O NEIL REESE 1999 DRILLED SHAFTS CONSTRUCTION PROCEDURES AND DESIGN METHODS.pdf

PUBLICATION No. Fl I\\' A-I F-99-025 U.S. Deportment of Transportation

Federal Highway Administration

DRILLED SHAFTS: CONSTRUCTION PROCEDURES AND DESIGN METHODS

Office Of Infrastructure

Printed August 1999

NOUCE . .The. cdntenta,of this report reflect the'Vi~\\'S of the authors, wpo are respon8ible fQr the facts a.Jld t:Ma.ecura.oy .of·fhe d$ta·presented herein; .The conwnts do not ~essarily reflect.the policy of tb~;Pepaiunent 9fTramsp0rtation. This report does not constitute a ;standard, specifications, or ~gwation..:The United States Oovernttlent does rtot end0tsf: products 01 m(ln~ae~. Trade. or manufaetUre~'s ttames··appear herem·anly. &ecauie they. aretonSidered ess~al to the objective of this d.Ocument. . · · · · ·

Technical Report Documentation Page 1. Report No.

2. Government Accession No.

3. Recipient's Catalog No.

FHWA-IF-99-025 4. Title and Subtitle

4. Report Date

Drilled Shafts: Construction Procedures and Design Methods

August 1999 6. Perfonning Organization Code:

7. Author(s)

8. Perfonning Organization Report No.

Michael W. O'Neil and Lymon C. Reese 9. Perfonning Organization Name and Address

10. Work UnitNo.(TRAIS)

All American Soils 17921 Sky Park Circle, Suite J Irvine, CA 92614

11. Contract or Grant No.

DTFH61-96-Z-00051

12. Sponsoring Agency Name and Address

13 Type of Report and Period Covered

Federal Highway Administration Office oflnfrastructure/Office of Bridge Technology HIBT, Room 3203 400 7th Street S.W. Washington D.C. 20590

Technical Manual

14. Sponsoring Agency Code

15. SupplementaryNotes

COTR: Mr. Chien-Tan Chang Technical Assistance: Mr. Richard S. Cheney, P.E. Technical Review and Revision: Mr. Sumant Singla 16. Abstract:

This manual is FHWA's primary reference of recommended construction procedures and design methods for drilled shafts. This document was written as a resource for participants in a short course covering the topic of construction and design of drilled shaft foundations for bridges and other structures. It is the second edition of an FHWA workbook on construction and design of drilled shafts. The first edition was written in 1988 ( FHWA Publication No. FHWA-SA-HI-88-042). While introductory material from the 1988 edition was retained, the emphasis in this document is on providing relatively comprehensive information for engineers who already have some experience with drilled shaft construction and/or design. The initial chapters cover an overview of the characteristics of drilled shafts, site investigations for drilled shafts (to collect information for both construction and design), and details of drilled shaft construction. These chapters are followed by several chapters on the design of drilled shafts in soil and rock for both axial and lateral loading, with examples. Both allowable stress design and load and resistance factor design principles are addressed. Details of design calculations procedures are provided in the appendices. Procedures for performing load tests, an important component of design, are then reviewed, following which model construction specifications are presented and discussed. The latter chapters of the document deal with construction inspection, structural integrity testing, repair of defective drilled shafts and cost estimation. The chapter on inspection includes acceptance criteria and is intended to complement other short courses and documents on drilled shaft construction inspection. 17.KeyWords

18. Distribution Statement

Foundations, Drilled Shafts, Construction, Design, Soil, Rock, Computations, Specifications

No restrictions. This document is available to the public from the National Technical Information Service, Springfield, Virginia 22161

19. Security Classif. (of this report)

Fnrm DO'f F l"J\\\\.1

120. Security Classification (of this page)

Unclassified

Unclassified (~·11)

121. No. of Pages 122. Price

758

Reproduction of completed page authorized

PREFACE

The Federal Highway Administration has produced two educational publications (in 1977 and 1988) on the construction and design of drilled shaft foundations. The second publication, Publication No. FHWA-Hl-88-042, July 1988, has been used as the textbook to teach over 50 three-day short courses on drilled shafts in over 30 states between 1989 and 1998. However, drilled shaft technology has advanced rapidly since 1988, and it became necessary to revise and update this publication. This present publication is a new, expanded, edition of the 1988 publication, which it is intended to replace. New material contained in the present publication includes operations with polymer drilling slurries, admixtures for drilled shaft concrete, new drilling equipment, specifications for performing non-destructive evaluations, design in intermediate geomaterials and in rock, additional material on structural design, LRFD procedures, and methods for analyzing groups of drilled shafts. The main text addresses most common design and construction conditions. The appendices contain supporting material that may need to be used in certain circumstances and that gives foundation engineers detailed information not available in the text. It is intended that this publication serve as a living reference document that will be updated continually as further advances in the construction and design of drilled shafts take place. The authors express gratitude to Axiom Engineering and Science company, which compiled the text for this publication. They are also grateful to ADSC: The International Association of Foundation Drilling, its Executive Director, Mr. Scot Litke, and its technical review committee, chaired by Mr. Ed Nolan; Dr. Alaa Ata and Mr. Jose Arrellaga, who each reviewed all or parts of the document and provided considerable valuable input. The senior author also thanks his colleagues at the University of Houston, Dr. Cumaraswamy Vipulanadan and Dr. Sarni Tabsh for their helpful comments about behavior of cementious materials and structural design of drilled shafts, respectively, and to many colleagues, too numerous to name here, who provided photographs. Michael W. O'Neill Lymon C. Reese

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ENGLISH TO METRIC (SI) CONVERSION FACTORS The primary metric (SI) units used in civil and structural engineering are: meter(m) kilogram (kg) second (s) newton (N) or kilonewton (kN) pascal (Pa= N/m 2) or kilopascal (kPa = kN/m2)

length mass time force pressure

The following are the conversion factors for units presented in this manual: Quantity Mass Force Force/unit length Pressure, stress, modulus of elasticity Length

Area

Volume

From English Units lb lb kip plf kif psf ksf psi ksi inch foot square inch square foot square yard cubic inch cubic foot cubic yard

To Metric (SI) Units kg N kN

Multiply by 0.453 592 4.448 22 4.448 22 14.593 9 14.593 9 47.880 3 47.880 3 6.894 76 6.894 76 25.4 0.3048 304.8 645.16 0.09290304 0.83612736 16386.064 0.0283168 0.764555

Nim kN/m Pa kPa kPa Mpa mm m mm mm" m2 m2 mm" m3 m3

For aid to Quick Mental Calculations 1 lb(mass) = 0.5kg 1 lb(force) = 4.5N 1kip(force)=4.5kN 1 plf = 14.5N/m 1 kif= 14.5kN/m 1psf=48 Pa 1ksf=48 kPa 1 psi = 6.9 kPa 1 ksi = 6.9 Mpa 1 in=25 mm 1ft=0.3 m 1 ft-300 mm 1 sq in = 650 mm" 1 sq ft= 0.09 m2 1 sq yd= 0.84 m2 1 cu in= 16,400 mm" 1 cu ft= 0.03 m3 1 cu yd= 0.76 m3

A few points to remember: 1. In a "soft" conversion, an English measurement is mathematically converted to its exact metric equivalent. -2. In a "hard" conversion, a new rounded, metric number is created that is convenient to work with and remember. 3. Use only the meter and millimeter for length (avoid centimeter). 4. The pascal (Pa) is the unit for pressure and stress (Pa= N/m2). 5. Structural calculations should be shown in MPa or kPa. 6. A few basic comparisons worth remembering to help visualize metric dimensions are: • One mm is about 1/25 inch or slightly less than the thickness of a dime. • One m is the length of a yardstick plus about 3 inches. • One inch is just a fraction (1/64 inch) longer than 25 mm (1 inch= 25.4 mm). • Four inches are about 1/16 inch longer than 100 mm (4 inches= 101.6 mm). • One foot is about 3/16 inch longer than 300 mm (12 inches= 304.8 mm).

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TABLE OF CONTENTS

CHAPTER 1: INTRODUCTION ................................................................................................... 1 TYPES OF DEEP FOUNDATIONS ................................................................................... 1 DESCRIPTION OF DRILLED SHAFTS ........................................................................... 1 BRIEF HISTORY OF DRILLED SHAFT FOUNDATIONS ............................................ .4 MOTIVATION FOR USING DRILLED SHAFTS ............................................................ 6 REVIEW OF CURRENT PRACTICE .............................................................................. 10 Construction ........................................................................................................... 10 Design for Axial Load ........................................................................................... 12 Design for Lateral Load ......................................................................................... 14 APPLICATIONS OF DRILLED SHAFTS ....................................................................... 14 ADVANTAGES AND DISADVANTAGES OF DRILLED SHAFTS ............................ 15 Advantages ........................................................................................................... 15 Disadvantages ........................................................................................................ 19 TRAINING RESOURCE .................................................................................................. 20 REFERENCES ................................................................................................................ 20 CHAPTER 2: SITE CHARACTERIZATION ............................................................................. 22 PURPOSE OF SITE CHARACTERIZATION ................................................................. 22 SITE INVESTIGATIONS ................................................................................................. 23 General ................................................................................................................... 23 Surface Features ..................................................................................................... 24 Subsurface Pipelines, Cables, and Other Obstructions .......................................... 25 Preliminary Subsurface Mapping ..........................................................................25 Detailed Site Investigations ...................................................................................27 TECHNIQUES FOR SUBSURFACE INVESTIGATIONS .............................................28 Information Required for Design ...........................................................................28 Information Required for Construction ................................................................ .33 Comments ............................................................................................................. 34 Full-Sized Test Excavations .................................................................................. 35 UNCERTAINTY IN SOIL OR ROCK PROPERTIES AT A SITE ................................ .36 EFFECTS OF PILES AND DRILLED SHAFTS ON SOIL AND ROCK PROPERTIES .................................................................................................................. 37 Installation in Clays ............................................................................................... 37 Installation in Sands ............................................................................................... 38 Installation in Rock ................................................................................................ 39 SOIL AND ROCK MECHANICS RELATED TO DRILLED SHAFT DESIGN .......... .40 REFERENCES .................................................................................................................. 46 CHAPTER 3: GENERAL CONSTRUCTION METHODS ....................................................... 49 INTRODUCTION ............................................................................................................. 49 UNDERREAMS (BELLS) ................................................................................................ 50 VERTICAL ALIGNMENT ............................................................................................... 53 DRY METHOD OF CONSTRUCTION ........................................................................... 53 CASING METHOD OF CONSTRUCTION ..................................................................... 56 WET METHOD OF CONSTRUCTION ........................................................................... 63 iii

The Static Process .................................................................................................. 64 The Circulation Process .........................................................................................68 RELATIONSHIP OF CONSTRUCTION METHOD TO DESIGN PHILOSOPHY ................................................................................................................... 69 REFERENCES .................................................................................................................. 71 CHAPTER 4: METHODS OF EXCAVATION ........................................................................... 72 EXCAVATION BY ROTARY METHODS ..................................................................... 72 Truck-Mounted Drilling Machines ........................................................................73 Crane-Mounted Drilling Machines ........................................................................ 73 Special Mounts For Drilling Machines ................................................................... 76 Low Headroom Drilling Machines ......................................... .-.............................. 77 Summary of Rotary Drilling Machine Characteristics .......................................... 77 Tools for Rotary Drilling ....................................................................................... 79 Drilling Bucket. .......................................................................................... 79 Flight Augers (Open Helix) ....................................................................... 80 Rock Auger ................................................................................................ 83 Core Barrel ................................................................................................. 85 Shot Barrel ................................................................................................. 85 Full-Faced Excavators ............................................................................... 87 Underreamers or Belling Buckets .............................................................. 87 Special Tools .............................................................................................. 87 EXCAVATION BY PERCUSSION METHODS ............................................................. 87 Lifting Machines .................................................................................................... 88 Clamshell or Grab Bucket ...................................................................................... 88 Rock Breakers ........................................................................................................ 88 Hammergrabs ......................................................................................................... 92 OTHER METHODS OF EXCAVATION ......................................................................... 92 Rodless Drill ..........................................................................................................92 Air-Operated Hammers ..........................................................................................94 Use of Drilling Fluid ..............................................................................................95 Grouting ................................................................................................................. 95 Mining Techniques ................................................................................................ 95 REFERENCES .................................................................................................... ,; ............ 96 CHAPTER 5: CASINGS AND LINERS ..................................................................................... 97 TEMPORARY CASING ................................................................................................... 97 PERMANENT CASING ................................................................................................... 98 INFLUENCE OF CASING ON LOAD TRANSFER ....................................................... 99 TYPES AND DIMENSIONS .......................................................................................... 101 PROBLEMS OF PLACEMENT AND RECOVERY .................................................... .103 DESIGN CONSIDERATIONS ....................................................................................... 105 REFERENCES ................................................................................................................ 105

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CHAPTER 6: DRILLING SLURRY.......................................................................................... 106 INTRODUCTION ........................................................................................................... 106 PRINCIPLES OF SLURRY OPERATION ..................................................................... 108 Mineral Slurries ................................................................................................... 108 Polymers .............................................................................................................. 111 Blended Slurries ................................................................................................... 114 APPLICATIONS ............................................................................................................. 115 MATERIALS ................................................................................................................... 117 Bentonite .............................................................................................................. 117 Polymers .............................................................................................................. 122 MIXING AND HANDLING ........................................................................................... 124 Mineral Slurry ...................................................................................................... 124 Polymer Slurry ..................................................................................................... 127 Blended Slurry ..................................................................................................... 128 SAMPLING AND TESTING .......................................................................................... 128 Sampling .............................................................................................................. 128 Testing.................................................................................................................. 129 Density .................................................................................................... 129 Viscosity .................................................................................................. 130 pH Value .................................................................................................. 134 Sand Content ............................................................................................ 13 5 Hardness ................................................................................................... 136 Free Water and Cake Thickness .............................................................. 136 Shear Strength .......................................................................................... 13 7 Comments on Field Testing of Drilling Slurries ...................................... 137 MEASURING THE VOLUME OF THE EXCAVATION UNDER DRILLING SLURRY ........................................................................................................................ 139 EXCESSIVE EXPOSURE OF SOIL OR ROCK TO DRILLING SLURRY ................. 142 DESIRABLE PROPERTIES OF DRILLING SLURRY ............................................... .143 INFLUENCE OF SLURRY ON AXIAL CAPACITY OF DRILLED SHAFTS ........... 147 Soil and Rock Resistance ..................................................................................... 147 Bond with Reinforcing Steel. ............................................................................... 151 EXAMPLES OF PROBLEMS WITH SLURRY CONSTRUCTION ........................... .152 TRAIN.ING RESOURCE ................................................................................................ 159 REFERENCES ................................................................................................................ 159 CHAPTER 7: REBAR CAGES .................................................................................................. 162 INTRODUCTION ........................................................................................................... 162 PROPERTIES OF STEEL ............................................................................................... 163 LONGITUDINAL REINFORCING ............................................................................... 163 TRANSVERSE REINFORCING .................................................................................... 167 SPLICES ........................................................................................................................ 168 SIZING HOOPS .............................................................................................................. 169 CENTERING DEVICES ................................................................................................. 170 STRENGTHENING THE CAGE TO RESIST LIFTING FORCES .............................. 173 ARRANGEMENTS FOR LIFTING CAGE ................................................................... 174

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FABRICATION AND STORAGE .................................................................................. 177 CONSIDERATIONS RELATED TO METHOD OF CONSTRUCTION .................... .177 REFERENCES ................................................................................................................ 179 CHAPTER 8: DESIGN AND PLACEMENT OF CONCRETE ................................................ 180 BASIC CHARACTERISTICS OF DRILLED SHAFT CONCRETE ............................ 180 MIX DESIGN ................................................................................................................... 182 Cementitious Materials ........................................................................................ 182 Cement ..................................................................................................... 182 Pozzolanic Additives ............................................................................... 182 Expansive Additives ................................................................................ 183 Chemical Admixtures .......................................................................................... 184 Air-entraining agents ............................................................................... 184 Retarders .................................................................................................. 185 Water Reducers ........................................................................................ 185 Accelerators ............................................................................................. 186 Other Admixtures..................................................................................... 186 Aggregate and Water ........................................................................................... 186 Workability .......................................................................................................... 187 Mix Proportions ................................................................................................... 187 Streqgth ................................................................................................................ 194 CONCRETE TESTS ........................................................................................................ 194 Tests at the Batch Plant ........................................................................................ 194 Tests at the Jobsite ............................................................................................... 195 Addition of Water at Job Site ............................................................................... 196 PLACEMENT OF CONCRETE ..................................................................................... 197 Placement by Free Fall ........................................................................................ 197 Placement of Concrete by Tremie .......................................................................200 Placement by Gravity-Fed Tremie ...........................................................201 Placement by Pump..................................................................................208 DRILLING NEAR A RECENTLY CONCRETED SHAFT ..........................................215 CONCRETING CURVES ...............................................................................................216 CONTAMINATED CONCRETE AT SHAFT HEAD ...................................................219 POST-GROUTING ..........................................................................................................220 REFERENCES ...............................................................................................................220 CHAPTER 9: CASE STUDIES OF DRILLED SHAFT CONSTRUCTION UNDER VARIOUS CONDITIONS ................................................................................................................ 224 INTRODUCTION ...........................................................................................................224 CHAPTER 10: DESIGN CONCEPTS FOR DRILLED SHAFTS ............................................225 INTRODUCTION ........................................................................................................... 225 The Design Process ..............................................................................................225 Importance of subsurface Investigation ...............................................................226 Influence of Construction on Geomaterial Properties .........................................231 Cohesive Soil ...........................................................................................232

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Granular soil and Granular IGM's ........................................................... 233 Rock and Cohesive IGM's ....................................................................... 234 Principal Design Considerations .......................................................................... 235 GENERAL APPROACHED TO DESIGN ..................................................................... 238 Allowable Stress Design ...................................................................................... 239 Load and Resistance Factor Design ..................................................................... 240 Comparison of ASD and LRFD ........................................................................... 241 COMPUTATION OF A NOMINAL ULTIMATE AXIAL RESISTANCE, RTN .......... 243 Nominal Base Resistance, RaN ............................................................................ 247 Cohesive Soil ........................................................................................... 24 7 Granular Soil and Cohesionless Intermediate Geomaterials ................... 248 Rock and Cohesive Intermediate Geomaterials ....................................... 250 Nominal Side Resistance, RsN ............................................................................. 250 Cohesive Soil ........................................................................................... 250 Granular Soil and Cohesionless Intermediate Geomaterials ................... 251 Rock and Cohesive Intermediate geomaterials ........................................ 252 COMPUTAION OF DEFORMATIONS ........................................................................ 253 GROUPS OF DRILLED SHAFTS .................................................................................. 254 TOLERABLE MOVEMENTS ........................................................................................ 257 STRUCTURAL DESIGN ................................................................................................ 258 REFERENCES ............................................................................................................... 259 CHAPTER 11: GEOTECHNICAL DESIGN FOR AXIAL LOADING ................................... 262 INTRODUCTION ........................................................................................................... 262 DIRECTION OF SIDE AND BASE RESISTANCE ...................................................... 262 DESIGN OF DRILLED SHAFTS UNDER AXIAL LOADING ................................... 264 STEP-BY-STEP DESIGN PROCEDURES FOR AXIAL LOAD DESIGN .................. 266 REFERENCES ............................................................................................................... 296 CHAPTER 12: DESIGN FOR VERTICAL MOVEMNET OF THE GROUND SURFACE .................................................................................................................... 297 INTRODUCTION ........................................................................................................... 297 DOWNDRAG ................................................................................................................. 297 Occurrence ........................................................................................................... 297 Estimating the Neutral Point Location and Distribution of Load and Resistance ............................................................................................................ 301 Design Solutions ................................................................................................. 303 UPLIFT .......................................................................................................................... 307 Occurrence and Identification of Expansive Soils .............................................. .307 Estimating the Depth of the Zone of Seasonal Moisture Change ....................... .309 Design Solutions ................................................................................................. 310 RESOURCE ................................................................................................................... 316 REFERENCES ............................................................................................................... 316 CHAPTER 13: DESIGN FOR LATERAL LOADING AND STRUCTURAL DESIGN ......... 319 INTRODUCTION ........................................................................................................... 319 EXAMPLES OF LATERAL LOADING ........................................................................ 319

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Single-Column Support for a Bridge ................................................................... 319 Foundation for an Overhead-Sign Structure ........................................................ 321 Drilled-Shaft-Supported Bridge Over Water ....................................................... 321 Foundation for a Bridge Abutment.. .................................................................... 322 Foundation for an Arch Bridge ............................................................................ 322 Stabilization of a Moving Slope and Earth Retaining Structures ........................ 324 COMPUTING PENETRATION, DEFORMATIONS, MOMENTS AND SHEARS ...................................................................................................................... 327 Characteristic Load Method ................................................................................. 327 p-y Method ........................................................................................................... 337 Simulation of Nonlinear Bending in Drilled Shafts Using the p-y Method .............................................................................. 342 Simulation of Group Action Using the p-y Method ................................ 347 Other Methods of Analysis of Laterally Loaded Drilled Shafts and Drilled Shaft Groups ........................................................................................................ 350 STRUCTURAL DESIGN ................................................................................................ 351 Cases with Axial Load Only ................................................................................ 352 Cases with Axial Load and Bending Moment ..................................................... 353 General Concepts ..................................................................................... 353 Structural Design Procedure: Longitudinal Reinforcement.. .................. .354 Structural Design Procedure: Minimum Longitudinal Reinforcement .......................................................................................... 362 Design of Transverse Reinforcement. ................................................................. .363 Spiral Column Design .............................................................................. 363 Tied Column Design ................................................................................366 Design for Transverse Shear Forces ....................................................... .367 Depth of Code-Controlled Transverse Reinforcement ........................... .370 Splices, Connections and Cutoffs ........................................................... .370 Analysis to Obtain Distribution of Moment and Shear with Depth: Step-by-Step Procedure for Design (p-y method) .................................. .371 STRUCTURAL ANALYSIS OF PLAIN-CONCRETE UNDERREAMS .................... .378 RESOURCES ..................................................................................................................381 REFERENCES ................................................................................................................ 381 CHAPTER 14: FIELD LOADING TESTS ............................................................................... .386 PURPOSE OF LOADING TESTS .................................................................................. 386 AXIAL LOADING TESTS ............................................................................................. 387 Considerations in Sizing, Locating and Constructing the Test Shaft .................. 387 Methods of Applying Compressive Loads .......................................................... 391 Conventional Loading Test Arrangements .............................................. 391 Osterberg Cell Testing Arrangement ....................................................... 393 StatnamicRTesting Arrangement ............................................................. 399 Conventional Uplift Testing ................................................................................ 402 Instrumentation .................................................................................................... 403 Proof Test ................................................................................................ 403 Load Transfer Test, .................................................................................. 405

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Testing Procedures ............................................................................................... 412 Data and Analysis ................................................................................................ 413 LATERAL LOADING TESTS ....................................................................................... 415 Conventional Test ................................................................................................ 416 Osterberg Cell Test .............................................................................................. 418 StatnaniicR Test ....................................................................................................419

CJiiiil~lfiliiiiiirr~~11~1~~1r~· INTRODUCTION ........................................................................................................... 423 Construction Method ...........................................................................................424 Drilling Slurry .....................................................................................................424 Payment for Shaft Excavation .............................................................................425 Qualification of Drilled Shaft Contractors for Bidding ....................................... 426 Special Bidding Requirement ..............................................................................426 GUIDE DRILLED SHAFT CONSTRUCTION SPECIFICATIONS ............................ .426 ITEM xxx. DRILLED SHAFTS .....................................................................................428 xxx.10 DESCRIPTION.......................................................................................428 xxx.11 QUALIFICATIONS OF DRILLED SHAFT CONTRACTOR: ............ .428 xxx.12 SUBMITTALS: .......................................................................................428 xxx.13 TRIAL SHAFT INSTALLATION: .........................................................430 xxx.20 MATERIALS: .......................................................................................... 431 xxx.30 CONSTRUCTION METHODS AND EQUIPMENT: .......................... .433 xxx.30.1 PROTECTION OF EXISTING STRUCTURES: ................................ 433 xxx.30.2 CONSTRUCTION SEQUENCE: ........................................................ .434 xxx.30.3 GENERAL METHODS AND EQUIPMENT: .................................... .434 xxx.31 DRY CONSTRUCTION METHOD: ...................................................... 435 xxx.32 WET CONSTRUCTION METHOD: ..................................................... .436 xxx.33 CASING CONSTRUCTION METHOD: ............................................... 436 xxx.34 EXCAVATION AND DRILLING EQUIPMENT: ................................ .437 xxx.35 EXCAVATIONS: ....................................................................................437 xxx.35.1 UNCLASSIFIED EXCAVATION: ..................................................... .438 xxx.35.2 CLASSIFIED EXCAVATION: ........................................................... .438 xxx.35.21 STANDARD EXCAVATION: .......................................................... 438 xxx.35.22 SPECIAL EXCAVATION: ................................................................439 xxx.35.3 OBSTRUCTIONS: ...............................................................................439 xxx.35.4 LOST TOOLS: ......................................................................................439 xxx.35.5 EXPLORATION (SHAFT EXCAVATION): ......................................439 xxx.36 CASINGS: ............................................................................................... 441 , xxx.36.1 TEMPORARY CASING: ..................................................................... 441 xxx.36.2 PERMANENT CASING: ..................................................................... 443 xxx.38 SLURRY: ................................................................................................. 443 xxx.40 EXCAVATION INSPECTION: ..............................................................447 xxx.41 CONSTRUCTION TOLERANCES: ...................................................... .448

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xxx.50 REINFORCING STEEL CAGE CONSTRUCTION AND PLACEMENT: ....................................................................................................451 xxx.60 CONCRE'fE PLACEMENT: ..................................................................452 xxx.61 TREMIES: ...............................................................................................453 xxx.62 PUMPED CONCRETE: .......................................................................... 453 xxx.63 DROP CHUTES: ..................................................................................... 454 xxx.64 NONDESTRUCTIVE EVALUATION: ................................................ .455 xxx.64.1 TESTS IN ACCESS TUBES: ...............................................................455 xxx.64.2 SONIC ECHO TESTS: .........................................................................456 xxx.70 DRILLED SHAFT LOAD TESTS: ........................................................ .458 xxx.71 METHOD OF MEASUREMENT: .........................................................460 xxx. 71.1 FURNISHING DRILLED SHAFT DRILLING EQUIPMENT: ........ .460 xxx.71.2 DRILLED SHAFTS: ............................................................................ 460 xxx.71.3 STANDARD EXCAVATION: ............................................................ 460 xxx.71.4 SPECIAL EXCAVATION: ................................................................. .460 xxx.71.5 UNCLASSIFIED SHAFT EXCAVATION: ........................................ 460 xxx.71.6 UNCLASSIFIED EXTRA DEPTH EXCAVATION: ......................... .461 xxx.71.7 OBSTRUCTIONS: ...............................................................................461 xxx.71.8 TRIAL SHAFT: .................................................................................... 461 xxx.71.9 EXPLORATION (SHAFT EXCAVATION): ..................................... .461 xxx.71.10 LOAD TESTS: .................................................................................... 461 xxx.71.11 PERMANENT CASING: ................................................................... 461 xxx.71.12.INSTRUMENTATION AND DATA COLLECTION: .................... .462 xxx.71.13 PROTECTION OF EXISTING STRUCTURES: ............................. .462 xxx.71.14 ACCESS TUBES: ...............................................................................462 xxx. 71.15 NON-DESTRUCTIVE EVALUATION TESTS: ............................. .462 xxx.72 BASIS OF PAYMENT: ...........................................................................462 xxx. 72.1 FURNISHING DRILLED SHAFT DRILLING EQUIPMENT: ........ .462 xxx.72.2 DRILLED SHAFTS: ............................................................................ 462 xxx.72.3 STANDARD EXCAVATION: ........................................................... .463 xxx. 72.4 SPECIAL EXCAVATION: ................................................................. .463 xxx.72.5 UNCLASSIFIED SHAFT EXCAVATION: ....................................... .463 xxx.72.6 UNCLASSIFIED EXTRA DEPTH EXCAVATION: .......................... 463 xxx.72.7 OBSTRUCTIONS: ............................................................................... 464 xxx.72.8 TRIAL SHAFT HOLES: ...................................................................... 465 xxx.72.9 EXPLORATION (SHAFT EXCAVATION): ......................................465 xxx.72.10 LOAD TESTS: ....................................................................................465 xxx. 72.11 PERMANENT CASING: ...................................................................465 xxx.72.12 INSTRUMENTATION AND DATA COLLECTION: .................... .465 xxx.72.13 PROTECTION OF EXISTING STRUCTURES: ..............................465 xxx.72.14 ACCESS TUBES: ...............................................................................465 xxx. 72.15 NON-DESTRUCTIVE EVALUATION TESTS: ..............................466 xxx. 72.16 ITEMS OF PAYMENT: .....................................................................466 ADDENDUM - SHAFT EXCAVATION IN ROCK BY BLASTING: ....................... .466 Construction Requirements ..................................................................................466 Payment ...............................................................................................................468

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CHAPTER 16: INSPECTION AND RECORDS ....................................................................... 469 RESPONSIBILITIES ......................................................................................................469 CONSTRUCTION CONFERENCES .............................................................................470 UNANTICIPATED CONDITIONS ................................................................................470 SITE CON·DITIONS ........................................................................................................471 CONSTRUCTION OPERATIONS ................................................................................ .471 Excavation............................................................................................................472 Reinforcing Steel ................................................................................................. 472 Drilling Slurry ......................................................................................................472 Concrete Quality and Placement ..........................................................................472 Completed Drilled Shaft ......................................................................................477 COMMON PROBLEMS ................................................................................................. 477 INSPECTION FORMS .................................................................................................... 477 ACCEPTANCE CRITERIA ............................................................................................ 478 RESOURCES ..................................................................................................................480 REFERENCES ................................................................................................................ 480 CHAPTER 17: TESTS FOR COMPLETED DRILLED SHAFTS ............................................ 481 INTRODUCTION ........................................................................................................... 481 SUMMARY DESCRIPTIONS OF INTEGRITY TESTS ............................................. .483 Sonic Echo Test ................................................................................................... 483 Impulse-Response Test ........................................................................................487 Impedance Log ..................................................................................................... 489 Parallel Seismic Test ............................................................................................ 490 Internal Stress Wave Test ....................................................................................491 Drilling and Coring .............................................................................................. 494 Crosshole Acoustic (Sonic and Ultrasonic) Tests ............................................... .495 Gamma-Gamma Testing ......................................................................................499 Concreteoscopy .................................................................................................... SO 1 Other Procedures .................................................................................................. 504 EXPECTED DEFECT RATE FOR DRILLED SHAFTS ............................................... 504 DESIGN OF AN INTEGRITY TESTING PROGRAM AND ACCEPTANCE CRITERIA BASED ON INTEGRITY TESTING ......................................................... 505 EVALUATING DEFECTS ............................................................................................. 511 REFERENCES ................................................................................................................ 512 CHAPTER 18: REPAIR OF DEFECTIVE DRILLED SHAFTS .............................................. 515 TYPES OF DEFECTS ..................................................................................................... 515 Defects at the Base of the Drilled Shaft ............................................................... 515 Poor Concrete Along the Length of the Shaft ...................................................... 516 Inadequate Contact Along Sides of Shaft ........................................................... .S 16 Incorrect Dimensions and/or Location................................................................. 517 METHODS OF REPAIR ................................................................................................. 517 Grouting ............................................................................................................... 517 Hand Repairs ........................................................................................................ 519

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Underpinning with Microshafts ........................................................................... 519 Removal and Replacement .................................................................................. 522 Straddle Shafts ..................................................................................................... 522 REFERENCES ............................................................................................................... 524 CHAPTER 19: COST ESTIMATION........................................................................................ 525 GENERAL ................................................................................................................... 525 FACTORS INFLUENCING COST ................................................................................ 525 COMMENTARY ABOUT COST ................................................................................... 527 COST SURVEY ............................................................................................................. 527 ON-LINE DATA BASES ............................................................................................... 533 CONTRACTORS' COST COMPUTATION .................................................................. 536 EXAMPLES .................................................................................................................. 536 Texas .................................................................................................................... 536 Florida ................................................................................................................. 537

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LIST OF APPENDICES

APPENDIX A: ELEMENTS OF LRFD FOR DRILLED SHAFTS ......................................... A-1 QUANTIFICATION OF UNCERTAINTY OF SOIL PROPERTIES .......................... A-1 Suggested Approximate Statistical Test for Site Variability .............................. A-3 Further Reading ................................................................................................ A-10 BASIC CONCEPT OF RELIABILITY ........................................................................ A-11 AASHTO LIMIT STATES ........................................................................................... A-17 RESISTANCE FACTORS FOR DRILLED SHAFTS ................................................ A-21 MODIFYING RESISTANCE FACTORS FOR DRILLED SHAFTS ......................... A-23 FORMAL STEP-BY-STEP PROCEDURE FOR APPL YING LRFD TO THE DESIGN OF DRILLED SHAFTS ................................................................................ A-24 EXAMPLE PROBLEM ................................................................................................ A-26 REFERENCES ............................................................................................................. A-29 APPENDIX B: COMMENTARY ON METHODS OF COMPUTING THE NOMINAL AXIAL RESISTANCE OF DRILLED SHAFTS ............................................................ B-1 INTRODUCTION ...........................................................................................................B-1 BASIC DESIGN EQUATIONS FOR GEOTECHNICAL AXIAL RESISTANCE ....... B-1 Compression Loading .......................................................................................... B-1 Uplift Loading ...................................................................................................... B-3 Downdrag ............................................................................................................. B-3 IDEALIZATION OF GEOMATERIALS ....................................................................... B-4 BASE RESISTANCE, R8 ...•.••.....•.•.....•.•.•......•••••.•........•.•.•....••••.•.•••......••••••.•....•...•.•...... B-7 Bearing Capacity Equation .................................................................................. B-7 Drained and Undrained Loading ..........................................................................B-8 Undrained Loading .............................................................................................. B-9 Evaluating the Shear Strength ..................................................................B-9 Drained Loading ............................................................................................... B-19 Drained Loading in Soil ......................................................................... B-19 Drained Loading in Preferentially Sloping, Jointed Rock ..................... B-22 SIDE RESISTANCE, Rs ............................................................................................... B-26 Undrained Loading ............................................................................................ B-26 Cohesive Soils ........................................................................................ B-26 Cohesive Intermediate Geomaterials - Compression Loading .............. B-28 Cohesive Intermediate Geomaterials - Uplift Loading ..........................B-37 Rock- Compression Loading ................................................................B-38 Rock - Uplift Loading ............................................................................ B-42 Rock - Adding Base and Shaft Resistance ............................................B-42 Drained Loading ................................................................................................B-43 Cohesive Soils - Compression Loading ................................................. B-43 Cohesive Soils - Uplift Loading ............................................................ B-45 Granular Soils - Compression Loading ..................................................B-45 Granular Soils - Uplift ...........................................................................B-49 Cohesionless Intermediate Geomaterials - Compression ...................... B-51 Cohesionless Intermediate Geomaterials - Uplift Loading .................... B-52

xiii

Intermediate Geomaterials -- Considerations for Desert Regions ......... B-52 Rock ......................................................................................................B-53 Cyclic Axial Loading .........................................................................................B-53 Combined Axial and Lateral Loading ................................................................B-55 AXIAL GROUP EFFECTS ...........................................................................................B-56 RELIABILITY OF DESIGN EQUATIONS FOR AXIAL RESISTANCE ..................B-61 ALTERNATIVE METHODS FOR ESTIMATING AXIAL RESISTANCE OF DRILLED SHAFTS .......................................................................................................B-62 OTHER SOURCES OF INFORMATION .................................................................... B-64 RESOURCES ................................................................................................................ B-64 REFERENCES .............................................................................................................. B-65 APPENDIX C: ESTIMATION OF AXIAL MOVEMENT OF DRILLED SHAFTS .............. C-1 INTRODUCTION ......................................................................................................... C-1 SOILS - SIMPLE FORMULAS ...................................................................................... C-2 Single Drilled Shafts in Soil ................................................................................ C-2 Groups of Drilled Shafts in Soil. .......................................................................... C-4 SOILS - NORMALIZED LOAD-TRANSFER METHODS (COMPRESSION) ........... C-5 SOILS AND IGM'S - COMPUTER SIMULATION METHODS ................................ C-12 IGM's - SIMPLIFIED EQUATIONS BASED ON ANALYTICAL SOLUTIONS ..... C-19 Cohesive IGM's .................................................................................................. C-19 Granular (Cohesionless) IGM's .......................................................................... C-21 ROCK ......................................................................................................................... C-27 GROUPS OF DRILLED SHAFTS IN SOIL AND ROCK ........................................... C-32 Equivalent Raft Method ..................................................................................... C-32 Equivalent Pier Method ..................................................................................... C-36 CYCLIC LOADING IN THE SERVICE LOAD RANGE ........................................... C-45 RESOURCES ................................................................................................................ C-46 REFERENCES .............................................................................................................. C-46 APPENDIX D: EXAMPLE DESIGN PROBLEMS ................................................................. D-1 EXAMPLE D-1: LRFD of a Drilled Shaft in Layered Cohesive Soil and Cohesive Intermediate Geomaterial. ............................................................................................. D-1 Work Table for Example D-1, Step 15 ........................................................................... D-5 EXAMPLE D-2: Drilled Shaft to Rock by LRFD .......................................................... D-8 EXAMPLE D-3: Design of a Drilled Shaft in Mixed Cohesionless Geomaterial by ASD .............................................................................................................................. D-15 Work Table for Example D-3, Step 14 ......................................................................... D-18 EXAMPLE D-4: Design of a Drilled Shaft in Cohesive Intermediate Geomaterial by LRFD ....................................................................................................................... D-21 APPENDIX E: EXAMPLE SOLUTIONS FOR A DOWNDRAG PROBLEM ........................ E-1 Example Ela: Hand Solution with total stress parameters .............................................. E-1 Example Elb: Hand Solution Using Effective Stress Parameters ................................... E-4 Example E2: Computer solution using elastic-plastic side load transfer relations .......... E-7 APPENDIX F: INSPECTION, REPORTING AND BIDDING FORMS ................................. F-1

xiv

APPENDIX G: CONSTRUCTION CASE HISTORIES ........................................................... G-1 CASE 1: STIFF CLAY, WATER TABLE SLIGHTLY BELOW BASE OF SHAFT ............................................................................................................................ G-1 CASE 2: HARD CLAY AND SHALE WITH LAYER OF WATER-BEARING SAND ............................................................................................................................. G-3 CASE 3: SOFT CLAY ABOVE JOINTED AND SLICKENSIDED CLAY ................ G-5 CASE 4: DRY SAND ..................................................................................................... G-6 CASE 5: GRANULAR SOIL BELOW THE WATER TABLE .................................... G-8 CASE 6: CAVING SOIL ABOVE SOUND ROCK .................................................... G-10 CASE 7: CAVING SOIL ABOVE FRACTURED ROCK .......................................... G-12 CASE 8: BOULDER FIELDS ...................................................................................... G-14 CASE 9: IRREGULARLY WEATHERED ROCK ..................................................... G-16 CASE 10: KARSTIC AND OLD MINING REGIONS ............................................... G-20 CASE 11: CONSTRUCTION IN OPEN WATER ..................................................... G-22 CASE 12: CONSTRUCTION IN AN ENVIRONMENTALLY SENSITIVE AREA ........................................................................................................................... G-23 REFERENCES ............................................................................................................. G-26

xv

LIST OF FIGURES No.

Title

Page No.

Schematic of a typical drilled shaft ...................................................................................... 2 A typical construction job in progress (Photograph courtesy of Watson, lnc.) .................. 3 Photograph of Queets River Bridge at time of completion (Note old bridge in background and flood debris against the columns) .............................................................. 8 1.4. Construction of drilled shafts from barge in the Great Pee Dee River .............................. 10 1.5. Cases for use of drilled shafts: (a) bearing in hard clay, (b) skin friction design, (c) socket into rock, (d) installation into expansive clay (continued) .................................... 16 1.5 (continued). Cases for use of drilled shafts: (e) stabilizing a slope, (f) foundation for overhead sign, (g) foundation near existing structure, (h) closely-spaced drilled shafts to serve as a cantilever or tied-back wall (drilled shafts installed prior to excavation) ............................................................................................................ 17 1.5 (continued). Cases for use of drilled shafts: (i) foundation at a marine site, and (j) · protect'o · ti'on at'd ...................................................................................... .. 18 pier 1 n or nav1ga 2.1. Subsurface characterization related to design and construction ........................................ 22 2.2. Low-frequency continuous seismic reflection profile for the Connecticut River at the Glastonbury-Wethersfield Bridge (Haeni, 1988) ......................................................... 26 2.3. Kriging surfaces for three layers at overconsolidated clay site (Yoon and O'Neill, 1996) .................................................................................................................................. 27 2.4. Schematic elevation showing definition of vertical and horizontal effective stresses in the ground ......................................................................................................... 32 2.5. Wet rotary-type soil boring rig .......................................................................................... 35 2.6. Illustration of the concept of dilation at the interface of concrete and rock (O'Neill et al., 1996) ........................................................................................................................ 41 2.7. Effect of borehole smear on load-settlement behavior of a drilled shaft in rock (Hassan and O'Neill, 1997) ................................................................................................ 41 2.8. Possible sliding surface when a drilled shaft is pushed downward .................................. .42 2.9. Friction angles for sand at or near the wall of a drilled shaft ............................................ 44 2.10. Failure relationship for saturated clay at or near the wall of a drilled shaft ...................... 44 3.1. Shapes of typical underreams (a) cut with "standard" conical reamer; (b) cut with "bucket," or hemispherical, reamer .................................................................................... 51 3.2. Dry method of construction: (a) initiating drilling (b) starting concrete pour, (c) placing rebar cage, (d) completed shaft ............................................................................ .55 3.3. Casing method of construction: (a) initiating drilling, (b) drilling with slurry; (c) introducing casing, (d) casing is sealed and slurry is being removed from interior of casing (continued) ............................................................................................ 61 3.3 (continued). Casing method of construction: (e) drilling below casing, (f) underreaming, (g) removing casing, and (h) completed shaft ...................................... 62 3.4. Alternate method of construction with casing: (a) installation of casing, (b) drilling ahead of casing, (c) removing casing with vibratory driver .................................. 63 3.5. Case-and-drill (full-depth-casing) rigs: (a) track-mounted rig with auger ....................... 65 3.5 (continued) (b) skid-mounted rig with hammergrab .......................................................... 65

1.1. 1.2. 1.3.

xvi

3.6 3. 7.

4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 4.7. 4.8. 4.9. 4.10. 4.11. 4.12. 4.13. 4.14. 4.15. 4.16. 4.17. 4.18. 4.19. 4.20. 4.21. 5.1. 5.2. 5.3. 5.4. 6.1. 6.2.

6.3. 6.4. 6.5. 6.6. 6.7.

Slurry method of construction (a) drilling to full depth with slurry; (b) placing rebar cage; (c) placing concrete; (d) completed shaft ........................................................ 67 Effect of time lapse between drilling and concreting on CPT resistance of sand adjacent to drilled shafts constructed by the wet method: (a) Two hours between completion of drilling and concreting, (b) Two weeks between completion of drilling and concreting (De Beer, 1988) ........................................................................... 70 A typical truck-mounted drilling machine ......................................................................... 74 A typical crane-mounted drilling machine (Photograph courtesy of Farmer Foundation Company, Inc.) .............................................................................................. 75 A typical crawler-mounted drilling machine (Courtesy of Case Pacific Company) ......... 76 Low-headroom drilling machine (crawler-mounted)(Photograph courtesy of A. H. Beck Foundation Company) .............................................................................................. 77 A typical drilling bucket .................................................................................................... 80 A typical "muck bucket" or "clean-out bucket" ................................................................. 81 A single-flight auger ......................................................................................................... 82 A typical double-flight auger ............................................................................................. 82 A typical rock auger ........................................................................................................... 84 Tapered rock auger for loosening fragmented rock (Photograph courtesy of John Turner) ............................................................................................................................... 84 A typical single-walled core barrel .................................................................................... 86 A double-wall core barrel (Photograph courtesy ofW. F. J. Drilling Tools, Inc.) ............ 86 Full-faced tool with roller bit (Photograph courtesy of Caissons, Inc.) ............................. 89 A typical closed belling tool inserted into a borehole ........................................................ 89 A typical belling bucket in drilling position ...................................................................... 90 A Glover rock-grab (Drawing courtesy of Steven M. Hain) ............................................. 90 A typical grab bucket (Photograph courtesy of John Turner) ........................................... 91 An example of a churn drill (Photograph courtesy of John Turner) .................................. 91 An example of a hammergrab (from LCPC, 1986) .......................................................... 93 An example of a rodless soil drill (Photograph courtesy of Tone Boring Corp., Ltd.) .................................................................................................................................... 93 Mach drill (Photograph courtesy of Tone Boring Corp., Ltd.) .......................................... 94 A typical view of stored temporary casing ........................................................................ 98 Examples of use of permanent casing ................................................................................ 99 J slots in top of casing for use with casing twister (Photograph courtesy of Herzog Foundation Drilling, Inc.) ................................................................................................ 104 Teeth for use in sealing casing into rock (Photograph courtesy of Herzog Foundation Drilling, Inc.) ................................................................................................ 104 Formation of mudcake and positive effective pressure in a mineral slurry in sand formation .......................................................................................................................... 110 Mineral slurry plates in pores of open-pored formation (modified after Fleming and Sliwinski, 1977) ........................................................................................................ 111 Stabilization of borehole by the use of polymer drilling slurries .................................... .113 Relation of viscosity of mineral slurries to dosage (after Leyendecker, 1978) ............... 120 Schematic diagram of unit for mixing and treating mineral slurry .................................. 126 Sampler for slurry (from Fleming and Sliwinski, 1977).................................................. 130 Schematic of viscometer .................................................................................................. 132

xvii

6.8. Interpretati n of data from a viscometer (Ata and O'Neill, 1997) .................................. .134 6.9. Photograp of sand content test (backwashing sand into burette) ................................... 135 6.10. Photograp of titration test for hardness .......................................................................... 136 6.11. Photograp of complete set of field testing equipment for drilling slurries ................... .13 8 6.12. Commerci borehole caliper (Western Atlas, Inc.) ........................................................ 141 (a) Sensors in retracted position ....................................................................................... 141 (b) Sensors extended ........................................................................................................ 141 6.13. Caliper log (Foundations for US 231 Crossing of Ohio River) ....................................... 142 6.14. The buildu of bentonite filter cake in a model apparatus in response to different pressure he s (after Wates and Knight, 1975) ............................................................... 149 6.15. Placing co crete through heavily-contaminated slurry .................................................... 153 6.16. Factors cau ing weakened resistance at base of a drilled shaft ....................................... 154 6.17. Placing cas ng into mineral slurry with excessive solids content .................................... 156 6.18. Pulling cas · g with insufficient head of concrete ............................................................ 157 6.19. Placing co rete where casing was improperly sealed .................................................... 158 7.1. View of a bar cage being assembled, showing longitudinal steel ............................... .166 7.2. View ofb dies of No. 18 rebar in a drilled shaft cage ................................................. .166 7.3. Transverse ies and spiral steel, showing hook anchors and spiral laps .......................... 168 7.4. Possible di tortion of poorly assembled cage due to pickup forces or hydraulic forces from fresh concrete ............................................................................................... 168 7.5. Sizing hoo assembly (from LCPC, 1986) ...................................................................... 170 7.6. Centering 'th plain, epoxy-coated rebar skids (from LCPC, 1986) .............................. 171 7. 7. Concrete ro lers ................................................................................................................ 172 7.8. Installation f rollers: (a) correct, (b) incorrect (from LCPC, 1986) .............................. 173 7.9. Transverse tiffeners for temporary strengthening of the rebar cage (after LCPC, 1986) ............................................................................................................................... 174 7.10. Longitudin stiffeners for temporary or permanent strengthening of a rebar cage (fromLCP , 1986) .......................................................................................................... 175 7.11. Photograph f bands used for strengthening lower part of a rebar cage .......................... 175 7.12. Photograph of rebar cage being lifted improperly (Photo courtesy of Barry Berkovitz, WA) ........................................................................................................... 176 7.13. Photograph f rebar cage being lifted properly ............................................................... 176 7.14. Inward-tum d hooks in a rebar cage for a drilled shaft at an abutment (photograph courtesy of arry Berkovitz, FHWA) .............................................................................. 179 8.1. Slump loss r lationship from a trial mix design .............................................................. 189 8.2. Concrete wi insufficient workability for use in drilled shafts ...................................... 193 8.3. Concrete th high workability but with improper mix design for tremie placement ........................................................................................................................ 193 8.4. Concrete wi high workability and with good mix design for tremie placement Strength ........................................................................................................................... 194 8.5. Placing cone ete directly from the ready-mix truck without a dropchute ....................... 198 8.6. Steel dropcb te with multiple windows ........................................................................... 199 8.7. Hinged clos e (from LCPC, 1986) ................................................................................. 202 8.8. "Hat" closur (from LCPC, 1986) ................................................................................... 202 8.9. Loose-plate losure .......................................................................................................... 202 8.10. Photograph f simple plywood loose plate closure on a gravity-fed tremie .................... 203

xviii

8.11. 8.12. 8.13. 8.14. 8.15. 8.16.

Photograph of gravity-fed tremie partially extracted ....................................................... 204 Capped tremie pipe with breather tube (from LCPC, 1986) ............................................ 205 Polystyrene plug (from LCPC, 1986) .............................................................................. 206 Plug of cement paste ........................................................................................................ 206 Notching oflower portion oftremie tube (from LCPC, 1986) ........................................ 207 Potential distribution of leached concrete resulting from excessive initial lifting of gravity-fed tremie (from LCPC, 1986) ............................................................................ 208 8.17a. Pumping operation with a portable, "tremieless" pump unit that does not require a crane to hold the pump line .............................................................................................. 210 8.l 7b. Pump unit from Figure 8.17 a operating beneath a bridge (Photograph courtesy of A. H. Beck, Inc.) .............................................................................................................. 210 8.l 7c. Typical tremie for placement of concrete by pump ......................................................... 211 8.17d. Large-scale concrete pumping operation for drilled shafts in a river .............................. 211 8.18. Technique of starting the placement of concrete with a pump (from LCPC, 1986) ........ 213 8.19 a. Defect in a drilled shaft caused by interruption in concrete supply during pumping (Photograph courtesy of Caltrans) ................................................................................... 214 8.19 b. Drilled shaft of excellent quality after exhumation .........................................................214 8.20. Comparison of actual amount of concrete required to fill excavation incrementally with theoretical volume of the excavation; Example 1 (LCPC, 1986) ............................ 217 8.21. Comparison of actual amount of concrete required to fill excavation incrementally with theoretical volume of the excavation; Example 2 (LCPC, 1986) ............................ 217 8.22. Comparison of actual amount of concrete required to fill excavation incrementally with theoretical volume of the excavation; Example 3 (ADSC/DFI, 1989) .................... 218 10.1. Schematic of the overall design process for drilled shaft foundations ............................ 227 10.2. Total cost vs. intensity of exploration (after Kulhawy et al., 1983) ................................ 229 10.3. Hypothetical load-settlement relations for drilled shafts, indicating factors that influence shaft behavior under axial load ........................................................................ 237 10.4. Idealized geomaterial layering for computation of compression resistance .................... 244 10.5. Idealized geomaterial layering for computation of uplift resistance ............................... 245 10.6. Potential effect of loading slightly above unfactored load on lateral deflection of a drilled shaft ............................................................................................................... 254 10.7. Concept of group behavior in drilled shafts ..................................................................... 256 11.1. Condition in which Rs + Re is not equal to actual ultimate resistance ............................ 263 11.2. Idealized geomaterial layering for computation of compression resistance .................... 267 11.3. Idealized geomaterial layering for computation of uplift resistance ............................... 267 11.4. Exclusion zones for computation of side resistance for drilled shafts in cohesive soils .................................................................................................................................. 275 11.5. Factor a for cohesive IGM's ............................................................................................ 283 11.6. Definition of geometric terms in Equation (11.25) .......................................................... 285 11.7. Definition of area A0 ••• : •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 287 11.8. Normalized side load transfer for drilled shaft in cohesive soil ...................................... 291 11.9. Normalized base load transfer for drilled shaft in cohesive soil.. .................................... 291 11.10. Normalized side load transfer for drilled shaft in cohesionless soil ................................ 292 11.11. Normalized base load transfer for drilled shaft in cohesionless soil ............................... 292 12.1. Examples of cases where downdrag could occur ............................................................ 299 12.2. Possible downdrag loading of drilled shafts supporting a bridge abutment .................... 300

xix

12.3. 12.4. 12.5.

12.6. 12.7. 12.8. 12.9. 12.10. 13.1. 13.2. 13.3. 13.4. 13.5. 13.6. 13.7. 13.8. 13.9. 13.10. 13.11. 13.12. 13.13. 13.14. 13.15. 13.16. 13.17. 13.18.

Potential geotechnical strength limit states for drilled shafts ......................................... .300 The equivalent pier concept applied to downdrag in groups of drilled shafts ................302 Elementary mechanics of downdrag: (a) example problem; (b) load transfer curves; (c) relative movement of drilled shaft with respect to geomaterial (neutral point assumed at bottom of settling stratum); (d) distribution of load along drilled shaft; (e) revised estimate of relative movement of drilled shaft with respect to geomaterial; (f) revised estimate of distribution of load along drilled shaft.................... 305 Definition of c' and f where curved failure envelope exists ........................................... 306 Example soil profile with expansive geomaterial ............................................................ 312 Use of a pertnanent surface casing for design in expansive soil.. ................................... .315 Raba method of design in expansive soil.. ...................................................................... .315 Use ofrebar cage for design in expansive geomaterial ................................................... 317 Single-column supports ................................................................................................... 320 Loadings on.single-column support for a bridge ··········································~··················320 Overhead sign .................................................................................................................. 321 Elevation view of an overhead sign structure (a) two-shaft foundation and (b) single-shaft foundation (from FHWA-IP-84-11) .......................................................322 Bridge abutment ...............................................................................................................323 Sketch of foundation for a bridge abutment (FHWA-IP-84-11) ..................................... 323 Arch bridge (photograph courtesy of Ronald C. O'Neill) ............................................... 324 Reaction block for arch bridge (photograph courtesy of Ronald C. O'Neill) ................ .325 Drilled shaftfoundation for an arch bridge (from FHWA-IP-84-11) ............................. .325 Drilled shafts for stabilizing a slide (Reese et al., 1987) ................................................. 326 Drilled shaft retaining structure for depressed section of highway ................................. 326 Groundline shear - deflection curves for (a) clay and (b) sand (Duncan et al., 1994) ...........,..................................................................................................................... 330 Groundline moment - deflection curves for (a) clay and (b) sand (Duncan et al., 1994) ................................................................................................................................ 330 Groundline shear- maximum moment curves for (a) clay and (b) sand (Duncan et al., 1994) .......................................................................................................................... 332 Parameters Am and Bm (Matlock and Reese, 1961) ........................................................ .332 Model of a deep foundation under lateral loading showing concept of soil response curves ................................................................................................................ 339 Definition of terms in Equations (13.12) and (13.13) ..................................................... .344 Variation of EI of a drilled shaft cross section with bending moment and axial

load ................................................................................................................................... 345 13.19. 13.20. 13 .21. 13.22. 13.23. 13.24. 13.25. 13.26. 13.27. 13.28.

Assumed stress-strain relation for concrete ..................................................................... 346 Assumed stress-strain curve for steel reinforcement ...................................................... .347 The p-multiplier (Brown and Shie, 1991) ....................................................................... .349 Modification of p-y curve for group action using the p-multiplier ................................. .349 Interaction diagram for a reinforced concrete column .................................................... 355 Interaction diagram for factored resistance for combined axial load and flexure ........... 364 Deflection, moment and shear as a function of depth for Example 13.5 ......................... 375 Results from computer solutions for Example 13.6 (after FHWA-IP-84-11) ................. 377 Typical underream (after Farr, 1974) ............................................................................... 379 Tensile stress contours for flat-bottom bell (after Farr, 1974) ........................................ .380

xx

14.1. 14.2. 14.3.

14.4. 14.5.

14.6. 14. 7. 14.8. 14.9. 14.10. 14.11. 14.12. 14.13. 14.14. 14.15. 14.16. 14.17. 14.18. 16.1. 16.2. 16.3. 17.1. 17.2. 17.3. 17.4. 17.5. 17.6. 17.7. 17.8.

17.9. 17.10.

Caliper log for deep drilled shaft in rock ........................................................................ .390 Arrangement for testing a drilled shaft conventionally under axial compressive loading .............................................................................................................................. 393 Osterberg cell loading system ......................................................................................... 396 (a) Schematic of Osterberg cell test ................................................................................ .396 (b) Photograph of Osterberg cell ..................................................................................... .396 Side and base load-movement results from an Osterberg cell test on a rock socket in granite (Osterberg, 1994) ............................................................................................. 397 Comparison of mobilized side shear stress along a drilled shaft in Florida limestone for both Osterberg cell (OC) and conventional surface loading at the load corresponding to side shear failure in the OC test from finite element analysis (from O'Neill et al., 1997, after McVay et al., 1994) ........................................ .398 Multiple-level arrangement for Osterberg cells (O'Neill et al., 1997) ............................ .399 Schematic of StatnamicR test. ........................................................................................... 400 Photograph of StatnamicR test arrangement, showing masses being accelerated inside gravel-filled sheath ................................................................................................ 401 Arrangement for testing a drilled shaft under uplift loading .......................................... .403 Photograph ofhead oftest shaft showing hydraulic jack and electronic load cell ......... .404 Photograph of a telltale system ........................................................................................ 406 Photograph of a vibrating wire sister bar ........................................................................ .407 The Mustran cell .............................................................................................................. 409 View of a test shaft with contact pressure cells at its base ............................................. .410 Typical set ofload distribution curveso btained from use ofMustran cells ................... .411 Method of analysis of data from axial loading test ......................................................... .414 Arrangement for a conventional full-scale field lateral loading test using a pushing procedure ............................................................................................................418 Osterberg Cell arranged for 26. 7 MN (3000 ton) lateral loading test in a 1.22m (4ft.) diameter rock socket ............................................................................................... 420 Concrete curve showing normal amount of overbreak ................................................... .475 Concrete curve showing an excessive amount of overbreak .......................................... .476 Decision tree for acceptance of drilled shafts (Baker et al., 1993) ................................. .479 Sonic echo method (after Sliwinski and Fleming, 1983) ................................................ .484 A severe defect that can likely be detected by sonic echo testing .................................. .487 Ideal response curve for the impulse-response or vibration test (after Weitman, 1977) ................................................................................................................................ 488 Examples of impedance logs (Davis and Hertlein, 1991)............................................... .489 The parallel seismic test (Davis, 1995) ........................................................................... .490 Compression wave propagation method with internal receivers (Hearne et al., 1981) ................................................................................................................................ 492 Typical results from internal stress wave test (from Harrell and Stokoe, 1984) ............ .492 Concrete cores from non-defective and defective drilled shafts ..................................... .493 (a) Shaft with no defect ................................................................................................... 493 (b) Shaft with defect caused when concrete began to set while removing the casing ............................................................................................................................... 493 Reinforcing cage to which PVC access tubes have been attached ................................. .496 Diagram of crosshole acoustic logging system (Weitman, 1977) .................................. .498

xxi

17.11. 17.12. 17.13. 17.14. 17.15. 18.1. 18.2. 18.3. 18.4. 19.1. 19.2. 19.3. A.1. A.2. A.3. AA. A.5. A.6. B.1. B.2. B.3. B.4. B.5. B.6. B.7. B.8. B.9. B.10. B.11. B.12. B.13. B.14. B.15. B.16. B.17. B.18.

B.19.

Crosshole sonic log for a shaft with a known defect (Baker et al., 1993) ...................... .498 Gamma-gamma testing system (after Preiss et al., 1978) ................................................ 501 Results from gamma-gamma logging of a drilled shaft with four access tubes ............. 502 Photograph of defect similar to the defect that produced the logs in Figure 17.12 ........ 503 Photograph of a small transverse crack in a concrete pile from a concreteoscope test ................................................................................................................................... 503 Visual inspection of the base of a defective drilled shaft ................................................ 520 Circular pattern of microshafts to underpin defective drilled shaft .................................521 Schemes for underpinning a defective drilled shaft with microshafts ............................. 522 Use of"straddle" shafts ................................................................................................... 523 Pricing scenario 1for1997 ADSC survey ....................................................................... 528 Pricing scenario 2 for 1997 ADSC survey ...................................................................... .529 Pricing scenario 3 for 1997 ADSC survey ....................................................................... 530 Plan view of characterization domain ............................................................................. A-7 Elevation of borings and values of Su in characterization domain .................................. A-8 Undrained shear strength (su) vs. elevation in upper stratum ......................................... A-8 Undrained shear strength (su) vs. elevation in lower stratum ......................................... A-9 Idealized probability distributions of load and resistance on a drilled shaft ................. A-12 Definition of the reliability index ................................................................................. A-14 Illustration of defelection-sofetening behavior of drilled shafts under compression loading ............................................................................................................................. B-2 Idealized geomaterial layering for computation of compression resistance .................... B-5 Idealized geomaterial layering for computation of uplift resistance ............................... B-5 Relation between Su from CIUC tests and UU tests (Chen and Kulhawy, 1994) .......... B-10 Relation between Su from UC tests and UU tests (Chen and Kulhawy, 1994) .............. B-11 Fracturing (punching) of a foundation in massive rock or IGM .................................... B-13 Bearing capacity factors (Chen and Kulhawy, 1994) .................................................... B-20 Bearing capacity factor Ncs as a function of joint slope and relative shear strength of joints and intact rock (Carter and Kulhawy, 1988) ...................................................B-24 Correlation between ex. and su/p8 ..................................................................................... B-28 Factor ex. for IGM's (O'Neill et al., 1996) ....................................................................... B-30 Factor M vs. concrete slump (O'Neill et al., 1996) ........................................................B-31 Parameter n for smooth cohesive IGM sockets (O'Neill et al., 1996) ........................... B-34 Roughness pattern assumed in the development of design equations (O'Neill et al., 1996) .............................................................................................................................. B-34 Simplified representation of Poisson=s effect (exaggerated) ........................................ B-38 Unit shaft resistance versus shear displacement for drilled shaft socket in rock of moderate roughness with qu = 3.0 MPa (Baycan, 1996)................................................ B-39 Definition of terms in Equation (B.48) .......................................................................... B-41 Variations of f3 with depth (O'Neill and Hassan, 1994) ................................................. B-48 11 vs. center-to-center spacing, s, normalized by shaft diameter, Bshatb for underreamed drilled shafts in compression in moist silty sand (Modified after Garg, 1979) ....................................................................................................................B-57 Relative unit side and base resistances for single shaft and typical shaft in a nineshaft groups (Liu et al., 1985) ........................................................................................ B-58

xxii

B.20. Block failure model for drilled shaft group in cohesive soil with cap in contact with the ground .............................................................................................................. B-60 B .21. Computed axial resistance (Re) vs. measured axial resistance (Rm) (Isenhower and Long, 1997) .................................................................................................................... B-62 C.1. Normalized load transfer relations for side resistance in cohesive soil ........................... C-6 C.2. Normalized load transfer relation for base resistance in cohesive soil ............................C-7 C.3. Normalized load transfer relations for side resistance in cohesionless soil .....................C-7 C.4. Normalized load transfer relations for base resistance in cohesionless soil .................... C-8 C.5. Mechanistic model of axially loaded drilled shaft ......................................................... C-14 C.6. Element from an axially loaded shaft ............................................................................ C-14 C.7. Illustration of the definition of \jJ ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• C-16 C.8. Segment of a load-distribution curve along an axially loaded drilled shaft .................. C-18 C.9. Idealized soil modulus profile for computing settlement in granular IGM's ................. C-22 C.10. Load-settlement relation for method for granular IGM's ............................................... C-22 C.11. Vertical strain influence factors below center of rectangular area (Poulos, 1993) ........ C-35 C.12. Embedment correction factor (after Poulos, 1993) ........................................................ C-36 C.13. Influence factor 15 for drilled shaft groups for EJE's = 88 and n 50u = 0.3 (Poulos, 1994) ..............................................................................................................................C-38 C.14. Weighting factors for equivalent pier method (Poulos, 1994) .......................................C-39 C.15. Ratio of load transferred to base to applied load for the equivalent pier method (Poulos, 1994) ................................................................................................................ C-40 G. l. Case 1: Construction in stiff clay with water table slightly below base of shaft ........... G-2 G.2. Case 2: Construction in hard clay and shale with layer ofwaterbearing sand .............. G-4 G.3. Case 3: Construction in soft and heavily-jointed clays ................................................. G-6 G.4. Case 4: Construction in dry sand ................................................................................... G-7 G.5. Case 5: Construction in granular soil below the water table ......................................... G-9 G.6. Case 6: Construction through caving soil into sound rock .......................................... G-11 G.7. Case 7: Construction through caving soil into fractured rock ..................................... G-13 G.8. Case 8: Construction through boulders ........................................................................ G-16 G.9a. Case 9 a: Blocky weathered rock profile (Sowers, 1994) ............................................ G-18 G.9b. Case 9 b: Construction where the founding rock is vertically slotted ......................... G-19 G.10. Case 10: Construction in karstic regions ...................................................................... G-21 G.11. Case 11: Construction in open water ........................................................................... G-23 G.12. Case 12: Construction through potentially contaminated surface water ...................... G-25

xxiii

LIST OF TABLES Table No. 2.1. 2.2. 4 .1. 6.1. 6.2. 6.3.

7 .1. 7.2. 7.3. 8.1. 8.2. 8.3. 8.4. 10.1. 11.1. 11.2. 11.3. 11.4. 12.1. 13.1. 13.2. 17.1. 17.2. 17.3. 17.4. 19.1 19.2 19.3.

Title

Page No.

Recommended frequency of borings for drilled shaft foundations for bridges when unclassified excavation is specified (FHWA, 1991) ................................................ 28 Geotechnical parameters from borings or soundings to be evaluated numerically if design procedures in this manual are used ......................................................................... 30 Brief listing of characteristics of some drilling machines ................................................. 78 Mineral slurry specifications for drilled shaft construction in fine sands (modified after Florida Department of Transportation, 1987).......................................................... 144 Slurry specifications for a rock-socketed drilled shaft (after Holden, 1984) .................. .145 Ranges of properties of various fresh-water slurries at time of concreting consistent with maintenance of angle of wall friction in sand of 0.67 ~ in laboratory tests (after Majano et al., 1994) ...................................................................... 146 Properties of reinforcing steel for concrete reinforcement .............................................. 164 Weights and dimensions of deformed bars (Customary) ................................................. 164 Weights and dimensions of deformed bars (Metric) ........................................................ 165 Typical mix proportions for workable drilled shaft concrete (after Sliwinski, 1980) ................................................................................................................................ 189 Concentrations of typical aggressive soil and groundwater contaminants (after Bartholomew, 1980) ........................................................................................................ 190 Typical proportions ofpozzolanic additives ................................................................... .191 Typical proportions of some prequalified chemical admixtures (extracted from 'fXDOT, 1996) ................................................................................................................. 192 Resistance factors, ~' for selected values of global safety factor, F ..............................242 Values oflr = Es (Young's Modulus of soil)/3su and N*c ................................................ 276 Descriptions of Rock Types for Use in Table 11.3 ..........................................................277 Values of sand m (Dimensionless) for Equation (11.7) based on Classification in Table 11.2 ........................................................................................................................278 Factors