h e Performance of Homogeneous E a r t h Dams, by S h e r a r d ) f o r c l a s s i f i c a t i o n of m a t e r i a l s a c c o r d i n g t o r e s i s t a n c e t o p i p i n g o r c r a c k i n g . Analyze t h e embankment s e c t i o n f o r p o t e n t i a l t e n s i o n zone development. P l a c e an i n t e r n a l d r a i n a g e l a y e r immediately downstream o f t h e c o r e t o c o n t r o l seepage from p o s s i b l e c r a c k i n g i f f o u n d a t i o n s e t t l e m e n t s a r e expected t o be high. c. D i s p e r s i v e S o i l . D i s p e r s i v e c l a y s should n o t be used i n dam embankments. Determine t h e d i s p e r s i o n p o t e n t i a l u s i n g Table 3 o r t h e method o u t l i n ed i n Reference 2, P i n h o l e T e s t f o r I d e n t i f y i n g D i s p e r s i v e S o i l s , by S h e r a r d , e t a l . A h o l e through a d i s p e r s i v e c l a y w i l l i n c r e a s e i n s i z e as water f l o w s t h r o u g h (due t o t h e breakdown of t h e s o i l s t r u c t u r e ) , whereas t h e s i z e of a h o l e i n a non-dispersive c l a y would remain e s s e n t i a l l y c o n s t a n t . T h e r e f o r e , dams c o n s t r u c t e d w i t h d i s p e r s i v e c l a y s a r e extremely s u s c e p t i b l e t o p i p i n g .
. US STANDARD SIEVE NUMBERS2
+
an n
83898
GRAIN SIZE MILLIMETERS
1
COARSE FINE COeeLES GRAVEL CATEGORY
-1
I
MEDIUM SAND
MATERIAL
I
HYDROMETER ANALYSIS
8
1
s I L T r n a * I ( ~ m c o ~NON-MK:)
I
CHARACTERISTICS
PIPING RESISTANCE:
0
CL AND CH WITH PI ) IS, WELL GRADED SC WITH PI ) 15.
CL AND ML WlTH PI( 15, WELL GRADED sc AND GC w r r ~ 15 ) PI )7.
SP AND UNIFORM SM AND ML WITH PI ( 7.
GRENEST RESISTANCE TO PIPING,SMALL AND MEDIUM CONCENTRATED LEAKS W l U HEALTHEMSELVES.EMBANKMENT MAY Fi4lL AS A RESULT OF SLOWLY PROGRESSIVE PIPING CAUSED BY LEAK OF ABOUT V2 CFS. INTERMEDINE RESISTANCE TO PIPING. SMLY RESISTS SATURATION OF LOWER PWION OF DOWNSTREAM SLOPE INDEFINITELY MAY M I L EVENTUALLY AS A RESULT OF EROSION CAUSED BYA SMALL CWCENTRATED LEAK OR BY PROGRESSIVE SLOUGHING. IF A LARGE LEAK DEVELOPS, PIPING CAUSES MIWRE IN A SHORT TIME. LEAST RESISTANCE TO PIPING.USUAUY FAILS IN A FEW YEARS AFTER FIRST RESERVOlR FILLING IF S E E M ISABLE TO BREAK OUT ON DOWNSTREAM S I D E . SMALL CONCENTRATED LEAK ON DOWNSTREAM SWPE CAN CWSE FAILURE IN A SHORT PERIOD OF TIME. HIGH DENSITY FROM COMPACTION INCREASES RESISTANCE SIGNIFICANTLY.
FIGURE 1 Resistance of Earth Dam Embankment Materials To Piping and Cracking
.
CATBGORY
MATERIAL
CHARACTERlSllCS
CRACKING RESISTC\NCE
@
CH WITH &(OXnMM PI )M
@
GC, SC,SM, SP WITH osO) 01.5 MM
0
CL, ML AND SM WITH PI< 20, 0.15 MM ) D 5 )~0.02 MM.
AND
HIGH POSTCONSTRUCTlON SETTLEMENT, PARTICULARLY IF COMWCTED DRY. HAS SUFFICIENT DEFORMABILITY TO UNDERGO LARGE SHEAR STRAINS FROM DIFFERENTIAL SETTLEMENT WITHOUT -KING. SMALL POSTCWSTRUCTlON SETTLEMENT. LITTLE CHANCE FOR CRACKING UNLESS POORtY COMP#CTED AND LARGE SETTLEMENT IS IMPOSED ON EMBANKMENT BY GONSOLlDATlON OF W E FOUNDATION. MEDIUM TO HIGH POSTCONSTRUCTION SETTLEMENT AND VULNERABLE TO CRCICKING. SHOULD BE COMPACTED AS WET AS POSSIBLE CONSISTENT WITH STRENGTH REWIREMENTS.
FIGURE 1 (continued) Resistance of Earth Dam Embankment Materials To Piping and Cracking
TABLE 3 Clay Dispersion P o t e n t i a l
*Percent Dispersion
D i s p e r s i v e Tendency
Over 40'
Highly D i s p e r s i v e (do not u s e )
15 t o 40 0 t o 15
Moderately D i s p e r s i v e Resistant t o Dispersion
*The r a t i o between t h e f r a c t i o n f i n e r t h a n 0.005 mm i n a soil-water suspension t h a t has been subjected t o a minimum of mechanical a g i t a t i o n , and t h e t o t a l f r a c t i o n f i n e r t h a n 0.005 mm determined from a r e g u l a r hydrometer t e s t x 100.
S e c t i o n 3.
1.
COMPACTION REQUIREMENTS AND PROCEDURES
COMPACTION REQUIREMENTS.
a. Summary. See Table 4 f o r a summary of compaction requirements o f f i l l s f o r v a r i o u s purposes. Modify t h e s e t o meet c o n d i t i o n s and m a t e r i a l s f o r s p e c i f i c projects. b. S p e c i f i c a t i o n Provisions. Specify t h e d e s i r e d compaction r e s u l t . S t a t e t h e r e q u i r e d d e n s i t y , moisture l i m i t s , and maximum l i f t t h i c k n e s s , allowing t h e - c o n t r a c t o r freedom i n s e l e c t i o n of compaction methods and e q u i p ment. Specify s p e c i a l equipment t o be used i f l o c a l experience and a v a i l a b l e m a t e r i a l s so d i c t a t e . 2. COMPACTION METHODS AND EQUIPMENT. Table 5 l i s t s commonly used c o m p a c t i o n equipment with t y p i c a l s i z e s and weights and guidance on use and a p p l i c a b i l i ty 3.
INFLUENCE OF MATERIAL TYPE.
a. S o i l s ~ n s e n s i t i v et o Compaction Moisture. Coarse-grained, g r a n u l a r well-graded s o i l s w i t h less than 4 p e r c e n t passing No. 200 s i e v e (8 p e r c e n t f o r s o i l of uniform g r a d a t i o n ) a r e i n s e n s i t i v e t o compaction moisture. (These s o i l s have a p e r m e a b i l i t y g r e a t e r than about 2 x 10-3 fpm.) P l a c e t h e s e m a t e r i a l s a t t h e h i g h e s t p r a c t i c a l moisture c o n t e n t , p r e f e r a b l y s a t u r a t e d . Vibratory compaction g e n e r a l l y i s t h e most e f f e c t i v e procedure. I n t h e s e m a t e r i a l s , 70 t o 75 percent r e l a t i v e d e n s i t y can be obtained by proper compact i o n procedures. I f t h i s i s s u b s t a n t i a l l y higher than Standard P r o c t o r maximum d e n s i t y , u s e r e l a t i v e d e n s i t y f o r c o n t r o l . Gravel, cobbles and b o u l d e r s a r e i n s e n s i t i v e t o compaction moisture. Compaction w i t h smooth wheel v i b r a t ing r o l l e r s i s t h e most e f f e c t i v e procedure. Use l a r g e s c a l e tests, a s o u t l i n e d i n Reference 3, Control of E a r t h R o c k f i l l f o r O r o v i l l e Dam, by Gordon and Miller. b. S o i l s S e n s i t i v e t o Compaction Moisture. S i l t s and some s i l t y s a n d s have s t e e ~moisture-density curves, and f i e l d moisture must be c o n t r o l l e d within nairow limits f o r e i f e c t i v e -compaction. Clays a r e s e n s i t i v e t o moist u r e i n that i f they a r e too w e t they a r e d i f f i c u l t t o d r y t o optimum m o i s ture, and i f t h e y a r e d r y i t i s d i f f i c u l t t o m i x t h e water i n uniformly. S e n s i t i v e c l a y s do not respond t o compaction because they l o s e s t r e n g t h upon remolding o r manipulation. c. E f f e c t of Oversize. Oversize r e f e r s t o p a r t i c l e s l a r g e r than t h e maximum s i z e allowed using a given mold (i.e. No. 4 f o r 4-inch mold, 3 / 4 i n c h f o r 6-inch mold, 2-inch f o r a-12-inch mold). Large s i z e p a r t i c l e s i n t e r f e r e w i t h compaction of t h e f i n e r s o i l f r a c t i o n . For normal embankment c o m p a c t i o n t h e maximum s i z e cobble should not exceed 3 inches o r 50 percent of t h e compacted l a y e r thickness. Where economic borrow s o u r c e s c o n t a i n l a r g e r s i z e s , compaction trials should be run before approval.
TABLE 4 Compaction Requirements
F i l l Utilized for:
Required Density, Percentof Modified Proctor
Tolerable Range of Moisture AboutOptimum, Percent
Maximum Permissible L i f t Thickness, Compacted in.
Special Requirements F i l l should be uniform. Blending o r processing of borrow may be required. For p l a s t i c c l a y s , i n v e s t i g a t e expansion under s a t u r a t i o n f o r v a r i o u s compaction moisture and d e n s i t i e s a t l o a d s equal t o those applied by s t r u c t u r e , t o determine c o n d i t i o n t o minimize expansion. Clays t h a t show expansive tendencies g e n e r a l l y should be compacted a t o r above optimum moisture t o a d e n s i t y c o n s i s t e n t with s t r e n g t h and i n c o m p r e s s i b i l i t y required of the f i l l .
Support of structure
95
-2 t o +2
12
Lining f o r canal o r small reservoir
90
-2 t o +2
6
Earth dam g r e a t e r than 50 f t . high
95
-1 t o +2
12 (+I
U t i l i z e l e a s t pervious m a t e r i a l s a s c e n t r a l core and c o a r e s t m a t e r i a l s i n o u t e r s h e l l s . Core should be f r e e of l e n s e s , pockets, o r l a y e r s of pervious m a t e r i a l and successive l i f t s well bonded t o each o t h e r . Amounts of o v e r s i z e exceeding 1 percent of t o t a l m a t e r i a l should be removed from t h e borrow p r i o r t o a r r i v a l on t h e embankment.
Earth dam l e s s than 50 f t . high
92
-1 t o +3
12(+)
In small dams t h a t lack e l a b o r a t e zoning, m a t e r i a l s t h a t a r e t h e most vulnerable t o cracking and piping should be compacted t o 98 percent d e n s i t y a t moisture content from optimum t o 3 percent i n excess of optimum.
Support of pavements: Highways.....
See NAVFAC DM-5
-2.t o +2
a(+)
Airfields....
See NAVFAC DM-21
-2 t o +2
90
-2 t o +2
a(+) a(+)
Backfill surrounding structure
For t h i c k l i n i n g s , GW-GC, GC, SC a r e p r e f e r a b l e f o r s t a b i l i t y and t o r e s i s t e r o s i v e forces. Single s i z e s i l t y sands with PI l e s s than f i v e g e n e r a l l y a r e not s u i t a b l e . Remove fragments l a r g e r than 6 inches before compaction.
Place c o a r e s t borrow m a t e r i a l s a t top of f i l l . I n v e s t i g a t e expansion of p l a s t i c c l a y s placed near pavement subgrade t o determine compaction moisture and d e n s i t y t h a t w i l l minimize expansion and provide required soaked CBR values. Where b a c k f i l l i s t o be drained, provide pervious coarse-grained s o i l s . For low w a l l s , do not permit heavy r o l l i n g compaction equipment t o o p e r a t e c l o s e r t o t h e wall than a d i s t a n c e equal t o about 213 t h e unbalanced height of f i l l a t any time. For highwalls or w a l l s of s p e c i a l design, e v a l u a t e the surcharge produced by heavy compaction equipment by t h e methods of Chapter 3 and s p e c i f y s a f e d i s t a n c e s back of the wall f o r i t s operations.
TABLE 4 (continued) Compaction Requirements
F i l l Utilized for:
Required Density, Percent of Hodif l e d Proctor
Tolerable Range of Moisture About Optimum, Percent
Backfill i n pipe or u t i l i t y trenchbs
90
Drainage blanket or filter
90
Thoroughly wetted
Subgrade of excavation f o r structure
95
-2 t o +2
Rock f i l l
-2 t o +2
----
-
Ihxipum Permissible L i f t Thickness, Compacted in.
a(+)
-
--
Special Requirements Material excavated from trench generally is s u i t a b l e f o r b a c k f i l l i f If backfill is fine grained, a cradle f o r the pipe is formed i n natural s o i l and b a c k f i l l placed by tamping to provide the proper bedding. Where f r e e draining sand and gravel i s u t i l i z e d , the trench bottom may be finished f l a t and the granular material placed saturated under and around the pipe and compacted by vibration.
i t does not contain organic matter o r refuse.
Thoroughly wetted
8
-
2 to 3 ft.
Ordinarily vibratory compaction e q u i h e n t i s u t i l i z e d . Blending of materials may be required for homogeneity. Segregation must be prevented i n placing and compaction. For compaction adjacent t o and above drainage pipe, use hand tamping or l i g h t t r a v e l l i n g vibrators. For rmifoxm bearing o r to break up pockets of f r o s t sueceptible mater i a l , s c a r i f y the upper 8 t o 12 in. of the subgrade, dry or moisten a s necessary and recompact. Certain materiaps, such a s heavily preconsolidated clays which w i l l not benefit by compaction, o r saturated silts and s i l t y f i n e sands that become quick during compaction, should be blanketed with a working mat of lean concrete or coarse grained material to prevent disturbance or softening. Depending on foundation conditions revealed i n exploration, a substantial thickness of loose s o i l s may have to be removed below subgrade and recompacted, o r compacted i n place by vibration, o r p i l e driving. For f i l l containing s i z e s no l a r g e r than ft., place i n layers not exceeding 24 in., thoroughly wetted and compacted by t r a v e l or heavy crawler t r a c t o r s i n spreading. Material with s i z e s up t o 2 f t . may be placed i n 3 f t l i f t s . Placing should be such t h a t the maximun s i z e of rock increases toward the outer slopes. Bocks l a r g e r than 1 cu yd i n volume should be embedded on the slope.
Notes:
1. Density and moisture content refer to "Modified Proctor" test values (ASTM D 1557) 2.
Generally, a f i l l compacted dry of OMC w i l l have higher strength and a lower compreesibility even a f t e r saturation.
3.
Cornpaction of "Coarse-grained, granular s o i l " i s not sensit i v e to moisture content so long a s bulking moisture i s avoided. Where practicable, they should be placed saturated and compacted by vibratory methods.
TABLE 5 Compaction Equipment and Methods s
Requirements f o r Compaction of 95 t o 100 P e r c e n t Standard P r o c t o r Maximum Density Equipment Type
Sheepsfoot Rollers
Applicability
For f i n e - g r a i n e d s o i l s o r d i r t y coarse-grained s o i l s with more t h a n 20 p e r c e n t p a s s i n g No. 200 s i e v e . Not s u i t a b l e f o r c l e a n coarsegrained soils. Particularly a p p r o p r i a t e f o r compaction of impervious zone f o r e a r t h dam o r l i n i n g s where bonding of l i f t s i s important.
Compacted Lift ~ h i ~ in.
Passes o r k coverages ~ ~ ~ ~
6
Foot Contact Area sq. f t .
Do.......
Smooth Wheel Rollers
Do....
For c l e a n , coarse-grained s o i l s with 4 t o 8 percent p a s s i n g t h e No. 200 s i e v e .
Foot Contact Pressures psi
S o i l Type
4 t o 6 passes f o r finegrained s o i l . 6 t o 8 passes f o r coarsegrained s o i l .
Rubber T i r e Roller
,Dimensions and Weight of Equipment
10
For f i n e - g r a i n e d s o i l s o r w e l l graded, d i r t y coarse-grained s o i l s w i t h more t h a n 8 p e r c e n t p a s s i n g t h e No. 200 sieve.
6 to 8
Appropriate f o r subgrade o r base c o u r s e compaction of we1 1-graded sand-gr a v e l mixtures. May be used f o r f i n e - g r a i n e d s o i l s o t h e r than i n e a r t h dams. Not s u i t a b l e f o r c l e a n well-graded sands o r s i l t y uniform sands.
8 t o 12
3 to 5 coverages
4 to 6 coverages
4 coverages 1
6 to 8
6 coverages
Fine-grained 5 t o 12 250 t o 500 s o i l P1>30 Fine-grained 7 t o 14 200 t o 400 s o i l PI0.4:
J
f
SECTON A-A PRESSURES FROM POlNT WAD Qp (BWSSINESQ EQUATION MODIFIED BY EXPERIMENT)
FIGURE 11 H o r i z o n t a l P r e s s u r e s on Rigid Wall from Sur-face Load
-
i
f
p = 0.5 q =SURCHARGE
L = LENGTH RPRALLELTDWALL m=-B Z
0
'
I
B = LENGTH PERPENDICULAR TO WALL
n = -Lp = q x I p
Z
2 n
3
4
L -----=-
z
FIGURE 12 Lateral Pressure on an Unyielding Wall due to Uniform Rectangular Surface Load
5.8
e. R e s t r a i n e d Walls. I f a w a l l i s prevented from even s l i g h t movement, t h e n t h e e a r t h remains a t o r n e a r t h e v a l u e of at-rest c o n d i t i o n s . The c o e f f i c i e n t of e a r t h p r e s s u r e a t - r e s t , KO, f o r normally c o n s o l i d a t e d c o h e s i v e o r g r a n u l a r s o i l s i s approximately:
where :
9'
= e f f e c t i v e f r i c t i o n angle
Thus f o r 8' = 30°, KO = 0.5. For over-consolidated s o i l s and compacted s o i l s t h e r a n g e of KO may b e on t h e o r d e r of 1.0. In cohesionless s o i l s , f u l l a t - r e s t pressure w i l l occur o n l y w i t h t h e most r i g i d l y s u p p o r t e d wall. In highly p l a s t i c c l a y s , s o i l may c r e e p , and i f w a l l movement i s p r e v e n t e d , a t - r e s t c o n d i t i o n s may redevelop even a f t e r a c t i v e p r e s s u r e s a r e e s t a b l i s h e d . f. Basement and Other Below Grade Walls. P r e s s u r e on w a l l s below g r a d e may be computed based on r e s t r a i n i n g c o n d i t i o n s t h a t p r e v a i l , t y p e of backf i l l , and t h e amount of compaction.
6.
EFFECT OF CONSTRUCTION PROCEDURES.
a. Staged Construction. A s e a r t h p r e s s u r e s a r e i n f l u e n c e d by w a l l movement, i t i s important t o c o n s i d e r each s t a g e of c o n s t r u c t i o n , e s p e c i a l l y w i t h r e g a r d t o b r a c e placement and i t s e f f e c t s . b. Compaction. Compaction of b a c k f i l l i n a c o n f i n e d wedge behind t h e w a l l t e n d s t o i n c r e a s e h o r i z o n t a l p r e s s u r e s beyond t h o s e r e p r e s e n t e d by a c t i v e o r a t - r e s t values. For guidance on h o r i z o n t a l p r e s s u r e computations a s s o c i a t e d w i t h t h e compaction of g r a n u l a r s o i l , s e e F i g u r e 13 ( a f t e r Reference 7 , R e t a i n i n g Wall Performance During B a c k f i l l i n g , by I n g o l d ) . Clays and o t h e r fine-grained s o i l s , a s w e l l a s g r a n u l a r s o i l s , w i t h c o n s i d e r a b l e amount of c l a y and s i l t 0 1 5 % ) a r e n o t normally used a s b a c k f i l l m a t e r i a l . Where t h e y must be used, t h e e a r t h p r e s s u r e should be c a l c u l a t e d on t h e b a s i s of " a t - r e s t " c o n d i t i o n s o r h i g h e r p r e s s u r e w i t h due c o n s i d e r a t i o n t o p o t e n t i a l poor d r a i n a g e c o n d i t i o n s , s w e l l i n g , and f r o s t a c t i o n . c. H y d r a u l i c F i l l s . Active p r e s s u r e c o e f f i c i e n t s f o r l o o s e h y d r a u l i c f i l l m a t e r i a l s r a n g e from about 0.35 f o r c l e a n sands t o 0.50 f o r s i l t y f i n e sands. P l a c e h y d r a u l i c f i l l by procedures which permit r u n o f f of wash w a t e r and p r e v e n t b u i l d i n g up l a r g e h y d r o s t a t i c p r e s s u r e s . For f u r t h e r guidance s e e d i s c u s s i o n on dredging i n DM-7.3, Chapter 3. EARTHQUAKE LOADING. The p r e s s u r e d u r i n g e a r t h q u a k e l o a d i n g c a n be com7. puted by t h e Coulomb t h e o r y w i t h t h e a d d i t i o n a l f o r c e s r e s u l t i n g from ground a c c e l e r a t i o n . For f u r t h e r guidance on t h e s u b j e c t s e e Reference 8, Design of E a r t h R e t a i n i n g S t r u c t u r e s f o r Dynamic Loads, by Seed and Whitman. A s y n o p s i s of some m a t e r i a l from t h i s Reference f o l l o w s :
Y
- --
--
a
- -
--
q P
--
\
FOR Z c L Z i d
FOR Z > d Fh= K~ y ' z
-
i
@h
P (ROLLER LOAD) = DEAD W7: OF ROLLER +CENTRIFUGAL FORCE WIDTH OF ROLLER a : DISTANCE OF ROLLER FROM WALL L: LENGTH OF ROLLER USE FIGURES 2 , 3 , 5 OR 6 FOR KA
FIGURE 13 Horizontal Pressure on Walls from Compaction Effort
( 1 ) A simple procedure f o r d e t e r m i n i n g t h e l a t e r a l f o r c e due t o an earthquake i s t o compute t h e i n i t i a l s t a t i c p r e s s u r e and add t o i t t h e i n c r e a s e i n p r e s s u r e from ground motion. For a v e r t i c a l w a l l , w i t h horizont a l b a c k f i l l s l o p e , and 8 of 35O, (which may be assumed f o r most p r a c t i c a l c a s e s i n v o l v i n g g r a n u l a r f i l l ) , t h e e a r t h p r e s s u r e c o e f f i c i e n t f o r dynamic i n c r e a s e i n l a t e r a l f o r c e can be approximated a s 314 kh, kh b e i n g t h e The combined e f f e c t of s t a t i c and dynamic horizontal a c c e l e r a t i o n i n g's. force is:
Assume t h e dynamic l a t e r a l f o r c e PE = 318 7 H2kh acts a t 0.6 H above t h e w a l l base. E f f e c t of l i q u e f a c t i o n i s c o n s i d e r e d i n DM-7.3, Chapter 1. ( 2 ) For o t h e r s o i l and w a l l p r o p e r t i e s , t h e combined r e s u l t a n t a c t i v e force:
where :
@ *= P 8*
=
F =
+$J = modified s l o p e of b a c k f i l l
8 + JI
= modified s l o p e of w a l l back
~ 0 ~ *2 8 cos JI cos 28
kv = v e r t i c a l ground a c c e l e r a t i o n i n g ' s .
*
For modifed s l o p e @ and 8 *, o b t a i n K A ( ~ *8, *) from t h e a p p l i c a b l e F i g u r e s 3 through 8. Determine F from F i g u r e 14. Dynamic p r e s s u r e increment A P E c a n be obtained by s u b t r a c t i n g PA ( a l s o t o be determined from F i g u r e s 3 , 7, o r 8 f o r given P and 8 v a l u e s ) from PAE. The r e s u l t a n t f o r c e w i l l v a r y i n i t s l o c a t i o n depending on w a l l movement, ground a c c e l e r a t i o n , and w a l l b a t t e r . For p r a c t i c a l purposes i t may b e a p p l i e d a t 0.6 H above t h e base. ( 3 ) Unless t h e w a l l moves o r r o t a t e s s u f f i c i e n t l y , p r e s s u r e s g r e a t e r t h a n a c t i v e c a s e w i l l e x i s t and the a c t u a l l a t e r a l p r e s s u r e s may be as l a r g e as t h r e e times t h e v a l u e d e r i v e d from Figure 14. I n such s i t u a t i o n s , d e t a i l e d a n a l y s i s u s i n g numerical t e c h n i q u e s may be d e s i r a b l e . ( 4 ) Under t h e combined e f f e c t of s t a t i c and earthquake l o a d a f a c t o r of s a f e t y between 1.1 and 1.2 i s a c c e p t a b l e .
( 5 ) I n c a s e s where s o i l i s below water, add t h e hydrodynamic p r e s s u r e computed based on:
(A) WALL CONFIGURATION
0
0.1
0.2 0.3 TAN $
0.4
Q5
FIGURE 14(a) Values of F for Determination of Dynamic Lateral Pressure C o e f f i c i e n t s
/rF
EXAMPLES: CASE I - VERTICAL WALL WlTH HORIZONTAL BACKflLL
H= 20'
COMBINED EFFECT OF STATIC AND DYNAMIC FORCE. PAE = Fl +F2 KA =0.27(FROM FIGURE 2 FOR
t$
=35O)
F1= 1/2 y ~ KA= 2 1/2 (120)(20)~ (0.27)= 6480 L B RESULTANT ACTING ATA DISTANCE OF H/3 = 6.7' FROM BASE OF WALL
F~ = 3/8 y ~ Kh 2= 318 (120) (2012 (0.2) = 3600 LB. ACTING AT 12FT. (0.6H) FROM BASEOFWALL
H/3 -6.7'
CASE 2 - SLOPING WALL WlTH SLOPING BACKFILL JI zTAN-l
'.2-=
1-0.05 TAN J/ = 0.21
8
120
9 = K)O
Kvz.05
0.6 x 20 =12.01
p = 15. F =0.9 (FROM FIGURE 140) ASSUME A S M WALL,^ ~ =O 9*= = IOt12.22O p*=p+J/ = 15+I2 = 2 7 O
e++
FROM THE EQUATION IN FIGURE8
**
KA (P,8 ) = KA
=Q71
(p,81=0.41,P ~ = I / ~ x ( I ~ o ) x ( ~ o ) ~ x o . ~ I = ~ ~ o L B .
PAE = 1/2 y~~KA ( I-KV) F = 1/2 (120) (20)2 (0.71 ) (1-0.05) (0.9)=I4569 LB.
A PE = 14569 -9840 = 4729 LB. FIGURE 14(b) Example Calculations for Dynamic Loading on Walls
.
where :
pw = hydrodynamic p r e s s u r e a t d e p t h z below w a t e r s u r f a c e
Yw
= u n i t weight of water
h = d e p t h of w a t e r z = d e p t h below t h e water s u r f a c e
( 6 ) Add t h e o t h e r i n e r t i a e f f e c t of t h e s t r u c t u r e i t s e l f f o r c a l c u l a t i n g t h e r e q u i r e d s t r u c t u r a l s t r e n g t h . An optimum d e s i g n i s t o s e l e c t t h e t h i n n e s t s e c t i o n w i t h t h e l a r g e s t bending and s h e a r r e s i s t a n c e ( i . e . most flexible). ( 7 ) When a p p l y i n g t h i s e a r t h q u a k e l o a d i n g a n a l y s i s t o e x i s t i n g e a r t h ret a i n i n g s t r u c t u r e s , p a r t i c u l a r l y where h i g h groundwater l e v e l s e x i s t , i t may be found t h a t r e s u l t i n g s a f e t y f a c t o r i s l e s s t h a n 1.1. In such c a s e s , proposed c o r r e c t i v e measures must be submitted t o NAVFAC HQ f o r r e v i e w and approval.
8. FROST ACTION. L a t e r a l f o r c e s due t o f r o s t a c t i o n a r e d i f f i c u l t t o pred i c t and may a c h i e v e high v a l u e s . B a c k f i l l m a t e r i a l s such a s s i l t s and c l a y e y s i l t s (CL, MH, ML, OL) a r e f r o s t s u s c e p t i b l e , and w i l l e x e r t e x c e s s i v e p r e s s u r e on w a l l i f proper p r e c a u t i o n s a r e n o t taken t o c u r b f r o s t . Swelling p r e s s u r e s may be e x e r t e d by c l a y s of high p l a s t i c i t y (CH). Under t h e s e c o n d i t i o n s , d e s i g n f o r a c t i v e p r e s s u r e s i s i n a d e q u a t e , even f o r y i e l d i n g w a l l s , a s r e s u l t i n g w a l l movement i s l i k e l y t o be e x c e s s i v e and continuous. S t r u c t u r e s u s u a l l y a r e n o t designed t o withstand f r o s t generated s t r e s s e s . I n s t e a d , p r o v i s i o n s should be made s o t h a t f r o s t r e l a t e d s t r e s s e s w i l l n o t develop o r be k e p t t o a minimum. Use of one o r more of t h e f o l l o w i n g may be n e c e s s a r y : ( i ) Permanently i s o l a t e t h e b a c k f i l l from s o u r c e s of w a t e r e i t h e r by providing a very permeable d r a i n o r a very impermeable b a r r i e r . ( i i ) Provide pervious b a c k f i l l and weep h o l e s . (See DM-7.1, Chapter 6 f o r t h e i l l u s t r a t i o n on complete d r a i n a g e and p r e v e n t i o n of f r o s t t h r u s t . ) ( i i i ) P r o v i d e impermeable s o i l l a y e r n e a r t h e s o i l s u r f a c e , and g r a d e t o d r a i n s u r f a c e water away from t h e wall.
9. SWELLING ACTION. Expansion of c l a y s o i l s can c a u s e v e r y h i g h p r e s s u r e s on t h e back of a r e t a i n i n g s t r u c t u r e . Clay b a c k f i l l s should be avoided whenever p o s s i b l e . Swelling p r e s s u r e s may be e v a l u a t e d based on l a b o r a t o r y t e s t s and w a l l designed t o w i t h s t a n d s w e l l i n g p r e s s u r e s . Providing g r a n u l a r nonexpansive f i l t e r between t h e c l a y f i l l and back of w a l l d i m i n i s h e s s w e l l i n g p r e s s u r e s and s i g n i f i c a n t l y l i m i t s a c c e s s t o moisture. Guidance on s o i l stab i l i z a t i o n methods f o r c o n t r o l of heave a r e given i n DM-7.3, Chapter 3. Comp l e t e d r a i n a g e ( s e e DM-7.1, Chapter 6 ) i s one of t h e t e c h n i q u e s t o c o n t r o l heave
.
10. SELECTION OF STRENGTH PARAMETERS. The c h o i c e of s t r e n g t h parameters is governed by t h e s o i l p e r m e a b i l i t y c h a r a c t e r i s t i c s , boundary d r a i n a g e and l o a d i n g c o n d i t i o n s , and time.
a. S a t u r a t e d Cohesive S o i l s . For s a t u r a t e d cohesive s o i l s of low permea b i l i t y , where s u f f i c i e n t t i e i s not a v a i l a b l e f o r complete drainage, u s e undrained shear s t r e n g t h , and t o t a l stress f o r e a r t h p r e s s u r e computations. Such condition w i l l e x i s t during and immediately a f t e r completion of construction. b. Coarse-grained S o i l s . In coarse-grained s o i l s such a s sand, which have high - permeability, - - use e f f e c t i v e s t r e s s s t r e n g t h parameter 6' , f o r e a r t h pressure computations. Also, where s u f f i c i e n t t i m e is a v a i l a b l e f o r t h e d i s s i p a t i o n of pore pressure i n l e s s than pervious s o i l , use e f f e c t i v e stress s t r e n g t h parameters c 1 and 8'. In t h i s c a s e , pore p r e s s u r e i s h y d r o s t a t i c and can be estimated f a i r l y accurately.
In s o i l s such a s s i l t and clayey sand, where p a r t i a l drainage o c c u r s during the time of c o n s t r u c t i o n , perform a n a l y s i s f o r l i m i t i n g c o n d i t i o n s , i.e. e f f e c t i v e stress with 6' only, t o t a l s t r e s s with c , and design f o r t h e worst case. Section 3.
R I G I D RETAINING WALLS
1. GENERAL CRITERIA. Rigid r e t a i n i n g walls a r e those t h a t develop t h e i r l a t e r a l r e s i s t a n c e primarily from t h e i r own weight. Examples of r i g i d s'truct u r e s a r e concrete g r a v i t y walls, t h i c k c o n c r e t e s l u r r y w a l l s , gabion walls, and some r e i n f o r c e d e a r t h w a l l s r e i n f o r c e d f o r l i m i t e d movements. T h e o r e t i c a l w a l l p r e s s u r e s a r e discussed i n Section 2. Requirements f o r r e s i s t a n c e a g a i n s t overturning and s l i d i n g of four p r i n c i p a l wall types a r e given i n Figure 15. Evaluate o v e r a l l s t a b i l i t y a g a i n s t deep foundation f a i l u r e . (See DM-7.1, Chapter 7.) Determine allowable bearing pressures on the base of t h e w a l l ( s e e Chapter 4). a. S l i d i n g S t a b i l i t y . Place t h e base a t l e a s t 3 f t below ground surf a c e i n f r o n t of t h e w a l l and below depth of f r o s t a c t i o n , zone of s e a s o n a l volume change, and depth of scour. s l i d i n g s t a b i l i t y must be adequate without i n c l u d i n g passive pressure a t t h e toe. I f i n s u f f i c i e n t s l i d i n g resistance i s a v a i l a b l e , i n c r e a s e base width, provide p i l e foundation o r , lower base of wall and consider passive r e s i s t a n c e below f r o s t depth. I f the wall i s supported by rock o r very s t i f f c l a y , a key may be i n s t a l l e d below t h e foundation t o provide a d d i t i o n a l r e s i s t a n c e t o s l i d i n g (see Figure 15). b. Settlement and Overturning. For w a l l s on r e l a t i v e l y incompressible foundations,- apply I f foundation i s com- - - overturning c r i t e r i a of Figure 15. p r e s s i b l e , compute settlement-by methods of DM-7.1, Chapter 5 and e s t i m a t e t i l t of r i g i d w a l l from the settlement. I f t h e consequent t i l t w i l l exceed acceptable limits, proportion t h e wall t o keep the r e s u l t a n t f o r c e a t t h e middle t h i r d of base. I f a w a l l settles such t h a t t h e r e s u l t i n g movement f o r c e s i t i n t o t h e s o i l which i t supports, then t h e l a t e r a l pressure on t h e active side increases substantially. c. Overall S t a b i l i t y . Where r e t a i n i n g w a l l s a r e u n d e r l a i n by weak s o i l s , t h e o v e r a l l s t a b i l i t y of the s o i l mass containing t h e r e t a i n i n g w a l l should be checked w i t h r e s p e c t t o t h e most c r i t i c a l s u r f a c e of s l i d i n g ( s e e DM-7.1, Chapter 7). A minimum f a c t o r of s a f e t y of 2.0 i s d e s i r a b l e .
LOCATION OF RESULTANT MOMENTS ABOUT TOE:
ASSUMING
g=O
OVERTURNING MOMENTS ABOUT m E :
IGNOREWERTI.R?NIffi IF R IS WITHIN MIDDLE THIRD (SOIL), MIDDLE HALF (ROCK). CHECK R AT DlFFERENT HORIZONTAL PLANES FOR GRAVITY WALLS. SEMKiRAVlTY
RESISTANCE ffiAINST SLIDING
----_F=(W+\) -
TAN
8 +ca B
--
,
FOR COEFFICIENTSOF FRICTION BETWEEN BASE AND SOlL SEE TABLE- I C q =ADHESION BETWEEN SOlL AND BASE
TAN 8 = FRICTION =TOR
BETWEEN SOIL
WINCWDES WEIGHT OF WALL AND SOlL IN FRONT FOR GRAVITY AND SEMIGRAVITY WALLS. lN U D E S WEIGHT OF WALL AND SOlL ABOVE FOOTING, FOR CANTILEVER AND COUNTERFORT
CONTACT PRESSURE ON FOUNDATION FOR ALLOWABLE BEARING PRESSURE FOR INCLINED LOAD ON STRIP FOUNDATION,SEE CHAPTER 4.
COUNTERFORT
FOR ANALYSIS OF PILE LOADS BENEATH STRIP FOUNDATION, SEE CHAPTER 7. OVERALL STABILITY SECTION A-A
FIGURE 1 5
Design Criteria for ~ i g i dRetaining Walls
51
:. .
.. . . :.; ::, -... - . .,'.'.A b
*
.:.-
"'-4
-
~
, .r--.;. I / / / / / ' =
-&'...
*.;
INTACT
PP
-
a,-
, A / / / / I /
--
:6
-. . '. d
- . ....
' .
. . . . 4?
b.'.
'
:: -_ --a
.-. . .-... A
.*
b
.
-...
C
= SHEAR STRENGTH OF
FOUNDATION SO1L Fs= FACTOR OF SAFETY CQ= ADHESION -CONCRETE ON SOIL Pp= PASSIVE RESISTANCE
8:
FRICTION ANGLECONCRETE ON SOlL RESISTANCE AGAl NST SLl DlNG ON KEYED FWNDATKINS COMWESOILS F = (w+PV)TAN 8 + c a ( e - a ~ ) t c ( a 7 ) + p p GRANULAR WLS F = (W +PV ) TAN 8 +pP Fs =E PH
FIGURE 15 (continued) Design Criteria for Rigid Retaining Walls
-
d. Drainage. P o s i t i v e d r a i n a g e of b a c k f i l l i s d e s i r a b l e . ( S e e DM-7.1, Chapter 6 f o r d r a i n a g e d e s i g n . ) A s a minimum, provide weep h o l e s w i t h p o c k e t s of coarse-grained m a t e r i a l a t t h e back of t h e w a l l . An impervious s u r f a c e l a y e r should cover t h e b a c k f i l l , and a g u t t e r should be provided f o r c o l l e c t ing runoff.
2. LOW WALLS. It h a s been t h e p r a c t i c e of t h e Naval F a c i l i t i e s E n g i n e e r i n g Command t o c o n s i d e r w a l l s l e s s t h a n 12 f e e t i n h e i g h t "low walls." For t h e s e , knowledge of s o i l p r o p e r t i e s could be a d e q u a t e f o r d e s i g n , and d e t a i l e d t e s t i n g and e l a b o r a t e p r e s s u r e computations may n o t be j u s t i f i e d economically. a. E q u i v a l e n t F l u i d P r e s s u r e s . Use e q u i v a l e n t f l u i d p r e s s u r e s of F i g u r e 16 (Reference 9 , S o i l Mechanics i n E n g i n e e r i n g P r a c t i c e , by T e r z a g h i and Peck) f o r s t r a i g h t s l o p e b a c k f i l l and of F i g u r e 17 (Reference 9 ) f o r broken s l o p e b a c k f i l l . I n c l u d e dead l o a d s u r c h a r g e a s a n e q u i v a l e n t weight of b a c k f i l l . For r e s u l t a n t f o r c e of l i n e l o a d s u r c h a r g e , s e e bottom l e f t p a n e l of F i g u r e 11. I f a w a l l r e s t s on a compressible f o u n d a t i o n and moves downward w i t h r e s p e c t t o t h e b a c k f i l l , i n c r e a s e p r e s s u r e s by 50 p e r c e n t . b. Drainage. The e q u i v a l e n t f l u i d . p r e s s u r e s i n c l u d e e f f e c t s of s e e p a g e and time c o n d i t i o n e d changes i n t h e b a c k f i l l . However, p r o v i s i o n s should be made t o prevent accumulation of water behind t h e wall. A s a minimum, p r o v i d e weep h o l e s f o r drainage. Cover b a c k f i l l of s o i l t y p e s 2 and 3 ( F i g u r e 1 6 ) w i t h a s u r f a c e l a y e r of impervious s o i l . S e c t i o n 4.
DESIGN OF FLEXIBLE WALLS
1. ANCHORED BULKHEADS. Anchored bulkheads a r e formed of f l e x i b l e s h e e t i n g r e s t r a i n e d by t i e b a c k and by p e n e t r a t i o n of s h e e t i n g below dredge l i n e . See Figure 18 f o r d e s i g n procedures f o r t h r e e common p e n e t r a t i o n c o n d i t i o n s . a. Wall P r e s s u r e s . Compute a c t i v e and p a s s i v e p r e s s u r e s u s i n g t h e a p p r o p r i a t e F i g u r e s 2 through 7. Determine r e q u i r e d d e p t h of p e n e t r a t i o n of s h e e t i n g and anchor p u l l from t h e s e p r e s s u r e s . See F i g u r e 18 f o r guidance. b. Wall Movements. Active p r e s s u r e s a r e r e d i s t r i b u t e d on t h e w a l l by d e f l e c t i o n , moving away from t h e p o s i t i o n of maximum moment. Reduce t h e computed maximum moment t o a l l o w f o r - f l e x i b i l i t y of s h e e t i n g . Moment r e d u c t i o n i s a f u n c t i o n of t h e w a l l f l e x i b i l i t y number. See F i g u r e 19 (Reference 10, Anchored S h e e t P i l e Walls, by Rowe). S e l e c t s h e e t i n g s i z e by s u c c e s s i v e approximations so t h a t s h e e t i n g s t i f f n e s s i s compatible w i t h reduced design moment
.
c. Drainage. Include t h e e f f e c t of probable maximum d i f f e r e n t i a l head i n computing w a l l p r e s s u r e s . Where p r a c t i c a b l e , provide weep h o l e s o r s p e c i a l d r a i n a g e a t a l e v e l above mean water t o l i m i t d i f f e r e n t i a l water p r e s s u r e s .
,
VALUES OF SLOPE ANGLE B DEGREES CIRCLED NUMBERS INDICATE THE FOLLOWING SOIL TYPES : CLEAN SAND AND GRAVEL: GW, GP, SW, SP. @ DIRTY SAND AND GRAVEL OF RESTRICTED PERMEABILITY GM,GM-GP, SM-SP,SM. @ STIFF RESIDUAL SILTS AND CLAYS, SILTY FINE SANDS, CLAYEY SANDS AND GRAVELS: CL,ML,CH,MH,SM,SC,GC.
a
-
FIGURE 16 Design Loads f o r Low Retaining Walls (Straight Slope ~ a c k f i l l )
. SOIL TYPE I
SOIL TYPE 2
SOIL T Y P E
0 VALUES
OF RATIO
0.2
0.4
0.6
3
0.8
1.0
HI/H
FOR DESCRIPTION OF SOILTYPE SEE flGURE I6
. FIGURE 17 Design Loads f o r Low Retaining Walls (Broken Slope B a c k f i l l )
I. COMPUTE PRESSURES BY METHODS OF FIGURES 2 TO 7 PASSIVE PRESSURES FOR CLEAN OARSE GRAIN SOILS INCLUDE WALL FRICTION (%).TABLE I. FOR ACTIVE OR PASSIVE PRESSURES IN ALLOTHER SOILTYPES, IGNORE WALL FRICTION.
FS = 2TO3 FWI COARSE GRAINED SOILS FS = 1.5 TO 2 FQR FINE GRAINED SOILS 3. ANCHOR PULL: Ap PA^ - Pp/FS] d l d=ANCHORM N G 4. MAXIMUM BENDING MOMENT (MMAx.) IN SHEETING COMPUTED BY THE FREE EARTH SUPPORT MEMOD AND APPLYING PA^ AP. FOR SHEETING IN SAND APPLY MOMENT REDUCTION FOR FLEXIBILITY OF FIGURE 19.
PA^
FREE EARTH SUPPORT
- GENERAL CASE
DESIGN STEPS I, 2, AND 3 SAME AS ABOVE EARTH SUPPORT. 4. COMPUTE MAXIMUM BENDING MOMENT ( M ~ x . IN 1 SHEETING BY FREE EARTH SUPPORT METHOD APPLYING PA ,Pp/FS AND Ap. 5. COMPUTEP KCORDINGTO FtGURE 19. IF P 20, M DESIGN IS COMPUTED FOR THE SWN @@ ASSMNG SIMPLE SUPPORT AT POINT @ IF P ( 20 OBTAIN MOMENT REDUCTION FOR FLEXIBILITY FROM FIGURE B. 6. INCREASE PENETRATIOW COMPUTED (D) BY =%TO ALLOW FOR DREDGING, SCOUR, ETC.
2
I. COMPUTE PRESSURES AS ABOVE. EXCEPT THAT PASSIVE PRESSURE DECREASES TO ZERO AT TOP OF HARD STRATUM. 2: PENETRATION IN HARD STRATUM : TAKE MOMENTSABOUT POINT@AND SOLVE FOR P ~ :
ESTIMATE IF REACTION PB CAN BE PROVIDW BY
4. MAXIMUM BENDING MOMENT IN SHEETING COMPUTED BY APPLYING PA, Pp AND Ap TO SPAN @@ASSUMING SIMPLE SUPPORTAT@. NO REDUCTION FOR FLEXIBILITY.
--
FIGURE 18 Design C r i t e r i a f o r Anchored Bulkhead (Free Earth Support)
1.o .9
.8
x
a .7 I I \ z .6
'3
8 P
I
E
2
.5 4 .3 .2 VALUE O F p = (H*')~
IN
[g]
PER RUNNING FOOT OF WALL
EXAMPLE: PENETRATION IN VERY COMPACT SAND MMAX = 950,000 IN. LB/FT. H=33FT, D=15FT. fS = 25,000 PSI, E=30,000,000 PSI TRY Z P 32,1=385.7IN.4,~=38.3 IN.^ (33+15)4 x 124 IN.^ p ' 30,000,000 x 3857 = 9'5 LB.
rn
-
-
MDES'~N2 0.68, ME MMAX.
4
- 645000
fs IC= 3a.'3j
~
=645,000 ~ G ~ IN. LB/ FT
= 16,800
PSI
16,800 ( 25,000 PSI TRY A SMALLER SECTION. LOAD DIAGRAM
MOMENT DIAGRAM
LEGEND MMAX = MAXIMUM POSITIVE MOMENT IN SHEETING COMPUTED BY METHODS OF FIGURE 18. M DESIGN = MAXIMUM POSITIVE MOMENT FOR DESIGN OF SHEETING.
P = FLEXIBILITY NUMBER
:
+ ' (H E I
E = SHEETING MODULUS OF ELASTICITY, PSI I= SHEETING MOMENT OF INERTIA, IN.^ PER RUNNING FOOT OF WALL.
NOTES I. MDES~GNIS OBTAINED BY SUCCESSIVE TRIALS OF SHEETING SIZE UNTIL MAX. BENDING STRESS IN SHEETING EQUALS ALLOWABLE BENDING STRESS. 2. NO REDUCTION IN M ~ x IS. PERMITTEDFOR PENETRATION IN FINE GRAINED SOILS OR LOOSE OR VERY LOOSE COARSE GRAINED SOILS. 3. FLEXIBILITY NUMBER IS COMPUTED ON THE BASIS OF LUBRICATED INTERLOCKS.
FIGURE 19 Reduction i n Bending Moments i n Anchored Bulkhead from Wall F l e x i b i l i t y
d. Anchorage System. Most of t h e d i f f i c u l t i e s w i t h anchored bulkheads a r e caused by t h e i r anchorage. A t i e b a c k may be c a r r i e d t o a buried deadman anchorage, t o p i l e anchorage, p a r a l l e l w a l l anchorage, o r i t may be a d r i l l e d and grouted anchor ( s e e DM-7.3, Chapter 3). See Figure 20 f o r criteria f o r design of deadman anchorage. I f a deadman must be positioned c l o s e t o a w a l l , anchorage r e s i s t a n c e i s decreased and an a d d i t i o n a l passive r e a c t i o n i s reP r o t e c t t i e rods by m a p p i n g , quired f o r s t a b i l i t y a t the wall base. p a i n t i n g , o r encasement t o r e s i s t corrosion. Where b a c k f i l l w i l l s e t t l e s i g n i f i c a n t l y o r unevenly, t o avoid loading by overburden, e n c l o s e t i e rod i n a r i g i d tube, providing v e r t i c a l support i f needed t o e l i m i n a t e sag. e. Example of Computation. anchored bulkhead. f . Construction Precautions. f 011ows :
See Figure 21 f o r example of a n a l y s i s of Precautions during c o n s t r u c t i o n a r e a s
( 1 ) Removal of s o f t material, o r placement of f i l l i n the "passive" zone should precede t h e d r i v i n g of s h e e t p i l e s . ( 2 ) Deposit b a c k f i l l by working away from t h e wall r a t h e r than toward i t t o avoid trapping s o f t m a t e r i a l adjacent t o sheeting. ( 3 ) Before anchorage i s placed, s h e e t i n g i s loaded a s a c a n t i l e v e r w a l l , and s a f e t y during c o n s t r u c t i o n s t a g e s should be checked. g. Sand Dike B a c k f i l l . When g r a n u l a r b a c k f i l l i s s c a r c e , a sand d i k e may be placed t o form a plug a c r o s s t h e p o t e n t i a l f a i l u r e s u r f a c e of t h e a c t i v e wedge a s shown i n Figure 22. Where such a d i k e r e s t s on f i r m foundat i o n s o i l , t h e l a t e r a l pressure on t h e bulkhead w i l l be only the a c t i v e press u r e of t h e dike m a t e r i a l . For f u r t h e r guidance, s e e Reference 11, Foundat i o n s , Retaining and E a r t h S t r u c t u r e s , by Tschebotarioff. 2. CANTILEVER SHEET PILE WALLS. A c a n t i l e v e r wall d e r i v e s support from t h e p a s s i v e r e s i s t a n c e below t h e dredge l i n e t o support t h e a c t i v e p r e s s u r e from t h e s o i l above t h e dredge l i n e without an anchorage. This type of w a l l i s s u i t a b l e only f o r h e i g h t s up t o about 15 f e e t and can be used only i n granul a r s o i l s o r s t i f f clays. See Figure 23 f o r a method of a n a l y s i s ( a f t e r Reference 12, S t e e l s h e e t P i l i n g Design Manual, by U.S. S t e e l Corporation). For cohesive s o i l s consider no n e g a t i v e pressure i n t e n s i o n zone. Figures 24 and 25 (Reference 12) may be used f o r simple cases. 3. INTERNALLY BRACED FLEXIBLE WALLS. To r e s t r a i n foundation o r t r e n c h excav a t i o n s , f l e x i b l e w a l l s can be braced l a t e r a l l y a s the excavation proceeds. This r e s t r a i n s l a t e r a l movement of t h e s o i l and cause l o a d s on t h e braces which exceed those expected from a c t i v e e a r t h pressure. Braces may be e i t h e r long raking braces o r r e l a t i v e l y s h o r t h o r i z o n t a l c r o s s braces between t r e n c h walls. Design e a r t h pressure diagram f o r i n t e r n a l l y braced f l e x i b l e w a l l s a r e shown i n Figure 26 ( a f t e r Reference 6 ) f o r excavations i n sand, s o f t c l a y , o r s t i f f clay.
EFFECT OF ANCHOR WCATION RELATIVE TO THE WALL
ANCHOR BUXm LEFT OF b~ PROVIDES NO RESISTANCE. ANCHOR BLOCK RIGHT OF bf PROVIDES FULL RESISTANCE WITH NO LOAD TRANSFERRED TO WALL. HOR B W K BETWEEN b~ AND bf PROVIDES PARTIAL RESISTANCE AND TRANSFERS LOAD aPp TO BASE OF WALL. FOR FREE BODY
ab ed
ERE PA =ACTIVE FORCE ON BACK OF de AT
CONTINWUS ANCHOR WALL LOCATE0 BETWEEN RUPTURE S U R F . AND S L O E AT FRICTION ANGLE
Kp OeTAlNED FROM FIGURE 5 USING 0.5
- b#
KA IS OBTAINED FROM FldURE 3
FIGURE 20 Design C r i t e r i a f o r Deadman Anchorage
J
EFFECT OF DEPTH AND S W I N G OF ANCHOR BUCKS i
2
L
T A-A CONTINUOUS WALL
A-A ANCHORS 'NwlwAL
M a R ESISTANCE FOR hl L CONTINUOUS WALL: ULTIMATE ApC/d Z P ~ - P A ~ H E RApc/d E IS ANCHOR RESISTANCE AND PO ,@ TAKEN PER LINEAL FOOT OF WALL. 2. INDIVIDUAL ANCHORS: ~F~~~+~,ULTIMATEA~=~(P~-P~)+~P~TAN(~WHEREP~=RESULTNT FORCE OF SOIL AT REST ON VERTICAL AREA c d e OR c"de. IF d = h + b , ~ ~ /sm%w~pdd d R R ~ ~ T I N U X ~ WALL. S L FOR THIS CONDITION IS AND L'=h. IF d< h+b,Ap/d - %(.3 ~ p d d )c=h. , N C H R RESISTANCE FOR hl (
=~d
a
ULTIMATE Ap/d OR Apc/d EQUALS B E A R M CAWCITY OF STRIP FO(mNG OF WIDTH hl AND SUCHCRE UYD Y ( h - +),SEEFIGURE I CHAPTER^ USE FRICTON ANGLE
f
:WHERE TAN @ =0.6TAN 6.
GENERAL REQUIREMENTS: I. ALUlWABLE VALUE OF Ap AND A ~ =ULTIMATE c VALUE/2, FAGTOR OF SAFETY OF 2 AGAlNST FAILURE. 2. V U E S OF KA AND Kp ARE FOR COHESIONLESS MATERIALS. IF BACKFILL HAS BOTH #AND C STRENGTHS,COMPUTE kMlVE AND M I V E FORCES ACCORDING TO FIGURES 7 AND9 FINE GRAINED SOILS OF MOMUM TO HIGH PLASTICITY SHOULD NOT BE USED AT THE ANCHORAGE. 3. SOILS WITHIN PASSIVE WEDGE OF ANCHORAGE SHALL 8E C O M M E D TO NO LESS THCIN 90%OF MAX. UNIT WEIGHT ( ASTM D698 TEST). 4. TIE ROD IS DESlGNEll FOR ALLOWABLE Ap OR A ~ c .TIE ROD CONNECTWS TO WALL AND ANCHORAGE ARE =NED FOR 1.2 (ALUDWABLE Ap OR Apc). 5. TIE ROD CONNETION TO ANCHORAGE IS MADE AT THE LOCATION OF THE RESULTANT EARTH PRESSURES KTING ON THE VERTICAL FACE OF THE ANCHORAGE.
FIGURE 20 (continued) Design Criteria f o r Deadman Anchorage
~q =so0 PSF
t.3'4 QL 5,000 PLF
.23 KSF
.TY.= +l; a
77 -1
-,A1
I
-An
r
25? C1=100PSF yT= 115 PCF
PH=2.75 KIP
I
21.09~
=I
KA (FROM FIGURE 3) z.41
PA^ = 10.4 KIP 24'
ACTIVE EARTH PRESSURE DIAGRAM NET WATER PRESSURE DIAGRAM
= 4.05
KIP
+2 = 3s0, C2=50 PSF
yT= 1% W F 9 ~ =410.9 KIP
5-94
Kp (FROM FIGURE 5)=6.0
+
SAFETY FACMR AGAINST TOE FAILURE : TAKE .... - MOMENTS .. - .. -. .. - ABOUT . -- p MOMENTS OF W ~ V E FORCES C MOMENTS OF ACTIVE FORCES
-
ll(A
,UH z.30x.41-2x.O
)=.n
1.a3
ACTIVE EARTH PRESSURE (SEE FIGURE 2) INCWDING UNIFORM SURCHARGE q U H = y Z K -2C ~
KA (FROM FIGURE5
W=O
,uH=(.m+5~.115).41-2x.10 m z . 2 3 KSF
,UH=(.30+5~.115+19~.053).41-2 %.I0
s.65 KSF =(.30+5x.115+19x.053).27-2~.~ Wz.46 M =.46+6~.068~.27=.57KSF
ANCHOR PULL
@,a~( = .46+(6+14)rD68~.27=.83KSF PRESSURE OF LINE LWD SURCHARGE (SEE FIGURE II)
m = +=&=o.I PH= 0.55 QL=0.55 ~5 ~ 2 . 7 5KIP
AP =CpA-CPp/FS
1
= 155 +2.75+0.4+4.05
+10.9-
%!@ = 12.37 KIPS
MAXIMUM BENDING MOMENT IN SHEETING POINT OF ZERO SHEAR: x2 12.37-1.55 -2.75-45X -.022 x -0 X z l 3 . 6 ' ~ OUTSIDE ~ ~ ) ~ WATER LEVEL
U)CATION OF RESULTANT : R=.60H =.60x30=18' NET WATER PRESSURE
MOMENT REDUCTION: ASSUME:^^ =~T,OOOPSI, E=JO,O,OOO TRY ZP 32, I =MS.? IN^, s = 3 a 3 IN^ + 4 P =(FROM FWRE 19 = ILLD)
PASSIVE PRESSURE UH'YZ
PSI
6
K ~ + ~ c
@,uH = o + ~ x D s ~ = . ~ ~ K s F
@, UHz . 0 6 8 x 14~6.0+2x . 0 5 W = 5.94 KSF
MMAx
= .83; Y ON z.83 x 669 ~72.1FT-KIPS
TRY A SMALLER SECTION
FIGURE 21 Example of Analysis of Anchored Bulkhead
-
'
l'~b60.1~ RETAlN1NG rnlJCTURE% /I
STABLE DREDGE SLOP€
' I H
. SAND DIKE . .
.
I
. . . . ...... .::.. . . . . . . . . . . .-.:.... :. :;.:-:.....: .....:.:........ ':...... :.:-:::. :-............. ...-.. ...;...-::.:: : ..:. . . . . . . . ........... ..:.... . ... .: :.... .:. '..-:-:'..::'..-.-;DENSE . . .;.SAND . . . .:::.a;.
........
FIGURE 22 Sand Dike Scheme f o r Controlling Active Pressure
.
NOTE: WATER LEVELS CAN BE D1FFEREb.F C:;'; ?-SITE SIDES DUE TO PUMPING,TlDAL FLUCTUATIONS AND OTHER REASONS.
E'
1.
Assume a t r i a l d e p t h of p e n e t r a t i o n , D. t h e f o l l o w i n g approximate c o r r e l a t i o n . Standard P e n e t r a t i o n Resistance, N Blows/foot
Depth of P e n e t r a t i o n *
0 - 4 5 - 10 30 11 50 31 +5 0
2.OH 1.5H 1.25H 1.OH 0.75H
-
* 2.
3.
T h i s may be e s t i m a t e d from
H = h e i g h t of p i l i n g above dredge l i n e Determine t h e a c t i v e and p a s s i v e l a t e r a l p r e s s u r e u s i n g a p p r o p r i a t e c o e f f i c i e n t s of l a t e r a l e a r t h p r e s s u r e . I f t h e Coulomb method i s used, i t should be used c o n s e r v a t i v e l y f o r t h e p a s s i v e p r e s s u r e .
S a t i s f y t h e r e q u i r e m e n t s of s t a t i c e q u i l i b r i u m : t h e sum of t h e f o r c e s i n t h e h o r i z o n t a l d i r e c t i o n must be z e r o and t h e sum of t h e moments about any p o i n t must be zero. The sum of t h e h o r i z o n t a l f o r c e s may be w r i t t e n i n terms of p r e s s u r e a r e a s :
-
_C
A(EA1A2) - A ( F B A ~ ) ~ ( E C J )= 0 Solve t h e above e q u a t i o n f o r t h e d i s t a n c e , 2. For a uniform granular s o i l , K~ ~ 2 KA ( H + D ) ~
z
-
=
(Kp
-
KA) (H+2D)
FIGURE 23 Analysis f o r C a n t i l e v e r Wall
4.
Take moments about p o i n t F. I f sum of moments i s o t h e r t h a n zero, r e a d j u s t D and r e p e a t c a l c u l a t i o n s u n t i l sum of moments around F i s zero.
5.
Compute maximum moment a t point of zero s h e a r .
6.
I n c r e a s e D by 20%.- 40% t o r e s u l t i n approximate f a c t o r of s a f e t y of 1.5 t o 2.
FIGURE 23 (continued) Analysis f o r C a n t i l e v e r Wall
c HVM.A/xw
w ' HIOIM.ld t13d OllVt1 I N 3 WOW
EXAMPLE Backfill:
fi = 30° Y = 120 pcf Y ' = 60 pcf
Underlying Cohesive Stratum:
C = 750 p s f
y a w 60 p s f
Depth H t o mud l i n e = 20 f t Depth t o water = 5 f t
a
=
5/20 = 0.25
Wall f r i c t i o n = 0.3 (Table 1 )
KA = 0.31 ( F i g u r e 5) YEH =
120 x 5
+
15 x 60 = 1,500 psf
qu = 2C = 1,500 p s f USING FIGURE 25:
-
2 q " - ~ ~
Y'KAH
Depth r a t i o
, !.
H
3000- I5O0 6 0 X 0.31 X 2 0
= 4.03
= 0.69
D c a l c u l a t e d = 0.69 x 20 = 13.8 f t D d e s i g n = 13.8 x 1.3 = 17.9 f t
Moment r a t i o = 0.33 = 0.33 x 60 x 0.31 x (2013 = 49,104 f t - l b / f t
of w a l l
FIGURE 25 ( c o n t i n u e d ) C a n t i l e v e r S t e e l Sheet P i l e Wall i n Cohesive S o i l w i t h Granular B a c k f i l l
CI F2
F3 Fq
-
;I
I1 12
13
(a)
SAND u h = 0 . 6 5 KA.YH WHERE K A - T A N ~(45-+/2)
e-+
FI
F2
5
4 12
(b)
--_ -
I
-
SOFT TO MEDIUM CLAY (No>6 For c l a y s b a s e t h e s e l e c t i o n o n No = Y H/c
0.75H d
u h = ~ A - y . ~
13 F4
-
KA = I - m - 4 C ; YH m = 1 except where c u t i s u n d e r l a i n by deep s o f t normally c o n s o l i d a t e d c l a y , t h e n m = 0. hFSB
% &
I I $'(+++)Q~ ASSUME HINGES AT STRUT LOCATIONS FOR CALCULATING STRUT FORCES
See F i g u r e 28 f o r F a c t o r of S a f e t y a g a i n s t bottom i n s t a b i l i t y , (FSB):
1LFS~L1.5
F- l F2 F3
F4
11 12
Om2SH
.-
I A
L
l3
-
0.50H I
(
STIFF CLAY (N0 2 -
(This i s a c o n s e r v a t i v e procedure; s e e t e x t f o r r e f e r e n c e on more d e t a i l e d a n a l y s e s procedures. )
.
a. Standard P e n e t r a t i o n Test. R e l a t i o n s h i p s a r e p r e s e n t e d i n Reference 7, Foundation Engineering, by Peck, Hanson and Thornburn, f o r a l l o w a b l e beari n g values i n terms of standard p e n e t r a t i o n r e s i s t a n c e and f o r l i m i t i n g s e t tlement. When SPT t e s t s a r e a v a i l a b l e , use t h e c o r r e l a t i o n i n DM-7.1, Chapter 2 t o determine r e l a t i v e d e n s i t y and Figure 6, DM-7.1, Chapter 3 t o e s t i m a t e 0 values. Use Figure 1 t o compute u l t i m a t e bearing p r e s s u r e . b. Cone P e n e t r a t i o n Test. The r e s u l t s of CPT may be used d i r e c t l y t o compute allowable bearing p r e s s u r e f o r coarse-grained s o i l s . See Figure 8 (Reference 8, Shallow ~ o u n d a t i o n s , by t h e Canadian Geotechnical S o c i e t y ) . c. Bearing Capacity Fr& pressuremeter. I f pressuremeter i s used t o determine i n s i t u s o i l c h a r a c t e r i s t i c s , b e a r i n g c a p a c i t y can be computed from these t e s t results. (See Reference 8.) S e c t i o n 3.
1.
FOUNDATION DEPTH.
SPREAD FOOTING DESIGN CONSIDERATIONS
I n g e n e r a l f o o t i n g s should be c a r r i e d below:
( a ) The depth of f r o s t p e n e t r a t i o n ; ( b ) Zones of h i g h volume change due t o moisture f l u c t u a t i o n s ; ( c ) Organic m a t e r i a l s ; ( d ) Disturbed upper s o i l s ; ( e ) Uncontrolled f i l l s ; ( f ) Scour depths i n r i v e r s and streams. ( g ) Zones of c o l l a p s e - s u s c e p t i b l e s o i l s .
-
2. AT..TERNATIVE FOUNDATION METHODS Light S t r u c t u r e s . Light s t r u c t u r e s may be supported by o t h e r types of shallow foundation treatment such a s : ( a ) deep perimeter wall f o o t i n g s ; ( b ) overexcavation and compaction i n f o o t i n g l i n e s ; ( c ) mat design w i t h thickened edge; (d) preloading surcharge.
3. PROPORTIONING INDIVIDUAL FOOTINGS. Where s i g n i f i c a n t compression w i l l not occur i n s t r a t a below a depth equal t o t h e d i s t a n c e between f o o t i n g s , i n d i v i d u a l f o o t i n g s should be proportioned t o g i v e equal s e t t l e m e n t s , using formulas from DM-7.1, Chapter 5. See Figure 9 f o r an example.
4. CORROSION PROTECTION. Foundation design should c o n s i d e r p o t e n t i a l l y d e t r i m e n t a l s u b s t a n c e s i n s o i l s , such a s c h l o r i d e s and s u l p h a t e s , w i t h approp r i a t e p r o t e c t i o n f o r reinforcement, c o n c r e t e and metal piping. I f t h e analysis i n d i c a t e s s u l p h a t e c o n c e n t r a t i o n t o be more than 0.5% i n t h e s o i l o r more than 1200 p a r t s p e r m i l l i o n i n t h e groundwater, t h e use of a s u l p h a t e resisti n g cement such a s Type V Portland cement should be considered. I n a d d i t i o n s , o t h e r p r o t e c t i o n such a s lower water-cement r a t i o , bituminous c o a t i n g , e t c . may be required depending upon t h e s u l p h a t e concentration. See Reference 9, Sulphates i n S o i l s and Groundwaters, BRS Digest, f o r guidance.
\ 0
u
B,FT qa = ALLOWABLE BEARING PRESSURE
%one =CONE RESISTANCE Df = DEPTH OF SURCHARGE ABOVE M E BASE OFFOOTING B = FOOTING WIDTH FIGURE 8 Allowable Bearing Pressure f o r Sand From S t a t i c Cone Penetration T e s t s
EXAMPLE
C0L.B LOAD = 160T
COL. A LOAD = 5 o T
I
f.
1 5'
Y
SAND
-
7
rrm-t
tt-tt
to-
t
YT = 120 PCF N -AVG. = 18 BLOWS/FT
N-AN.= I 5 BLOW/FT.
.
.
Column l o a d A = 50 t o n s , Avg N = 15 b l o w s / f t Column load B = 160 t o n s , Avg. N = 18 b l o w s / f t . S o i l : w e l l graded sand (SW) , YT = 120 pcf Column A Assume s q u a r e f o o t i n g 5 f t . x 5 f t . , B = 5 f t . Average overburden p r e s s u r e a t 6.5 f t . (Df + B/2) below ground level : Po = 120 x 6.5 = 780 psf = 0.39 t s f From Figure 3, DM-7.1, Chapter 2, Dr = 80% From Figure 7, DM-7.1, Chapter 3, 6 = 37.5' a ) Determine Bearing Capacity 1 From Figure 1, q u l t = El20 x 4 x 45 + 0.4 x 120 x 5 x 7 0 7 2 0 0 0 = 19.2 t s f q u l t (net) = 19.2 - 120 x 4 e 19 t s f 2000 Use Fs = 3, Qall = 19 = 6 . 3 t s f 3 3 f t . x 3 f t . which i s less t h a n Minimum r e q u i r e d f o o t i n g s i z e : I50 assumed s i z e 5f t x 5 f t . 6.3 b) Check f o r s e t t l e m e n t . To l i m i t s e t t l e m e n t , assume a 5 f t . x 5 f t . f o o t i n g w i t h q = 5oT =:2 t s f From Figure 6, DM-7 . l , Chapter 5 q, = 255 t o n s / f t 3 5ft. x 5ft. A H E ~X 2 X S2 x 12 = 0.26 i n c h e s 255 x ( 5 + 1) Column B Assume 8 f t . x 8 f t . s q u a r e f o o t i n g Average overburden p r e s s u r e a t 8 f t . = (Df ~ / 2 )below ground l e v e l . Po = 120 x 8 x 1 = 0.48 t s f 2000 From Figure 3, DM-7.1, Chapter 2, Dr = 87% From Figure 7, DM-7.1, Chapter 3, t8 = 39' a ) Determine Bearing Capacity 0.4 x 120 x 8 x 961 1 32.3 t s f From Figure 1 , q u l t = El20 x 4 x 58 2000 q u l t ( n e t ) = 32.3 120 x 4 % 3 2 t s f 2Q00 U s e Fs = 3.0.'- q a l l = 32 = 10.7 t s f 3
.'.
.
.
+
+
-
-
. FIGURE 9 Example of Proportioning Footing S i z e t o Equalize S e t t l e m e n t s 7.2-148
Minimum required f o o t i n g s i z e :
160 = 3.9 f t . x 3.9 f t . 10.7
Footing s i z e required f o r settlement equal t o that o f Column A . From Figure 6, DM-7.1, Chapter 5, Kvl = 290 t o n s / f t 3 4 x 160 x 8 2 x 12 0 ' 2 6 = 290 x B~ x (B + 1 ) 2
b)
.
- 1 = 9.1 )) 3.9 0.26 x 290 Settlement Governs Use 9.1 x 9.1 f o o t i n g f o r Column B Or B =
FIGURE 9 (continued) Example of Proportioning Footing S i z e t o Equalize Settlements
E l e c t r i c a l c o r r o s i v e p r o p e r t i e s of s o i l a r e i m p o r t a n t where metal s t r u c t u r e s such as p i p e l i n e s , e t c . a r e b u r i e d underground. A r e s i s t i v i t y survey of t h e s i t e may be n e c e s s a r y t o e v a l u a t e t h e need f o r c a t h o d i c p r o t e c t i o n . S e c t i o n 4.
MAT AND CONTINUOUS BEAM FOUNDATIONS
1. APPLICATIONS. Depending on economic c o n s i d e r a t i o n s m a t f o u n d a t i o n s a r e g e n e r a l l y a p p r o p r i a t e i f t h e sum of i n d i v i d u a l f o o t i n g b a s e a r e a s exceeds about one-half t h e t o t a l f o u n d a t i o n a r e a ; i f t h e s u b s u r f a c e s t r a t a c o n t a i n c a v i t i e s o r compressible l e n s e s ; i f s h a l l o w s h e a r s t r a i n s e t t l e m e n t s predomin a t e and t h e mat would e q u a l i z e d i f f e r e n t i a l s e t t l e m e n t s ; o r i f r e s i s t a n c e t o h y d r o s t a t i c u p l i f t i s required. 2. STABILITY AND SETTLEMENT REQUIREMENTS. A s with o t h e r t y p e s of foundat i o n s , a-mat f o u n d a t i o n must have an ample f a c t o r of s a f e t y ( s e e S e c t i o n 2) a g a i n s t o v e r a l l s h e a r f a i l u r e and i t must not e x h i b i t i n t o l e r a b l e s e t t l e m e n t ( s e e DM-7.1, Chapter 5). S i n c e mat f o o t i n g s a r e simply l a r g e f o o t i n g s , t h e b e a r i n g c a p a c i t y p r i n c i p l e s o u t l i n e d i n S e c t i o n s 2 and 3 of t h i s c h a p t e r a r e a p p l i c a b l e . The u l t i mate b e a r i n g c a p a c i t y of l a r g e mats on coarse-grained s o i l s i s u s u a l l y v e r y h i g h and d e s i g n i s u s u a l l y c o n t r o l l e d by s e t t l e m e n t ( s e e DM-7.1, Chapter 5). For mats on c o h e s i v e s o i l s , s h e a r s t r e n g t h parameters f o r s o i l s a t d e p t h must be determined f o r t h e proper e v a l u a t i o n of f a c t o r of s a f e t y a g a i n s t deepseated failure. 3. DESIGN PROCEDURES. A d e s i g n method based on t h e t h e o r y f o r beams o r p l a t e s on d i s c r e e t e l a s t i c f o u n d a t i o n s (Reference 10, Beams on E l a s t i c Found a t i o n , by Hetenyi) h a s been recommended by A C I Committee 436 (Reference 11, Suggested Design Procedures f o r Combined Footings and Mats) f o r d e s i g n of m a t foundations. This a n a l y s i s i s s u i t a b l e f o r f o u n d a t i o n s on coarse-grained soils. a. Two-dimensional Problems. For w a l l s o r c r a n e t r a c k f o o t i n g s o r mat f o u n d a t i o n s s u b j e c t e d t o p l a n e s t r a i n , such a s drydock w a l l s and l i n e a r blocki n g l o a d s , u s e t h e procedures of Table 3 and F i g u r e s 10 and 11 (Reference 1 0 ) . Superpose s h e a r , moment, and d e f l e c t i o n produced by s e p a r a t e l o a d s t o o b t a i n t h e e f f e c t of combined loads. b. Three-dimensional'Problems. For i n d i v i d u a l l o a d s a p p l i e d i n i r r e g u l a r p a t t e r n t o a roughly equi-dimensional mat, a n a l y z e s t r e s s e s by methods of p l a t e s on e l a s t i c foundations.
Use t h e procedures of Table 4 and F i g u r e 12.
Superpose s h e a r , moment, o r d e f l e c t i o n produced by s e p a r a t e l o a d s t o o b t a i n k f f e c t of combined loads.
TABLE 3 . D e f i n i t i o n s and P r o c e d u r e s , A n a l y s i s of Beams on E l a s t i c F o u n d a t i o n
--
).
Definitions: Kv,
= Modulus of s u b g r a d e r e a c t i o n f o r a 1 s q f t b e a r i n g p l a t e .
Kb = Modulus of s u b g r a d e r e a c t i o n f o r beam of w i d t h b, Kb = (K,, ) / b y = D e f l e c t i o n of beam a t a p o i n t . p = P r e s s u r e i n t e n s i t y on t h e s u b g r a d e a t a p o i n t , p = y(Kb) b
=
Width of beam a t c o n t a c t s u r f a c e
I = Moment of i n e r t i a of beam E = Modulus of e l a s t i c i t y of beam m a t e r i a l
Beam l e n g t h
=!,
A = C h a r a c t e r i s t i c s of t h e system of beam and s u p p o r t i n g s o i l =
;4j3E EI
Procedure f o r Analysis: Chapter 5 o r
1.
Determine E and e s t a b l i s h K,, from p l a t e b e a r i n g t e s t s .
2.
Determine d e p t h of beam from s h e a r r e q u i r e m e n t s a t c r i t i c a l s e c t i o n and w i d t h from a l l o w a b l e b e a r i n g p r e s s u r e . Compute c h a r a c t e r i s t i c X of beam and s u p p o r t i n g s o i l .
3.
C l a s s i f y beams i n a c c o r d a n c e w i t h r e l a t i v e s t i f f n e s s i n t o t h e f o l l o w i n g t h r e e groups. A n a l y s i s p r o c e d u r e d i f f e r s w i t h e a c h group.
-
from F i g u r e 6 i n D M - 7 . 0 4
.,
S h o r t beams: 4 Beam i s c o n s i d e r e d r i g i d . Assume Group 1 l i n e a r d i s t r i b u t i o n of f o u n d a t i o n c o n t r a c t p r e s s u r e as f o r a r i g i d footing. Compute s h e a r and moment i n beam by s i m p l e s t a t i c s .
TABLE 3 ( c o n t i n u e d ) D e f i n i t i o n s and Procedures, A n a l y s i s of Beams on E l a s t i c Foundation ,
-
Group 2 Beams of medium l e n g t h : 7 1 4 1.5 S.F.
PH 3oK-
:. OK HORIZ.
MAKE ADDITIONAL TRIALS VARYING h ,x,y, L
FIGURE 18 Tower Guy Anchorage i n S o i l by C o n c r e t e Deadman
-
analyzed a s shown i n Figure 17. Tower guy anchorage i n s o i l i s a n a l y z e d i n Figbre 18. For a deadman i n weak s o i l , i t may be f e a s i b l e t o r e p l a c e a cons i d e r a b l e volume of s o i l with g r a n u l a r b a c k f i l l and c o n s t r u c t t h e b l o c k withi n t h e new b a c k f i l l . I f t h i s i s done, t h e p a s s i v e wedge should be c o n t a i n e d e n t i r e l y within t h e g r a n u l a r f i l l , and t h e s t r e s s e s on t h e remaining weak m a t e r i a l should be i n v e s t i g a t e d . See Reference 6 f o r guidance. 3. CORROSION. For temporary anchors minimal p r o t e c t i o n i s needed u n l e s s t h e environments a r e such t h a t r a p i d d e t e r i o r a t i o n t a k e s place. Permanent anchor b a r s a r e covered with grout. I n c o r r o s i v e environments i t i s common p r a c t i c e t o provide a d d i t i o n a l p r o t e c t i o n by c o a t i n g w i t h m a t e r i a l (epoxy, p o l y e s t e r r e s i n ) with proven r e s i s t a n c e t o e x i s t i n g o r a n t i c i p a t e d c o r r o s i v e a g e n t s . The c o a t i n g agent should not have any adverse e f f e c t on t h e bond.
4. ROCK AND SOIL ANCHORS. When t h e load t o be r e s i s t e d i s l a r g e , w i r e tendons which can a l s o be p r e s t r e s s e d t o reduce movements a r e employed. Also, because of c o r r o s i o n s p e c i a l p r e c a u t i o n s may be necessary when permanent anchors a r e provided i n marine environments. I n t h e a n a l y s i s of a n c h o r s , because of submergence, t h e bouyant u n i t weight of s o i l s should be used. The buildup of excess pore p r e s s u r e due t o r e p e t i t i v e l o a d s should a l s o b e evaluat e d i n t h e c a s e of g r a n u l a r s o i l s . For a d i s c u s s i o n of c y c l i c m o b i l i t y and l i q u e f a c t i o n s e e DM-7.3, Chapter 1. For t h e d e s i g n of anchors s e e DM-7.3, Chapter 3.
REFERENCES 1.
Meyerhof, G.G., Influence of Roughness of Base and Ground Water Condition on the Ultimate Bearing Capacity of Foundations, Geotechnique, 1955.
2.
Meyerhof, G.G., The Bearing Capacity of Foundations Under Eccentric and Inclined Loads, Proceedings, Third International Conference on Soil Mechanics and Foundation Engineering, Zurich, 1953.
3.
Meyerhof, G.G., The Ultimate Bearing Capacity of Foundations on Slopes, Proceedings, Fourth International Conference on Soil Mechanics and Foundation Engineering, London, 1957.
4. Button, S.F.,
The Bearing Capacity of Footings on a Two-Layer Cohesive Subsoil, Proceedings, Third International Conference on Soil Mechanics and Foundation Engineering, Zurich, 1953.
5.
Vesic, A.S., Bearing Capacity of Shallow Foundations, Foundation Engineering Handbook, Winterkorn and Fang, eds., Van Nostrand Reinhold Company, New York, Chapter 3, 1975.
6.
Bowles, J.E., Foundation Analysis and Design, McGraw Hill Book Co., New York, pp. 137-139, 1977
7.
Peck, R.B., Hanson, W.E. and Thornburn, T.H., Foundation Engineering, 2nd Edition, John Wiley & Sons, Inc., New York, 1974.
8.
Canadian Geotechnical Society, Shallow Foundations, Canadian Foundation Engineering Manual, Montreal, Canada, Part 2, 1978.
9.
CP2004, Sulphates in Soils and Groundwaters, Classification and Recommendations, BRS Digest, No. 90, Second Series, London, England, 1972.
10.
Hetenyi, M., Beams on Elastic Foundation, University of Michigan Press, Ann Arbor, MI, 1946.
11.
ACI Committee 436, Suggested Design Procedures for Combined Footings and Mats, American Concrete Institute, 1966.
12.
Terzaghi, K., Evaluation of Coefficient of Subgrade Reaction, Geotechnique, Vol. 5, No. 4, 1955.
13.
Parcher, J.V. and Means, R.E., Soil Mechanics and Foundations, Charles E. Merril Publishing Company, Columbus, OH, 1968.
14.
Lytton, R.L. and Woodburn, J.A., Design and Performance of Mat Foundations on Expansive Clay, Proceedings ot the Third International Conference on Expansive Soils, 1973.
15.
Chen, F.H., Foundations on Expansive Soils, Footing Foundations, Elsevier Scientific Publishing Co., New York, Chapter 5, 1975.
16.
Teng, W.C., Foundation Drainage and Waterproofing, Foundation Design, Prentice Hall, Englewood Cliffs, NJ, Chapter 5, 1962.
17.
NAVFAC TS-07110, Membrane Waterproofing, Naval Facilities, Engineering Command, Guide Specifications, 1979.
18.
NAVFAC TS-07160, Bituminous Dampproofing, Naval Facilities, Engineering Command, Guide Specifications, 1978.
19.
Littlejohn, G.S. and Bruce, D.A., Rock Anchors-State of the Art, Foundation Publications Ltd., England, 1977.
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CHAPTBR
5.
S e c t i o n 1.
DEEP FOUNDATIONS
INTRODUCTION
1. SCOPE. T h i s c h a p t e r p r e s e n t s i n f o r m a t i o n on t h e common t y p e s of deep f o u n d a t i o n s , a n a l y s i s and d e s i g n p r o c e d u r e s , and i n s t a l l a t i o n p r o c e d u r e s . Deep f o u n d a t i o n s , a s used i n t h i s c h a p t e r , r e f e r t o f o u n d a t i o n s which o b t a i n s u p p o r t a t some d e p t h below t h e s t r u c t u r e , g e n e r a l l y w i t h a f o u n d a t i o n d e p t h t o width r a t i o (D/B) exceeding f i v e . These i n c l u d e d r i v e n p i l e s , d r i l l e d p i l e s , d r i l l e d p i e r s / c a i s s o n s , and f o u n d a t i o n s i n s t a l l e d i n open o r b r a c e d e x c a v a t i o n s w e l l below t h e g e n e r a l s t r u c t u r e . Diaphragm w a l l s a r e d i s c u s s e d i n DM-7.3, Chapter 3. APPLICATION. 2. including :
Deep f o u n d a t i o n s a r e used i n a v a r i e t y of a p p l i c a t i o n s
( a ) To t r a n s m i t l o a d s through a n upper weak a n d / o r c o m p r e s s i b l e s t r a t u m t o u n d e r l y i n g competent zone. ( b ) To p r o v i d e s u p p o r t i n a r e a s where s h a l l o w f o u n d a t i o n s a r e i m p r a c t i c a l , such a s underwater, i n c l o s e p r o x i m i t y t o e x i s t i n g s t r u c t u r e s , and o t h e r conditions. ( c ) To p r o v i d e u p l i f t r e s i s t a n c e a n d / o r l a t e r a l l o a d c a p a c i t y . 3. RELATED CRITERIA. For a d d i t i o n a l c r i t e r i a r e l a t i - n g t o t h e d e s i g n of deep f o u n d a t i o n s and t h e s e l e c t i o n of d r i v i n g equipment and a p p a r a t u s , s e e t h e f o l lowing s o u r c e s : Source
Subject
P i l e Driving Equipment................................... NAVFAC DM-38 DM-2! General C r i t e r i a f o r P i l i n g i n W a t e r f r o n t Construction....NAVFAC
4.
LOCAL PRACTICE. The c h o i c e of t h e t y p e of deep f o u n d a t i o n s u c h a s p i l e t y p e ( s ) , p i l e d e s i g n c a p a c i t y , and i n s t a l l a t i o n p r o c e d u r e s i s h i g h l y dependent on l o c a l e x p e r i e n c e and p r a c t i c e . A d e s i g n e n g i n e e r u n f a m i l i a r w i t h t h e s e l o c a l p r a c t i c e s should c o n t a c t l o c a l b u i l d i n g l e n g i n e e r i n g d e p a r t m e n t s , l o c a l foundation c o n t r a c t o r s , and/or l o c a l foundation consultants.
5.
INVESTIGATION PROGRAM. d e s i g n of p i l e foundations.
Adequate s u b s u r f a c e e x p l o r a t i o n must p r e c e d e t h e I n v e s t i g a t i o n s must i n c l u d e t h e f o l l o w i n g :
( a ) Geological s e c t i o n showing p a t t e r n of major s t r a t a and p r e s e n c e o f p o s s i b l e o b s t r u c t i o n s , such a s b o u l d e r s , b u r i e d d e b r i s , e t c . ( b ) S u f f i c i e n t t e s t d a t a t o e s t i m a t e s t r e n g t h and c o m p r e s s i b i l i t y paramet e r s of major s t r a t a . ( c ) Determination of probable p i l e b e a r i n g s t r a t u m . For . f i e l d e x p l o r a t i o n s and t e s t i n g r e q u i r e m e n t s , s e e DM-7.1,
Chapter 2.
6. CONSTRUCTION INSPECTION. The performance of a deep f o u n d a t i o n i s h i g h l y dependent on t h e i n s t a l l a t i o n p r o c e d u r e s , q u a l i t y of workmanship, and i n s t a l l a t i o n l d e s i g n changes made i n t h e f i e l d . Thus, i n s p e c t i o n of t h e deep found a t i o n i n s t a l l a t i o n by a g e o t e c h n i c a l e n g i n e e r normally s h o u l d be r e q u i r e d . S e c t i o n 2.
FOUNDATION TYPES AND DESIGN CRITERIA
1. COMMON TYPES. T a b l e s 1 and 2 summarize t h e t y p e s of deep f o u n d a t i o n s , f a b r i c a t e d from wood, s t e e l , o r c o n c r e t e , i n common usage i n t h e United S t a t e s . Table 1 p r e s e n t s p i l e t y p e s and Table 2 p r e s e n t s excavated f o u n d a t i o n General comments on a p p l i c a b i l i t y of types including d r i l l e d piers/caissons. t h e v a r i o u s foundation t y p e s a r e g i v e n i n Table 2, b u t l o c a l e x p e r i e n c e and p r a c t i c e s , comparative c o s t s , and c o n s t r u c t i o n c o n s t r a i n t s should be reviewed c a r e f u l l y f o r each s i t e . a. Driven P i l e s . These a r e p i l e s which a r e d r i v e n i n t o t h e ground and Low d i s p l a c e m e n t i n c l u d e b o t h low displacement and h i g h displacement p i l e s . p i l e s i n c l u d e H and I s e c t i o n s t e e l p i l e s . Open end p i l e s which do n o t form a p l u g , j e t t e d p i l e s , and pre-bored d r i v e n p i l e s may f u n c t i o n as low d i s p l a c e ment p i l e s . S o l i d s e c t i o n p i l e s , hollow s e c t i o n c l o s e d end p i l e s , and open end p i l e s forming a s o i l p l u g f u n c t i o n a s h i g h displacement p i l e s . A l l t h e p i l e types i n Table 1 except auger-placed p i l e s a r e d r i v e n p i l e s . b. Excavated Foundations. These f o u n d a t i o n s i n c l u d e b o t h d r i l l e d p i l e s and p i e r s and f o u n d a t i o n s c o n s t r u c t e d i n open o r braced e x c a v a t i o n s ( s e e Reference 1, Foundation Design, by Teng). ' ~ r i l l e dp i l e s i n c l u d e auger-placed p i l e s and d r i l l e d p i e r s / c a i s s o n s e i t h e r s t r a i g h t s h a f t o r b e l l e d . 2. OTHER DEEP FOUNDATION TYPES. Tables 1 and 2 i n c l u d e o n l y t h e most commonly used p i l e t y p e s and deep f o u n d a t i o n c o n s t r u c t i o n procedures. New and i n n o v a t i v e t y p e s a r e being developed c o n s t a n t l y , and each must be a p p r a i s e d on i t s own m e r i t s . a. D r i l l e d - i n Tubular P i l e s . These c o n s i s t of heavy-gauge s t e e l t u b u l a r p i l e c a p a b l e of being r o t a t e d i n t o t h e ground f o r s t r u c t u r e s u p p o r t . S o i l s i n t h e tube may be removed and r e p l a c e d w i t h c o n c r e t e . Used i n p e n e t r a t i o n of s o i l c o n t a i n i n g b o u l d e r s and o b s t r u c t i o n s , o r d r i l l i n g of rock s o c k e t t o res i s t u p l i f t and l a t e r a l f o r c e s . S t e e l H-sections w i t h i n c o n c r e t e c o r e s a r e used t o develop f u l l end b e a r i n g f o r h i g h load c a p a c i t y . b. TPT (Tapered P i l e T i p ) P i l e s . These c o n s i s t of a mandrel d r i v e corr u g a t e d s h e l l w i t h a n e n l a r g e d p r e c a s t c o n c r e t e base. This t y p e of p i l e i s u s u a l l y considered i n c o n d i t i o n s s u i t a b l e f o r p r e s s u r e i n j e c t e d f o o t i n g s . The p r i n c i p a l claimed advantage i s t.he avoidance of punching through a r e l a t i v e l y t h i n b e a r i n g stratum. c. I n t e r p i l e s . These c o n s i s t of an uncased c o n c r e t e p i l e , formed by a mandrel d r i v e n s t e e l p l a t e . A s t e e l p i p e mandrel of smaller d i a m e t e r t h a n t h e p l a t e i s used, and t h e void c r e a t e d by t h e d r i v e n p l a t e i s k e p t c o n t i n u o u s l y f i l l e d with c o n c r e t e . It i s claimed t h a t t h i s p i l e develops g r e a t e r s i d e f r i c t i o n i n a g r a n u l a r s o i l t h a n d r i l l e d p i e r s and c o n v e n t i o n a l d r i v e n p i l e s .
-
d
TABLE 1 Design C r i t e r i a f o r Bearing P i l e s L
PILE TYPE CONSIDER FOR LENGTH OF
TIMBER
STEEL
-
H SECTIONS
3 0 -60 FT
40 -100 FT
APPLICABLE MATERIAL SPECIFICATIONS.
ASTM -025
ASTM -A36
MAXIMUM STRESSES.
MEASURED AT MOST CRITICAL PDINT, 1200 PSI FOR SOUTHERN PINE AND DOUGLAS FIR. SEE U.S.D.A. WOOD HANDBOOK NO72 FOR STRESS VALUES OF OTHER SPECIES.
12,000 PSI.
CONSIDER FOR DESIGN LOADS OF.
10-50 TONS
4 0 -120 TONS
DISADVANTAGES
DIFFICULT TO SPLICE. VULNERABLE TO DAMAGE IN HARD DRIVING, TIP MAY HAVE TO BE PROTECTED. VULNERABLE TO DECAY UNLESS TREATED, WHEN PILES ARE INTERMITTENTLY SUBMERGED.
VULNERABLE TO CORROSION WHERE EXPOSED H P SECTION MAY BE DAMAGED OR DEFLECTEDBY MAJOR OBSTRUCTIONS.
ADVANTAGES
COMPARATIVELY LOW INITIAL COST. PERMANENTLY SUBMERGED PILES ARE RESISTANT TO DECAY. EASY TO HANDLE.
REMARKS
BEST SUITED FOR FRICTION PILE IN GRANULAR BEST SUITED FOR ENDBEARING ON ROCK. MATERIAL. REDUCE ALLOWABLE CAWCITY FOR CORROSIVE LOCATIONS
EASY TO SPLICE. AVAILABLE IN VARIOUS LENGTHS AND SIZES. HIGH CAPACITY. SMALL DISPLACEMENT. ABLETOPENETRATETHROUGHLIGHT OBSTRUCTIONS. HARDER OBSTRUCTIONS MAY BE PENETRATED WITH APPROPRIATE POINT PROTECTION OR WHERE PENETRATIW OF SOFT ROCK IS REQUIRED.
.
BUTT DIA 12" TO 22" @
H
CROSS SECTION
TYPICAL ILLUSTRATIONS. CROSS SECTION
TIF' D U 5" TO 9"
L
#
TABLE 1 (continued) Design C r i t e r i a f o r Bearing P i l e s -
PILE TYPE
PRECAST CONCRETE (INCLUDING PRESlESSED)
-
CAST-IN-PLACE CONCRETE (THIN SHELL DRIVEN WITH MANDREL )
CONSIDER FOR LENGTH OF
40-50 FT. FOR PRECAST 00 I00FT FOR PRESTRESSED.
10-120 FT BUT TYPICALLY IN THE 5 0 80 fl RANGE
APPLWLE MATERAL SPECIFICATIONS.
ACI 318 FOR CONCRETE ASfM AIS-FDR REINFORCING STEEL
ACI CODE 318 -FOR CONCRETE.
MAXIMUM STRESSES.
FOR PRECAST-33% OF 28 DAY STRENGTH OF CONCRETE. FOR PRESTRESSED- Fc = 0.33 F;-0.27 F~ (WHERE: FplS THE EFFECTIVE PRESTRESS STRESS ON THE GROSS SIXTION 1.
33OlO OF 28-DAY STRENGTH OF CONCRETE,WITH INCREASE TO 40°/o OF 28 DAY !XRENGTH. PROVIDlNG : (A) CASING IS A MINIMUM 14 GAUGE THICKNESS ( BICASING IS SEAMLESS OR WITH WELDED SEAMS (C) RATIO OFSTEELYIELD STRENGTH TO CONCRETE 28 DAY STRENGTH S NOT LESS THAN 6. (D)PILE M E T E R IS NOT GREATER THAN 17 .
SPEC1FICALLY DESIGNED FOR A WIDE RANGE OF W.
SPECIFICALLY DESGNED FOR A WIDE RANGE OF U D S
UNLESS PRESTRESSED,WLNERABLE TO HANDLING RELATIVEW HIGH BREAK= RATE ESPOClAUY WHEN PILES ARE TO BE SPLICED. HIGH INITIAL COST. CONSIDERABLE DISPLACEMENT PRESTRESSED DIFFICULT TO SPLICE.
DlFFICULT RI SPLICE AFTER CONCRETING. REDRIVING NOT RECOMMENDED. THIN SHELL VULNERABLE DURING DRIVING TO EXCESSIVE EARTH PRESSURE OR IMPACT,
MSADVANTmS
-
ADVANTAGES
HIGH LOAD CARIICITIES. CORROSION RESISTANCE CAN BE ATTAINED. HARD DRIVING POSSIBLE.
REMARKS
CYLINDER PILES IN WRTICULAR ARE SUITED FOR BENDING RESISTANCE. G€N€RAL W I N G RAWE IS 40-400 TONS.
I
-
CONSIDERABLE DISPLACEMENT. INITIAL ECONOMY. TAPERED SECTIONS PROVIDE HIGHER BEARING RESISTANCE IN GRANULAR STRATUM CAN BE INTERNALLY INSPECTEDAFTER DRIVING RELATIVLY LESS WASTE STEEL MATERIAL. CAN BE DESIGNEDAS END BEARING OR FRICTION PILE,GENERALLY LOADED IN THE 40-IOOTON RANGE. BEST SUITED FOR MEDIUM UMD FRICTION PILES IN GRANULAR MATERIALS. --
-
- -
--- -.
12" TO 24" DIA
RADE
TYPICAL I U U S r n
12" TO 24" DIA.
8" T O 18" DIA
t-3
0
NOTE REINFORCING MAY BE PRE-STRESSED 12" TO 54" DIA.
BE OMITTED TYPICAL CROSS SECTIONS
CROSS SECTION
CORRUGATED S H E L L THICKNESS 1 2 GA. T O 2 0 GA. SIDES STRAIGHT OR TAPERED
TABLE 1 (continued) Design C r i t e r i a f o r Bearing P i l e s i
PILE TYPE CONSIDER FOR LENGTH OF
CAST-IN -PLACE CONCRETE PILES (SHELLS DRIVEN WITHOUT MANDREL)
10 TO 60 FT
3 0 - 8 0 FT
ACI CODE 318
AC I CODE 318 APPLICABLE MATERIAL SPECIFICATION. MAXIMUM STRESSES
PRESSURE INJECTED FOOTINGS
33 % OF 2 8 -DAY STRENGTH OF CONCRETE. SIOOO PSI IN SHELL,MORE THAN 1/6 INCHTHICK.
5 0 -70 TONS. CONSIDER FOR DESIGN LQllDS OF DISADVANT#iES HARD lD SPLICE AFTER CONCRETING. CONS1DERABLE DISPLACEMENT. ADVANTXES
CAN BE REDRIVEN.
REMARKS
BEST SUITED FOR FRICTION PILES OF MEDIUM LENGTH.
SHELL NOT EASlLY DAMAGED.
3S0/o OF 28-DAY STRENGTH OF CONCRETE. 91000PSI FOR PIPE SHELL IF THICKNESS GREATER THAN 1/8 INCH
6 0 -120 lDNS. BASE OF FOOTING CANNOT BE MADE INCLAY OR WHEN HARD SPOTS (E.G.ROCK LEDGES) ARE PRESENT IN SOIL PENETRATED. WHEN CLAY LAYERS MUST BE PENETRATED TO REACH SUITABLE MATERAL, SPECIAL PRECAUTIONS ARE REQUIRED FOR SHAFTS IF IN GROUPS. PROVIDES MEANS OF PLACING HIGH CAPACITY FOOTINGS ON BEARING STRATUM WITHOUT NECESSITY FOR EX-@VATION OR DEWAERIEI- HlGH BLOW ENERGY AVAILABLE FOR OVERCOMING OBSTRUCTIONS. GREAT UPLIFT RESISTANCE IF SUITABLY REINFORCED BEST SUITED FOR GRANULAR SOILS WHERE BEARING IS ACHIEVED THROUGH COMMTION AROUND BASE. MINIMUM SPACING 4'-6"ON CENTER.
12" TO 18" DIA. 17" TO
IYPICAL I L W W r n S
12" TO
TYPICAL CROSS SECTION_ (FLUTED SHELL)
TYPICAL CROSS SECTION (SPIRAL WELDnD SHELL) UNCASED SHAFT
CASED SHAFT
.
TABLE 1 (continued) Design Criteria f o r Bearing P i l e s
+ PILE TYPE
COMPOSITE PILES
CONCRETE FILLED STEEL PIPE PILES
CONSIDER FOR LENGTH OF
40-120FT OR MORE
60 - 200 FT
APPLICABLE MATERIAL SPECIFICATIONS.
ASTM A36 - FOR CORE. ASTM A252- FOR PIPE. ACI CODE 318- FOR CONCRETE.
MAXIMUM STRESSES.
9,000 PSI FOR PIPE SHELL 33% OF 28-DAY STRENGTH OFCONCRETE. 12,000 PSI ON STEEL CORES OF STRUCTURAL REINFORCING STEEL.
ACI CODE 318- FOR CONCRETE. ASTM A36 - FOR STRUCTURAL SECTION. ASTM A252-FOR STEEL R E . ASTM D25 -FOR TIMBER. 33% OF 26-DAY STRENGTH OF WKRETE. 9,000 PSI FOR STRUCTURAL AND PIPESECTlONS. SAME AS TIMBER PILES FOR WOOD WMPOSITE.
CONSlDER FOR DESIGN LOAD OF
8 0 - 120 TONS WITHOUT CORES. 500-1,500 TONS WITH CORES.
3 0 - 100 TONS.
DISADVANTAGES
HIGH INITIAL COST DISPLACEMENT FOR CLOSED END PIPE.
DIFFICULT TO ATTAIN GOOD JOINT BETWEENtWO MATERIALS EXCEPT FOR PIPE COMPOSITE PILE
ADVANTAGES
BEST CONTROL DURING INSTALLATION. NO DISPLACEMENT FOR OPEN END INSTALLATION. OPEN END PIPE BESTAGAINST OBSTRUCTIONS. CAN BECLEANED OUT AND DRIVEN FURTHER. HIGH LOAD CAWITIES. EASY TO SPLICE.
COFtSlDERABLE LENGTH CAN BE PROVIDED AT COMPARATIVELY U M COST. FOR W000 00kl#)6m PILES. HlGH CAPACITY FOR PlPE AND HP COMPOSITE PIUS. INTERNAL INSPECTION FOR PIPE COMPOSITE PILES.
REMARKS
PROVIDES HIGH BENDING RESISTANCE WHERE UNSUPPORTED LENGTH IS LOADED LATERALLY.
THE WEAKEST OF ANY MATERIALUSED SHALL GWERN ALLOWABLE STRESSES AND CAMCITY.
-8" TO 36" DIA.
..
.. .-.
.
- --
.
TYPICAL COMBINATIONS
TYPICAL ILLUSTRATlONS
OF PIPE PILE WITH CORE SOCKET REQ'D FOR VERTICAL E m CLOSURE MAY BE OMITTED
-
TABLE 1 (continued) Design C r i t e r i a f o r Bearing P i l e s AUGER -PLACED, PRESSUREINJECTED CONCRETE PILES
PILE TYPE
CONSIDER FOR 3 0 - 6 0 FT LENGTH OF AC I 318 APPLICABLE MATERIAL SPECIFICATIONS.
-
MAXIMUM !TRESSES.
33% OF 28-DAY STRENGTH OF CONCRETE.
CONSIDER FOR DESlGN LQLID OF
35 -70 TONS
THAN AVERSE DEPENDENCE ON QUALITY ~ ~ A M Z K Z MORE S WOAKMANSHIP. NOT SUITABLE THRU PEAT OR SIMILAR HIGHLY COMPRESSIBLE MATERIAL. REWIRES RELATIVELY MORE EXTENSIVE SUBSURFACE INVESTIGATION. AMIANTAGES
ECONOMY. COMPLETE NONDISPLACEMENT. MINIMAL DRIVING VIBRATION TO ENDANGER ADJACENT STRUCTURES. HIGH SKIN FRICTION. 0000 CONTAM ON ROCK FOR END BEARING. CONVENIENT FOR U)W-HEADROOM UNDERPINNING WORK. VISUAL INSPECTION OF AUGERED MATERIAL. NO SPLICING REWIRED.
REMARKS
BEST SUITED AS A FRICTION PILE.
T Y P I C A L CROSS SECTION
TYPICAL ILLUSTRPITIONS
+*y:; ;*. F L U I D CONCRETE CAUSES EXPANSION OF P I L E D I A 3 T E H I F h%AK S O I L ZONES. S O I L IS COldPACTED AND CONSOLIDATJD.
DRILLED PILES CAN BE PROPERLY SEATED F~RM SUBSTRATA
GENERAL NOTES I. STRESSES GIVEN FOR STEEL PILES ARE FOR NONCORROSIVE LOCATIONS. FOR CORROSIVE WTIONS,ESTIMATE POSSIBLE REDUCTION IN STEEL CROSS SECTION OR PROVIDE PROTECTION FROM CORROSION. 2. LENGTHS AND LOADS INDICATED ARE FOR FEASlBlLlTY GUIDANCE WY.THEY GENERALLY REPRESENT TYPICAL CURRENT PRACTICE,GREATER LENGTHS ARE OFTEN USED. 3. OESlGN LOAD CAPACITY SHOULD BE DETER MINED BY SOIL MECHANICS PRINCIPLES, LIMITING STRESSES IN PILES,AND TYPE AND NNCTlON OF STRUCTURE.SEE TEXT
TABLE 2 C h a r a c t e r i s t i c s of Common ExcavatedIDrilled Foundations
1.
PIERS ( a l s o c a l l e d S h a f t s )
-
a.
Formed by d r i l l i n g o r e x c a v a t i n g a D e s c r i p t i o n and Procedures h o l e , removing t h e s o i l , and f i l l i n g with concrete. Casing may b e necessary f o r s t a b i l i z a t i o n , and/or t o a l l o w f o r i n s p e c t i o n and may o r may n o t be p u l l e d a s t h e c o n c r e t e i s poured. *Types i n c l u d e s t r a i g h t s h a f t p i e r s and b e l l e d o r underreamed p i e r s . Drilled s h a f t diameters a r e t y p i c a l l y 18 t o 36 i n c h e s but can exceed 8 4 inches; b e l l e d diameters vary but a r e g e n e r a l l y n o t l a r g e r t h a n 3 t i m e s t h e diameter of t h e s h a f t . Excavated p i e r s can be l a r g e r ( s h a f t diameters exceeding 12 f e e t w i t h b e l l e d diameters exceeding 30 f e e t have been c o n s t r u c t e d ) . Lengths can exceed 200 f e e t . P i e r s i z e depends on design load and allowable s o i l l o a d s .
b.
Advantages b
Completely non-displacement. Excavated m a t e r i a l can be examined and bearing s u r f a c e can be v i s u a l l y i n s p e c t e d i n cased p i e r s exceeding 30 i n c h e s i n diameter ( o r s m a l l e r using TV cameras). Applicable f o r a wide v a r i e t y of s o i l c o n d i t i o n s . P i l e caps u s u a l l y not needed s i n c e most loads can be c a r r i e d on a single pier. No d r i v i n g v i b r a t i o n . With b e l l i n g , l a r g e u p l i f t c a p a c i t i e s p o s s i b l e . Design p i e r depths and diameters r e a d i l y modified based on f i e l d conditions. Can be d r i l l e d i n t o bedrock t o c a r r y very h i g h loads.
c.
Disadvantages More than average dependence on q u a l i t y of workmanship; i n s p e c t i o n required. Danger of l i f t i n g c o n c r e t e when p u l l i n g c a s i n g can r e s u l t i n v o i d s o r i n c l u s i o n s of s o i l i n concrete. Loose granuLar s o i l s below t h e water t a b l e can cause c o n s t r u c t i o n problems.
-
TABLE 2 ( c o n t i n u e d ) C h a r a c t e r i s t i c s of Common ~ x c a v a t e d / D r i l l e dFoundations O
O
d.
B e l l u s u a l l y cannot be formed i n g r a n u l a r s o i l s below t h e w a t e r table. Small d i a m e t e r p i e r s ( l e s s t h a n 30 i n c h e s ) c a n n o t be e a s i l y i n s p e c t e d t o confirm bearing and a r e p a r t i c u l a r l y s u s c e p t i b l e t o necking problems.
Typical I l l u s t r a t i o n CASING PULLED WRING
2.
INTERNALLY-BRACED COFFERDAM I N OPEN WATER a.
D e s c r i p t i o n and Procedures e x t e n d s below mudline.
(1)
-
Generally o n l y a p p l i c a b l e i f s t r u c t u r e
Cofferdam c o n s t r u c t e d and dewatered b e f o r e pouring of foundation. (a)
I n s t a l l cofferdam and i n i t i a l b r a c i n g below water i n Cofferdam s h e e t i n g d r i v e n i n t o e x i s t i n g r i v e r / s e a bottom. bearing s t r a t a t o c o n t r o l underseepage.
(b)
Pump down water i n s i d e cofferdam.
(c)
Excavate t o bearing s t r a t u m completing b r a c i n g s y s t e m d u r i n g excavation.
(d)
C o n s t r u c t f o u n d a t i o n w i t h i n completed and dewatered cofferdam.
(e)
Guide p i l e s o r t e m p l a t e r e q u i r e d f o r d r i v i n g cofferdams.
(f)
Cofferdam designed f o r h i g h water, i c e f o r c e s , o r l o a d o f f l o a t i n g debris.
(g)
C e l l u l a r w a l l o r double-wall cofferdams w i l l e l i m i n a t e o r reduce r e q u i r e d b r a c i n g system.
TABLE 2 ( c o n t i n u e d ) C h a r a c t e r i s t i c s of Common ~ x c a v a t e d / D r i l l e dF o u n d a t i o n s
(2)
Cofferdam excavated m d e r w a t e r (a)
I n s t a l l cofferdam and i n i t i a l t r a c i n g below water+ t o e x i s t i n g r i v e r / s e a bottom.
(b)
Excavate underwater and p l a c e a d d i t i o n a l b r a c i n g t o subgrade i n b e a r i n g s t r a t u m .
(c)
S e a l bottom with t r e m i e mat of s u f f i c i e n t weight t o b a l a n c e expected h y d r o s t a t i c u p l i f t .
(d)
Pump o u t cofferdam and e r e c t remainder of f o u n d a t i o n structure.
( e ) , ( f ) and ( g ) same a s dewatered cofferdam. (h)
R e l i e f of w a t e r p r e s s u r e s below t r e m i e s l a b may be used t o d e c r e a s e weight of tremie s l a b .
-
b.
Advantages G e n e r a l l y more economical t h a n c a i s s o n s i f f o u n d a t i o n i s i n l e s s t h a n 40 f e e t of water.
c.
Disadvantages
d.
Typical I l l u s t r a t i o n
-
Requires complete dewatering o r t r e m i e mqt.
COFFERDAM EXCAVATED IN DRY
P
COFFERDAM EXCAVATED UNDER WATER
TABLE 2 ( c o n t i n u e d ) C h a r a c t e r i s t i c s of Common E x c a v a t e d l D r i l l e d F o u n d a t i o n s
3.
I
OPEN CAISSON a.
D e s c r i p t i o n and Procedure - An open box o r c i r c u l a r s e c t i o n w i t h a The c a i s s o n i s sunk i n t o p l a c e c u t t i n g shoe on i t s lower edge. under i t s own weight by removal of t h e s o i l i n s i d e t h e c a i s s o n , j e t t i n g on t h e o u t s i d e w a l l i s o f t e n used t o f a c i l i t a t e t h e p r o c e s s .
(1)
C a i s s o n s should be c o n s i d e r e d when one o r more of t h e f o l l o w i n g conditions exist : (a)
A s u b s t r u c t u r e i s r e q u i r e d t o extend t o o r below t h e r i v e r / s e a bed.
(b)
The s o i l c o n t a i n s l a r g e b o u l d e r s which o b s t r u c t p e n e t r a t i o n of p i l e s o r d r i l l e d p i e r s .
(c)
The f o u n d a t i o n i s s u b j e c t t o v e r y l a r g e l a t e r a l f o r c e s .
I f t h e s e c o n d i t i o n s do n o t e x i s t t h e u s e of a c a i s s o n i s n o t w a r r a n t e d because i t i s g e n e r a l l y more e x p e n s i v e t h a n o t h e r t y p e s of deep f o u n d a t i o n s . I n open w a t e r , i f t h e b e a r i n g s t r a t u m i s l e s s t h a n about 40 f e e t below t h e w a t e r s u r f a c e , a s p r e a d f o o t i n g f o u n d a t i o n c o n s t r u c t e d w i t h i n cofferdams i s g e n e r a l l y l e s s expensive. (2)
General method of c o n s t r u c t i o n i n c l u d e s : (a)
Float caisson s h e l l i n t o position.
(b)
B u i l d up s h e l l i n v e r t i c a l l i f t s and p l a c e f i l l w i t h i n s h e l l u n t i l i t s e t t l e s t o s e a bottom.
(c)
Continue buildup and e x c a v a t e by d r e d g i n g w i t h i n c a i s s o n s o a s t o s i n k i t through u n s u i t a b l e upper, s t r a t a .
(d)
Upon r e a c h i n g f i n a l e l e v a t i o n i n b e a r i n g s t r a t u m , pour t r e m i e base.
(e)
Provide anchorage o r g u i d e s f o r c a i s s o n s h e l l d u r i n g sinking.
(f)
F l o a t i n g and s i n k i n g o p e r a t i o n s c a n be f a c i l i t a t e d by t h e u s e of f a l s e bottoms o r temporary domes.
(g)
Dredging o p e r a t i o n s may be a s s i s t e d by t h e u s e of jets o r airlifts.
I I
I
I
TABLE 2 ( c o n t i n u e d ) C h a r a c t e r i s.*t J c s of Common ~ x c a v a t e d l ~ r i l l eFdo u n d a t i o n s
Generally a p p r o p r i a t e f o r d e p t h s exceeding 50 t o 60 f e e t and when f i n a l subgrade i n t h e b e a r i n g s t r a t u m i s n o t t h r e a t e n e d by u p l i f t from u n d e r l y i n g p e r v i o u s s t r a t a .
-
b.
Advantages
c.
Disadvantages
F e a s i b i l i t y of extending t o g r e a t d e p t h s .
Bottom of t h e c a i s s o n cannot be t h o r o u g h l y c l e a n e d and i n s p e c t e d . Concrete s e a l placed i n water i s n o t a s s a t i s f a c t o r y a s placed i n t h e dry. S o i l d i r e c t l y under t h e haunched p o r t i o n n e a r t h e c u t t i n g edges may r e q u i r e hand e x c a v a t i o n by d i v e r . C o n s t r u c t i o n i s slowed down i f o b s t r u c t i o n of b o u l d e r s o r l o g s i s encountered. d.
Typical I l l u s t r a t i o n
E
WATER LEVEL
0
SHAFTS FOR ANDCONSTRU
TREMIE
CIRCULAR TYPE
BOX TYPE
-
CROSS SECTIOP
4.
PNEUMATIC CAISSON a.
-
S i m i l a r t o a n open c a i s s o n b u t t h e box D e s c r i p t i o n and Procedure i s c l o s e d and compressed a i r i s used t o keep water and mud from flowing i n t o t h e box. Because of h i g h c o s t s , i t i s g e n e r a l l y o n l y used on l a r g e p r o j e c t s where an a c c e p t a b l e b e a r i n g s t r a t u m cannot b e reached by open c a i s s o n methods because of e x c e s s i v e d e p t h of water.
(1)
G e n e r a l l y r e q u i r e d f o r s i n k i n g t o g r e a t d e p t h s where i n f l o w of m a t e r i a l during e x c a v a t i o n can be damaging t o s u r r o u n d i n g a r e a s a n d / o r where u p l i f t i s a t h r e a t from u n d e r l y i n g p e r v i o u s strata.
TABLE 2 (continued) C h a r a c t e r i s t i c s of Common ExcavatedIDrilled foundation^ (2)
General method of c o n s t r u c t i o n i n c l u d e s : ( a ) Float caisson i n t o position. ( b ) Build up on t o p of c a i s s o n i n v e r t i c a l l i f t s u n t i l t h e s t r u c t u r e s e t t l e s t o s e a bottom. ( c ) Continue buildup and excavate beneath t h e c a i s s o n , u s i n g compressed a i r when passing through u n s t a b l e s t r a t a . ( d ) Pour c o n c r e t e base i n t h e dry upon r e a c h i n g f i n a l p o s i t i o ~ i n t h e bearing stratum. ( e ) Provide anchorage o r guides f o r c a i s s o n during s i n k i n g . For excavation i n t h e d r y , a i r p r e s s u r e i s g e n e r a l l y made equal t o t o t a l head of water above bottom of caisson.
b.
Advantages A l l work i s done i n t h e dry; t h e r e f o r e , c o n t r o l s over t h e foundation p r e p a r a t i o n and m a t e r i a l s a r e b e t t e r . Plumbness of t h e c a i s s o n i s e a s i e r t o c o n t r o l a s compared w i t h thc open caisson. O b s t r u c t i o n from boulders o r l o g s can be r e a d i l y removed. Excavation by b l a s t i n g may be done i f necessary.
c.
Disadvantages The c o n s t r u c t i o n c o s t i s h i g h due t o t h e u s e of compressed a i r . The depth of p e n e t r a t i o n below water i s l i m i t e d t o about 120 f e e t (50 p s i ) . Higher p r e s s u r e s a r e beyond t h e endurance of t h e human body. Use of compressed a i r r e s t r i c t s allowable working hours p e r man and r e q u i r e s s t r i c t s a f e t y precautions.
d.
Typical I l l u s t r a t i o n n A I R SHAFTS
WATER LEVEL?
y A l R LOCK
SEA BOT BEARING
,COMPRESSED AIR I N WORKING CHAMBER UP TO
TABLE 2 ( c o n t i n u e d ) C h a r a c t e r i s t i c s of Common ~ x c a v a t e d / D r i l l e dF o u n d a t i o n s
5.
BOX CATSSON ( F l o a t i n g C a i s s o n ) E s s e n t i a l l y a cast-on-land a. D e s c r i p t i o n and Procedure f o u n d a t i o n sunk i n t o p o s i t i o n by b a c k f i l l i n g .
-
floating
(1)
Used p r i m a r i l y f o r w h a r f s , p i e r s , bulkheads, and b r e a k w a t e r s i n water n o t more t h a n 40 f e e t deep.
(2)
General c o n s t r u c t i o n method i n c l u d e s : ( a ) P r e p a r e subgrade a t s e a bottom by d r e d g i n g , f i l l i n g , o r combination of dredging and f i l l i n g . (b) Float caisson i n t o position. ( c ) S i n k c a i s s o n t o prepared f o u n d a t i o n a t t h e s e a bottom by u s e of b a l l a s t . ( d ) Provide anchorage o r g u i d e s t o p r o t e c t f l o a t i n g c a i s s o n a g a i n s t water currents. ( e ) B a c k f i l l f o r s u i t a b l e f o u n d a t i o n should be c l e a n g r a n u l a r m a t e r i a l and may r e q u i r e compaction i n p l a c e under water.
b.
Advantages The c o n s t r u c t i o n c o s t i s r e l a t i v e l y low. B e n e f i t from p r e c a s t i n g c o n s t r u c t i o n .
c.
No dewatering necessary. Disadvantages The ground must be l e v e l o r excavated t o a l e v e l s u r f a c e .
Use i s l i m i t e d t o only t h o s e c o n d i t i o n s where b e a r i n g s t r a t u m i s c l o s e t o ground s u r f a c e . P r o v i s i o n s must be made t o p r o t e c t a g a i n s t undermining by scour. The b e a r i n g s t r a t u m must be a d e q u a t e l y compacted t o a v o i d a d v e r s e settlements.
d.
Typical I l l u s t r a t i o n
-
.
-
d. E a r t h S t a b i l i z a t i o n Columns. Many methods a r e a v a i l a b l e f o r f o r m i n g compression r e i n f o r c e m e n t elements ( s e e DM-7.3, Chapter 2 ) i n c l u d i n g : (1) lime p i l e .
Mixed-In-Place
Piles.
A mixed-in-place
soil-cement o r s o i l -
( 2 ) Vibro-Replacement Stone Columns. A v i b r o f l o t o r o t h e r d e v i c e i s used t o make a c y l i n d r i c a l , v e r t i c a l h o l e which i s f i l l e d w i t h compacted g r a v e l o r crushed rock. ( 3 ) Grouted Stone Columns. This i s s i m i l a r t o t h e above b u t i n c l u d e s f i l l i n g v o i d s w i t h bentonite-cement o r water-sand-bentonite cement mixtures. ( 4 ) Concrete Vibro Columns. i n t r o d u c e d i n s t e a d of g r a v e l . S e c t i o n 3.
S i m i l a r t o s t o n e columns b u t c o n c r e t e
BEARING CAPACITY AND SETTLEMENT
1. DESIGN PROCEDURES. The d e s i g n of a deep f o u n d a t i o n system s h o u l d i n clude t h e following s t e p s : ( 1 ) Evaluate the subsurface conditions. ( 2 ) Review t h e f o u n d a t i o n requirements i n c l u d i n g d e s i g n l o a d s and allowable settlement o r deflection. (3)
valuate t h e a n t i c i p a t e d c o n s t r u c t i o n c o n d i t i o n s and p r o c e d u r e s .
( 4 ) I n c o r p o r a t e l o c a l e x p e r i e n c e and p r a c t i c e s .
(5) S e l e c t a p p r o p r i a t e f o u n d a t i o n t y p e ( s ) based on t h e above i t e m s , c o s t s , and comments on T a b l e s 1 and 2. ( 6 ) Determine t h e a l l o w a b l e a x i a l f o u n d a t i o n d e s i g n l o a d s based on a n e v a l u a t i o n of u l t i m a t e f o u n d a t i o n c a p a c i t y i n c l u d i n g r e d u c t i o n s f o r group a c t i o n o r downdrag i f a p p l i c a b l e , a n t i c i p a t e d s e t t l e m e n t and l o c a l r e q u i r e ments and p r a c t i c e s . The a x i a l l o a d c a p a c i t y of deep f o u n d a t i o n s i s a f u n c t i o n of t h e s t r u c t u r a l c a p a c i t y of t h e l o a d c a r r y i n g member ( w i t h a p p r o p r i a t e r e d u c t i o n f o r column a c t i o n ) and t h e s o i l l o a d c a r r y i n g c a p a c i t y . Usually, t h e l a t t e r The methods a v a i l a b l e f o r e v a l u a t i n g t h e u l t i c o n s i d e r a t i o n c o n t r o l s design. mate a x i a l l o a d c a p a c i t y a r e l i s t e d below. Some o r a l l of t h e s e should b e considered by t h e d e s i g n e n g i n e e r a s a p p r o p r i a t e . (a) S t a t i c analysis u t i l i z i n g s o i l strength. ( b ) Empirical a n a l y s i s u t i l i z i n g standard f i e l d s o i l t e s t s . ( c ) B u i l d i n g code requirements and l o c a l experience.
(d) Full-scale load t e s t s . ( e ) Dynamic d r i v i n g r e s i s t a n c e . ( 7 ) Determine d e s i g n and c o n s t r u c t i o n r e q u i r e m e n t s , and i n c o r p o r a t e t h e requirements i n t o c o n s t r u c t i o n s p e c i f i c a t i o n s . I n s p e c t i o n of f o u n d a t i o n c o n s t r u c t i o n should be c o n s i d e r e d a n i n t e g r a l The p a r t of t h e d e s i g n procedures. Perform a p i l e t e s t program as r e q u i r e d . p i l e t e s t can a l s o be used a s a d e s i g n t o o l i n i t e m ( 6 ) . 2.
BEARING CAPACITY OF SINGLE PILE
a. Allowable S t r e s s e s . See Table 1 f o r a l l o w a b l e s t r e s s e s w i t h i n t h e p i l e and q u a l i t y requirements f o r p i l e m a t e r i a l s . Allowable s t r e s s e s should be reduced f o r column a c t i o n where- t h e p i l e e x t e n d s above f i r m ground, i.e. through water and v e r y s o f t bottom sediments. b. S o i l Support. The s o i l must be c a p a b l e of s u p p o r t i n g t h e element when i t i s i n compression, t e n s i o n , and s u b j e c t t o l a t e r a l f o r c e s . The s o i l s u p p o r t can be computed from s o i l s t r e n g t h d a t a , determined by l o a d t e s t s , These d e t e r m i n a t i o n s s h o u l d i n c l u d e and/or e s t i m a t e d from d r i v i n g r e s i s t a n c e . t h e following stages: ( 1 ) Design Stage. Compute r e q u i r e d p i l e l e n g t h s from s o i l s t r e n g t h d a t a t o determine bidding l e n g t h and p i l e type. ( 2 ) E a r l y i n C o n s t r u c t i o n Stage. Drive test p i l e s a t s e l e c t e d l o c a tions. For s m a l l p r o j e c t s where performance of nearby p i l e f o u n d a t i o n s i s known, base d e s i g n l e n g t h and l o a d c a p a c i t y on knowledge of t h e s o i l p r o f i l e , nearby p i l e performance, and d r i v i n g r e s i s t a n c e of t e s t p i l e s . On l a r g e proj e c t s where l i t t l e e x p e r i e n c e i s a v a i l a b l e , perform l o a d t e s t s on s e l e c t e d p i l e s and i n t e r p r e t t h e r e s u l t s a s shown i n F i g u r e 7.
( 3 ) Throughout C o n s t r u c t i o n Stage. Record d r i v i n g r e s i s t a n c e of a l l p i l e s f o r comparison w i t h t e s t p i l e s and t o i n s u r e a g a i n s t l o c a l weak subsurf a c e formations. Record a l s o t h e type and c o n d i t i o n of c u s h i o n i n g m a t e r i a l used i n t h e p i l e hammer. c. T h e o r e t i c a l Load Capacity. See F i g u r e 1 f o r a n a l y s i s of u l t i m a t e l o a d c a r r y i n g c a p a c i t y of s i n g l e p i l e s i n homogeneous g r a n u l a r s o i l s ; f o r p i l e i n homogeneous c o h e s i v e s o i l s e e F i g u r e 2 (upper p a n e l r i g h t , Reference 2, The Bearing Capacity of Clays, by Skempton; remainder of f i g u r e , Reference 3, The Adhesion of P i l e s Driven i n Clay S o i l s , by Tomlinson). ( 1 ) Compression Load Capacity. Compression l o a d c a p a c i t y e q u a l s end-bearing c a p a c i t y , p l u s f r i c t i o n a l c a p a c i t y on p e r i m e t e r s u r f a c e . ( 2 ) P u l l o u t Capacity. P u l l o u t c a p a c i t y e q u a l s t h e f r i c t i o n a l f o r c e on t h e p e r i m e t e r s u r f a c e of t h e p i l e o r p i e r .
"'. \' \
Y3 BEARING STRATUM I, C
7P B
PRESSURE DIAGRAM K H c P ~ AND K H ~ P o
( A) ULTIMATE LOAD CAPACITY IN COMPRESSION
Quit = PT Nq AT
H=HotD (KHcXP~TAN8 ) ( ~ ) H = HO
+C
WHERE
Quit 'ULTIMATE LOAD CAPACITY IN COMPRESSDN PT = EFFECTIVE VERTICAL STRESS AT PlLE TIP (SEE NOTE I ) Nq = BEARING CAPACITY FKTOR (SEE TABLE, FIGURE I CONTINUED ) AT = AREA OF PlLE TIP KHC= RATIO OF HORIZNTAL TO VERTICAL EFFECTIVE STRESS ON SIDE OF ELEMENT WHEN ELEMENT IS IN COMPRESSION. Po = EFFECTIVE VERTICAL STRESS OVER LENGTH OF EMBEDMENT, D (SEE NOTE I) 8 = FRICTION ANGLE BETWEEN PILE AND SOIL (SEE TABLE, FIGURE ICONTINUED) S = SURFACE AREA OF PlLE PER UNIT LENGTH FOR CALCULATING Qall ,USE FS OF 2 FOR TEMPORARY LOADS, 3 FOR PERMANENT WDS.(SEE NOTE 2) (8) ULTIMATE LOAD CAPACITY IN TENSION H=Ho+D Tult'
C H=Ho
(KH~)(P0)(TAN8) (s)(H)
WHERE: Tult = ULTIMATE LOAD CAPACITY IN TENSION, PULLOUT KHT = RATIO OF HORIZONTAL TO VERTICAL EFFECTIVE STRESS ON SlDE OF ELEMENT WHEN ELEMENT IS IN TENSION
V+wp
USE FS = 3 ONTul+ PLUS THE WEIGHT OFTHE PIG (Wp),THUS Tall = (SEE NOTE 2 NOTE-I :EXPERIMENTAL AND FIEU) EVIDENCE INDICATE THAT BEARING PRESSURE AND SKIN FRICTION INCREASE WITH VERTICAL EFFECTIVE STRESS Po UPTO A LIMITING DEPTH WEMBEDMENT, DEPENDING ON THE RELATIVE DENSITY OFTHE GRANULAR SOIL AND POSITION OF THE WATER TABLE. BEYOND THIS LIMITING DEPTH ( IOB k TO 4 0 8 ) THERE IS VERY LITTLE INCREASEIN END BEARING, AND INCREASE IN SlDE FRICTION IS DIRECTLY PROPORTIONALTOM E SURFACE AREAOF THE PILE. THEREFORE,IF D IS GREATER THAN 20 9, Ll MlT Po AT THE PlLE TIP TO THAT VALUE CORRESPONDING TO D = 209. NOTE.2: IF BUILDING LOADS AND SUBSURFACE CONDITION ARE WELL DOCUMENTED IN THE OPINION OF THE ENGINEER, A LESSER FACTOR OF SAFETY CAN BE USED BUT NOT LESS THAN 2.0 PROVIDED PlLE CAPACITY IS MRlFlED BY LOAD TEST AND SETTLEMENTS ARE ACCEPTABLE. FOR CALCULATING Tall
I
*
FIGURE 1 Load Carrying Capacity of S i n g l e P i l e i n Granular S o i l s
BEARING CAPACITY FACTORS - Nq >
I
di*
26
Nq (DRIVENP~~E 10 DISPLKEMENT)
**
Nq (DRILLED PIERS)
5
28 30 31 32 33
34
35
36
37
39
38
40
15
21
a
29 35
42
50
62
n as
I
146
8
I0
I2
14 17
21
25
30
38
60
72
.
.
2
43
A
b
EARTH PRESSURE COEFFICIENTS KHC AND KHT J
PILE TYPE
K HT
KHC
DRIVEN SINGLE H -PILE
0.5
- 1.0
0.3
- 0.5
DRIVEN SINGLE DISPLACEMENT PlLE
1.0
- 1.5
0.6
- 1.0
DRIVEN SINGLE DISPLACEMENT TAPERED PlLE
1.5
-
2.0
1.0
-
DRIVEN JETTED PILE
0.4
-
0.9
0.3
- 0.6
1.3
I
w
DRILLED PILE (LESS THAN 24" DIAMETER)
.
FRICTION ANGLE
-8
.
>
PILE TYPE
8
STEEL
20°
CONCRETE
3wj
TIMBER
v4
b
* **
0.4
0.7
+
4
UMlT TO 28' IF JETTING IS USED (A) IN CASE A BAILER OR GRAB BUCKET IS USED BELOW GROUNDWATERTABLE,CALCULATE END BEARING BASED ON NOT EXCEEDING 28'. (0) FOR PIERS GREATER THAN 24-INCH DIAMETER,SETTLEMENT RATHER THAN BEARING CAPACITY USUALLY CONTROLS THE DESIGN. FOR ESTIMATING SETTLEMENT, TAKE 50% OF THE SETTLEMENT FOR AN EQUIVALENT FOOTING RESTING ON THE SURFACE OF COMPARABLE GRANULAR SOILS. (CHAPTER 5 ,DM -7. I).
#
.
.-
FIGURE 1 (continued) Load Carrying Capacity of Single P i l e i n Granular S o i l s
.
BEARING STRATUM 165 PCF DENSE SAND ,
EFFECTIVE VERTICAL STRESS, Po, FOR PILE DESIGN FOR A DIAMETER CLOSED END, DRIVEN P I E PILE, CONCRETE FILLED, FIND Qdl A =FOOT LONG PILE. Po MAX OCCURS AT 208, OR 20' INTO BEARING STRATUM. 30°, Nq = 21 KHC=1.5,8 = 20° KHT = 10 . AT = r X 0.5?=0.78 SF CIRCUM. AREA/If = IX r =3.14SF/If
AND Tal
FOR
+=
Quit
'1.535 ~ 2 x0.78+ 1
( 1.5 X(0'235;1.535
1
) x TAN 20 ~20x314)t (1.5 xL535xTAN 20 x 5~3.14)
-
~68.64K FOR Fs =3,0qll TUlt = 1.0 x ( 0'235
=2
68 64 3
= 22.9 K
+
) x TAN 20x20~314 1.0 x 1.535 xTAN 20x 5 x 3.14
FIGURE 1 ( c o n t i n u e d ) Load Carrying Capacity of S i n g l e P i l e i n Granular S o i l s
1.25
Y .n 4
s
.SO
.25
1
I
0
500
1000 I500 2000 COHESION C, PSF
2500
JOOO
I I1 I
POSITION OF GROUND
ONLY. PILE WEIGHT IS BALANCED BY WEIGHT OF OVERBURDEN AND IS NOT CONSIDERED.
(Nee)
I
1
I
1
4
PILE TYPE
~~ONSIS~YCT OF SOIL
TIMBER
1 SOFT
,C
0
VERY SOFT
1
250
-
IADHESION~ I
250 500
PSF
0
1
250
- 250
- 480
-
QuH IS APPLIED LO*D
Quit =c ( N s ) T R ~ + Q 2 r R ~
I
RECOMMENDED VALUES OF ADHESON
WNER HAS NO EFFECT ON ULTIMATE WAD CAPACITY UNLESS COHESION IS CHANGED.
ULTIMATE L M D CAPACITY IN COMPRESSION
I
I
I 2 3 RATIO OF DEPTH TO WIDTH FOUNMTION Z / B OR Z/2R
0 0
WITH WIDTH, &AND LENGTH, L,THE BEARING CAPACIM FACTOR IS NCR = NCC ( 1+0.2 B/L)
VERY SOFT STEEL
-
250
-
250 250-460
SOFT
0 250-
MED. STIFF
500-1000
460-700
STIFF
DOO-2000
700-720
2000-4000
720-750
VEmm
500
0
ULTIMATE LOAD CAPACITY IN TENSION Tult = CA 2 r R z Tu(t UNDER SUSTAINED LOAD MAY BE LIMITED BY OTHER FACTORS, SEE TEXT.
vTS1JPF 2 U l t i m a t e Load Canacity of S i n g l e P i l e or P i e r i n Cohesive Soils
I1
( 3 ) D r i l l e d P i e r s . For d r i l l e d p i e r s g r e a t e r t h a n 24 i n c h e s i n A reduced end diameter s e t t l e m e n t r a t h e r t h a n b e a r i n g c a p a c i t y may c o n t r o l . b e a r i n g r e s i s t a n c e may r e s u l t from entrapment of b e n t o n i t e s l u r r y i f used t o m a i n t a i n a n open e x c a v a t i o n t o t h e p i e r ' s t i p . Bells, o r enlarged bases, a r e usually not s t a b l e i n granular s o i l s . ( 4 ) P i l e s and D r i l l e d P i e r s i n Cohesive S o i l s . See F i g u r e 2 and Table 3. Experience demonstrates t h a t p i l e d r i v i n g permanently alters s u r f a c e adhesion of c l a y s having a s h e a r s t r e n g t h g r e a t e r t h a n 500 p s f ( s e e F i g u r e 2). I n s o f t e r c l a y s t h e remolded m a t e r i a l c o n s o l i d a t e s with t i m e , r e g a i n i n g adhesion approximately e q u a l t o o r i g i n a l s t r e n g t h . Shear s t r e n g t h For f o r point-bearing r e s i s t a n c e i s e s s e n t i a l l y unchanged by p i l e d r i v i n g . d r i l l e d p i e r s , u s e Table 3 from Reference 4, S o i l s and Geology, P r o c e d u r e s f o r Foundation Design of B u i l d i n g s and Other S t r u c t u r e s , by t h e Departments of Army and A i r Force, f o r determining s i d e f r i c t i o n . Ultimate r e s i s t a n c e t o p u l l o u t cannot exceed t h e t o t a l r e s i s t a n c e of reduced adhesion a c t i n g o v e r t h e p i l e s u r f a c e o r t h e e f f e c t i v e weight of t h e s o i l mass which i s a v a i l a b l e t o r e a c t a g a i n s t p u l l o u t . The a l l o w a b l e s u s t a i n e d p u l l o u t l o a d u s u a l l y i s l i m i t e d by t h e tendency f o r t h e p i l e t o move upward g r a d u a l l y w h i l e m o b i l i z i n g a n adhesion l e s s t h a n t h e f a i l u r e value. Adhesion f a c t o r s i n F i g u r e 2 may be v e r y c o n s e r v a t i v e f o r e v a l u a t i n g p i l e s d r i v e n i n t o s t i f f but normally c o n s o l i d a t e d c l a y s . A v a i l a b l e d a t a s u g g e s t s t h a t f o r p i l e s d r i v e n i n t o normally t o s l i g h t l y o v e r c o n s o l i d a t e d c l a y s , t h e s i d e f r i c t i o n i s about 0.25 t o 0.4 t i m e s t h e e f f e c t i v e overburden.
( 5 ) P i l e s P e n e t r a t i n g Multi-layered S o i l P r o f i l e . Where p i l e s p e n e t r a t e s e v e r a l d i f f e r e n t s t r a t a , a simple approach i s t o add s u p p o r t i n g c a p a c i t y of t h e i n d i v i d u a l l a y e r s , e x c e p t where a s o f t l a y e r may c o n s o l i d a t e and r e l i e v e l o a d o r cause drag on t h e p i l e . For f u r t h e r guidance on b e a r i n g c a p a c i t y when a p i l e p e n e t r a t e s l a y e r e d s o i l and t e r m i n a t e s i n g r a n u l a r s t r a t a s e e Reference 5, U l t i m a t e Bearing Capacity of Foundations on Layered S o i l s Under I n c l i n e d Loads, by Meyerhoff and Hanna, which c o n s i d e r s t h e u l t i m a t e b e a r i n g c a p a c i t y of a deep member i n sand underlying a c l a y l a y e r and f o r t h e c a s e of a sand b e a r i n g s t r a t u m o v e r l y i n g a weak c l a y l a y e r .
( 6 ) P i l e Buckling. For f u l l y embedded p i l e s , b u c k l i n g u s u a l l y i s n o t a problem. For a f u l l y embedded, f r e e headed p i l e w i t h l e n g t h e q u a l t o o r g r e a t e r t h a n 4T, t h e c r i t i c a l l o a d f o r buckling i s a s f o l l o w s ( a f t e r Reference 6 , Design of P i l e Foundations, by Vesic): Pcrit where :
Pcrit
= 0.78 ~~f
f o r L> - 4T
= c r i t i c a l l o a d f o r buckling
f = c o e f f i c i e n t of v a r i a t i o n of l a t e r a l s u b g r a d e r e a c t i o n ( s e e Figure 10) T = r e l a t i v e s t i f f n e s s f a c t o r ( s e e F i g u r e 10) L = l e n g t h of p i l e .
TABLE 3 Design Parameters f o r S i d e F r i c t i o n f o r D r i l l e d P i e r s i n Cohesive S o i l s L
Side Resistance Design Category A.
B.
cA/~
Limit on s i d e s h e a r
-
tsf
Remarks
Straight-sided s h a f t s i n e i t h e r homogeneous o r l a y e r e d s o i l w i t h no s o i l of e x c e p t i o n a l s t i f f n e s s below t h e base 1.
S h a f t s i n s t a l l e d d r y o r by t h e s l u r r y displacement met hod
0.6
2.
S h a f t s i n s t a l l e d with d r i l l i n g mud a l o n g some p o r t i o n of t h e h o l e w i t h p o s s i b l e mud entrapment
0.3(a)
( a ) CA/C may b e i n c r e a s e d t o 0.6 and s i d e s h e a r i n c r e a s e d t o 2.0 t s f f o r segments d r i l l e d dry
Belled s h a f t s i n e i t h e r homogeneous o r l a y e r e d c l a y s w i t h no s o i l of e x c e p t i o n a l s t i f f n e s s below t h e base 1. 2.
S h a f t s i n s t a l l e d d r y o r by t h e s l u r r y displacement methods
0.3
S h a f t s i n s t a l l e d with d r i l l i n g mud along some p o r t i o n of t h e h o l e w i t h p o s s i b l e mud entrapment
0.15(b)
( b ) CA/c may be i n c r e a s e d t o 0.3 and s i d e s h e a r i n c r e a s e d t o 0.5 t s f f o r segments d r i l l e d dry
TABLE 3 ( c o n t i n u e d ) Design Parameters f o r S i d e F r i c t i o n f o r D r i l l e d P i e r s i n Cohesive S o i l s
Side Resistance Design Category
C.
D.
Note:
CA/~
S t r a i g h t - s i d e d s h a f t s with b a s e r e s t i n g on s o i l s i g n i f i c a n t l y s t i f f e r t h a n s o i l around s t em
0
B e l l e d s h a f t s w i t h base r e s t i n g on s o i l s i g n i f i c a n t l y s t i f f e r t h a n s o i l around stem
0
Limit on s i d e s h e a r
-
tsf
Remarks
0
I n c a l c u l a t i n g load c a p a c i t y , exclude: (1) t o p 5 f e e t of d r i l l e d s h a f t : ( 2 ) p e r i p h e r y of b e l l : and ( 3 ) bottom 5 f e e t of s t r a i g h t s h a f t and bottom 5 f e e t of stem of s h a f t above b e l l .
For p i l e s w i t h t h e head f i x e d a g a i n s t r o t a t i o n and t r a n s l a t i o n , i n c r e a s e Pcrit by 13%. I f t h e p i l e head i s pinned (i.e. prevented from t r a n s l a t i o n but f r e e t o r o t a t e ) , i n c r e a s e Pcrit by 62%. For a p a r t i a l l y embedded p i l e , assume a f r e e s t a n d i n g column f i x e d a t depth 1.8T below t h e s o i l surface. Compute t h e c r i t i c a l buckling l o a d by methods of s t r u c t u r a l a n a l y s i s . For such p i l e s compute a l l o w a b l e p i l e s t r e s s e s t o avoid buckling. For t h e c a s e where t h e c o e f f i c i e n t of l a t e r a l subgrade r e a c t i o n (Kh) of t h e embe merit s o i l is c o n s t a n t w i t h depth, calcul a t e t h e depth of f i x i t y a s 1 . 4 ~ 4 , h e r t i E I is t h e f l e x u r a l r i g i d i t y o f t h e p i l e , B is p i l e width (diameter) and Kh i s defined i n t h e u n i t s of f o r a f u l l y embedded l e n g t h of o t h e r p i l e types ~ o r c e ~ ~ e n g t Buckling h~. does not c o n t r o l p i l e s t r e s s . For f u r t h e r guidance see Reference 6. d. Empirical Bearing Capacity. R e s u l t s from t h e Standard P e n e t r a t i o n Test, S t a t i c Cone penetrometer (Dutch Cone with f r i c t i o n s l e e v e ) , and Pressuremeter have been c o r r e l a t e d w i t h model and f u l l s c a l e f i e l d tests on p i l e s and deep foundations s o t h a t e m p i r i c a l expressions a r e a v a i l a b l e t o estimate foundation c a p a c i t i e s . ( 1 ) Standard Penetration. Use of t h e Standard P e n e t r a t i o n T e s t t o p r e d i c t c a p a c i t i e s of deep foundations should be l i m i t e d t o g r a n u l a r s o i l s and must be considered a crude estimate. Tip Resistance of d r i v e n p i l e s ( a f t e r Reference 7, Bearing Capacity and Settlement of P i l e Foundations, by Meyerhof): q ult
where : N = standard p e n e t r a t i o n r e s i s t a n c e ( b l o w l f t ) near p i l e t i p 20 ( f o r p> 0.25 TSF) CN = 0.77 l o g l o P
-
-
p = e f f e c t i v e overburden stress a t p i l e t i p (TSF) quit =
u l t i m a t e p o i n t r e s i s t a n c e of d r i v e n p i l e (TSF)
-
N = average c o r r e c t e d Standard P e n e t r a t i o n R e s i s t a n c e near p i l e t i p ( b l o w s l f t )
D = depth d r i v e n i n t o g r a n u l a r bearing s t r a t u m ( f t ) B = width o r diameter of p i l e t i p ( f e e t )
q 1 = l i m i t i n g p o i n t r e s i s t a n c e (TSF), equal t o 4N f o r sand and 3N f o r non-plastic s i l t .
For d r i l l e d p i e r s , use 113 times
quit
computed from t h e above
expression.
-
.
t ance
..
Use a f a c t o r of s a f e t y of 3 t o compute allowable t i p resis-
Skin F r i c t i o n of d r i v e n p i l e s :
where :
N = average standard p e n e t r a t i o n along p i l e s h a f t
f s = u l t i m a t e s k i n f r i c t i o n f o r d r i v e n p i l e (TSF) f l = l i m i t i n g s k i n f r i c t i o n ( f o r d r i v e n p i l e , f l = 1 TSF) Use f a c t o r of s a f e t y of 3 f o r allowable s k i n f r i c t i o n . For d r i v e n p i l e s tapered more t h a n 1 p e r c e n t , use 1.5 t i m e s above expression. For d r i l l e d p i e r s , use 50 p e r c e n t of above expression ( 2 ) The Cone Penetrometer. The Cone Penetrometer provides u s e f u l information a s a "model p i l e " and i s b e s t s u i t e d f o r l o o s e t o dense sands and s i l t s . Penetrometer r e s u l t s a r e not considered a c c u r a t e f o r very dense sands o r d e p o s i t s with gravel. Point Resistance: quit where :
quit
= qc
= ultimate t i p resistance for driven p i l e
qc = cone p e n e t r a t i o n r e s i s t a n c e Depth of p e n e t r a t i o n t o g r a n u l a r bearing s t r a t u m i s a t l e a s t 1 0 times t h e p i l e t i p width. S h a f t Resistance : fult where:
=
fC
f u l t = u l t i m a t e s h a f t f r i c t i o n of d r i v e n c y l i n d r i c a l p i l e f c = u n i t r e s i s t a n c e of l o c a l f r i c t i o n s l e e v e of s t a t i c penetrometer Use f a c t o r of s a f e t y of 3 f o r allowable s k i n f r i c t i o n .
For d r i l l e d p i e r s i n cohesionless s o i l , u s e 1/2 of £,I+ o r based on t h e above expressions f o r d r i v e n p i l e s .
quit.
(3) Pressuremeter. R e s u l t s from pressuremeter t e s t s can be used t o e s t i m a t e d e s i-m c a v a c i t v of deep foundation elements. See Reference 8.= - The Pressuremeter and Foundation Engineering, by Baguelin, e t a l . , o r Reference 9, Canadian Foundation Engineering Manual, by t h e Canadian Geotechnical S o c i e t y , f o r d e t a i l s of design c o r r e l a t i o n . The pressuremeter method i s u s e f u l i n s o f t rock, weathered o r c l o s e l y jointed rock, g r a n u l a r s o i l s , and very s t i f f cohesive s o i l s . R e s u l t s a r e g e n e r a l l y not s u i t a b l e i n s o f t c l a y s because of t h e d i s t u r b a n c e during d r i l l i n g . The self-boring pressuremeter i s designed t o reduce t h i s problem.
e.
Bearing Capacity from Dynamic Driving Resistance.
(1) General. The u l t i m a t e c a p a c i t y of a p i l e may be estimated on t h e b a s i s of d r i v i n g r e s i s t a n c e during i n s t a l l a t i o n ' o f t h e p i l e . The r e s u l t s a r e not always r e l i a b l e , and may over-predict o r g r o s s l y under-predict p i l e c a p a c i t i e s , and t h e r e f o r e should be used with caution. Use must be supported Dynamic r e s i s t a n c e based on t h e wave e q u a t i o n by l o c a l experience o r t e s t i n g . a n a l y s i s i s a more r a t i o n a l approach t o c a l c u l a t i n g p i l e c a p a c i t i e s . (2)
P i l e Driving Formulas:
( a ) General. Because of t h e u n c e r t a i n t i e s of t h e dynamics of p i l e d r i v i n g , t h e use of formulas more e l a b o r a t e than those i n Table 4 i s n o t warranted. A minimum of t h r e e test p i l e s should be d r i v e n f o r each i n s t a l l a t i o n , with more t e s t s i f subsurface c o n d i t i o n s a r e e r r a t i c . ( b ) Control During Construction. The embedment of p i l e s should be c o n t r o l l e d by s p e c i f y i n g a minimum t i p e l e v a t i o n on t h e b a s i s of t h e subs u r f a c e p r o f i l e and d r i v i n g t e s t s o r load t e s t s , i f a v a i l a b l e , and a l s o by r e q u i r i n g t h a t t h e p i l e s be d r i v e n beyond t h e s p e c i f i e d e l e v a t i o n u n t i l t h e d r i v i n g r e s i s t a n c e equals o r exceeds t h e value e s t a b l i s h e d a s necessary from t h e r e s u l t s of t h e t e s t p i l e s . However, i f t h e p i l e p e n e t r a t i o n c o n s i s t e n t l y overruns t h e a n t i c i p a t e d depth, t h e b a s i s f o r t h e s p e c i f i e d depth and d r i v i n g r e s i s t a n c e should be reviewed. ( c ) Formulas. Dynamic p i l e d r i v i n g formulas should not be used a s c r i t e r i a f o r e s t a b l i s h i n g load c a p a c i t y without c o r r e l a t i o n with t h e res u l t s of an adequate program of s o i l e x p l o r a t i o n . For c r i t i c a l s t r u c t u r e s and where l o c a l experience i s l i m i t e d , o r where u n f a m i l i a r p i l e types o r equipment a r e being used, load t e s t s should be performed.
( 3 ) Wave Equation Analysis. The wave equation a n a l y s i s i s based on For t h e a n a l y s i s t h e p i l e i s t h e theory of one dimensional wave propagation. divided i n t o a s e r i e s of masses connected by s p r i n g s which c h a r a c t e r i z e t h e p i l e s t i f f n e s s , and dashpots which s i m u l a t e t h e damping below t h e p i l e t i p and along p i l e embedded length. T h i s method was f i r s t put i n t o p r a c t i c a l form i n 1962 (Reference 10, P i l e Driving by t h e Wave ~ ~ u a t i o hby, ~ m i i h ) . The wave equation a n a l y s i s provides a means of e v a l u a t i n g t h e s u i t a b i l i t y of t h e p i l e s t i f f n e s s t o t r a n s m i t d r i v i n g energy t o t h e t i p - t o achieve p i l e - p e n e t r a t i o n , a s w e l l a s t h e a b i l i t y of p i l e s e c t i o n t o withstand d r i v i n g s t r e s s e s without damage. The r e s u l t s of t h e a n a l y s i s can be t n t e r p r e t e d t o g i v e t h e following:
4
TABLE 4 Application of P i l e Driving Resistance Formulas BASIC PlLE DRIVING FORMULAS (SEE COMMENT IN SECTION 2 )
-
FOR DROP HAMMER
I
FOR SINGLE ACTING HAMMER
2WH {USE WHEN D R M N W E m Qall= S+O.I
FOR DOUBLE-ACTING DlFFEREHllAL HAMMER
Pall = *{USE
ARE SMALLER THAN STRIKING WEIGHTS.
2 WH
Qa11' s+l QaW
WH S+O.I- WD
{ USE WHEN DRIVEN WEIGHTS
Ws
ARE LARGER THAN STRIKING WEIGHTS.
2E
all=
S+O.l-
Ws
WHEN DRIVEN WEIGHTS AR SMALLER THEN STRIKING WEIGHTS. {USE WHEN DRIVEN WEIGHTS ARE LARGER THAN STRIKING WEIGHTS.
Qall = ALLOWABLE PlLE LOAD IN POUNDS.
= WEIGHT OF STRIKING
W H E S WD WS
= = = = =
PARTS OF HAMMER IN POUNDS. THE EFFECTIVE HEIGHT OF FALL IN FEET. THE ACTUAL ENERGY DELIVERED BY HAMMER PER BLOW IN FOOT- POUNDS. AVERAGE NET PENETRATION IN INCHES PER BLOW FOR THE LAST 6 IN. OF DRIVING. DRIVEN WEIGHTS NOTE: RATIO OF DRIVEN WEIGHTS TO STRIKING WEIGHTS SHOULD NOT WEIGHTS OF STRIKING B W S EXCEED 3.
1
MODIFICATONS OF BASIC PlLE DRIVING FORMULAS A. FOR PILES DRIVEN TO AND SEATED IN ROCK AS HIGH CAPACITY END-BEARING PILES: DRIVE TO REFUSAL (APPROXIMATELY 4 TO 5 BLOWS FOR THE LAST QUARTER INCH OF DRIVING). REDRIVE OPEN END PIPE PILES REPEATEDLY UNTIL RESISTANCE FOR REFUSAL IS REACHED WITH IN I IN. OF ADDITIONAL PENETRATION. 8. PILES DRIVEN THROUGH STIFF COMPRESSIBLE MATERIALS UNSUITABLE FOR PlLE BEARING TO AN UNDERLYlNG BEARING STRATUM : ADD BLOWS ATTAINED BEFORE REACHING BEARING STRATUM TO REQUIRED BU)WS ATTAINED IN BEARING STRATUM (SEE EXAMPLE). PILE EXAMPLE: REQUIRED LOAD W I T Y OF PlLE Qall =25TONS HAMMER ENERGY ////Ip E = 15,000 FT.-LB.
fi
-
COMPRESS1BLE
v/"/"/>;
-
..-....-:. :.:.:: i....
:.'BEARING . ::.STRATUM
-
... ....;...:.;.-; . ..... .::...::::.::..
~
wd ( I ws
PENETRAm(S) AS PER BASlC FORMULA = 1/2" OR 2 BUWS PER
4 BU)WS/FT: 2
INCH (24 BUIWS/FT). REQUIRED BLOWS FOR PILE 24 + I8 = 42 BUIWS/FT. I
C. PILES DRIVEN INTO LIMITED THIN BEARING STRATUM, DRIVE TO PREDETERMINED TIP ELEVATION. DETERMINE ALIDWABLE IDAD BY U)AD TEST.
STRATUM
LBUJ UNSUITABLE FWZ P O W BEARING
( a ) Equipment compatibility:,appropriate
hammer s i z e and
cushion. (b) Driving s t r e s s e s : p l o t s of stress vs. set can be made t o evaluate the potential f o r p i l e overstress. ( c ) P i l e capacity:
p l o t of u l t i m a t e p i l e c a p a c i t y vs. set can
be developed. The s o i l i s modeled by approximating t h e s t a t i c r e s i s t a n c e (quake), t h e viscous r e s i s t a n c e (damping), and t h e d i s t r i b u t i o n of t h e s o i l r e s i s t a n c e along t h e p i l e . The assigned parameter f o r s p r i n g s and dashpots cannot be r e l a t e d t o r o u t i n e l y measured s o i l parameters which c o n s t i t u t e s t h e major draw back of t h e wave equation a n a l y s i s . The i n p u t f o r t h e d r i v i n g system i s provided by t h e a n t i c i p a t e d hammer performance, c o e f f i c i e n t of r e s t i t u t i o n of t h e cushion, and s t i f f n e s s of t h e p i l e . Computer programs a r e a v a i l a b l e t o perform t h e lengthy c a l c u l a t i o n s .
( 4 ) Case Method. The wave equation a n a l y s i s can be used i n conjunct i o n with f i e l d measurements by using t h e Case Method (Reference 11, S o i l Resistance P r e d i c t i o n s from P i l e Dynamics, by Rausche, e t a l . ) . This procedure e l e c t r o n i c a l l y measures t h e a c c e l e r a t i o n and s t r a i n n e a r t h e top of .the p i l e , and by usingv t h e wave equation a n a l y s i s e s t i m a t e s t h e s t a t i c s b i l r e s i s tance f o r each blow of t h e hammer. Energy t r a n s f e r r e d t o t h e p i l e i s computed by i n t e g r a t i n g t h e product of f o r c e and v e l o c i t y . A d i s t r i b u t i o n of t h e s o i l r e s i s t a n c e along t h e p i l e l e n g t h i s assumed and t h e wave equation a n a l y s i s i s performed. The assumed s o i l s t r e n g t h parameters a r e checked a g a i n s t t h e measured f o r c e a t t h e p i l e top and t h e s e a r e then a d j u s t e d t o r e s u l t i n a n i m proved match between t h e a n a l y t i c a l and measured p i l e f o r c e a t t h e top.
-
3.
BEARING CAPACITY OF PILE GROUPS.
a. General. The bearing c a p a c i t y of p i l e groups i n s o i l s i s normally l e s s than t h e sum of i n d i v i d u a l p i l e s i n t h e group and must be considered i n design. Group e f f i c i e n c y i s a term used f o r t h e r a t i o of t h e c a p a c i t y of a p i l e group t o t h e sum of t h e c a p a c i t i e s of s i n g l e p i l e s a t t h e same depth i n t h e same s o i l d e p o s i t . I n e v a l u a t i n g t h e performance of p i l e groups i n compression, s e t t l e m e n t i s a major consideration. Expressions f o r e s t i m a t i n g u p l i f t r e s i s t a n c e of p i l e groups a r e included i n t h i s s e c t i o n . b. Group Capacity i n Rock. The group c a p a c i t y of p i l e s i n s t a l l e d t o rock i s t h e number of members times t h e i n d i v i d u a l c a p a c i t y of each member. Block f a i l u r e i s a c o n s i d e r a t i o n only i f foundations a r e on a s l o p i n g rock formation, and s l i d i n g may occur along unfavorable dipping, weak planes. The p o s s i b i l i t y of such a n occurrence must be evaluated from t h e s i t e geology and f i e l d exploration. c. Group Capacity i n Granular S o i l . P i l e s d r i v e n i n t o c o h e s i o n l e s s s o i l i n a group c o n f i g u r a t i o n a c t a s i n d i v i d u a l p i l e s i f t h e spacing i s g r e a t e r than 7 times t h e average p i l e diameter. They a c t a s a group a t c l o s e spacings. Center t o c e n t e r spacing of a d j a c e n t p i l e s i n a group should be a t l e a s t two times t h e b u t t diameter.
-
Block f a i l u r e of a p i l e group i n g r a n u l a r s o i l s i s n o t a d e s i g n cons i d e r a t i o n provided each i n d i v i d u a l p i l e has an adequate f a c t o r of s a f e t y a g a i n s t bearing f a i l u r e and t h e c o h e s i o n l e s s s o i l i s n o t u n d e r l a i n by a weaker d e p o s i t . I n l o o s e sand a n d / o r g r a v e l d e p o s i t s , t h e l o a d c a r r y i n g c a p a c i t y of a n i n d i v i d u a l p i l e may be g r e a t e r i n t h e group t h a n s i n g l e because of d e n s i f i c a t i o n d u r i n g d r i v i n g . T h i s i n c r e a s e d e f f i c i e n c y s h o u l d be i n c l u d e d i n d e s i g n w i t h c a u t i o n , and o n l y where demonstrated by f i e l d e x p e r i e n c e o r t e s t s . The u l t i m a t e c a p a c i t y of a p i l e group founded i n dense c o h e s i o n l e s s s o i l of l i m i t e d t h i c k n e s s u n d e r l a i n by a weak d e p o s i t i s t h e s m a l l e r o f : (1)
sum of t h e s i n g l e p i l e c a p a c i t i e s
( 2 ) block f a i l u r e of a p i e r e q u i v a l e n t i n s i z e t o t h e p i l e s a n d enclosed s o i l mass, punching through t h e dense d e p o s i t i n t o t h e u n d e r l y i n g weak d e p o s i t (Reference 12, U l t i m a t e Bearing Capacity of F o o t i n g s on Sand Layer Overlying Clay, by Meyerhof). d. Group C a p a c i t y i n Cohesive S o i l . E s t i m a t e t h e group c a p a c i t y u s i n g he method i n F i g u r e 3 (upper p a n e l , Reference 13, Experiments w i t h Model P i l e s i n Groups, by Whitaker). e.
U ~ l i f tR e s i s t a n c e of G ~ O U D S .
(1) l e s s e r of:
Granular Soil.
U l t i m a t e u p l i f t r e s i s t a n c e of p i l e group i s
( a ) Sum of s k i n f r i c t i o n on t h e p i l e s i n t h e group (no reduct i o n f o r t a p e r e d p i l e s ) , u s e a f a c t o r of s a f e t y of 3.0. ( b ) E f f e c t i v e weight of block of s o i l w i t h i n t h e group and w i t h i n a 4 v e r t i c a l on 1 h o r i z o n t a l wedge extending up from p i l e t i p s weight of p i l e s ' assumeil e q u a l t o volume of s o i l they d i s p l a c e . F a c t o r of s a f e t y should be u n i t y .
-
(2) l e s s e r of:
Cohesive S o i l .
(a)
where:
Ultimate u p l i f t r e s i s t a n c e of p i l e group i s t h e
Sum of s k i n f r i c t i o n on t h e p i l e s i n t h e group
Tu = u l t i m a t e u p l i f t r e s i s t a n c e of p i l e group A = l e n g t h of group B = width of group
L = d e p t h of s o i l block below p i l e cap C = average undrained s t r e n g t h of s o i l around t h e s i d e s of t h e group Wp = weight of p i l e s , p i l e cap, and block of s o i l e n c l o s e d by t h e piles.
d
3 x 3 PILE GROUP
3 x 3 PlLE GRWP 9 x 9 PlLE GROUP
PlLE GROUP EFFICIENCY FOR COHESIVE SOILS
a 1.5
2O .
2.5 3.O SPACING IN PILE DIAMETERS
3.5
4.0
4.5
PERIMETER
pO""l
PlLE SPACING
DEFlNITIONS QG = ULTIMATE LOAD CAMITY OF PlLE IN GROUP Quit = ULTIMATE LOAD W I T Y OF ISOLATED PILE n = NUMBER OF PILES IN GROUP G
OG
= Qult 2R = PILE
FOR COHESIVE SOILS
DIAMETER QG AND Quit ARE APPLIED LOADS ONLY. WEIGHT OF PILES AND ENCLOSED SOIL IS BALANCED BY WEIGHT OF OVERBURDEN AND IS NOT CONSIDERED.
BEARING CAWlTY B
BEARING CAPACITY OF PILE GROUP R ~ CA 2 T R L (OBTAIN CA AND Nc FROM FIGURE 2 ) ULTIMATE LOAD OF GROUP = nQG = Ge n Quit
Quit = (cNc) W
+
FIGURE 3 Bearing Capacity of P i l e Groups i n Cohesive S o i l s
-
F a c t o r s of S a f e t y : u p l i f t i n g loading.
4.
2 f o r short-term l o a d s , 3 f o r s u s t a i n e d
SETTLEMENTS OF PILE FOUNDATIONS
The s e t t l e m e n t a t t h e t o p of p i l e can be broken down a. S i n g l e P i l e . i n t o t h r e e components ( a f t e r Reference 6 ) .
(1)
where:
Q
P
S e t t l e m e n t due t o a x i a l deformation of p i l e s h a f t ; W s
= p o i n t l o a d t r a n s m i t t e d t o t h e p i l e t i p i n t h e working
stress
range.
Qs = s h a f t f r i c t i o n load t r a n s m i t t e d by t h e p i l e i n t h e working s t r e s s range(in force units) = 0.5
f o r p a r a b o l i c o r uniform d i s t r i b u t i o n of s h a f t f r i c t i o n
0.67 f o r t r i a n g u l a r d i s t r i b u t i o n of s h a f t f r i c t i o n s t a r t i n g from z e r o f r i c t i o n a t p i l e head t o a maximum v a l u e a t p i l e point 0.33 f o r t r i a n g u l a r d i s t r i b u t i o n of s h a f t f r i c t i o n s t a r t i n g from a maximum a t p i l e head t o - z e r o a t t h e p i l e point. L = pile length A = p i l e cross sectional area
Ep = modulus of e l a s t i c i t y of t h e p i l e
(2) W
~
~
where :
S e t t l e m e n t of p i l e p o i n t caused by l o a d t r a n s m i t t e d a t t h e p o i n t
:
Cp = e m p i r i c a l c o e f f i c i e n t depending on s o i l type and method of c o n s t r u c t i o n , s e e Table 5 B = p i l e diameter
q0 = u l t i m a t e end b e a r i n g c a p a c i t y
( 3 ) S e t t l e m e n t of p i l e p o i n t s caused by l o a d t r a n s m i t t e d a l o n g t h e p i l e s h a f t , Wps;
TABLE 5 Typical* Values of C o e f f i c i e n t C f o r Estimating Settlement of a Sing e P i l e
P
I
L
S o i l Type
Driven P i l e s
Bored P i l e s
Sand (dense t o l o o s e )
0.02 t o 0.04
0.09 t o 0.18
Clay ( s t i f f t o s o f t )
0.02 t o 0.03
0.03 t o 0.06
S i l t (dense t o l o o s e )
0.03 t o 0.05
0.09
*
t o 0.12
Bearing s t r a t u m under p i l e t i p assumed t o extend a t l e a s t 10 p i l e diameters below t i p and s o i l below t i p i s of comparable o r h i g h e r stiffness.
D = embedded l e n g t h (4)
b.
T o t a l s e t t l e m e n t of a s i n g l e p i l e , Wo:
Settlement of P i l e Group i n Granular S o i l s .
Compute group s e t t l e m e n t
Wg based on ( a f t e r Reference 6):
where :
-
B = t h e s m a l l e s t dimension of p i l e group B = diameter of i n d i v i d u a l p i l e
Wo = Settlement of a s i n g l e p i l e estimated o r determined from load t e s t s
c. Settlement of P i l e Groups i n S a t u r a t e d Cohesive S o i l s . group s e t t l e m e n t a s shown i n Figure 4.
Compute t h e
d. Limitations. The above a n a l y s e s may be used t o e s t i m a t e s e t t l e m e n t , however, s e t t l e m e n t estimated from t h e r e s u l t s of load t e s t s a r e g e n e r a l l y considered more a c c u r a t e and r e l i a b l e .
5.
NEGATIVE SKIN FRICTION.
a. General. Deep foundation elements i n s t a l l e d through compressible m a t e r i a l s can experience "downdrag" f o r c e s o r n e g a t i v e s k i n f r i c t i o n along t h e s h a f t which r e s u l t s from downward movement of adjacent s o i l r e l a t i v e t o t h e p i l e . Negative s k i n f r i c t i o n r e s u l t s p r i m a r i l y from c o n s o l i d a t i o n of a s o f t d e p o s i t caused by dewatering o r t h e placement of f i l l . Negative s k i n f r i c t i o n i s p a r t i c u l a r l y severe on b a t t e r p i l e i n s t a l l a t i o n s because t h e f o r c e of subsiding s o i l i s l a r g e on t h e o u t e r s i d e of t h e This can b a t t e r p i l e and s o i l s e t t l e s away from t h e i n n e r s i d e of t h e p i l e . r e s u l t i n bending of t h e p i l e . B a t t e r p i l e i n s t a l l a t i o n s should be avoided where negative s k i n f r i c t i o n i s expected t o develop. b. D i s t r i b u t i o n of Negative Skin F r i c t i o n on S i n g l e P i l e . The d i s t r i b u t i o n and magnitude of negative s k i n f r i c t i o n along a p i l e s h a f t depends on: (1)
r e l a t i v e movement between compressible s o i l and p i l e s h a f t ;
(2)
r e l a t i v e movement between upper f i l l and p i l e s h a f t ;
(3)
e l a s t i c compression of p i l e under working load;
(4)
r a t e of c o n s o l i d a t i o n of compressible s o i l s . --
1 FRICTION PILES IN CLAY 1
FRICTION PILES IN SAND UNDERLAIN BY CLAY
1
1
n Qall
I
L, Y SOFT CLAY
L
nQall -
+
............ . . . . ....! .. I .:....... SAND ..... ...... . . ..:(':;:.-. ...:...:. ......\ ..... : ... .: : : ...: :. ~w. ~ S F .. T C L -A. Y .. :. ......... ....... . .:;.:. ::.:-.=.sspfl :: :. . .:..... V
,
..*
/
-I
II
SETTLEMENT OF PILE GROUP = COMPRESSION OF LAYER H UNDER PRESSURE DISTRIBUTION SHOWN.
1
I
\
/
' n ~ a l l +rLl, q = i m T
(
POINT BEARING PILES IN SAND UNDERLAIN BY CLAY
/
\\
\
n e
\\
(B) (A)
OD = DRAG PER PlLE FOR LENGTH = L 3 L3 = DEPTH TO TOP OF BEARING STRATUM OR 2/3 (L2 FOR FRICTION PILES.
I
FRICTION PILES IN a A y WITH RECENTFILL
NUfES: I. PLAN AREA TO OUTSIDE OF PlLE GROUP = B x A. 2FOR RELATlVEW RIGID PlLE CAP, PRESSURE DISTRIBUTION IS ASUMED TD VARY WITH DEPTH AS SHOWN. 3FOR FLEXIBLE SLAB OR GROUP OF SMALL SEPARATE CAPS,COMWTE PRESSURES BY ELASTIC SOUJTONS (DM-?. 1 CHAPTER 4) FOR LOAD APPLIED N LEVEL SHOWN. 4. COMPUTE SETTLEMENTS BY METHODS OF DM 7.1 CHAPTER 5.
FIGURE 4 Settlement of Pile Groups
1
.
.
-
Negative s k i n f r i c t i o n develops along t h a t p o r t i o n of t h e p i l e s h a f t where s e t t l e m e n t of t h e a d j a c e n t s o i l exceeds t h e downward displacement of t h e s h a f t . The " n e u t r a l p o i n t " i s t h a t p o i n t of no r e l a t i v e movement between t h e p i l e and adjacent s o i l . Below t h i s p o i n t , s k i n f r i c t i o n a c t s t o s u p p o r t p i l e loads. The r a t i o of t h e depth of t h e n e u t r a l p o i n t t o t h e l e n g t h of t h e p i l e The p o s i t i o n of i n compressible s t r a t a may be roughly approximated a s 0.75. t h e n e u t r a l p o i n t can be estimated by a t r i a l and e r r o r procedure which comp a r e s t h e s e t t l e m e n t , o f t h e s o i l t o t h e displacement of a d j a c e n t s e c t i o n s of , (For f u r t h e r guidance s e e Reference 14, P i l e Design and Constructhe pile. t i o n P r a c t i c e , by Tomlinson. ) Observations i n d i c a t e t h a t a r e l a t i v e downward movement of 0.6 i n c h i s expected t o be s u f f i c i e n t t o mobilize f u l l n e g a t i v e s k i n f r i c t i o n (Reference 6 ) . The peak negac. Magnitude of Negative Skin F r i c t i o n on S i n g l e P i l e . t i v e s k i n f r i c t i o n i n g r a n u l a r s o i l s and cohesive s o i l s i s determined as f o r positive skin friction. The peak u n i t n e g a t i v e s k i n f r i c t i o n can a l s o be estimated from ( a f t e r Reference 15, P r e d i c t i o n of Downdrag Load a t t h e C u t l e r C i r c l e Bridge, by Garlanger):
where :
f n = u n i t n e g a t i v e s k i n f r i c t i o n ( t o be m u l t i p l i e d by a r e a of s h a f t i n zone of subsiding s o i l r e l a t i v e t o p i l e ) Po = e f f e c t i v e v e r t i c a l stress
p
= e m p i r i c a l f a c t o r from f u l l s c a l e t e s t s
Soil Clay Silt Sand Since n e g a t i v e s k i n f r i c d. S a f e t y F a c t o r f o r Negative Skin F r i c t i o n . t i o n i s u s u a l l y estimated on t h e s a f e s i d e , t h e f a c t o r of s a f e t y a s s o c i a t e d w i t h t h i s load i s u s u a l l y unity. Thus:
where :
Q a l l = allowable p i l e l o a d Qult
= ultimate p i l e load
F, = f a c t o r of s a f e t y P,
= ultimate negative skin f r i c t i o n load
For f u r t h e r d i s c u s s i o n of f a c t o r of s a f e t y i n d e s i g n i n c l u d i n g t r a n s i e n t l o a d s , s e e Reference 16, Downdrag on P i l e s Due t o - ~ e ~ a t i vs ke i n F r i c t i o n , by F e l l e n i u s . e. Negative Skin F r i c t i o n on P i l e Groups. The n e g a t i v e s k i n f r i c t i o n on a p i l e group does n o t u s u a l l y exceed t h e t o t a l weight of f i l l a n d / o r comp r e s s i b l e s o i l enclosed by t h e p i l e s i n t h e group. For t h e c a s e of r e c e n t f i l l u n d e r l a i n by a compressible d e p o s i t over t h e b e a r i n g s t r a t u m :
where :
l'total
= t o t a l l o a d on p i l e group
W = working l o a d on p i l e group B = width of p i l e group
L = l e n g t h of p i l e group
3 , y2
= e f f e c t i v e u n i t weight of f i l l and u n d e r l y i n g
compressible s o i l respectively D l , D2 = d e p t h over which f i l l and compressible s o i l i s moving downward r e l a t i v e t o t h e p i l e s f . Reduction of Negative Skin F r i c t i o n . S e v e r a l methods have been developed t o reduce t h e expected n e g a t i v e s k i n f r i c t i o n on deep f o u n d a t i o n s . These i n c l u d e : ( a ) Use of s l e n d e r p i l e s , such as H-sections, s u b j e c t t o drag.
t o reduce s h a f t a r e a
( b ) P r e d r i l l e d o v e r s i z e d h o l e through compressible m a t e r i a l p r i o r t o i n s e r t i o n of p i l e ( r e s u l t i n g a n n u l a r space f i l l e d w i t h b e n t o n i t e s l u r r y o r vermiculite) ( c ) P r o v i d e c a s i n g o r s l e e v e around p i l e t o p r e v e n t d i r e c t c o n t a c t with s e t t l i n g s o i l . ( d ) Coat p i l e s h a f t with bitumen t o a l l o w s l i p p a g e . Bitumen compounds which can be sprayed o r poured on c l e a n p i l e s a r e a v a i l a b l e t o reduce n e g a t i v e s k i n f r i c t i o n . Coatings should be a p p l i e d o n l y t o t h o s e p o r t i o n s of t h e p i l e a n t i c i p a t e d t o be w i t h i n a zone of BLbsidence and t h e lower p o r t i o n of t h e p i l e ( a t l e a s t t e n times t h e d i a m e t e r ) should remain uncoated so t h a t t h e f;ll ldwer s h a f t and p o i n t r e s i s t a n c e may be mobilized. Reductions of n e g a t i v e f r i c t i o n of 50% o r g r e a t e r have been meas u r e d f o r bituminous c o a t i n g s on c o n c r e t e and s t e e l p i l i n g ( s e e Reference 1 7 , Reducing Negative Skin F r i c t i o n w i t h Bitumen Layers, by Claessen and Horvat, and Reference 18, Reduction of Negative Skin F r i c t i o n on S t e e l P i l e s t o Rock, by Bjerrum, e t a l . ) .
S e c t i o n 4.
1.
PILE INSTALLATION AND LOAD TESTS
PILE INSTALLATION. a.
General C r i t e r i a .
See Table 6.
b. I n s t a l l a t i o n Techniques. Table 7 summarizes t h e more common s u p p l e mentary procedures and appurtenances used i n d r i v e n p i l e i n s t a l l a t i o n s . c. P i l e Driving Hammers. Table 8 (Reference 6) summarizes t h e Figure c h a r a c t e r i s t i c s of t h e more common types of hammers i n u s e i n t h e U.S. 5 shows p r i n c i p a l o p e r a t i o n of p i l e d r i v e r s (modified from Reference 6 ) : ( 1 ) Drop Hammer. Generally, i t i s only a p p r o p r i a t e on s m a l l , r e l a t i v e l y i n a c c e s s i b l e jobs due t o t h e i r slow r a t e of blows. ( 2 ) S i n g l e Action Steam o r Air Hammers. Blow r a t e i s h i g h e r t h a n drop hammer with maximum speeds g e n e r a l l y ranging from about 35 t o 60 blows per minute. S i n g l e a c t i n g hammers have an advantage over double a c t i n g hammers when d r i v i n g pi.les i n f i r m cohesive s o i l s s i n c e t h e slower r a t e a l l o w s t h e s o i l and p i l e t o r e l a x before s t r i k i n g t h e next blow; thereby , g i v i n g g r e a t e r p e n e t r a t i o n p e r blow. I n d r i v i n g b a t t e r p i l e s , s i n g l e a c t i n g hammers can l o s e c o n s i d e r a b l e energy due t o t h e s h o r t e n i n g f a l l and i n c r e a s e s i n friction.
( 3 ) Double Acting Steam o r A i r Hammers. They provide a blow r a t e n e a r l y double t h a t of t h e s i n g l e a c t i n g hammers and l o s e less energy d r i v i n g b a t t e r p i l e s . They a r e g e n e r a l l y b e s t s u i t e d f o r d r i v i n g p i l e s i n g r a n u l a r s o i l s o r i n s o f t clays. The energy per blow d e l i v e r e d by a double-acting hammer decreases r a p i d l y a s i t s speed of o p e r a t i o n drops below t h e r a t e d speed.
( 4 ) D i e s e l Hammers. They have a r e l a t i v e l y low f u e l consumption, o p e r a t e without a u x i l i a r y equipment, and can o p e r a t e a t low temperatures and a r e more e f f i c i e n t f o r d r i v i n g b a t t e r p i l e s . Maximum blow r a t e s a r e about 35 t o 60 blows p e r minute f o r s i n g l e a c t i n g and about 80 t o 100 blows p e r minute f o r double a c t i n g . Diesel hammers o p e r a t e b e s t i n medium t o hard ground; i n s o f t ground t h e r e s i s t a n c e and r e s u l t i n g compression may be too low t o i g n i t e the fuel. (5) Vibratory Hammers. They a r e b e s t s u i t e d t o w e t s o i l s and low displacement p i l e s but o c c a s i o n a l l y have been used s u c c e s s f u l l y i n c o h e s i v e s o i l s and 'with h i g h displacement p i l e s . They can a l s o be e f f e c t i v e i n ext r a c t i n g p i l e s . When c o n d i t i o n s a r e s u i t a b l e , v i b r a t o r y hammers have s e v e r a l advantages over impact hammers i n c l u d i n g lower d r i v i n g v i b r a t i o n s , reduced n o i s e , g r e a t e r speed of p e n e t r a t i o n and v i r t u a l l y complete e l i m i n a t i o n of p i l e damage. However, t h e r e i s t h e p o s s i b i l i t y t h a t t h e . p i l e may not be e f f ic i e n t l y advanced, o b s t r u c t i o n s g e n e r a l l y can not be p e n e t r a t e d , and t h e r e i s no g e n e r a l l y accepted method of determining u l t i m a t e p i l e c a p a c i t y based on t h e r a t e of p e n e t r a t i o n .
TABLE 6 General Criteria for I n s t a l l a t i o n of P i l e Foundations -
--
GEOMETRIC REQUIREMENTS
PW
OVER BURDEN
-
d
5
SKETCH A
SUM OF PILE LOPDS LMINIMUM AREA 2 A W A B L E BEARING CAPAClTY
AT LEAST 2 INTERIOR ANGLES
60'
REQUIRED MIN. PlLE SPACING
SKETCH B
ITEM CRITERIA AND LIMITATIONS WNERAL REPUIRFMENTS MINIMUM SWING (CENTER TO CENTER) (I) PlLES TO ROCK : TWICE THE AVERAGE PlLE DIAMETER OR 1.75 TIMES THE DIAGONAL DIMENSION OF P I E CROSS SECTION, BUT NO LESS THAN 24':
-
(2)
ALL OTHER PILES: TWICE THE AVERAGE MAMETER OFTHE PlLE OR 1.75 VMES THE DIAGONAL DIMENSION OF PlLE CROSS SECTION, BUT NO LESS THAN 30: IN ADDITION ,THE MINIMUM SPACING SHALL BE LIMITED BY THE REQUIREMENT THAT THE PlLE LOAD DISTRIBUTED INTO THE BEARING STRATUM SHALL NOf EXCEED THE NOMINAL BEARING CAWITY OF THE STRATUM (TABLE I, CHAPTER 4. ).PILES OR PlLE GROUPS SHALL BE ASSUMED TO TRANSFER THEIR LOADS TO THE UNDERLYING MATERIALS BY SPREADING THE LDAD UNIFORMLY AT AN ANGLE OF 6j1° WITH THE HORIZONTAL, STARTING AT A POLYGON CIRCUMSCRIBING THE PILES AT THE TOP OF THE BEARING !7RATUM IN WHICH THEY ARE EMBEDDED. THE AREA CONSIDERED AS SUPPORTING THE LOAD SHALL NOT EXTEND BEYOND THE INTERSECTION OF THE 60' PLANES OF ADJACENT PlLES OR PlLE GROUPS. (SEE SKETCH A )
MINIMUM NUMBER OF PILES IN GROUP
-
8-
PlLE GROUPS SUPPORTING SUPERSTRUCTURE UMS NORMALLY CONSIST OF AT LEAST 3 PlLES (FOR ARRANGEMENT SEE SKETCH B),EXCEPT FOR INDIVIDUAL PILES SUPPORTING THE FLOOR SLAB OR IN CASES WHERE LATERALTIES ARE PRUUIDED.
TA.BLE 6 (continued) General C r i t e r i a f o r I n s t a l l a t i o n of P i l e Foundations C r i t e r i a and L i m i t a t i o n s
Item
S i n g l e p i l e s u p p o r t s may be used i f t h e p i l e has a b u t t diameter of 12" o r g r e a t e r , i f t h e upper s o i l s a r e not of a weak n a t u r e , and i f proper c o n s i d e r a t i o n i s given t o reinforcement of column and p i l e t o accommodate potential eccentricities. Embedment i n p i l e cap. Pile length
...........
Tolerances i n p i l e l o c a t i o n and alinement
Tops of p i l e s s h a l l extend a t l e a s t 4" i n t o t h e p i l e cap. No p i l e s h a l l be s h o r t e r t h a n 10 f e e t .
( 1 ) V e r t i c a l p i l e s s h a l l n o t vary more than 2 p e r c e n t from t h e plumb p o s i t i o n . ( 2 ) No p i l e s h a l l be d r i v e n more t h a n 4" i n h o r i z o n t a l dimension from i t s design l o c a t i o n , u n l e s s t h e e f f e c t of t h i s d e v i a t i o n i s analyzed and found a c c e p t a b l e
(3) E c c e n t r i c i t y of r e a c t i o n of t h e p i l e group with r e s p e c t t o t h e l o a d r e s u l t a n t s h a l l not exceed a dimension t h a t would produce overloads of more t h a n 10 percent i n any p i l e . Driving Order.........
P i l e groups s h a l l be d r i v e n from t h e i n t e r i o r outward t o preclude d e n s i f i c a t i o n and e x c e s s i v e l y hard d r i v i n g c o n d i t i o n s on t h e i n t e r i o r .
Allowable loads:
.... ..
Allowable overload of piles-. 0.
(1)
Up t o 10 percent overload i s permitted due t o e c c e n t r i c i t y of r e a c t i o n of t h e p i l e group.
(2)
Overload due t o wind i s permitted i f i t does n o t exceed 33 p e r c e n t of allowable c a p a c i t y of p i l e under dead p l u s l i v e loads.
TABLE 6 (continued) General C r i t e r i a f o r I n s t a l l a t i o n of P i l e Foundations
Item L a t e r a l l o a d s on v e r t i c a l piles........
R e l a t i v e load c a p a c i t y of p i l e s i n a group... Maximum allowable p i l e load.................. S t a t i c and dynamic pick-up loads.......
Splices.............,.
C r i t e r i a and L i m i t a t i o n s Maximum 1 t o n p e r p i l e , i f p i l e i s embedded i n s o i l f o r i t s e n t i r e l e n g t h , except t h a t no l a t e r a l load i s permitted on v e r t i c a l p i l e s i n very s o f t f i n e grained s o i l s o r very l o o s e coarse-grained s o i l s . For p i l e s with unsupported l e n g t h o r f o r l a r g e r h o r i z o n t a l l o a d s , use b a t t e r p i l e s o r use a n a l y s i s of Figure 10 t o determine l a t e r a l load c a p a c i t y of v e r t i c a l p i l e s . A l l bearing p i l e s w i t h i n a group s h a l l be of t h e same type and be of e q u a l load capacity.
S h a l l be l i m i t e d by both allowable stress i n p i l e a s given i n Table 1 and supporting c a p a c i t y of s o i l . Induced f l e x u r a l s t r e s s e s i n c u r r e d during pick-up and placement of long conc r e t e p i l e s s h a l l not exceed t h e allowable bending s t r e s s e s p r e s c r i b e d f o r t h a t p i l e length. S h a l l be a b l e t o t r a n s m i t t h e r e s u l t a n t v e r t i c a l and l a t e r a l f o r c e s adequately.
Load t e s t s :
o.............. Load t e s t s t o
Conditions r e q u i r i n g tests..
be performed f o r any of t h e following c o n d i t i o n :
( 1 ) To v e r i f y o r modify e s t i m a t e of p i l e load c a p a c i t y determined by o t h e r means.
TABLE 6 (continued) General C r i t e r i a f o r I n s t a l l a t i o n of P i l e Foundations
C r i t e r i a and L i m i t a t i o n s
Item
( 2 ) Where s i z e of p r o j e c t and s o i l c o n d i t i o n s i n d i c a t e a s i g n i f i c a n t s a v i n g s i s possible.
(3) Where unique o r u n f a m i l i a r types a r e t o be used. (4) Number of load t e s t s . .
Where bearing stratum i s u n d e r l a i n by a more compressible o r quest i o n a b l e stratum.
A minimum of 3 test p i l e s s h a l l be driven p e r i n s t a l l a t i o n with uniform subs o i l conditions. Two of t h e s e p i l e s s h a l l be test loaded, but no l e s s than 1 load t e s t f o r each 15,000 square f e e t of b u i l d i n g area.
Supervision: Inspection............
A l l p i l e d r i v i n g p r o j e c t s s h a l l have on t h e s i t e i n s p e c t i o n by a person who has experience i n such work, p r e f e r a b l y a Registered P r o f e s s i o n a l Engineer.
Records...............
Records s h a l l be kept f o r t h e d r i v i n g of each p i l e . The record s h a l l include: d a t e of d r i v i n g , type, s i z e , l e n g t h , d e v i a t i o n from design l o c a t i o n and a l i g n ment, p i l e hammer used, hammer speed, type and c o n d i t i o n of cushion, and blows per f o o t f o r each foot of p e n e t r a t i o n f o r t h e f u l l l e n g t h of t h e p i l e , blows p e r i n c h f o r t h e f i n a l 6 inches of d r i v i n g , except where an abrupt high i n c r e a s e i n r e s i s t a n c e i s encountered, t h e f i n a l counts may be reduced t o p e n e t r a t i o n f o r t h e l a s t 5 blows.
General items t o be checked..............,
M a t e r i a l , q u a l i t y of t h e p i l e s t r a i g h t n e s s , a p p l i c a t i o n of p r e s e r v a t i v e s , radiographic i n s p e c t i o n of marine p i l i n g welds. For l i g h t weight mandrel d r i v e n s h e l l p i l e s , check i n t e r i o r f o r damage p r i o r t o concreting, check d r i v i n g equipment f o r o p e r a t i o n a l c a p a b i l i t i e s .
TABLE 7 Supplementary P r o c e d u r e s and Appurtenances Used i n P i l e D r i v i n g Method
Equipment and procedure utilized
Means of reducing driving resistance above bearing stratum: . Temporary casing..
.. . .
Precoring..
Spudding
........... .
. ......... ....
Applicability
Open end pipe casing driven and cleaned out. May be pulled later.
a. b. c. d.
By continuous flight auger or churn drill, a hole is formed into which the pile is lowered. P i l e is then driven t o bearing below the cored hole.
a.
Heavy structural sections or closed end pipes are alternately raised and dropped t o form a hole into which pile is lowered. P i l e is then driven to bearing below the
b. c. d. a. b.
T o drive through minor obstructions. T o minimize displacement. To prevent caving or squeezing of holes. T o permit concretingof pile before excavation to subgrade of foundation. To drive through thick stratum of stiff to hard cloy. T o avoid displacement and heave of surrounding soil. To avoid injury to timber and thin shell pipes. To eliminate driving resistance in strata unsuitable for bearing. To drive past individual obstruction To drive through strata of fill with large boulders or rock fragments.
jets are sometimes
driven with large butt downward.
timber or steel pipes.
jacks are used to advance pile.
a. T o be used instead of pile hammer where access is difficult.
TABLE 8 Impact ana V i b r a t o r y P i l e - D r i v e r Data '\
I
1.
IMPACT PILE HAMMER
**
Rated Energy Kip - f t . 180.0 130.0 120.0 113.5 97.5 79.6 60.0 60.0 56.5 50.2 48.7 48.7 44.5 42.0 40.6 39.8 37.5 36.0 32.5 32.5 32.5 32.0 30.2 26.3 26.0 26.0 26.0 24.4 24.4 24.3 24.0 22.6 22.4 24.4 19.8 19.8 19.5 19.2 18.2
Make of Hammer*
Model No.
Vulcan MKT Vulcan S-Vulcan
S-A S-A S-A Diff. S-A
KObe Vulcan MKT Kobe S-Vulcan Vulcan Raymond Kobe Vulcan R v n d Delmag
Dies.
rn
rn
S-Vulcan MKT Vulcan Raymond MKT Vulcan Link-Belt MKT Vulcan MKT S-Vulcan Vulcan Vulcan MKT Dehg MKT Kobe Union MKT Vulcan S-Vulcan Link-Belt
S-A S-A Dies. Mff. S-A S-A Dies. S-A S-A Dies. S-A Diff. S-A S-A S-A Dies. S-A Mes. D-A
S-A S-A Diff. Mff. S-A D-A Dies.
Dies. Dies. D-A D-A
S-A Mff. Mes.
Blows per min
Stroke a t Rated Energy
62 55 60 100 60 52 60 60 52 98 60 46 52 60 50 52 60 103 55 50 50 48 50, 82 81 50 55 111 111 50 90 51 48 52 110 95 60 117 88
36 39 36 16.5 39 98 36 36 98 15.5 36 39 98 36 39 N/A 32 15.5 39 39 39 96 39 43.2 20 39 39 16.2 N/A 39 18 N/A 96 98 24 19 36 15.5 36.9
Weight Strikirg Parts Kips 60.0 40.0 40.0 40.0 30.0 9.2 20.0 20.0 7.0 20.0 16.2 15.0 4.8 14.0 12.5 4.8 14.0 14.0 10.0 10.0 10.0 4.0 9.3 5.0 8.0 8.0 8.0 8.0 8.0 7.5 8.0 2.7 2.8 2.8 3.0 5.0 6.5 6.5 4.0
Total Weigh Kips 121.0 96.0 87.5 83.0 - 86.0 22.0 39.0 38.6 15.4 39.0 30.2 23.0 10.6 27.5 21.0 10.0 31.6 27.9 22.2 18.7 18.5 11.2 16.7 12.5 18.7 16.7 18.1 17.8 18.4 16.2 17.7 5.4 9.0 6.4 14.5 14.5 11.2 14.8 10.3
TABLE 8 ( c o n t i n u e d ) Impact and V i b r a t o r y P i l e - D r i v e r Data
2
Rated** Energy Kip-f t
Make of Hammer*
16.2 16.0 16.0 15.1 15.1 15.0 15.0 13.1 12.7 9.0 9.0 9 .O 8.8 8.7 8.2 8.1 7.2 7.2 7.2 6.5 4.9 3.6 3.6 .4 .4 .4 .3
*
MKT
Mm. MKT S-Vulcan Vulcan Vulcan Link-Belt
Ma.' Union DeI= MKT MKT MKT
MKT Union Link-Belt Vulcan S-Vulcan Vulcan Link-Belt Vulcan Union MKT Union Vulcan MKT Union
Blows Model No. S5 DE-20 C5 50C
Types*
per min
S-A Dies. Comp Dif f. Diff. S-A Dies. D-A D-A Dies. P A S-A Dies. D-A D-A Dies. S-A Diff. Diff. Dies. Diff. D-A D-A D-A D if f D-A D-A
.
5M
1 312 10B3 1 D5 C-3 S3 DE- 10 9B3 1.5A 180 2 30C 3M
105 DGH900 3 7 6 DGHl OOA 3 7A
.
60 48 110 120 120 60 100 105 125 51 130 65 48 145 135 92 70 133 133 94 238 160 225 340 303 400 400
Stroke atRated Energy
39 96 18 15.5 15.5 36 30.9 19 21 N/A
16 36 96 17 18 37.6 29.7 12.5
N/A 35.2 10 14 9.5 7 6 5.7 6
Weight Striking Parts Kips
5.0 2 .O 5.0 5 .O 5.0 5.0 3.8 3.0 1.6 1.1 3.0 3.0 11.0 1.6 1.5 1.7 3.0 3.0 3.0 1.4 .9 .7 .8 .1 .1 .06 -08
Total Weight Kips
12.3 6.3 11.8 11.7 12.9 10.1 10.3 10.6 10.0 2.4 8.5 8.8 3.5 7.0 9.2 4.5 7.1 7.0 8.4 3.8 5.0 4.7 5.0 -9 .8 -7
-5
Codes
-
MKT McKiernan-Terry S-Vulcan Su'per-Vulcan Single-Acting S-A
-
-
D-A Double-Acting Diff. Differential Dies. Diesel
Comp.
** In
- Compound
calculations of p i l e capacities by dynamic formula, e f f e c t i v e energy delivered by hammr should be used. Hammer energy i s affected by pressures used t o operate t h e hammer, stroke r a t e , etc. Double-acting, d i f f e r e n t i a l , and d i e s e l hammers may operate a t less than rated energies; double-acting hammrs deliver s i g n i f i c a n t l y less than rated energy when operated a t l e s s than rated speed. Consult manufacturers.
TABLE 8 (continued) Impact and Vibratory Pile-Driver Data
2.
VIBRATORY DRNWS
Total Weight Kips
Available
HP
Frequency Range cps
2-17 2-35 2-50
6.2 9.1 11.2
34 70 100
18-2 1 14-19 11-17
Men& (Germany)
M\r 622-30
MVB65-30 IWB44-30
4.8 2.0 8.6
50 7.5 100
Muller (Germany)
MS-26 MS-26D
9.6 16.1
72 145
Uraga (Japan)
VHW1 VHD-2 VHD-3
8.4 11.9 15.4
40 80 120
Bodine (USA)
B
Make Foster (France)
(Russia)
*** Forces
hodel
BT-5 WP-2 100 VP VP-4
22
2.9 4.9 4.0 11.0 25.9
1000
37 54 37 80 208
Force Kips***, Frequency cps
62/19 101117 481 141 971
16-20 16-20 16-20
0-1%
42 25 13 6.7
43/20 86/20 129120
631100
- 175/100
48/42 49/25 44/13 3517 1981
g i w n a r e present maximums. These can usually be raised o r lor~eredby changing w i g h t s i n the oscillator.
AIR OR STEAM
WEIGHT
(A) DROP HAMMER
(6) SINGLE-ACTING HAMMERS
(C) DIFFERENTIAL AND DOUBLE-ACTING HAMMERS
(D) DIESEL HAMMERS
FIGURE 5 Principles of Operation of P i l e Drivers
(E) VIBRATORY MilVER
-
See Table 6 f o r g e n e r a l guidance and Referd. I n s p e c t i o n Guidelines. ence 19, I n s p e c t o r s ' Manual f o r P i l e Foundations, by t h e Deep Foundation Institute. .
( 1 ) Driven P i l e s . The i n s p e c t o r should normally a s s e s s t h e performance of t h e d r i v i n g equipment, record t h e d r i v i n g r e s i s t a n c e s , p a r t i c u l a r l y t h e f i n a l s e t ( n e t p e n e t r a t i o n p e r blow), record t h e d r i v e n depth and t i p e l e v a t i o n , and c o n t i n u a l l y observe t h e p i l e f o r evidence of damage o r e r r a t i c driving. The c r i t e r i a f o r t e r m i n a t i o n of p i l e d r i v i n g i s normally a p e n e t r a Normally, a set t i o n r e s i s t a n c e c r i t e r i a o r a r e q u i r e d depth of p e n e t r a t i o n . c r i t e r i a would be used f o r end bearing p i l e s o r p i l e s where s o i l f r e e z e i s n o t a major f a c t o r while p e n e t r a t i o n c r i t e r i a would be more a p p r o p r i a t e f o r f r i c t i o n p i l e s , p i l e s i n t o c l a y , and/or when s o i l f r e e z e i s a major f a c t o r . ( a ) Timber P i l e s . (Reference 20, AWPI Technical G u i d e l i n e s f o r Pressure-Treated Wood, Timber P i l i n g , and A S R l Standard D25, Round Timber P i l e s . ) S i t e E n g i n e e r l I n s p e c t o r should check t h e following items:
-
O v e r s t r e s s i n g a t t h e top of p i l e , u s u a l l y v i s i b l e brooming.
- Properly
f i t t e d d r i v i n g cap.
- Straightness. - Sound wood f r e e of decay - Pressure treatment. - Low frequency of knots.
and i n s e c t a t t a c k .
( b ) Concrete P i l e s . (Reference 21, Recommendations f o r Design, Manufacture, and I n s t a l l a t i o n of Concrete P i l e s , by t h e American Concrete I n s t i t u t e . ) S i t e Engineer/Inspector should check t h e f o l l o w i n g items:
(c) following items:
-
That p i l e l e n g t h , geometry, t h i c k n e s s , and s t r a i g h t n e s s conforms t o s p e c i f i c a t i o n s .
-
Note e x t e n t , amount, and l o c a t i o n of s p a l l i n g o r cracki n g i n t h e p i l e during d r i v i n g and p i c k up, and set.
-
Thickness and type of cushion specification.
S t e e l Piles.
-
should comply w i t h
S i t e Engineer/Inspector should check t h e
- Compliance with
a p p l i c a b l e codes and s p e c i f i c a t i o n s .
-
S t r u c t u r a l damage t o p i l e due t o over-driving/ overstressing.
-
P i l e o r i e n t a t i o n conforms t o t h e plans.
( 2 ) D r i l l e d P i e r s . Minimum requirements f o r proper i n s p e c t i o n of d r i l l e d s h a f t c o n s t r u c t i o n a r e a s follows: (a)
For Dry o r Casing Method of Construction;
-A
q u a l i f i e d i n s p e c t o r should record t h e m a t e r i a l t y p e s being removed from t h e hole a s excavation proceeds.
- When
t h e bearing s o i l has been encountered and i d e n t i f i e d and/or t h e designated t i p e l e v a t i o n has been reached, t h e s h a f t w a l l s and base should be observed f o r anomalies, unexpected s o f t s o i l c o n d i t i o n s , o b s t r u c t i o n s o r caving.
(b)
-
Concrete placed f r e e f a l l should not be allowed t o h i t t h e s i d e w a l l s of t h e excavation.
-
S t r u c t u r a l s t a b i l i t y of t h e r e b a r cage should be maint a i n e d during t h e c o n c r e t e pour t o prevent buckling.
-
The volume of c o n c r e t e should be checked t o ensure v o i d s d i d not r e s u l t during e x t r a c t i o n of t h e casing.
-
Concrete must be tremied i n t o p l a c e with an adequate head t o d i s p l a c e water o r s l u r r y i f groundwater has e n t e r e d t h e bore hole.
-
P u l l i n g c a s i n g with i n s u f f i c i e n t c o n c r e t e i n s i d e should be r e s t r i c t e d .
-
Bottom of hole should be cleaned.
For S l u r r y Displacement Method of Construction.
-
A check on t h e c o n c r e t e volume and recording t h e mater i a l types and depth of s h a f t apply t h e same a s above.
-
The tremie p i p e should be w a t e r t i g h t and should be f i t t e d with some form of valve a t t h e lower end.
( 3 ) Caissons on Rock. accomplished by e i t h e r :
I n s p e c t i o n of c a i s s o n bottom i s u s u a l l y
( a ) Probing with a 2-112" diameter probe hole t o a minimum of 8 f e e t o r 1.5 times t h e c a i s s o n s h a f t diameter (whichever i s l a r g e r ) . ( b ) Visual i n s p e c t i o n by a q u a l i f i e d g e o l o g i s t a t c a i s s o n bottom with proper s a f e t y precautions o r from t h e s u r f a c e u t i l i z i n g a borehole camera. The purpose of t h e i n s p e c t i o n i s t o determine t h e e x t e n t of seams, c a v i t i e s and f r a c t u r e s . The allowable cumulative seam t h i c k n e s s w i t h i n t h e probe depth v a r i e s depending on performance c r i t e r i a . Values a s low a s 114" of cumulative t h i c k n e s s can be s p e c i f i e d f o r t h e top 112 diameter.
e.
I n s t a l l a t i o n Guidelines. (1)
Driven P i l e s .
( a ) For p i l e groups, d r i v e i n t e r i o r p i l e s f i r s t t o a v o i d hard d r i v i n g c o n d i t i o n s , o v e r s t r e s s i n g , and t o minimize heave. (b)
Make s u r e p i l e d r i v i n g caps and/or cushions are a p p r o p r i -
ate. ( c ) Check f o r compression bands around t h e t o p of c o n c r e t e and timber p i l e s t o avoid o v e r s t r e s s i n g . (d)
Check f o r proper alignment of t h e d r i v i n g head.
( e ) I f t h e p i l e suddenly changes d i r e c t i o n s o r a s u b s t a n t i a l l y reduced d r i v i n g r e s i s t a n c e i s noted, t h e p i l e i s probably broken. Table 9 summarizes some of t h e common i n s t a l l a t i o n problems and recommended procedures. Table 10 (Reference 22, D r i l l e d S h a f t s : Design and Construction Guideline Manual. Vol 1: Construction Procedures and Desien f o r Axial Load, by Reese and Wright) summarizes some of t h e more common i n s t a l l a t i o n problems and procedures f o r d r i l l e d p i e r s .
-
( 2 ) Performance Tolerance. It i s normal p r a c t i c e t o t a i l o r t h e s p e c i f i c a t i o n s t o p a r t i c u l a r s i t e c o n d i t i o n s and t o s t r u c t u r a l performance c r i t e r i a . I n many a p p l i c a t i o n s t h e following c r i t e r i a may apply: ( a ) Allowable Deviation,from S p e c i f i e d Location. I n t h e absence of another over-riding p r o j e c t s p e c i f i c a t i o n c r i t e r i a , use 4 i n c h e s . Consider t h e t e c h n i c a l f e a s i b i l i t y of i n c r e a s i n g t o more than 4 i n c h e s f o r caps with 4 p i l e s o r less. ( b ) Allowable out-of-vertical. I n t h e absence of t h e overr i d i n g p r o j e c t s p e c i f i c a t i o n c r i t e r i a , use 2% provided t h a t t h e a l l o w a b l e d e v i a t i o n i s not exceeded. Values of 4%, 2% and 1/4 i n c h o u t of plumb have been used. ( c ) Allowable Heave Before Redriving. Require r e d r i v i n g of p i l e s i f heave exceeds 0.01 f e e t f o r e s s e n t i a l l y f r i c t i o n p i l e s , o r any d e t e c t a b l e heave i f p i l e s a r e known t o be e s s e n t i a l l y end-bearing. ( d ) Minimum Distance of P i l e Being Driven from Fresh Concrete. I n t h e absence of over-riding p r o j e c t s p e c i f i c a t i o n c r i t e r i a , u s e 15 f e e t . Values of 10 f e e t t o 50 f e e t have been used i n p r a c t i c e .
TABLE 9 Treatment of F i e l d Problems Encountered During P i l e D r i v i n p
I
Description of problem
Procedures to be applied
Category: Obstructions: Old foundations, boulders, rubble fill, cemented lenses, and similar obstacles to driving. General problems: Vibration in Driving: May compact loose granular materials causing settlement of existing struc( tures near piles. Effect most pronounced i n driving displacement piles. Damage to Thin Shells: Driven shells may have been crimped, buckled, or torn, or be leaking a t joints a s the results of driving difficulties or presence of obstructions. Inappropriate Use of P i l e Driving Formula: P i l e s driven t o a penetration determined solely by driving resistance may be bearing i n a compressible stratum. This may occur i n thick strata of silty fine sarid, varved silts and clays, or medium stiff cohesive soils. Difficulties a t pile tip: Fracturing of Bearing Materials: Fracturing of material immediately below tips of piles driven t o required resistance a s a result of driving adjacent piles. Brittle weathered rock, clay-shale, shale, siltstone, and sandstone are vulnerable materials. Swelling of stiff fissured clays or shales a t pile tip may complicate this problem. Steeply Sloping Rock Surface: Tips of high capacity end bearing piles may slide or move laterally on a steeply sloping surface of sound hard rock which h a s little or no overlying weathered material. L o s s of Ground: May occur during installation of open end pipe piles. Materials vulnerable t o piping, particularly fine sands or silts, may flow into pipe under the influence of a n outside differential head, causing settlement i n surrounding areas or l o s s of ground beneath tips of adjacent piles. Movement of piles subsequent to driving: Heave: Completed piles rise vertically a s the result of driving adjacent piles. Particularly common for displacement piles i n soft clays and medium compact granular soils. Heave becomes serious i n soft clays when volume displaced by piles exceeds 2%% of volume of soil enclosed within the limits of the pile foundation.
I
Excavate or break up shallow obstruction if practical. For deeper obstructions use spudding, jetting, or temporary c a s ings, or u s e drive shoes and reinforced tips where pile is strong enough to be driven through obstructions. Select pile type with minimum disp!acement, and/or precore or jet with temporary casing or substitute jacking for pile driv1 ing. Each pile is inspected with light beam. If diameter a t any location varies more than 15% from original diameter or if other damage t o shell cannot be repaired, pile is abandoned, filled with sand and a replacement is driven. Concrete shall b e vlaced in dry shell only. Unsuitable bearing strata should be determined by exploration -program. P i l e s should not be permitted to stop in these strata, regardless of driving resistance. For bearing i n stiff and-brittle cohesive soils and i n soft rock. load t e s t s a r e particularly important.
I
I-
For piles bearing in these materials specify driving resistance t e s t o n selected piles after completion of driving adjacent piles. If damage .to the bearing stratum is evidenced, require redriving until specified resistance is met.
Provide special shoes or pointed tips or use open end pipe pile socketed into sound rock.
Avoid cleaning i n advance of pile cutting edge, and/or retain sufficient material within pipe t o prevent inflow of s o i l from below.
For piles of solid cross sections (timber, steel, precast concrete), survey top elevations during driving of adjacent piles t o determine possible heave. For piles that have risen more than 0.01 ft, redrive to at least the former tip elevation, and beyond that a s necessary to reach required driving resistance. Heave is minimized by driving temporary open-end casing, precoring, or jetting s o that total volume displaced by pile driving is l e s s than 2 or 3% of total volume enclosed within limits of pile foundation. Lateral Movement of Piles: Completed piles move Survey horizontal position of completed piles during the driving horizontally a s the result of driving adjacent of adjacent piles. Movement is controlled by procedures used piles. to minimize heave.
I
I
-
Drilled Piers: Problem
TABLE 10 Construction Problems Solution
Pouring c o n c r e t e through wqter
Removal of water by b a i l i n g o r use o f tremie
Segregation of c o n c r e t e during placing
I f f r e e - f a l l i s employed, e x e r c i s i n g c a r e t o see t h a t concrete f a l l s t o f i n a l l o c a t i o n without s t r i k i n g anything, o r u s e of t r emie
R e s t r i c t e d flow of c o n c r e t e through o r arouna r e b a r cage
Designing of r e b a r cage with adequate spacing f o r normal c o n c r e t e ( a l l c l e a r spaces a t l e a s t t h r e e times t h e s i z e of l a r g e s t aggregate) o r u s e of s p e c i a l mix with small-sized c o a r s e aggregate
Torsional buckling of r e b a r cage during c o n c r e t e placement with casing method
Strengthening r e b a r cage by use of c i r c u m f e r e n t i a l bands welded t o lower p o r t i o n of cage, u s e of c o n c r e t e w i t h improved flow c h a r a c t e r i s t i c s , use of r e t a r d e r i n c o n c r e t e allowing c a s i n g t o be p u l l e d very slowly
P u l l i n g casing with i n s u f f i c i e n t concrete i n s i d e
Always having casing extending above ground s u r f a c e and always having c a s i n g f i l l e d w i t h a s u f f i c i e n t head of c o n c r e t e with good flow c h a r a c t e r i s t i c s b e f o r e casing i s p u l l e d
Weak s o i l o r undetected c a v i t y beneath base of foundation
Requiring e x p l o r a t i o n t o a depth of a few diameters below t h e bottom of t h e excavation
Deformation o r c o l l a p s e of s o i l
Such problems a r e r e a d i l y detected by even t h e minimums of i n s p e c t i o n
2.
PILE LOAD TEST.
a. ~ e n e r a l . The r e s u l t s of p i l e l o a d t e s t s a r e t h e most r e l i a b l e means of e v a l u a t i n g t h e l o a d c a p a c i t y of a deep foundation. Load tests can be p e r formed d u r i n g t h e d e s i g n phase as a d e s i g n t o o l and/or d u r i n g c o n s t r u c t i o n t o v e r i f y d e s i g n loads. P i l e l o a d tests should be considered f o r l a r g e and/ o r c r i t i c a l p r o j e c t s , f o r p i l e t y p e s and s o i l c o n d i t i o n s f o r which t h e r e i s l i m i t e d p r e v i o u s l o c a l experience, when proposed d e s i g n l o a d s exceed t h o s e normally used, and f o r o t h e r d e s i g n / s i t e c o n d i t i o n s such a s t h e need t o u s e lower t h a n s p e c i f i e d f a c t o r of s a f e t y i n t h e design. The t y p e s of p i l e l o a d t e s t s normally performed i n c l u d e : ( 1 ) Standard Loading Procedures o r Slow Maintained-Load T e s t Method. For procedure, r e f e r t o ASTM Standard D3689, I n d i v i d u a l P i l e s under S t a t i c A x i a l T e n s i l e Load. It i s t h e most common l o a d t e s t c u r r e n t l y used. It i s a long d u r a t i o n t e s t ( t y p i c a l l y 70 hours o r l o n g e r ) loaded t o 200 p e r c e n t of t h e d e s i g n l o a d , o r t o f a i l u r e . To determine curve of p l a s t i c deformation, t h e t e s t procedure should be a l t e r e d t o i n c l u d e a t l e a s t t h r e e unload-reload c y c l e s . T h i s procedure i s d e s c r i b e d i n ASTM Standard D1143, P i l e Under A x i a l Compressive Load. ( 2 ) Quick Maintained-Load T e s t Method. For p r o c e d u r e , r e f e r t o ASTM Standard D1143. This i s a s h o r t d u r a t i o n t e s t , t y p i c a l l y 1 t o 4 h o u r s , genIt i s s u i t a b l e e r a l l y loaded t o 300 p e r c e n t of t h e d e s i g n l o a d o r f a i l u r e . f o r d e s i g n l o a d t e s t and can be e f f e c t i v e l y used f o r l o a d proof t e s t i n g d u r i n g c o n s t r u c t ion. ( 3 ) Constant Rate of P e n e t r a t i o n ( o r U p l i f t ) T e s t Method. A d i s placement-controlled method. For procedure, r e f e r t o ASTM S t a n d a r d Dl143 o r ASTM Standard D3689. It i s a s h o r t d u r a t i o n t e s t , t y p i c a l l y 2 t o 3 h o u r s , and may r e q u i r e s p e c i a l l o a d i n g equipment a s d e s c r i b e d i n Reference 23, A Device f o r t h e Constant Rate of P e n e t r a t i o n T e s t f o r P i l e s , by Garneau and Samson. This method i s recommended f o r t e s t i n g p i l e s i n cohesive s o i l s and f o r a l l t e s t s where o n l y t h e u l t i m a t e c a p a c i t y i s t o be measured. The method can provide i n f o r m a t i o n r e g a r d i n g behavior of f r i c t i o n p i l e s and i s w e l l s u i t e d f o r l o a d t e s t s d u r i n g design. b. I n t e r p r e t a t i o n of R e s u l t s . There a r e numerous procedures f o r i n t e r p r e t a t i o n of p i l e l o a d t e s t r e s u l t s i n c l u d i n g t h o s e s p e c i f i e d by l o c a l b u i l d i n g codes. A d e f l e c t i o n c r i t e r i a i s normally used t o d e f i n e f a i l u r e . I n t h e absence of a n o v e r - r i d i n g p r o j e c t s p e c i f i c a t i o n c r i t e r i a , u s e 314 i n c h n e t s e t t l e m e n t a t twice t h e d e s i g n load. Values of 114 and 1 i n c h a t twice t h e design l o a d and 1/4 i n c h a t t h r e e t i m e s t h e d e s i g n l o a d have been used. Figu r e 6 p r e s e n t s a procedure f o r determining t h e f a i l u r e load based on a perman e n t s e t of 0.15 + D/120 i n c h e s (where D i s t h e p i l e diameter i n i n c h e s ) . T h i s procedure can be used f o r e i t h e r of t h e t h r e e t e s t methods p r e s e n t e d above. Where n e g a t i v e s k i n f r i c t i o n (downdrag) may a c t on t h e p i l e , o n l y l o a d c a r r i e d by t h e p i l e below t h e compressible zone should be considered. T h i s may be determined by minimizing s h a f t r e s i s t a n c e d u r i n g t h e l o a d t e s t (e.g., p r e d r i l l i n g o v e r s i z e d h o l e , c a s e and c l e a n , u s i n g b e n t o n i t e s l u r r y , e t c . ) o r by measuring movement of t i p d i r e c t l y by e x t e n s i o n r o d s a t t a c h e d t o t h e p i l e t i p and a n a l y z i n g t e s t r e s u l t s i n accordance w i t h F i g u r e 7.
I
APPLIED
LOAD (TONS)
I
TYPICAL TEST PLOT
column by:
"
aE= %L AE
Q = t e s t load, l b s
Lp = p i l e l e n g t h , i n . ( f o r end-bearing p i l e ) A = c r o s s - s e c t i o n a l a r e a of p i l e m a t e r i a l , sq i n E = Young's Modulus f o r p i l e m a t e r i a l , p s i
2.
Determine s c a l e s of p l o t such t h a t s l o p e of p i l e e l a s t i c compression l i n e i s approximately 20'.
3.
P l o t p i l e head t o t a l displacment vs. a p p l i e d l o a d .
4.
F a i l u r e l o a d i s d e f i n e d a s t h a t l o a d which produces a displacement of t h e p i l e head e q u a l t o : D sf.=SEt (.15+-)120
I
S f = displacement a t f a i l u r e , i n . D = p i l e diameter, in.
5.
Plot f a i l u r e c r i t e r i o n a s described i n ( 4 ) , represented a s a s t r a i g h t l i n e , p a r a l l e l t o l i n e of p i l e e l a s t i c compression. I n t e r s e c t i o n of f a i l u r e c r i t e r i o n with observed l o a d d e f l e c t i o n curve d e f i n e s f a i l u r e l o a d , Qf.
'6.
Where observed l o a d displacement curve does n o t i n t e r s e c t f a i l u r e c r i t e r i o n , t h e maximum t e s t l o a d should be t a k e n a s t h e f a i l u r e l o a d .
7.
Apply f a c t o r of s a f e t y of a t l e a s t 2.0 a l l o w a b l e load.
to f a i l u r e load t o determine
FIGURE 6 I n t e r p r e t a t i o n of P i l e Load T e s t
I
c. P u l l o u t T e s t s . Methods or a e ~ e m ~ l ~ fi anigl u r e load f o r t e n s i o n l o a d In g e n e r a l , t e s t s vary depending on t h e t o l e r a b l e movement of t h e s t r u c t u r e . f a i l u r e load i s more e a s i l y defined than f o r compression load tests s i n c e a v a i l a b l e r e s i s t a n c e g e n e r a l l y de r e a s e s more d i s t i n c t l y a f t e r reaching f a i l t h a t value a t which upward movement suddenure. F a i l u r e load may be taken l y i n c r e a s e s d i s p r o p o r t i o n a t e l y t o l o a d a p p l i e d , i.e. t h e p o i n t of s h a r p e s t c u r v a t u r e on t h e load-displacement curve. d. L a t e r a l Load Tests. L a t e r a l load t e s t s a r e u s u a l l y performed by jacking a p a r t two adjacent p i l e and recording d e f l e c t i o n s of t h e p i l e s f o r See Reference 24, Model Study of L a t e r a l l y Loaded P i l e , each load increment. by Davisson and S a l l e y , f o r f u r t h e r guidance. In some a p p l i c a t i o n s t e s t i n g of a- p i l e group may be required. e. Other Comments. A response of a d r i v e n p i l e i n a load t e s t can be I n most g r e a t l y a f f e c t e d by t h e time elapsed between d r i v i n g and t e s t i n g . c a s e s , a g a i n i n p i l e bearing c a p a c i t y i s experienced w i t h time and i s governed by t h e r a t e of d i s s i p a t i o n of excess pore water p r e s s u r e s generated by d r i v i n g t h e p i l e throughout t h e surrounding s o i l mass. This i s f r e q u e n t l y termed "freezing." The time r e q u i r e d f o r t h e s o i l t o r e g a i n i t s maximum s h e a r s t r e n g t h can range from a minimum of 3 t o 30 days o r longer. The a c t u a l req u i r e d waiting period may be determined by r e d r i v i n g p i l e s o r from previous experience. Generally, however, e a r l y t e s t i n g w i l l r e s u l t i n an underestimate of t h e a c t u a l p i l e c a p a c i t y e s p e c i a l l y f o r p i l e s d e r i v i n g t h e i r c a p a c i t y from s a t u r a t e d cohesive s o i l s . P i l e s d r i v e n through s a t u r a t e d dense f i n e sands and s i l t s may experience l o s s of d r i v i n g r e s i s t a n c e a f t e r periods of r e s t . When r e d r i v e n a f t e r p e r i o d s of rest t h e d r i v i n g r e s i s t a n c e (and bearing c a p a c i t y ) w i l l be less compared t o t h e i n i t i a l d r i v i n g r e s i s t a n c e (and c a p a c i t y ) . This phenomenon i s commonly r e f e r r e d t o a s r e l a x a t i o n . S e c t i o n 5.
1.
D I S T R I B ~ I O N OF LOADS ON PILE GROUPS
VERTICAL PILE GROUPS.
a. E c c e n t r i c V e r t i c a l Loading. D i s t r i b u t i o n of design load on p i l e s i n groups i s analyzed by r o u t i n e procedures a s follows: (1) For d i s t r i b u t i o n of a p p l i e d load e c c e n t r i c about one o r two axes, s e e Reference 6.
( 2 ) Overload from e c c e n t r i c i t y between a p p l i e d l o a d and c e n t e r of g r a v i t y of p i l e group s h a l l be permitted up t o 10 percent of allowable working load when a s a f e t y ' f a c t o r of 2-112 t o 3 i s a v a i l a b l e f o r t h e working load. ( 3 ) Overload from wind plus o t h e r temporary l i v e l o a d s up t o 33 perc e n t of t h e allowable working load i s permitted, when a s a f e t y f a c t o r of 2-112 t o 3 i s a v a i l a b l e f o r t h e working load. ( 4 ) Except i n unusual circumstances, a l l bearing p i l e s i n a group s h a l l be of t h e same type, and of equal load capacity.
t
I.
IF SKlN FRICTION ACTING ON TEST PlLE MAY BE REVERSED IN THE PROTOTYPE BY CONSOLIDATION OF MATERIALS ABOVE THE BFARING CrRATUM,ANALYZE UADTEST TD DETERMINE RELATION
2. 3.
OF U)AD VS SETTLEMENT FOR PlLE TIP AUNE . COMPUTE THEORETICAL ELASTIC SHORTENING ASSUMING SEVERAL POSSIBU VARIATIONS OF SKIN FRICTION ON PlLE AS SHOWN BELOW FOR A CYLINDRICAL PILE. COMPARE THEORETICAL WltH OBSERVED ELASTIC SHORTENING AND DETERMINE PROBABLE VARIATION OF SKlN FRICTION ON PILE. USING THIS VARIATION OF SKlN FRICTUN, COMPUTE LaAD AT TIP. CYLINDRICAL PILE: MODULUS OF ELASTICITY =E
-
CA=MAXIMUM SKlN FRICTION
A
Q
n
I I '
BEARING STRATUM R =RADIUS A = AREA
/acA
DIVISION OF APPLIED LOAD BETWEEN TIP LOAD ,AND SKlN FRICTION F = TOTAL SKIN FRICTION
8E = ELASTIC SHORTENING
OF PILE WITH LOAD QA AT BUTT AND Qp' AT TIP.
BE = ( a * - 2 n ~ ~ ~ (
-3
Q
,'
IN~ENSITYOF SKIN FRICTION
a
CASE ,SKIN FRICTION CONSTANT WITH DEPTH : L 8~ = (QA-rr R C A L I AE
ap' = CASE @ ,SKIN FRICTION DECREASING TD a CA AT TIP :
I
I
F
I
L
CASE @ ,SKIN FRICTION DECREASING TO ZERO AT TIP :
BE = ( Q A -
4 T R3C A L
'
Ln
-+
~ A E ~ E QP'= 2, *
FIGURE 7 Load Test Analysis Where Downdrag Acts on Pile
~
2. GROUPS WITH VERTICAL AND BATTER PILES. Analyze d i s t r i b u t i o n of p i l e l o a d s according t o c r i t e r i a i n Reference 25, P i l e Foundations, by C h e l l i s . The f o l l o w i n g l i m i t a t i o n s apply: ( 1 ) Assume i n c l i n a t i o n of b a t t e r p i l e s no f l a t t e r t h a n 1 h o r i z o n t a l t o 3 v e r t i c a l u n l e s s s p e c i a l d r i v i n g equipment i s s p e c i f i e d .
( 2 ) When b a t t e r p i l e s a r e i n c l u d e d i n a group, no allowance i s made f o r p o s s i b l e r e s i s t a n c e of v e r t i c a l p i l e s t o h o r i z o n t a l f o r c e s .
( 3 ) For a n a l y s i s of l o a d s on p i l e s i n r e l i e v i n g p l a t f o r m s , s e e Reference 26, American C i v i l Engineering P r a c t i c e , Vol. 1, by Abbett.
(4)
For a n a l y s i s of b a t t e r p i l e anchorage f o r tower guys, s e e F i g u r e
8.
S e c t i o n 6.
DEEP FOUNDATIONS ON ROCK
1. GENERAL. For o r d i n a r y s t r u c t u r e s , most rock f o r m a t i o n s p r o v i d e an i d e a l f o u n d a t i o n capable of s u p p o r t i n g l a r g e l o a d s w i t h n e g l i g i b l e s e t t l e m e n t . Norm a l l y , t h e a l l o w a b l e l o a d s on p i l e s d r i v e n i n t o rock a r e based on p i l e s t r u c t u r a l c a p a c i t y while t h e allowable b e a r i n g p r e s s u r e s f o r f o o t i n g s / p i e r s on rock a r e based on a nominal v a l u e s of a l l o w a b l e b e a r i n g c a p a c i t y ( s e e Chapter 4 1. There a r e however c e r t a i n u n f a v o r a b l e r o c k c o n d i t i o n s ( e . g. , cavernous l i m e s t o n e , s e e DM-7.1, Chapter 1 ) which can r e s u l t i n e x c e s s i v e s e t t l e m e n t and/or f a i l u r e . These p o t e n t i a l h a z a r d s must be c o n s i d e r e d i n t h e d e s i g n and c o n s t r u c t i o n of f o u n d a t i o n s on rock. 2. PILES DRIVEN INTO ROCK. P i l e s d r i v e n i n t o rock normally meet r e f u s a l a t a nominal d e p t h below t h e weathered zone and can be designed based on t h e s t r u c t u r a l c a p a c i t y of t h e p i l e imposed by b o t h t h e dynamic d r i v i n g s t r e s s e s and t h e s t a t i c stresses. Highly weathered r o c k s such as decomposed g r a n i t e o r l i m e s t o n e and weakly cemented rocks such as s o f t c l a y - s h a l e s can be t r e a t e d a s soils. The p o s s i b i l i t y of buckling below t h e mudline should b e e v a l u a t e d f o r h i g h c a p a c i t y p i l e d r i v e n through s o f t s o i l s i n t o bedrock ( s e e Reference 27, The Design of Foundations f o r B u i l d i n g s , by Johnson and Kavanaugh).
3. ALLOWABLE LOADS ON PIERS I N ROCK. P i e r s d r i l l e d through s o i l and a nominal d e p t h i n t o bedrock shciuld be designed on t h e b a s i s of a n a l l o w a b l e b e a r i n g p r e s s u r e g i v e n i n Chapter 4 o r o t h e r c r i t e r i a ( s e e Reference 28, Foundation ~ n ~ i n e e r i nby~ peck, , e t al.). P i e r s a r e normally d r i l l e d a nominal d e p t h i n t o t h e rock t o e n s u r e b e a r i n g e n t i r e l y on rock and t o e x t e n d t h e p i e r through t h e upper, more f r a c t u r e d zones of t h e rock. I n c r e a s e i n a l l o w a b l e b e a r i n g with embedment depth should be based on e n c o u n t e r i n g more competent rock w i t h depth.
EL-33 VERTICAL EFFECTIVE STRESS IN BEARING STRATUM FOR A SIX PILE GROUP -4 TENSION, 2 COMPRESSION ASSUME A SQUARE STRAIGHT CONCRETE PILE, PILE CAP WEIGHT (DW)=10 X ll X 3 X 0.b KCF AS SHOWN , ~ = 2 0 '(D(20B) =*.5K FIND Fs AGAINST Quit AND Tult
DETERMINE PILE FORCES BY A FORCE DIMRAM. IGNORE RESISTANCE ABOVE FIRM SAND STRATUM. BEARING STRATUM = 30°, Nq = 2 1 KHC =I.5, K~~ = 1.0,8=) (-=22d0
4
(mFIGURE I)
A ~ = ( # ) ~1=. 3 6 ~ ~ PERIM. AREA /lf =4 X
Quit = 1.98 X 21 X 1.36
+$= 4.7 SF&( . --
+ (1.5 x ( "'l
x TAN 22.5 x4.7 i 2 0 )
= !5654+81.47 = 138 K COMPRESSION LOAD ON PILES FROM FORCE MAGRAM IS 70KIPS. UMD PER PILE 70K h = 35K F ~ = ~ 3 . 9 )~,REQ'D Fs ) xTAN 225 x 4.7 x 20 T u l t = I.Ox( 0.81+Isg8
= 54.31 K TENSION LOAD ON PILES FROM FORCE DIAGRAM IS 80 KIPS. LOIO PO1PILE
= 2 0K
WEIGHT OF PlLE ~0.204Kp/' X 37 = Z6 K -4.3 > 3 REQ'D FS Fs- 54.3 (20.0 -7.6)
-
i
FIGURE 8
Example Problem
- Batter
Pile Group as Guy Anchorage 7.2-233 -
Rock-socketed d r i l l e d p i e r s extending more t h a n a nominal depth i n t o rock d e r i v e capacity from both s h a f t r e s i s t a n c e and end bearing. The p r o p o r t i o n of t h e load t r a n s f e r r e d t o end bearing depends on t h e r e l a t i v e s t i f f n e s s of t h e rock t o concrete and t h e s h a f t geometry. Generally, t h e p r o p o r t i o n t r a n s f e r r e d t o end bearing decreases f o r i n c r e a s i n g depth of embedment and f o r inc r e a s i n g rock s t i f f n e s s . This proportion i n c r e a s e s with i n c r e a s e d loading. F i e l d t e s t s i n d i c a t e t h a t t h e u l t i m a t e s h a f t r e s i s t a n c e i s developed w i t h v e r y l i t t l e deformation ( u s u a l l y less t h a n 0.25 i n c h e s ) and t h a t t h e peak r e s i s t a n c e developed tends t o remain c o n s t a n t with f u r t h e r movement. Based on load test d a t a , t h e u l t i m a t e s h a f t r e s i s t a n c e can be estimated approximately from: Sr = (2.3 t o 3 ) ( f w ~ ) l / ~( p i e r diameter >16 i n c h e s ) Sr = ( 3 t o 4 ) ( f w ' ) l I 2 ( p i e r diameter (16 i n c h e s ) where :
Sr
ultimate shaft resistance i n force per s h a f t contact area
fw' = unconfined compressive s t r e n g t h of e i t h e r t h e rock o r t h e concrete, whichever i s weakest. See Reference 29, S h a f t Resistance of Rock Socketed D r i l l e d P i e r s , by Horvath and Kenney. Settlement i s normally n e g l i g i 4. SETTLEMENT OF DEEP FOUNDATIONS I N ROCK. b l e and need not be evaluated f o r foundations on rock designed f o r an approp r i a t e allowable bearing pressure. For very heavy o r f o r extremely s e t t l e m e n t s e n s i t i v e s t r u c t u r e s , t h e s e t tlement can be computed based on t h e s o l u t i o n f o r e l a s t i c s e t t l e m e n t presented i n Chapter 5 of DM-7.1. The choice of the e l a s t i c modulus, E, t o use i n t h e a n a l y s i s should be based on t h e rock mass modulus which r e q u i r e s f i e l d invest i g a t i o n . For guidance s e e Reference 9 and Reference 30, Rock Mechanics i n Engineering P r a c t i c e , by Stagg and Zienkiewicz, eds. In c a s e s where t h e seismic Young's modulus is known, t h e s t a t i c modulus can be c o n s e r v a t i v e l y assumed t o be 1110th t h e seismic modulus. S e c t i o n 7.
1. DESIGN OONCEPTS. A top, resists t h e load by ing s o i l . The magnitude f u n c t i o n of t h e r e l a t i v e
LATERAL LOAD CAPACITY
p i l e loaded by l a t e r a l t h r u s t and/or moment a t i t s d e f l e c t i n g t o mobilize t h e r e a c t i o n of t h e surroundand d i s t r i b u t i o n of t h e r e s i s t i n g p r e s s u r e s a r e a s t i f f n e s s of p i l e and s o i l .
Design c r i t e r i a i s based on maximum combined stress i n t h e p i l i n g , allowa b l e d e f l e c t i o n a t t h e top o r permissible bearing on t h e surrounding s o i l . Although 114-inch a t t h e p i l e top i s o f t e n used a s a l i m i t , t h e allowable l a t e r a l d e f l e c t i o n should be based on t h e s p e c i f i c requirements of t h e structure.
2.
-
DEFORMATION ANALYSIS
-
SINGLE PILE.
a . General. Methods a r e a v a i l a b l e (- e o-n . ,- Reference 9 and Reference 31, Non-Dimensional S o l u t i o n s f o r L a t e r a l l y Loaded P i l e s , w i t h S o i l Modulus Assumed P r o p o r t i o n a l t o Depth, by Reese and Matlock) f o r computing l a t e r a l p i l e load-deformation based on complex s o i l c o n d i t i o n s and/or non-linear s o i l s t r e s s - s t r a i n r e l a t i o n s h i p s . The COM 622 computer program (Reference 32, L a t e r a l l y Loaded P i l e s : Program Documentation, by Reese) has been documented and i s widely used. Use of t h e s e methods should o n l y be considered when t h e s o i l s t r e s s - s t r a i n p r o p e r t i e s a r e w e l l understood. P i l e deformation and s t r e s s can be approximated through a p p l i c a t i o n of s e v e r a l s i m p l i f i e d procedures based on i d e a l i z e d assumptions. The two b a s i c approaches presented below depend on u t i l i z i n g t h e concept of c o e f f i It i s assumed t h a t t h e l a t e r a l l o a d does c i e n t of l a t e r a l subgrade r e a c t i o n . not exceed about 113 of t h e u l t i m a t e l a t e r a l load c a p a c i t y . b. Granular S o i l and Normally t o S l i g h t l y Overconsolidated Cohesive S o i l s . P i l e deformation can be estimated assuming t h a t t h e c o e f f i c i e n t of subgrade r e a c t i o n , Kh, i n c r e a s e s l i n e a r l y with depth i n accordance with: fz Kh = D where :
Kh = c o e f f i c i e n t of l a t e r a l subgrade r e a c t i o n ( t o n s i f t 3 )
f = c o e f f i c i e n t of v a r i a t i o n of l a t e r a l subgrade r e a c t i o n (tons/f t3) z = depth ( f e e t ) D = widthldiameter of loaded a r e a ( f e e t )
Guidance f o r s e l e c t i o n of f i s given i n Figure 9 f o r fine-grained and coarse-grained s o i l s . c. Heavily Overconsolidated Cohesive S o i l s . For h e a v i l y overconsolidated hard cohesive s o i l s , t h e c o e f f i c i e n t of l a t e r a l subgrade r e a c t i o n can be assumed t o be c o n s t a n t w i t h depth. The methods presented i n Chapter 4 can be used f o r t h e a n a l y s i s ; Kh v a r i e s between 35c and 70c ( u n i t s of force/length3) where c i s t h e undrained shear s t r e n g t h . d. Loading Conditions. Three p r i n c i p a l loading c o n d i t i o n s a r e i l l u s t r a t e d with t h e design procedures i n Figure 10, using t h e i n f l u e n c e diagrams of Figure 11, 12 and 13 ( a l l from Reference 31). Loading may be l i m i t e d by allowable d e f l e c t i o n of p i l e top o r by p i l e s t r e s s e s . Case I. P i l e with f l e x i b l e cap o r hinged end condition. Thrust and moment a r e a p p l i e d a t t h e t o p , which is f r e e t o r o t a t e . Obtain t o t a l d e f l e c t i o n , moment, and s h e a r i n t h e p i l e by a l g e b r a i c sum of t h e e f f e c t s of t h r u s t and moment, given i n Figure 11.
I
I
FIGURE 9
,
Coefficient of Variation of Subgrade Reaction
.
CASE I. FLEXIBLE CAP, ELEVATED POSITION LQLID AT DESIGN PROCEDURE GROUND LINE FOR DEFINITION OF PARAMETERS SEE FIGURE 12 FOR EACH PILE:
CONDITION
"r==? L !
I.
=
PH
2.
M
3. OBTAIN COEFFICIENTS Fs, FM, FV AT DEPTHS DESIRED. 4. COMPUTE DEFLECTION, MOMENT AND SHEAR AT DESIRED DEPTHS USING FORMULAS OF FEURE II
M
H
n
I
7
TT mnTITmm,'Tnrtrz I1
,
P =
i
COMPUTE RELATIVE STIFFNESS FACTOR. E I )ID T =(f SELECT CURVE FOR FROPER IN FIGURE II.
9
.
NOTE : 'If I' VAWES FROM FIGURE 9 AND CONVERT TO LB/IN?
DEFLECTED POSITION
n = NUMBER OF PILES
CASE 1.PILES WITH RIGID CAP AT GROUND SURFACE
P
PT
T-
1 CASE
1
m.RIGID
I. 2.
3.
PROCEED ASINSTEP 1,CASEI. COMPUTE DEFLECTION AND MOMENT AT DESIRED DEPTHS USING COEFFICIENTS 4,FM AND FORMULAS OF FIGURE 12. MAX!MUM SHEAR OCCURS AT TOP OF PlLE AND EQUALS p = Pf IN EACH PILE.
n
CAP, ELEVATED POSITION
DEFLECTED I. ASSUME A HINGE AT POINT A WlTH A BALANCING
MOMENT M APPLl ED #r POINT A. 2. COMPUTE SLOPE e2 ABOVE GROUND AS A FUNCTION OF M FROM CHARACTERISTICS OF SUPERSTRUCTURE. 3. COMPUTE SLOPE el FROM SLOPE COEFFICIENTS OF FIGURE 13 AS FOUMIVS:
8, =Fe ( &E) I+ F ~
MT
4. EQUATE = e2 AND SOLVE FOR VALUE OF M. 5. KNOWING VALUES OF P AND M, SOLVE FOR DEFLECTION, SHEAR,AND MOMENT AS IN CASE I. NOTE : IF GROUND SURFACE AT PlLE LOCATION IS INCLINED, LOAD P TAKEN BY EACH PlLE IS PROPORTIONAL TO 1 1 ~ ~ 3 .
FIGURE 10 Design Procedure f o r L a t e r a l l y Loaded P i l e s
I
FIGURE 11 Influence Values for Pile with Applied Lateral Load and Moment (Case I . Flexible Cap or Hinged End Condition)
ND GROUND S U R F . .
ES=f(Z) SOIL MODULUS OF ELASTICITY f = COEFFICIENT OF VARIATION OF LATERAL SUBGRAOE REACTION (SEE FWRE 9 ) L= LENGTH OF PlLE BELOW GROUND SURFACE T = RELATIVE STIFFNESS FAClDf? E- MODUU S OF ELASTICITY OF PlLE I = MOMENT OF INERTIA OF PILE CROSS SECTON
Mp ,Vp=DERECT(ONIMOMENT,8 SHEAR AT ANY DEPTH Z DUE TO FORCE P.
FIGURE 12 Influence Values for Laterally Loaded Pile (Case 11. Fixed Against Rotation at Ground Surface) 7.2-239
ADDITIONAL DEFINITIONS OF PARAMETERS
-3.0
-25
-2.0 -1.5 SLOPE COEFFICIENT, Fg
- 1.0
-0.5
SU)PE COEFFICIENT, Fg
FIGURE 13 Slope Coefficient for P i l e with Lateral Load or Moment
0
Case 11. P i l e w i t h r i g i d cap f i x e d a g a i n s t r o t a t i o n a t ground surface. Thrust i s a p p l i e d a t t h e t o p , which must m a i n t a i n a v e r t i c a l t a n g e n t . Obtain d e f l e c t i o n and moment from i n f l u e n c e v a l u e s of F i g u r e 12. Case 111. P i l e w i t h r i g i d cap above ground s u r f a c e . R o t a t i o n of p i l e top depends on combined e f f e c t of s u p e r s t r u c t u r e and r e s i s t a n c e below ground. Express r o t a t i o n a s a f u n c t i o n of t h e i n f l u e n c e v a l u e s of F i g u r e 1 3 Knowing t h r u s t and moment a p p l i e d a t p i l e and determine moment a t p i l e top. top, o b t a i n t o t a l d e f l e c t i o n , moment and s h e a r i n t h e p i l e by a l g e b r a i c sum of t h e s e p a r a t e e f f e c t s from F i g u r e 11. 3.
CYCLIC LOADS.
L a t e r a l subgrade c o e f f i c i e n t v a l u e s d e c r e a s e t o about 25% t h e i n i t i a l v a l u e due t o c y c l i c l o a d i n g f o r s o f t / l o o s e s o i l s and t o about 50% t h e i n i t i a l v a l u e for stiffldense soils. 4. LONG-TERM LOADING. Long-term l o a d i n g w i l l i n c r e a s e p i l e d e f l e c t i o n c o r responding t o a d e c r e a s e i n l a t e r a l subgrade r e a c t i o n . To approximate t h i s c o n d i t i o n reduce t h e subgrade r e a c t i o n v a l u e s t o 25% t o 50% of t h e i r i n i t i a l v a l u e f o r s t i f f c l a y s , t o 20% t o 30% f o r s o f t c l a y s , and t o 80% t o 90% f o r sands.
-
5. ULTIMATE LOAD CAPACITY SINGLE PILES. A l a t e r a l l y loaded p i l e c a n f a i l by exceeding t h e s t r e n g t h of t h e surrounding s o i l o r by exceeding t h e bending moment c a p a c i t y of t h e p i l e r e s u l t i n g i n a s t r u c t u r a l f a i l u r e . Several methods a r e a v a i l a b l e f o r e s t i m a t i n g t h e u l t i m a t e l o a d c a p a c i t y . The method p r e s e n t e d i n Reference 33, L a t e r a l R e s i s t a n c e of P i l e s i n Cohesive S o i l s , by Broms, p r o v i d e s a simple procedure f o r e s t i m a t i n g u l t i m a t e l a t e r a l c a p a c i t y of p i l e s . 6. GROUP ACTION. Group a c t i o n should be c o n s i d e r e d when t h e p i l e s p a c i n g i n t h e d i r e c t i o n of l o a d i n g i s l e s s t h a n 6 t o 8 p i l e diameters. Group a c t i o n c a n be e v a l u a t e d by reducing t h e e f f e c t i v e c o e f f i c i e n t of l a t e r a l subgrade react i o n i n t h e d i r e c t i o n of l o a d i n g by a r e d u c t i o n f a c t o r R (Reference 9 ) a s f o l lows : P i l e Spacing i n D i r e c t i o n of Loading D = P i l e Diameter 8D 6D
4D 3D
Subgrade R e a c t i o n Reduction F a c t o r R 1-00 0.70 0.40 0.25
REFERENCES
I.
Teng, W . C . , u-**-.lation Design, Prentice Hall International, 1962
2.
Skempton, A.W., The Bearing Capacity of Clays, Proceedings, Building Research Congress, London, 1951.
3.
Tomlinson, M.F., The Adhesion of Piles Driven in Clay Soils, Proceedings, Fourth International Conference on Soil Mechanics and Foundation Engineering, London, 1957.
4.
Departments of the Army and Air Force, Soils and Geology, Procedures for Foundation Design of Buildings and Other Structures (~xceptHydraulic Structures), TM51818-1lAFM88-3, Chapter 7, Washington, D.C. 1979.
5.
Meyerhof, G.G., and Hanna, A.M., Ultimate Bearing Capacity of Foundations on Layered Soils Under Inclined Load, Canadian Geotechnical Journal, Vol. 15, No. 4, 1978.
6.
Vesic, A.S., Design of Pile Foundations, National Cooperative Highway Research Program Synthesis 42, Transportation Research Board, 1977.
7.
Meyerhof, G.G., Bearing Capacity and Settlement of Pile Foundations, Journal of Geotechnical Engineering Division, ASCE, Vol. 102, No. GT3, 1976.
8. Baguelin, F., Jexequel, J.F., and Shields, D.H., The Pressuremeter and Foundation Engineering, TransTech Publications, 1978. 9.
Canadian Geotechnical Society, Canadian Foundation Engineering Manual, Canadian Geotechnical Society, 1978.
10.
Smith, E.A., Pile Driving by the Wave Equation, Transactions, American Society of Civil Engineers, Vol. 127, Part 11, pp 1145-193, 1962.
11.
Rausche, F., Moses, F., and Goble, G.G., Soil Resistance Predictions from Pile Dynamics, Journal of the Soil Mechanics and Foundation Division, ASCE, Vol. 98, No. SM9, 1972.
12.
Meyerhof, G.G., Ultimate Bearing Capacity of Footings on Sand Layer Overlying Clay, Canadian Geotechnical Journal, Vol. 11, No. 2, 1974.
13.
Whitaker, T., Experiments with Model Piles in Groups, Geotechnique, London, 1957.
14.
Tomlinson, M.J., Pile Design and Construction Practice, Viewpoint Publications, Cement and Concrete Association, London, 1957.
15.
Garlanger, J.E., Prediction of the Downdrag Load at Culter Circle Bridge, Symposium on Downdrag of Piles, Massachusetts Institute of Technology, 1973.
16.
Fellenius, B.H., Downdrag on Piles Due to Negative Skin Friction, Canadian Geotechnical Journal, Vol. 9, No. 4, 1972.
17.
Claessen, A.I.M. and Horvat, E., Reducing Negative Skin Friction with Bitumen Slip Layers, Journal of the Geotechnical Engineering Division, ASCE, Vol. 100, No. GT8, 1974.
18.
Bjerrum, L., Johannessin, I.J., and Eide, O., Reduction of Negative Skin Friction on Steel Piles to Rock, Proceedings of the Seventh International Conference on Soil Mechanics and Foundation Engineering, Vol. 2, pp 27-34, 1960.
19.
Deep Foundation Institute, Inspectorsf Manual for Deep Foundations, The Deep Foundations Institute, Springfield, NJ, 1978.
20.
AWPI, Technical Guidelines for Pressure-Treated Wood, Timber Piling, P1 American Wood Preservers Institute, 1976.
21.
ACI Committee 543, Recommendations for Design, Manufacture and Installation of Concrete Piles, ACI Manual of Concrete Practice, American Concrete Institute, Part 3, October, 1974.
22.
Reese, L.C. and Wright,S.J., Drilled Shafts: Design and Construction, Guideline Manual, Vol. 1; Construction Procedures and Design for Axial Load, Federal Highway Authority, July, 1977.
23.
Garneau, R., and Samson, L., A Device for the Constant Rate of Penetration Test for Piles, Canadian Geotechnical Journal, Vol. 11, No. 2, 1974.
24.
Davisson, M.T. and Salley, J.R., Model Study of Laterally Loaded Pile, Journal of Soil Mechanics and Foundation Division, ASCE, Vol. 96, No. SM5, 1970.
25.
Chellis, R.D.,
26.
Abbett, American Civil Engineering Practice, Vol. 1.
27.
Johnson, S.M. and Kavanaugh, T.C., The Design of Foundations for Buildings, McGraw Hill Book Company, 1968.
28.
Peck, R.B., Hanson, W.E., and Thornburn, T.H., Foundation Engineering, John Wiley & Sons, Inc. , 1974.
29.
Horvath, N.G. and Kenney, T.C., Shaft Resistance of Rock-Socketed Drilled Pier. ASCE, Preprint #3698. 1979.
30.
Stagg, K.G. and Zienkiewiez, O.C., Eds., Rock Mechanics in Engineering Practice, John Wiley & Sons, Inc., 1968.
31.
Reese, L.C. and Matlock, H., Non-Dimensional Solutions for Laterally Loaded Piles with Soil Modulus Assumed Proportional to Depth, Proceedings, Eighth Texas Conference on Soil Mechanics and Foundation Engineering, Austin, Texas, ASCE, 1956.
-
Pile Foundations, McGraw Hill Book Company, 1961
32.
Reese, L.C., Laterally Loaded Piles: Program Documentation, Journal of Geotechnical Engineering Division, ASCE, Vol. 103, No. GT4, 1977.
33.
Broms, B.B., Lateral Resistance of Piles in Cohesive Soils, Journal of Soil Mechanics and Foundations Division, ASCE, Vol. 90, No. S M ~and SM3, 1964.
)ut of Date
I
BIBLIOGRAPHY American Petroleum Institute, Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms, API RP 2A, January 1971. '
Casagrande, L., Comments on Conventional Design of Retaining Wall Structures, Journal of the Soil Mechanics and Foundation Engineering Division, ASCE, Vol. 99, No. SM2, 1973. Davisson, M.T., Inspection of Pile Driving Operations, Tech. Report M-22, Cold Regions Research Engineering Laboratories Corps of Engineers, U.S. Department of the Army, 1972. Foster, C.R., Field Problems: Compaction, Foundation Engineering, Leonards, G.A., Editor, McGraw-Hill Book Co., Inc., New York, Chapter 12, 1952. Fuller, F.N. and Hoy, H.E., Pile Load Tests Including Quick Load Test Method, Conventional Methods and Interpretations, Highway Research Record No. 333, HRB U.S. National Research Council, pp 74-86, 1970. Hunt, H.W., Design and Installation of Pile Foundations, Associated Pile Fitting Corporation, Clifton, NJ, 1974. McClelland, Be, Design of Deep Penetration Piles for Ocean Structures, Terzaghi Lectures: 1963-1972, ASCE, New York, pp 383-421, 1974. Meyerhof, G.G., Bearing Capacity and Settlement of Pile Foundations, Journal of the Geotechnical Engineering Division, ASCE, Vol. 102, No. GT3, 1976. National Bureau of Standards, Corrosion of Steel Pilings in Soils, Monographs 58 and 127, U.S. Department of Commerce, Washington, D.C. Reese, L.C. and Welch, R.C., Lateral Loading of Deep Foundations in Stiff Clay, Journal of the Geotechnical Engineering Division, ASCE, Vol. 101, NO. GT7, 1975. USBR, Earth Manual, Second Edition, U.S. Department of Interior, Bureau of Reclamation, U.S. Government Printing Office, Washington, D.C., 1974. Vesic, A.S., Ultimate Loads and Settlements of Deep Foundations in Sand, Procs., Symposium on Bearing Capacity and Settlement of Foundations, Duke University, Durham, NC. , 1967. Winterkorn, H.F., and Fang, H.Y., Editors, Foundation Engineering Handbook, Van Nostrand Reinhold Co., New York, 1975. Woodward, R.J., Gardner, W.S. and Greer, D.M., McGraw-Hill Book Co., Inc., New York, 1972.
Drilled Pier Foundations,
APPENDIX A Listing of Computer Programs ,
Subject Shallow Foundations (Chapter 4)
Excavation, and Earth Pressures (Chapter 1) and (Chapter 3)
Deep Foundations (Chapter 5)
Program QULT GESA Catalog No. E03-0001-00043
Description
Availability
Bearing capacity analysis by Balla, Brinch Hansen, MeyerhofPrandtl, Sokoluvski and Terzaghi Methods.
Geotechnical Engineering Software Activity University of Colorado Boulder, CO 80309
SOIL-STRUCT
Two dimensional finite element program to analyze tieback walls.
Stanford University
SSTINCS-2DFE
Two dimensional finite element program to analyze tieback walls.
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
Program solves for deflection and bending moment in a laterally loaded pile based on theory of a beam on an elastic foundation using finite difference techniques. Soil properties are defined by a set of load-deflection curves.
GESA or University of Texas at Austin
Program for analysis of pile driving by the Wave Equation; developed at Texas A&M University.
U.S. Department of Transportation FHWA R&D Implementation Div.
COM622 GESA Catalog No. E04-0003-00044
TTI
WEAP GESA Catalog No. E04-0004-00046
Wave Equation analysis for pile driven by impact hammers, diesel hammers and airlsteam hammers.
GESA
APPENDIX A Listing of Computer Programs (continued) A
Subject Deep Foundations (Chapter 5 )
Program
Description
Availability GESA
WINIT GESA Catalog No. E04-005-00047
Auxillary program for WEAP.
WEHAM GESA Catalog No. E04-006-00048
Hammer data f o r WEAP.
I.
WEAP data generator.
I.
WDATA GESA Catalog No. E04-007-00049
GLOSSARY -
Downdrag. Force induced on deep foundation r e s u l t i n g from downward movement of a d j a c e n t s o i l r e l a t i v e t o foundation element. Also r e f e r r e d t o a s negative skin friction. Homogeneous Earth Dam. An e a r t h dam whose embankment i s formed of one s o i l type without a s y s t e m a t i c zoning of f i l l m a t e r i a l s . Modulus of Subgrade Reaction. The r a t i o between t h e bearing p r e s s u r e of a foundation and t h e corresponding s e t t l e m e n t a t a given point. Nominal ~ e a r i n gPressures. Allowable bearing p r e s s u r e s f o r spread foundation on v a r i o u s s o i l t y p e s , derived from experience and g e n e r a l usage, which provide s a f e t y a g a i n s t s h e a r f a i l u r e o r excessive s e t t l e m e n t . Optimum Moisture Content. The moisture c o n t e n t , determined from a l a b o r a t o r y compaction t e s t , a t which t h e maximum dry d e n s i t y of a s o i l i s obtained u s i n g a s p e c i f i c e f f o r t of compaction. Piping. The movement of s o i l p a r t i c l e s a s t h e r e s u l t of unbalanced seepage f o r c e s produced by p e r c o l a t i n g water, l e a d i n g t o t h e development of b o i l s o r e r o s i o n channels. Swell. Increase i n s o i l volume, t y p i c a l l y r e f e r r i n g t o volumetric expansion of p a r t i c u l a r s o i l s due t o changes i n water content. Zoned E a r t h Dam. An e a r t h dam embankment zoned by t h e systematic d i s t r i b u t i o n of s o i l types according t o t h e i r s t r e n g t h and permeability c h a r a c t e r i s t i c s , u s u a l l y with a c e n t r a l impervious c o r e and s h e l l s of c o a r s e r materials.
d
SYMBOLS Designation
Symbol
Cross-sectional a r e a . Anchor p u l l i n t i e b a c k system f o r f l e x i b l e wall. Width i n g e n e r a l , o r narrow dimension of a foundation u n i t . Unit adhesion between s o i l and p i l e s u r f a c e o r s u r f a c e of some o t h e r foundation m a t e r i a l . Allowable cohesion t h a t can be mobilized t o resist shear stresses. Shape f a c t o r c o e f f i c i e n t f o r computation of immediate settlement. Cohesion i n t e r c e p t f o r Mohrts envelope of s h e a r s t r e n g t h based on total stresses. Cohesion i n t e r c e p t f o r Mohrts envelope of s h e a r s t r e n g t h based on effective stresses. C o e f f i c i e n t of consolidation. Depth, diameter, o r d i s t a n c e . Relative density. Grain s i z e d i v i s i o n of a s o i l sample, percent of dry weight smaller than t h i s g r a i n s i z e i s i n d i c a t e d by s u b s c r i p t . Modulus of e l a s t i c i t y of s t r u c t u r a l m a t e r i a l . Modulus of e l a s t i c i t y o r "modulus of deformation" of s o i l . Void r a t i o . Safety f a c t o r i n s t a b i l i t y o r shear s t r e n g t h a n a l y s i s . C o e f f i c i e n t of - v a r i a t i o n of s o i l modulus o f - e l a s t i c i t y w i t h d e p t h f o r a n a l y s i s of l a t e r a l l y loaded p i l e s . ~ ~ e c i f i gk r' a v i t y of s o l i d p a r t i c l e s i n s o i l sample, o r s h e a r modulus of s o i l . In general, height o r thickness. Height of groundwater o r of open water above a base l e v e l . Influence value f o r v e r t i c a l s t r e s s produced by superimposed l o a d , equals r a t i o of s t r e s s e s a t a p o i n t i n t h e foundation t o i n t e n s i t y of applied load. Gradient of groundwater pressures i n underseepage a n a l y s i s . C o e f f i c i e n t of a c t i v e e a r t h pressures. Ratio of h o r i z o n t a l t o v e r t i c a l e a r t h p r e s s u r e s on s i d e of p i l e o r o t h e r foundation. C o e f f i c i e n t of l a t e r a l subgrade r e a c t i o n . C o e f f i c i e n t of passive e a r t h p r e s s u r e s . Modulus of subgrade r e a c t i o n f o r bearing p l a t e o r foundation of width b Modulus of subgrade r e a c t i o n f o r 1 f t square bearing p l a t e a t ground s u r f ace. C o e f f i c i e n t of permeability. Kips per s q f t pressure i n t e n s i t y . Kips per sq i n pressure i n t e n s i t y .
.
.k ksf ksi
Designation
Symbol
Lengtn l u g e n e r a l o r l o n g e z t dimension 9f f o u n d a t i c r u n i t . Bearing c a p a c i t y f a c t o r s .
S t a b i l i t y number f o r s l o p e s t a b i l i t y . P o r o s i t y of s o i l sample. Effective porosity. Optimum moisture c o n t e n t of compacted s o i l . Resultant active e a r t h force. Component of r e s u l t a n t a c t i v e f o r c e i n h o r i z o n t a l d i r e c t i o n . Density i n pounds p e r c u b i c f o o t . Resultant horizontal e a r t h force. Resultant passive e a r t h force. Component of r e s u l t a n t p a s s i v e e a r t h f o r c e i n h o r i z o n t a l direction. Resultant v e r t i c a l e a r t h force. R e s u l t a n t f o r c e of water p r e s s u r e . I n t e n s i t y of a p p l i e d l o a d . E x i s t i n g e f f e c t i v e overburden p r e s s u r e a c t i n g a t a s p e c i f i c height i n the s o i l profile. Preconsolidation pressure. Allowable l o a d c a p a c i t y of deep f o u n d a t i o n element. U l t i m a t e load t h a t causes s h e a r f a i l u r e of f o u n d a t i o n u n i t . I n t e n s i t y of v e r t i c a l l o a d a p p l i e d t o f o u n d a t i o n u n i t . Allowable b e a r i n g c a p a c i t y of s h a l l o w f o u n d a t i o n u n i t . Unconfined compressive s t r e n g t h of s o i l sample. U l t i m a t e b e a r i n g p r e s s u r e t h a t c a u s e s s h e a r f a i l u r e of foundation uni t Radius of w e l l o r o t h e r r i g h t c i r c u l a r c y l i n d e r . Shear s t r e n g t h of s o i l f o r a s p e c i f i c s t r e s s o r c o n d i t i o n i n s i t u , used i n s t e a d of s t r e n g t h parameters c and 0. Thickness of s o i l s t r a t u m , o r r e l a t i v e s t i f f n e s s f a c t o r of s o i l and p i l e i n a n a l y s i s of l a t e r a l l y loaded p i l e s . Depth. Dry u n i t weight of s o i l . E f f e c t i v e u n i t weight of s o i l . Maximum d r y u n i t weight of s o i l determined from m o i s t u r e c o n t e n t d r y u n i t weight curve; o r , f o r c o h e s i o n l e s s s o i l , by v i b r a t o r y compaction. Minimum d r y u n i t weight. Submerged (buoyant) u n i t weight of s o i l mass. W e t u n i t weight of s o i l above t h e groundwater t a b l e . Unit weight of w a t e r , v a r y i n g from 6 2 . 4 pcf f o r f r e s h w a t e r t o 64 pcf f o r s e a water. Magnitude of s e t t l e m e n t f o r v a r i o u s c o n d i t i o n s . Angle of i n t e r n a l f r i c t i o n o r "angle of s h e a r i n g r e s i s t a n c e , " o b t a i n e d from Mohr's f a i l u r e envelope f o r s h e a r s t r e n g t h . P o i s s o n ' s Ratio.
.
INDEX
A Anchorages, tower guy..........7.2-169 See Foundations, shallow, Tower Guy Anchorages
B
Embankment compacted, compaction procedures, and hydraulic fills (continued) Cross-section design (continued) Material type influence..7.2-38 Utilization...........7.2-38 Settlement...............7.2-38
Embankment consolidation................7.2-38
Bibliography...................7.2-B-1
C Cofferdams, double-wall........7.2-116 See Walls and retaining structures Compaction procedures..........7.2-45 Computer Programs, Listing of..7.2-A-1
.
E Embankments compacted, compaction procedures, and hydraulic fill~..............o..o.o7o2-37 Applications................7.2-37
Compaction control, embankment......................7.2-50 Analysis of control test data..............7.2-51 Compactive effort.....7.2-52 Moisture contro1......7.2-52 Statistical study.....7.2-52 Number of field density tests..................7.2-51
Number of laboratory compaction tests.......7.2-51 Compaction requirements and procedures............7.2-45 Material type influence..7.2-45 Oversize effect -7.2-45 Soils insensitive to compaction moisture .7.2-45 Soils sensitive to compaction moisture.7.2-45 Methods..................7.2-45
......
Requirements.............7.2-45
Specification provisions.............7.2-45 Cross-section design........7.2-38 Earth dam embankments....7.2-41 Piping and cracking...7.2-41 Seepage contro1.......7.2-41
Foundation settlement.7.2-38 Secondary compression.7.2-41 Stable foundation........7.2-38 Weak foundation..........7.2-38 Excavation, borrow..........7.2-52 Methods of excavation.. .7.2-53 Utilization of excavated materials..............7.2-53 Borrow volume.........7.2-53 Rock fi11.............7.2-53 Fills, hydraulic and underwater.....................7.2-54 Construction methods.....7.2-54 Hydraulic fill on land................7.2-54 Underwater fills......7.2-54 Performance of fill materials..................7.2-54 Coarse-grained fills..7.2-54 Hard clay fills.......7.2-56 Equipment, pile driving........7.2-213 See Foundations, deep, 5pes Excavation, borrow.............7.2-52 See Embankments , compacted , Excavation.
.
Fills, hydraulic and underwater........................7.2-54 See Embankments compacted, Fills. Foundations, deep..............7.2-177 Application.................7.2-177 Bearing capacity............7.2-191 Dynamic Driving Resistance..................7.2-202
Pile group, theoretica1..7.2-204 Single pile, theoretical.7.2-192
Foundations. deep (continued) D i s t r i b u t i o n of l o a d s on p i l e groups 7. 2-230 Downdrag 7. 2-209 Installation 7. 2-213 I n v e s t i g a t i o n program 7. 2-177 L a t e r a l load c a p a c i t y 7. 2-234 Load tests 7. 2-228 Rock. deep foundations on 7. 2-232 Settlement.. 7. 2-207 P i l e group 7. 2-209 Single p i l e 7. 2-207 Types 7. 2-178 Allowable stresses 7. 2-179 Design c r i t e r i a 7. 2-179 Foundations. shallow 7. 2-129 Applications 7. 2-129 Bearing c a p a c i t y 7. 2-129 Footings. proportioning individual 7. 2-146 Nominal bearing pressures 7. 2-141 Modifications 7. 2-141 U t i l i z a t i o n ...........7. 2-141 Ultimate s h e a r f a i l u r e 7. 2-129 Bearing c a p a c i t y diagrams 7. 2-129 T h e o r e t i c a l bearing capacity 7. 2-129 Uplift capacity 7. 2-169 Rock anchorages 7. 2-169 S o i l anchorages .7.2-169 Collapsing s o i l s 7. 2-163 Engineered f i l l 7. 2-159 Compaction c o n t r o l 7. 2-159 U t i l i z a t i o n ..............7. 2-159 Expansive s o i l s 7. 2-159 Eliminating s w e l l 7. 2-161 Minimizing s w e l l effects.7.2-161 P o t e n t i a l s w e l l i n g conditions 7. 2-159 Mat and continuous beam foundations ...............7. 2-150 Applications 7. 2-150 Design ...................7. 2-150 Settlement ...............7. 2-150 S t a b i l i t y requirements 7. 2-150 Tower guy anchorages 7. 2-169 Anchoring tower guy l o a d s ..................L 2-169 Deadman anchorages 7. 2-172 P i l i n g anchorages 7. 2-233 Rock ..................7. 2-169
o.............. .................... ................ ....... ....... .................. ... ................. ............... .............. ....................... ....... .......... ........... ................ ............ ............. ..............:... ......... ... ............... ............ .......... ........ ...... ............ ............. ....... ............. ........ ................ ............. ... ........
.... .....
Foundations. shallow ( c o n t i n u e d ) Underdrainage and waterproofing 7. 2-163 Pressure s l a b s 7. 2-163 Relieved s l a b s 7. 2-169 Waterproofing r e q u i r e ments 7. 2-169
.................. ........... ........... ..................
Glossary
.......................7.2- G-1
................7. 2-150
Mat foundations See Foundations. shallow. Mat
.
Piles : Foundations ( s e e Foundations. deep) 7. 2-177
.....................
Walls and r e t a i n i n g s t r u c t u r e s . analysis 7. 2-59 Cofferdams. double-wall 7. 2-116 Analysis 7. 2-116 Exterior pressures 7. 2-116 S t a b i l i t y requirements 7. 2-116 Cell fill 7. 2-125 Drainage 7. 2-125 Materials 7. 2-125 Types 7. 2-116 F l e x i b l e w a l l s design 7. 2-85 Anchored bulkheads 7. 2-85 Anchorage system 7. 2-90 Computation example 7. 2-93 Construct i o n pr ecautions 7. 2-90 Drainage 7. 2-85 Movements. w a l l 7. 2-85 Pressures. w a l l 7. 2-85 Braced s h e e t p i l e w a l l s ..7. 2-90 Computation example 7. 2-107 Narrow c u t s braced 7. 2-101
..................... ..... ................. .... ............... ................ .............. ............. .................... ....... ....... ...... ... ............ .............. ....... ....... ... ....
kralls and r e t a i n i n g s t r u c t u r e s . . a n a l y s i s (continued) ~ l e k b l 'ew a l l s design (continued) Braced s h e e t pile w a l l s (cont inued ) Raking braces with wall 7. 2-101 S t a b i l i t y of base of 7. 2-104 excavation Tied backwalls 7. 2-101 Crib w a l l s 7. 2-116 Gabions 7. 2-112 Pressures. wall. computa7. 2-59 tions Active p r e s s u r e s 7. 2-59 Stratified backfill. s l o p i n g groundwater 7. 2-61 level Uniform b a c k f i l l . no groundwater 7. 2-61 Uniform b a c k f i l l . s t a t i c groundwater ..7. 2-61 C o e f f i c i e n t s with wall 7. 2-61 friction E f f e c t of c o n s t r u c t i o n 7. 2-76 procedures 7. 2-76 Compacted f i l l s 7. 2-76 Hydraulic f i l l s E f f e c t of seepage and Drainage 7. 2-70 Beneath w a l l s seepage.7.2-70 Conditions. genera1 7. 2-70 R a i n f a l l on drained walls 7. 2-70 Static differential 7. 2-70 head Loading. surcharge 7. 2-70 7. 2-73 Area l o a d s Live l o a d s 7. 2-73 Movement. w a l l 7. 2-73 Braced f l e x i b l e 7. 2-73 sheeting Restrained walls 7. 2-76 Tilting retaining 7. 2-73 walls 7. 2-59 Passive p r e s s u r e s Stratified backfill. sloping groundwater 7. 2-61 level Uniform b a c k f i l l . no 7. 2-61 groundwater Uniform b a c k f i l l . s t a t i c groundwater 2-61 l e v e l ...............7,
................ .......... ........ ............... .................. ..................... ......... ............... .........
Walls and r e t a i n i n g s t r u c t u r e s . a n a l y s i s (continued) P r e s s u r e s . w a l l . computation (continued) 7. 2-116 Reinforced e a r t h Rigid r e t a i n i n g w a l l s 7. 2-82 C r i t e r i a . genera1 7. 2-82 7. 2-85 Drainage Settlement and overt u r n i n g .............7, 2-82 7. 2-82 Stability 7. 2-82 High w a l l s 7. 2-85 Low w a l l s Drainage 7. 2-85 Equivalent f l u i d 7. 2-85 pressures
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7.2:INDEX
. 3 U . S . GOVERNMENT PRINTING OFFICE : 1984 0
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