Lateral Support Systems and Underpinning Construction Methods

 

Report No. FHWA-RD-75-130

LATERAL SUPPORT SYSTEMS AND UNDERPINNING

Vol. Ill Construction Methods D T. Goldberg W E Jaworski and M. D Gordon

April 1976 Final Report This document is available t the public through the National Technical Information Service, Springfield, Virginia 22 6

Prepared for DMINISTR TION

FEDER L HIGHW Y

Offices of Research Washington D C

Development

20590

 

NOTICE

This document i s dis s em inated under the sponsorship o f the Department o f T r a n s p o r t a t i o n i n the i n t e r e s t o f information exchange. The United S t a t e s overnment assumes no l i b i l i t y for i t s contents or use.

The contents of t h i s r e p o r t r e f l e c t the views o f Goldberg-Zoino and A s s ociates , I n c . , who are r e s p o n s i b l e for the f a c t s and the accuracy o f the data pr es ented The c o n t e n t s do not n e c e s s a r i l y r e f l e c t the h e r e in . o f f i c i l views o r p o l i c y of the Depart~ent o f Trans portation. This r e p o r t does not c o n s t i t u t e a standard, s p e c i f i c a t i o n , o r r e g u la tio n .

The United S t a t e s o r manufactures.

overnment does not endorse products Trade o r m a n u fa c t u re rs names

appear her ein only because they are con s idered essen t i l t o the o b j e c t o f t h i s document.

FHW

DISTRIBUTION

S u f f i c i e n t copies o f t h i s r e p o r t are being d i s t r i b u t e d by FHW B u l l e t i n t o pro~ide two copies to each r e g i o n a l o f f i c e , one copy t o each d i v i s i o n o f f i c e , and two copies t o each S t a t e highway department. d i s t r i b u t i o n i s being made t o the d i v i s i o n Doi fre f icct e s .

 

Technical Report Documentation Page 1.

Report No.

2.

FHWA-RD-75-130 4.

·

b

;i 5 7

Title and Subtitle LATERAL SUPPORT SYSTEMS AND UNDERPINNING

Volume III. 7

Government Ac c e s s ion No.

3 A7

Construction Methods

1 Au th0r s)Dona l d T. Gold berg,

3.

Recipient s Catalog No

5.

Report Date

6.

8.

Water E. Jaworski, and

Aoril

,.

1976

Performing Organization Code

Performing Organization Report No.

Daniel

M

Gordon

Goldberg-Zoino

Associates, Inc.

30 Tower Road Newton Upper Falls

363

Work Unit No (TRAIS) FCP 35 B

10.

Performing Organization Nome and Address

9.

Contract or Grant No

11

Massachusetts

DOT-FH-11-8499

02164

13.

Type of Report and Period Covered

Sponsoring Agency Name-and Address

12.

Final report

Offices of Research and Development FHWA u. s. Department of Transportation Washinaton. D. C. 20590

14.

Sponsoring Agency Code

Supplementary Notes

15.

Contract manager for this study: 16.

J.

R

Sallberg HRS-11)

Abstract

This provides specific design recommendations, design considerations, and construction techniques for the construction of lateral support systems and underpinning. The design considerations are presented for each technique or method (soldier piles steel sheeting, diaphragm,walls, internal bracing, The factors affecting the tiebacks, underpinning, grouting, and freezing). design or implementation of these schemes are discussed. Construction techniques are presented, and literature references are provided for those seeking even greater detail. An overview of the construction methods compares the applicability of the techniques and the construction costs of each. Other reports developed from the study are FHWA-RD-128, Volume I Design and Construction; FHWA-RD-129, Volume I I Design Fundamentals; and FHWA-RD131, Concepts for Improved Lateral Support Systems.

17.

Key Words Bracing, Ground Support, Excavation, Underpinning, Cut-and-Cover Construction. Security Classif. (of this report)

19.

OT

F 1700 7

Distribution Statement

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

Security Classif. (of this

page

Unclassified

Unclassified Form

20.

18.

cs-n;

21.

No of Pages

22.

Price

477

Reproduction o f completed poge a uthor iz e d

 

PREFACE '

V o l u m e s I I a n d III o f t h i s t h r e e v o l u m e s e t p r e s e t j t the c u r r e n t s t a t e - o f - t h e - a r t o n the e n g i n e e r i n g a s p e c t s o f the q e s i g n a n d c o n s t r u c t i o n o f g r o u n d s u p p o r t w a l l s a n d the c l o s e l y r e l a t e ~ n i n g , g r o u n d freezing_, a n d g r o u t i n g . sol t h a t t e c h n i q u e s o f u n d e r p i n ni the r e a d e r w i l l u n d e r s t a n d the r a t i o n a l e behind the s u b j e c t m a t ~ e r , the t e x t c o n t a i n s d e t a i l e d d i s c u s s i o n s , es_pecially i n a r e a s o f ~ n  t r o v e r ~ i a l o r t e c h n i c a l l y n e w i s s u e s . O n t h e o t h e r h a n d Vo l e I, s u m m a r y o f V o l u m e s I I a n d III, i s f r e e f r o m the d e t a i l e d d i s u s s i o n s ·

e m b o d i e d i n the l a t t e r two. erence manual.

I t s p u r p o s e i s to p r o v i d e a r e a d y

~

-

i

O v e r a l l , the p r i m a r y i n t e n t i s t o p r o v i d e i n f o r m a H o n a n d g u i d e l i n e s to p r a c t i c i n g e n g i n e e r s , i n p a r t i c u l a r t h o s e e n g i n e e r s w i t h a n a d v a n c e d b a c k g r o u n d in the disc_iplines of So il M e c h a n i ~ s a n d Foundation Engineering. I

I

V o l u m e II i n c o r p o r a t e s d e s i g n f u n d a m e n t a l s , p r i r p a r i l y

t h o s e o f a g e o t e c h n i c a l n a t u r e . I t p a c e s conside}."~ble ~_ nphas\s u p o n d i s p l a c e m e n t s o f a d j a c e n t g r o u n d a n d a d j a c e n t s t r u c t u r e s a n d c l onsi de rs t h o s e p a r a m e t e r s w h i c h a r e p r i m a r y c o n t r i b u t o r s t o e x c e s s i v e jd is placements. V o l u m e III i s d i r e c t e d t o w a r d the e s s e n t i a l desigtj. a n d c o n s t r u c t i o n c r i t e r i a a s s o c i a t e d with e a c h o f the following t e c h b i q u e s : (a) S u p p o r t W a l l s - s o l d i e r p i l e w a l l s , s h e e t p i l e w a l l s , c o n c r b t e

d i a p h r a g m w a l l s ; (b) S u p p o r t M e t h o d s - i n t e r n a l b r a c i n g a n d t i ~ b a c k a n c h o r a g e s ; (c) Under_pinnin_g; (d) Grouti.t1g; (e) G r o u n d F r e e z i n , . Also, i t p r e sen t s a n o v e r v i e w o f t h e s e c o n s t r u c t i o n m e t h o d s w l t h r e g a r d t o s e l e c t i o n , p e r f o r m a n c e , a n d r e l a t i v e c o s t . T hr oug~out, a n a t t e m p t h a s b e e n m a d e t o p r o v i d e a b a l a n c e b e t w e e n t he pralc tical engineering considerations of construction and appropriatb corresponding considerations of engineering fundamentals. I

T h e s e p u b l i c a t i o n s a r e p r o d u c e d u n d e r the s p o n s t j r s h i p o f the D e p a r t m e n t o f T r a n s p o r t a t i o n r e s e a r c h p r o g r a m , a long r a n g e p l a n to a d v a n c e the t e c hnol ogy o f b o r e d a n d c u t - a n d - c o v e r tunn4ls, i n p a r t i c u l a r th o se c o n s t r u c t e d i n the u r b a n e n v i r o n m e n t .

ii

 

 

a r t o f t h i s p r o g r a m in v o lv es a s y n t h e s i s an d evalualtion o f e x i s t i n g knowledge a n d p a r t involves a R e s e a r c h a n d Developn{.ent

e f f o r t . T h e s e v o l u m e s fall u n d e r the c a t e g o r y o f the f o r m e r , 1·1 s t 1 t e of the A r t , - aspect o f the p r o g r a m f r o m w h i c h i t i s hope d t h a t pro1 g r e s s t h r o u g h d e v e l o p m e n t o f bol d innovative a p p r o a c h e s w i l l ·em~nate.

iii  

AC KNOW L E DGE ME NT S

The aut hors acknowledge with gratitude: The assilstance o f M e l v i n F e b e s h o f U r b a n F o u n d a t i o n C o m p a n y , New Y o r k , whp c o n t r i b u t e d s o h e a v i l y t o the u n d e r p i n n i n g c h a p t e r a n d w h o s e in ~ ig h t a n d c o n s t r u c t i o n e x p e r i e n c e a s s u r e d p r o p e r d i r e c t i o n to the e f t o r t . T h e c o n t r i b u t i o n s o f D r . J a m e s P . Go u ld , o f M u e ~ e r , R ut l e dge , W e n t w o r t h a n d J o h n s t o n , New Y o r k , t h r o u g h h i s re vi ~ w o f

th e c h a p t e r s i n V o l u m e I d e a l i n g w i t h d i s p l a c e m e n t s , e a r t h p r e ~ s u r e , a n d d e s i g n a s p e c t s o f l a n d c o f f e r d a m s . T h a n k s a l s o to: To Mr.

John Shuster of Ter r af r eeze Corporation, ' B e t h e s d a , M a r y l a n d f o r the r e v i e w a n d c o n t r i b u t i o n s f or the s e ¢ t i o n o n the t e c h n i q u e s o f g r o u n d f r e e z i n g .  

'

I

T o M r . J o h n J o n e s o f S c h n a b e l F o u n d a t i o n , C o . , Washi n g t o n , D . C . f or hi s r e v i e w a n d c o m m e n t s o n V o l u m e III, " C o ~ s t r u c t i o n

Methods''. T o M r . D. M a i s h m a n o f F o r a k y , L t d . , G r e a t B r i t a i n f o r a l l owi ng the a u t h o r s th e o p p o r t u n i t y t o r e v i e w h i s y e t u n p u b l i s h e d m a n u s c r i p t on g r o u n d freezing. I

T o t h o s e m a n y e n g i n e e r s , m a n u f a c t u r e r s , a n d COil-tract o r s who g r a c i o u s l y p r o v i d e d c o m m e n t s , d a t a , a n d p h o to g r ap h si. '

T o M r . J o h n Dunniclif f o f Soi l R oc k I n s t r u m e n t ~ t i o n , I n c . , o f Newto n U p p e r F a l l s M a s s a c h u s e t t s f o r th e c h a p t e r on Construction Monitoring. T o t h o s e individuals a s s o c i a t e d w i t h G o l d b e r g - Z o i ~ o & A s s o c i a t e s , Inc . who c o n t r i b u t e d g r e a t l y t o th e v a r i o u s c h a p t ~ r s i n t h e s e m a n u a l s : D r . St e phe n A . A l s u p o n G r o u n d F r e e z i n g ; : M r . P e t e r R i o r d a n o n B e a r i n g C a p a c i t y ; M r . J a c k s o n Ho f o r

o u t s t a n d i n g e f f o r t o n c o m p u t e r w o r k ; the e f f o r t s o f M s . A n d r e a 1 W i z e r a n d M r s . J o a n J e n n i n g s f o r t h e i r p a t i e n c e a n d endur:3-nce i n the typing o f t h e s e m a n u s c r i p t s . T o M r G a r d n e r L . H a y w a r d , J r . f o r a j ob w e l l 4 o n e on the drafting of the figures. ·

Sallberg, cont ract mana~ er f o r th e D e p a r t m e n t o f T r a n s p o r t a t i o n and F e d e r a l Highway A d n i i n i s  t r a t i o n , f o r his p ·atien ce, s u p p o r t , a n d w e l c o m e c r i t i c i s m s thr tjughout th e p r o g r a m . And finally, to M r .

J.

R.

iv  

T A B L E O F CO N TEN TS

INTRODUCTORY T E X T

Page Number TITLE PAGE PREFACE ACKNOWLEDGEMENTS

i

ii v

T A B L E O F CO N TEN TS CONVERSION FA CTO RS SYMBOLS

V

viii X

TEXT CHAPTER 1

OVERVIEW O F CONSTRUCTION METHODS P u r p o s e and Scope 1 10 1.20 G e n e r a l C o n c l u s i o n s Concerning Displacements 1.30 Wall Type 1 . 40 Support Method 1. 50 Underpinning

1.60

1 . 70 1 . 80

CHAPTER 2

CHAPTER 3

Stabilization Methods Soil and Ground W a t e r Conditions Costs

1 1 1 3 5

8 8

10

11

SOLDIER P I L E W A LLS 2.10 In tr odu ction 2.20 T y p e s o f Soldier P i l e W a l l s Design C o n s i d e r a t i o n s 2.30 2.40 Construction Considerations

29 45

STEEL SHEET PILING

50

3 . 10 3. 20 3 . 30

Introduction Design Considerations Construction Considerations

17 17 19

50 50 57

V

 

T A B L E O F CO N TEN TS (con't)

P a g e Number I

CHAPTER 4

CO N CRETE DIAPHR ,>GM W A LLS 4 . 10 Introduction 4;20 P r o p e r t i e s o f Bentonite S l u r r y S l u r r y T r e n c h Stability 4 . 30 4 . 40 P r a c t i c a l Aspects of S l u r r y Stabilized Excavations ·

59

:59 ,60 i67 185

4. 50

CHAPTER

5

CHAPTER 6

CHAPTER 7

St r u c t u r a l Aspects of C a s t - i n - P l a c e Walls

I

4. 60 4 . 70

Excavation of S l u r r y Trenches D i a p h r a g m Walls Other than Continuous C a s t - i n - P l a c e C o n c r e t e A ppendix A ppendix B

11 5

lN TERN A L BRA GING 5. 1 In.tr odu ction 5 . 20 Design C o n s i d e r a t i o n s 5 . 30 ·I n s t a l l a t i o n 5. 40 Temperature Effects 5. 50 S t r u t R e m o v a l and R e - b r a c i n g

li40 1 40

TIEBACKS 6 . 10 Introduction D e s i g n and T h e o r e t i c a l C o n s i d e r a t i o n s 6. 20 6. 30 C o n s t r u c t i o n C o n s i d e r a t i o n s for Tiebacks 6. 4 0 Field Testing

1155

lil2

114

1j44 1149 I

1 54

UNDERPINNlNG 7." 10 Introduction 7 .'20 Design and T h e o r e t i c a l C o n s i d e r a t i o n s 7. 3 0 C l a s s i c a l Underpinning P r o c e d u r e s 7. 40 Grouted Piles 7. 5 0 Tunneling Below S t r u c t u r e s 7. 60 Load T r a n s f e r 7 . 70 T e m p o r a r y Support o r "Shoring" 7. 80 Performance

1155

1157 I

2 27 2144

2j61 2167 I

2169 I

2172 I

31 '

31 7

3l23 3:24 3129

vi  

. T A B L E O F CO N TEN TS (con t) Page Ijumber CHAPTER 8

GROUTING 8 . 10 · I n t r o d u c t i o n 8. 20 D e s i g n and. T h e o r e t i c a l C o n s i d e r a t i o n s 8. 30 Construction Considerations 8 . 40 F i e l d T e s t i n g and Q u a l i t y C o n t r o l S p e c i f i c Applications 8. 50

335 33 5

335 35P 358

360

CHAPTER 9

FREEZING 9. 10 Introduction

366 36~

9. 20 9. 30

368 40 ) 41~

9. 40

Design and Theoretical Considerations Construction Pr o c e d u r e T y p i c a l A p p l i c a t i o ns ns

BIBLIO G RA P H Y

411

vii

 

LIST O F CONVERSIONS

I

The list of conversions is designed to aid in converting frorq B r i t i s h u n its o f m e a s u r e t o m e t r i c u n i t s . T h i s s e c t i o n h a s b e e n d vided into two p a r t s ; g e n e r a l n o t a t i o n a n d a r i t h m e t i c c o n v e r s i o n . I

G e n e r a l Notation

BTU cm

B r i t i s h T h e r m a l Unit centimeter

cm

square centimeter

cm

3 .

CC

cubic c e n t i m e t e r

cf s

cubic f e e t p e r s e c o n d

ft

feet

ft2

square feet

n

cubic f e e t

fps

feet p er second

gal

gallon

gpm

gallons p e r m i n u t e

gr

g

grams

hr

hour

in

inches

in

square inches

in

3

cubic i n c h e s

k

k ilo (t housa nd)

kg

kilogram

m

meters

m

square meters

m

3

min

cubic m e t e r s

minute

viii

 

L i s t O f Sy mb o ls I

The f ollowing ollowing l i s t o f s y m b o l s h a s b e e n p r e p a r e d t o a i d th e i ~ t e r p r e t a t i o n o f s y m b o l u s e i n th e t e x t . T h i s l i s t i d e n t i f i e s only th e t j o r with s y m b o l s u s e d i n th e t e x t an d t h e i r g e n e r a l m e a n i n g . E a c h s y m b o s u b s c r i p t s ) i s d efin ed i n t h e t e x t for i t s p a r t i c u l a r u s a g e . T h i s l s t i s n o t a c o m p l e t e l i s t o f a l l s y m b o l s o r a l l s y m b o l u s a g e i n th e t e x t u t i s a s u m m a r y o f m a j o r s y m b o l s an d t h e i r u s a g e . I

S ym bol

Represents g e n e r a l s y m b o l for

B, b

re

g e n e r a l s y m b o l s f o r width

C

co h esio n i n t e r c e p t

C

heat capacity

D d

g e n e r a l s y m b o l s fo r d i s t a n c e and diameter

E

g e n e r a l s y m b o l fo r m o d u l u s

f

g e n e r a l s y m b o l fo r s t r e s s

F. s

factor of safety

H

d ep th o f ex cav atio n ; a l s o g e n e r a l s y m b o l fo r hei ght

K

g e n e r a l s y m b o l fo r co efficien t of l t e r l e a r t h p r e s s u r e

K

K K

0

a p

K

I I

Vo lu me r C h a p t e r 1 6 Volum e IP: C h a p t e r 9

co efficien t o f l a t e r a l e a r t h p r e s s u r e at rest co efficien t o f a c t i v e e a r t h p r e s s u r e co efficien t o f p a s s i v e e a r t h p r e s s u r e t h e r m a l co n d u ctiv ity

L, 1

g e n e r a l s y m b o l s fo r len g th or distance

N

g e n e r a l s y m b o l fo r s t a b i l i t y µumber or standard penetration resistance

OCR

o v e r co n so lid atio n r a t i o

V o l u m e I C h a p t e r 16 1 Vo lu me :q:r C h a p t e r 9

X  

Symbol

Represents

p

g e n e r a l sym.bol fo r lo ad o r f o r c e

p

general symbol for p r s s u r

p

n e g a t i v e l o g a r i t h m o f effective hydrogen ion concentration

R

s

r

g e n e r a l s y m b o l s for r a d i u s g e n e r a l s y m b o l s fo r s h e a r r e s i s t a n c e or shear strength

Ref er enjce

undrained shear strength u

u

pore pr ssur

w

g e n e r a l s y m b o l f o r weig h t

w

g e n e r a l s y m b o l f o r w a t e r co n ten t g e n e r a l s y m b o l fo r d i s p l a c e m e n t o r m o v e m e n t ; a l s o an g le o f w a l l f r i ct i o n

v

(max)

h(.max)

vertical displacement (maximum) h o r i z o n t a l d i s p l a c e m e n t (maximum.) general symbol for stra in

£

g e n e r a l s y m b o l f o r u n i t weight; t o t a l u n i t weight of s o i l u n l e s s otherwise specified

d r y u n i t weight of fiOil t o t a l u n i t weig h t o f s o i l

b o u y a n t u n i t weight o f s o i l

u n i t weig h t o f w a t e r

P o i s s o n s Ratio P o i s s o n s Ratio general symbol for friction angle of soil

xi

 

Symbol

Represents

Reference

L

g e n e r a l sym.bol for s e t t l e m e n t j

f

-

f vm

g en er al s y m b o l f o r

str

ss

t o t al v e r t i c a l s t r e s s effective v e r t i c a l s t r e s s ) total horizontal str ss effective h o r i zo n t al s t r e s s ) maximum past vertical consolidation p r e s s u r e

effectiv e s t r e s s )

g e n e r a l s y m b o l for s h e a r or shear resistance

No te:

str

ss

i

L i n e o v e r s y m b o l s indicates effective s t r s s p a r a m e t e r s ~ r e t o b e u s ed . e.g. I v e r t i c a l effective s t r e s s ) . 1

V

xii  

C H A P T E R I - OVER VIEW OF. CONSTRUCTION METHODS

1 1

P U R P O S E AND S C O P E

T h i s s e c t i o n prE:sents a s y n t h e s i s o f the m a i n c o n •

c l u s i o n s c o n c e r n i n g t h e p e r f o r m a n c e o f underp:inning and o f v a r i d u s t e c h n i q u e s f o r supporting open e x c a v a t i o n s . E m p h a s i s i s p l a c e d upon the genera_l applicability o f e a c h o f ~ v a r i o u s t e c h n i a u e s , and c o m p a r i s o n s a r e m a d e , w hen a p p r o p r i a t e , i n o r d e r t o c o n s i d e r t h e influence o f s u c h v a r i a b l e s a s s o i l type, wall type, and meth~d o f l a t e r a l s u p p o r t . A n a t t e m p t h a s b e e n m a d e to identify k e y

o p e r a t i o n a l contingencies which have the p o t e n t i a l of contributing, t o e x c e s s i v e h o r i z o n t a l a n d v e r t i c a l d i s p l a c e m e n t s i n the a d j a c e n t g r o u n d . F i n a l l y , s o m e g e n e r a l guidelines a r e p r o v i d e d concerni:hg cost~ · l . 20

G E N E R A L CONCLUSIONS CONCERNING D I S P L A C E M E N t s

L a t e r a l Support Methods

1 21

Competent Soils

(granular soils, v e r y stiff clays, etc

i

a, Displacements r e p o r t e d in the l i t e r a t u r e on wetl c o n s t r u c t e d , w e l l - d o c u m e n t e d c a s e s a r e of insufficient magnitud~ to distinguish var i at i ons t hat may be i nher ent in wall type o r in m e t h o d o f l a t e r a l s u p p o r t . N e v e r t h e l e s s , t h e r e i s s t r o n g evidenc~ t o s u g g e s t t h a t c o n c r e t e d i a p h r a g m w a l l s will exhibit l e s s d i s p l a c ¢  m e n t than o t h e r w a l l t y p e s and w a l l s s u p p o r t e d b y t i e b a c k s w i l l perform better than internally braced walls. b . M a x i m u m d i s p l a c e m e n t s a r e t y p i c a l l y i n the ork).er o f O. 25 p e r c e n t t o O. 3 5 p e r c e n t o f wall height. The l o w e r r a n g e h a s s o c i a t e d w i t h g r a n u l a r s o i l s ; the u p p e r r a n g e i s a s s o c i a t e d w i t h cohesive s o i l s .

c . Typically, m a x i m u m h o r i z o n t a l and v e r t i c a l d i s p l a c e m e n t s a r e about e q u a l .

 

  Weaker Soils

(soft t o m e d i u m c l a y s , o r g a n i c s o i l s , etc.I)

Maximum displacements typically exceed l i p e r c e n t o f depth o f cut f o r flexible w a l l s s u c h a s s t e e l s h e e t pilin~. C o n c r e t e d i a p h r a g m w a l l s d r a m a t i c a l l y r e d u c e the m a g n i t u d e o f d i s p l a c e m e n t s t o about O 25 p ~ r c e n t o f the depth o f cut o r abo\jlt t h e s a m e a s t h o s e o b s e r v e d f o r competent s o i l s . d.

e . Typically, the m a x i m u m v e r t i c a l d i s p l a c e m e n t s exceed maximum horizontal displacement. .

I

f . W h en the excavation i s u n d e r l a i n b y d e e p d e p o i i t s · o f w e a k s o i l s , the cumulative t o t a l o f al l d i s p l a c e m e n t s o c c u r r i n b e l o w the l a s t p l a c e d s t r u t l e v e l a m o u n t s t o about 60 p e r c e n t o f t e t o t a l :measur_ed m o v e m e n t . 1

W a l l TyPe

 

With c o n c r e t e d i a p h r a g m w a l l s , d i s p l a c e m e n t ~ a r e t y p i c a l l y l e s s t h a n O 25 p e r c e n t o f . w a l l height, r e g a r d l e s s o~ g.

I

s o i l type.

I

h . The s t i f f n e s s o f w a l l s c a n b e i n c r e a s e d n ~ t onl{y . b y u s i n g r i g i d c o n c r e t e w a l l s b u t b y r e d u c i n g s p a c i n g between sut,port l e v e l s o f s o l d i e r p i l e w a l l f o r s t e e l s h e e t p i l e w a l l s . Comparablje w a l l s t i f f n e s s (defined a s ~ will result in comparable p e r f o r m ~ c e p r o v i d e d t h a t the i n s t a l l a t i ~ n s a r e c a r e f u l l y c a r r i e d out and g r o 4 d loss is minimal. i

A comparison f r o m observational data betwee~ s o l d i e r p i l e w a l l s a n d s h e e t pile w a l l s (of c o m p a r a b l e stiffness) :ts not p o s s i b l e i n v e r y stiff t o h a r d c l a y s a n d d e n s e g r a n u l a r s o i l s i because sheet piles a re infrequently used under such h a r d drivin~ conditions. Therefore, data a r e lacking. i i.

i

E f f e c t of Wall S t i f f n e s s i n C o h e s i v e Soil

j.

EI 1 T h e influence of w a l l s t i f f n e s s (defined a s L 4) land

o f s t a b i l i t y n u m b e r o f c o h e s i v e s o i l (defined a s N = ~ H u

was e x ~ i n e d

2

 

i n s o m e detail The t r e n d s a r e c l e a r , and the data indeed show i n c r e a s i n g d i s p l a c e m e n t s with w e a k e r s o i l s and with m o r e flexible

w a l l s . D i s p l acem en t s with sheet piling m a y exceed 4 t o 5 inches, but in s i m i l a r c a s e s , d i a p h r a g m w al l s would control d i s p l a c e m e n t s t o l e s s t h an 1-1/2 i n ch es .

L.2.2

Underpinning

Underpinning i t s e l f h a s a n i n h e r e n t so u r c e o f d e  f o r m a t i o n a s s o c i a t e d with the p h y s i c a l t r a n s f e r o f load f r o m t h e existing to the new foundation. W el l - ex ecu t ed c o n s t r u c t i o n p r o  c e d u r e s can n o r m a l l y control this v e r t i c a l d i s p l a c e m e n t t o 1/2 inch or less. Underpinning m a y a l s o b e influenced by the adjacent excavation b e c a u s e the underpinning e l e m e n t s w i l l b e i n st a l l e d within t h e zone of v e r t i c a l and h o r i z o n t a l d i s p l a c e m e n t s . Thus, t h i s c r e a t e s the potential f o r additional d i s p l a c e m e n t s a n d / o r additional load i m p o s e d upon t h e underpinning e l e m e n t s . Ex p e r i e n c e h a s shown that horizontal m o v em en t s cau s e m o r e d a m a g e t h a n

v e r t i c a l m o v em en t s . l . 30

WALL T Y P E

I . 31

Concrete Diaphragm W alls I . 31. 1 Applicability

D i ap h r ag m w al l s a r e ap p l i cab l e i n p r a c t i c a l l y e v e r y soil condition with t h e p o s s i b l e exception o f v e r y soft clays ., p e a t , o r co h es i v e hydraulic fill. They a r e u s ed f r eq u en t l y t o m i n i m i z e d i s p l a c e m e n t s behind the wall. I t i s common i n

E u r o p e a n p r a c t i c e t o i n c o r p o r a t e the d i a p h r a g m w al l into the p e r m a n e n t s t r u c t u r e ; w h e r e a s i n the United St a t e s , d i a p h r a g m w al l s have h i s t o r i c a l l y b een u s e d a s a method o f ground s u p p o r t without being i n c o r p o r a t e d into the p e r m a n e n t s tr uctur e. 1. 3 .1, 2 O p er at i o n al Consideraticm.s I

P r e c a u t i o n a r y m e a s u r e s should b e t ak en t o p r o t e c t a g a i n s t fluid l o s s d u r i n g excavation i n highly p e r v i o u s O t h er conditions { co ar s e s an d , c o a r s e sand and g~avel m i x t u r es .

 

c o n t i n g e n c i e s l i e i n c o n t a m i n a t io io n o f t h e f l u i d i n s o i l s w i t h a d v e r s e pH,,high salinity, o r h ig h c a l c i u m co n ten t. I t i s b e l i e v e d

t h a t m o s t o f t h e s e p o t e n t i a l c o n t i n g e n c i e s c a n b e i d e n t i f i e d d u r i n g thie initial investigation and by proper quality control during const ruc t i on. Another potential probl em is spalling (local c o l l a p s e ) of t he t r e n c h w a l l n e a r t he g r o u n d s u r f a c e . T h i s m a y b e c a u se d by unstable soils o r loose fill, particularly when containing

A

misc e lla n e o u s rubble o r old foundations. well-constructed g u id e w a l l , s u f f i c i e n t h e a d o f s l u r r y , a n d p r e v e n t i o n o f s l u r r y flocculation a r e essential m e a s u r e s . 1 32

Soldier Pi l e Walls 1 . 32. 1 A p p l i c a b i l i t y

Soldier piles a r e applicable in all soils except perhaps soft to m e d iu m clays and in loose o r soft dilatant soils of low plasticity below the w a t e r table. These soils have a tendency tJ run after exposure. · · 1

1. 32. 2 O p e r a t i o n a l C o n s i d e r a t i o n s

T h e f o llo win g c i t e d i t e m s h a v e t h e p o t e n t i a l o f l e a d i n g t o a d d i t i o n a l d i s p l a c e m e n t s : d e f l e c t i o n o f l a ggi ng; o v e r c u t b e h i n d l a ggi ng; g r o u n d l o s s d u e t o s u r f a c e a n d g r o u n d water ;

and ground loss associated with pre-excavation for soldier piles. A d d i t i o n a l l y , t h e r e i s t he r i s k f a c t o r a s s o c i a t e d w i t o p e n l a g g i n g due to a n u n u su a l o c c u r r e n c e whi c h m a y c a u s e heavy c onc e nt ra t i onsi o f w a t e r t o fl o w t o w a r d t h e e x c a v a t i o n . This ma y include b ro k e n w a t e r m a i n s o r f lo o d in g . P r e - d r a i n i n g of saturated soils is essential, e s p e c i a l l y t h o s e w h i c h m a y h a v e a t e n d e n c y to r u n s i l t o r s i l t y f i ne s a n d f o r e x a m p l e ) . A c o m m o n , d i f f i c u l t s i t u a t i o n i s w h e n s u c h so il~ a r e underlain by rock o r by impervious soil within the depth of e x c a v a t i o n . T h i s s e q u e n c e - m a k e s i t e x t r e m e l y d i f f i c u l t t o ful l y d e w a t e r t o t he l o w e s t e x t e n t o f t he w a t e r b e a r i n g f o r m a t i o n .

-4 

1

33

Steel Sheet Pile Walls

I . 33.

I

Applicability

These r e m o s t generally u s e d in soil types that re inappropriate for soldier pile walls, such a s the soft clays, o r g a n i c ,soils, a n d d i l a t a n t s o i l s o f low p l a s t i c i t y . S h e e t i n g i s als ou s e d i n s i t u a t i o n s w h e r e t h e r e i s a d e s i r e t o cutoff g r o u n d w a t e r o r

·

t o r e d u c e s e e p a g e g r a d i e n t s a t t h e b o t t o m o f t h e excavation,.

I . 33. 2 O p e r a t i o n a l C o n s i d e r a t i o n s S t e e l s h e e t p i l e w a l l s r e r e l a t i v e l y fl ex i b l ~ with n o r m a l wale spacing, and they re frequently a s s o c i a t e d with relatively large displacements when installed in weak cohesive soils. Contingencies lie in tearing of interlocks under h a r d driving conditions and associated ground loss occur;ing with gro*nd water infiltration. While i n t e r l o c k e d s t e e l s h e e t piling e f f e c t i v e l y i n t e r c e p t s g r o u n d w a t e r flow w i t h i n p r e v i o u s l a y e r s , t h i s i s n o t n e c e s s a r i l y a g u a r a n t e e a g a i n s t d e p r e s s i o n of the p i e z o m e t r i c l e v e l outside the excavation. Simply stated, relatively impervious soil r e of equivalent t y p s including c l a y e y s a n d s , s i l t s , a n d c l a y s ) permeability to the steel sheet pile wall itself. Therefore, a s a p r a c t i c a l m a t t e r , t h e p r e s e n c e of t h e i n t e r l o c k e d s t e e l s h e e t p ile wall does not p r e v e n t a seepage p a t t e r n to the fa c e of the excavation. S uch a s e e p a g e p a t t e r n i s a c c o m p ~ n i e d b y a· d r o p i n p i e z o m e t r i c l e v e l s w hich m a y i n d u c e c o n s o l i d a t i o n o f c o m p r e s s i b l e s o i l s . Removal of steel sheet piling f r o m cohesive soils m y also remove s o i l s w i t h i t a n d i n t u r n l e a d to s e t t l e m e n t of a d j a c e n t g r o u n d .

I . 40

SUPPORT METHOD 1

41

Tiebacks

I . 41.

I

Applicability

Tiebacks r e m o s t applicable in v e r y stiff to h a r d c o h e siv e s o i l s o r in g r a n u l a r s o i l s . In l o w e r s h e a r s t r e n g t h , cohesive solis, the regroutable tieback has been used successfully, while other anchor types have displayed relatively l a r g e movements.

-5 

1

41. 2 O per at i onal Considerations

V e r t i c a l Wall Movement The v e r t i c a l components o f l oad m a y 4 a u s e s e t t l e m e n t o f so l d i e r pile w al l s and this m a y l e a d t o h o r i z o n t a l displacement.

~

essive

Prestressing

With a r e l a t i v e l y flexible wall, excess~ ve p r e s t r e s s i n g o f the u p p e r l e v e l s m a y c a u s e inward movemen~ o f t he top and outward bowing below. The magnitude o f the bo~ing i n c r e a s e s i n r e s p o n s e t o excavation a s t he r e st r a i n i n g f o r c e 1is r em oved o n the inside o f the wall. The p r o b l e m i s accent uat ed i n a soil sequence o f l oos e - h a r d - l o o s e f r o m the top t o t he bqt t om o f the cut. · i

A n unusual c a se was r e v e a l e d i n a papler b y M cR os t i e, e t a l (1972) which cites a n excavation i n a sensiti {e

c l a y and tiebacks d r i l l e d i nt o r ock. The e x c e s s i v e p r e s t r e s , i n g induced horizontal s t r e s s e s somewhat i n e x c e ss of the a t - r e ~ t e a r t h p r e s s u r e . T hi s e s t a b l i s h e d a new s t r e s s condition whith led t o significant consolidation o f t h e c l a y behind the wall. ·

W a t e r F l o w and Ground L o s s into Dr i l l Holes

  i

i

W a t e r flow through the d r i l l e d anchor i r e s u l t i n ground l o ss par t i cul a· r l y i n l oos e fine s and. The m o f the ground l o ss i s affected b y the h y d r o s t a t i c head, d r i l l i c e d u r e , and soil conditions. W a t e r flow m a y a l so l e a d t o a p i e z o m e t r i c level and consolidation of c o m p r e s s i b l e s ,

ge can gnitude g pro rop i n

L a t e r a l Cr e e p L a t e r a l m ovem ent , s e v e r a l t i m e s g r e ~t e r t han se t t l e m e n t and extending r e l a t i v e l y l a r g e d i s t a n c e s behind th~ f ace o f t he excavation, has been r e p o r t e d in highly over cons ol i dat ed clays and soft sh a l e s. The m o v e m e n t i s believed t o b e a sso c i a t e d with l a t e r a l expansion following s t r e s s r elief f r o m the excavation~

-6 

o t h er potential s o u r ce of l a t e r a l c r e e p is i n the p r e s e n c e o f a w e a k l a y e r o f c o h e s i v e s o i l b e l o w the e x c a v a t i o n . A

1. 4 2

n tern al

l . 42.

l

Bracing

Applicability

I n t e r n a l b r a c i n g i s m o s t applicable to s i t u a t i o n s i n wh ich a r e a s o n a b l y e c o n o m i c a l m e m b e r s ect i o n can b e u s e d with o u t n e e d of i n t e r m e d i a t e s u p p o r t o r i n c a s e s w h e r e i n c l i n e d r a k e r s a r e f eas i b l e. A s the d i s t an ce b e t w e e n t h e s i d e s o f the excavation i n c r e a s e s , i n t e r n a l b r a c i n g b e c o m e s l e s s ef f i ci en t , an d ck s b e c o m e m o r e a t t r a c t i v e . t h e r e f o r e t i e b a ck 1

42. 2

Operational Considerations

T he m o s t i m p o r t a n t contingency i t e m i s be l i ev ed t o b e a s s o c i a t e d with i m p r o p e r connection d e t a i l s , e s p e c i a l l y with r e g a r d t o alignment o f m e m b e r s and welding.

D i s p l a c em e m e n t s m a y a r i s e f r o m s l a c k i n the s u p p o r t s y s t e m c o n s i s t i n g o f ax i al c o m p r e s s i o n of the m e m b e r , d e f o r m a t i o n s i n c o n n e c t i o n s , b e a r i n g b e t w e e n w a l e a n d w a l l an d t h e adjoining ground). H o w e v e r , t h i s c a n b e l a r g e l y e l i m i n a t e d b y p r e o ad in g .

B r a c e r e m o v a l i s an o t h er s o u r c e o f d i s p l a c e  m en t . However, t h i s c a n b e c o n t r o l l e d b y a c o m b i n a t i o n o f w e l l p l a n n e d r e s t r u t t i n g a n d effective compaction o f b a c k f i l l b e t w e e n t h e w a l l a n d the s t r u c t u r e . P r e l o a d i n g t o a b o u t 50 p e r c e n t o f t h e d e s i g n load i s c o m m o n p r a c t i c e i n a r e a s w h e r e d i s p l a c e m e n t s r e o f concern.

E x t r e m e t e m p e r a t u r e v a r i a t i o n s affect load. R e a s o n a b l e p r ecau t i o n s t o p r e v e n t o v e r s t r e s s i n g c a n b e t a k e n b y c o v e r i n g s t e e l m e m b e r s o r b y painting with r ef l ect i v e s i l v e r paint.

-7 

I.SO

UNDERPINNING

1.51

Applicability 1

U nderp1nning o f a . s t r u c t u r e t r a n s f e r s t h e l o a d f r o m i t s e x i s t i n g fotlndation t o a new foundation b e a r i n g b e l o w t h e zone o f influence o f the a d j a c e n t e x c a v a t i o n . H i s t o r i c a l l y , d e c i s i o n s t o u n d e r p i n o r n o t h a v e s t e m m e d l a r g e l y f r o m the s u b j e c t i v e j u d g e m e p t s o f p r a c t i t i o n e r s . A m o r e r a t i o n a l a s s e s s m e n t o f r e l a t e d issu~.s c a ~ b e m a d e o n t h e b a s i s o f insight into a n t i c i p a t e d d i s p l a c e m e n t s a t i

1 •

adjoining s t r u c t u r e s a n d u p o n the t r a d i t i o n a l e n g i n e e r i n g a s s e s s m e ~ t · of cost, expediency, and risk.

1.52

Operational Considerations

It is a x i o m a t i c t h a t a th o r o u g h s tu d y b e m a d e b e f o r e ~ a n d o f the s t r u c t u r e t o b e u n d e r p i n n e d c o n c e r n i n g i t s l o a d a n d d i s t r i b u t i o n o f load. T e m p o r a r y c o n d i t i o n s t h a t o c c u r - d u r i n g u n d e r p i n n i n g w i l l 1ialso r e q u i r e evaluation. B e c a u s e t h e e l e m e n t s p a s s t h r o u g h a z o n e u n d ~ r  going v e r t i c a l and h o r i z o n t a l d i s p l a c e m e n t , u n d e r p i n n i n g i s not neciessarily f r e e f r o m picking u p d o w n d r a g f o r c e s , l a t e r a l f o r c e s , a n d / o r m o v i p g . L a t e r a l mo v e me n t s have p r o v e n to b e a s o u r c e of g r e a t d a m a g e . I

i

n u m b e r o f f a c t o r s h a v e the potential o f c a u s i n g g r o u n d loss. L a g g e d u n d e r p i n n in in g p i t s f o r c o n s t r u c t i o n o f p i e r s h a v e m a 4 y o f the s a m e c o n t i n g e n c i e s m e n t i o n e d p r e v i o u s l y f o r s o l d i e r p i l e e s p e c i a l l y w hen a g g r a v a t e d b y g r o u n d w a t e r c o n d i t i o n s ( s e e S e c t i o n 1 . 32). The potential f o r g r o u n d l o s s a l s o e x i s t s w hen blow c o n d i t o n s d e v e l o p i n open s h a f t s o r o p e n - e n d e d p i l e s b e l o w g r o u n d w a t e r t a b l f · A

walls

1. 60

STABILIZATION M ETH O D S 1. 61

S co p e I

T h i s s e c t i o n m a k e s a b r i e f o v e r v i e w o f g r o u t i n g and: freezing. Both of these methods r e u s e d to control ground w a t e r o r t o s olidify a s o i l m a s s . A p p l i c a t i o n s m a y b e t o c r e a t e a n arch•I• o v e r a t u n n e l o r a r o u n d a s h a f t o r t o solidify p o t e n t i a l ly ly u n s t a b l e · soils and badly jointed rock encountered within the excavation I

1

-8  

Both methods a r e an a rt performed by specialty s u b c o n t r a c t o r s o f t e n with p r o p r i e t a r y e q u i p m e n t o r m a t e r i a l . D e t a i l s o f t e c h n i q u e s a r e n o t highly publicized., although s u c c e s s f u l r e s u l t s o f applications a r e .

P e r f o r m a n c e type s p e c i f i c a t i o n s a r e b e l i e v e d t o b e the appropriate contracting procedure for both grouting and freezin~. 1

6

Grouting

B a s i c s o i l classification., p a r t i c u l a r l y g r a i n s i z e c h a r a c t e r i s t i c s . , i s e s s e n t i a l f o r s e l e c t i n g the t y p e of grout. and p l a n n i n g the g r o u t i n g p r o g r a m . T h e 15 p e r c e n t s i z e o f s o i l t o b e grouted is commonly us ed a s a criterion for grout selection.

·

L e a s t e x p e n s i v e g r o u t s c e m e n t a n d bentonite) a r e u s e d i n c o a r s e s a n d a n d g r a v e l s . S i l i c a te t e s m a y b e u s e d i n fine t o m e d i u m s a n d s . The m o s t expensive a r e t h e c h e m i c a l grouts., w h i c h a r e u s e d f o r fine s a n d s and c o a r s e s i l t s . I n s t r a t i f i e d depos its ., m u l t i - s t a g e g r o u t i n g c o n s i s t s o f g r o u t i n g with the c e m e n t o r bentonite t o r e d u c e the p e r m e a b i l i t y o f r e l a t i v e l y c o a r s e s o i l s followed by successive stages of finer grouts a n d / o r l e s s viscous c h e m i c a l g r o u t s t o p e n e t r a t e m o r e f i n e - g r a iin ned soils. I. 6

:

Ground F r e e z i n g

y a n d large., g r o u n d f r e e z i n g m e t h o d s have b e e n u s e d p r i m a r i l y i n c o n j u n c t io io n w i t h s h a f t s a n d s m a l l d i a m e t e r t u n n e l s . Frequently., i t h a s b e e n u s e d i n difficult situations o f g r o u n d w a t e r w h e r e m o r e conventional m e t h o d s h a v e f a i l e d o r a r e i n a d e q u a t e . However., the u s e o f g r o u n d f r e e z i n g a s · a p r i m a r y c o n s t r u c t i o n m e t h o d i s i n c r e a s i n g a n d i s expected t o continue t o i n c r e a s e i n the f u t u r e . In evaluating e n e r g y r e q u i r e m e n t s for f r e e z i n g a given zone., the l a t e n t h e a t o f f u s i o n o f the p o r e w a t e r u s u a l l y r e p r e s e n t s the s i n g l e m o s t i m p o r t a n t p a r a m e t e r t o b e c o n s i d e r e d . I t i s d i r e c t l y p r o p o r t i o n a l t o t h e w a t e r content o f t h e soil.

-9 

C r e e p c h a r a c t e r i s t i c s o f the f r o zen s o i l a r e o f intel ~st i _n deep shafts o r tunnels. C r e e p i s r e l a t e d to the s t a b i l i t y o f th e i ce s t r u c t u r e an d d i s p l acem en t s outside the f r o z e n zo n e, 1

70

SOIL AND GROUND WAT E R CONDITIONS i

I

Th e following i s a b r i e f c h e c k l i s t o f t h o s e soil•

conditions t h a t h a v e t h e p o t e n t i a l o f c o n t r i b u t i n g t o additional ~ i s p l acem en t . S o m e o f t h e s e w e r e m e n t i o n e d above. i I

L

Drawd o wn o f g r o u n d w a t e r t a b l e : m e n t w i l l o ccu r i f c o m p r e s s i b l e s o i l s r e p r e s e n t ,

G r o u n d s ~ t t l e

2 . Soft s h al e a n d highly o v e r c o n s o l i d a t e d clay~~ This m a y d i s p l a y l a t e r a l c r e e p i n t i eb ack i n s t al l at i o n s o r m a c o n t r i b u t e t o w a r d load b u ild u p i n b r a c e d excavations. Th e h i h

u n d r a i n e d s t r en g t h o f c l a y sh o u ld n o t b e co u n ted o n f o r p e r m a e n t p a s s i v e r e s i s t a n c e o n the i n s i d e face o f th e b o t t o m o f the cu t . : R a t h e r , drained. s t r en g t h p a r a m e t e r s should b e u s ed . i

3.

Ro ck within cu t: A n u m b e r o f p o t e n t i a l p r o ~ l e m s

ex i s t :

a.

Undermining o f s u p p o r t wall f r o m r ~ c k f al l s ; 1

i

b.

O v e r - b l a s t i n g b elo w and behind wali; i

c.

Difficu lty in controlling flow a t r o e ~ / s o i l c o n t a c t o r through j o i n t s ;

d.

In ad q u ate toe r e s t r a i n t f o r s o l d i e r ~ i l e s ; I

e,

Inability t o c o m p l e t e l y d e w a t e r ovei,lying

s o i l s t o top o f r o c k ; i

G r o u n d w a t e r flow through highly jofoted zones i n t h e r o c k : T h i s m a y d e p r e ~ s th e g r d u n d w a t e r t ab l e a n d / o r c r r y fi:ilies

( F o r f u r t h e r d i s c u s s i o n s e e Wh ite, 19741 .

1

 

Pervious soils underlain by impervious soil w i t h i n depth o f e:x:cavation: T h i s will m a k e i f difficult to complet~ly d e w a t e r t o t h e b o t t o m o f p e r v i o u s f o r m a t i o n s . T h i s c o n c e r n i s tj:lost relevant to soldier pile walls. 4.

5 . Soft c l a y below e:x:cavation: D e f o r m a t i o n . c h a r a c t e r i s t i c s o f s o i l { e l a s t i c range) will c a u s e f l e x u r e o f the, w a l l p e l o w t h e b o t t o m o f the e x c a v a t i o n a t i n t e r m e d i a t e s t a g e s amd a t

final depths. T h e s e uncontrolled d i s p l a c e m e n t s r e p r e s e n t about , 6 p e r c e n t o f the t o t a l . I n d e e p e:x:cavations, the i m b a l a n c e c r e a t e ~ b y load r e m o v a l c a u s e s e:x:cessive s h e a r s t r a i n s i n the p l a s t i c : range of st re sse s.

6.

S e e p a g e : Seepage a t toe w i l l w e a k e n p a s s i v e

r e s t r a i n t a n d / o r c a u s e g r o u n d flow into t h e e x c a v a t i o n .

1.

s ··

COSTS 1 8

P u r p o s e and Scope

T h i s s e c t i o n i s intended t o p r o v i d e s o m e g e n e r a l guidelines to enable e n g i n e e r s t o m a k e a f i r s t p a s s appro:x:ima~ion o f c o s t s o r t o m a k e c o m p a r i s o n s o f a l t e r n a t e s c h e m e s . Obvious1y, these cost guidelines a r e not p re c is e , and they will v a r y by geog~aphic a r e a and job conditions. ·

C o s t s h a v e b e e n developed o n the b a s i s o f 1975 p r i ~ e s and l a b o r conditions p r e v a i l i n g i n the u r b a n n o r t h e a s t ,

-11 

1. 8Z

WALLS

Soldier P i l e s and Wood Lagging Steel Sheet Piling

C ost p e r Sq. F t ,

(Typical Con4itions)

Exposed Wall Only

Exposed w i j Allowance f ~ Toe

*

4 to

7

PZ-Z7 PZ-38

Conc r e t e D iaphragm Tangent Pile ( single row) 1 C a s t - i n - p l a c e Sl ur r y W a l l (3 0 11 ± thick)

6 to 8 to

7

15 t o

18

Z0 t o

8 to 9 10 t o 11

9

35

19 t o

Z3

31 t o

44

*When applied t o the exposed por t i on o f the w all, th is includes carry in g the toe pe ne t r a t i on t o about 25 p e r c e n t o f e x p o s e d w:all h e i g h t b e l o w the b o t t o m of the e x c a v a t i o n . 1. 8 3

· Supported

alls

T h e following di s c us s i on p r e s e n t s c o s t s o f w alls . supported with tiebacks o r br a c i ng. The u p p e r and l o w e r lim its o t e a c h d o not r e p r e s e n t c o r r e s p o n d i n g situations and t h e r e f o r e d o not r e p r e s e n t the c o s t differential betw een t he two s uppor t m e t h o d . • I n ge ne r a l , tiebacks a r e slightly m o r e costly; how ever, m any I s i t u a t i o n s e x i s t w h e r e t i e b a c k s a r e l e s s c o s t l v . TVl[O e x a m p l e s a f e r o c k within the excavation and a wide excavation, such a s a t a station. ' (1)

P r i c e va r i a t i on i s relativ ely i ns e ns i t i ve t o va r i a t i ons i n w all thickness i n the r a nge o f 2 t o 3 feet thick. Difficult excavation i n h a r d m a t e r i a l s (:till, b o u l d e r s , we a t he r e d rock) will r a i s e c o s t s t o f r o m 4 0 t o 6 0 p e r s q. ft. ( Ta m a r o, 1975).

12  

1. 83. l

Tiebacks

Ty p ic a l t i eback c o s t s of s m a l l d i a m e t e r (4 - 6 i n c h e s ±. u s u a l l y p e r c u s s i o n d r i l l e d ) a n d l a r g e d i a m e t e r a n c h o r s ( 1 2 - 18 i n c h e s ±. u s u a l l y i n s t a l l e d w i t h a u g e r e q u i p m e n t ) d o not, v a r y g r e a t l y . T h e a p p l i c a b i l i t y o f one t y p o r the o t h e r w i l l g e n e r a l l y d e p e n d upon so il co n d itio n s.

T o t a l c o s t o f tiebacks., including i n s t a l l a t i o n

.

.

\

'

a n d p r e s t r e s s i n g · i s s u m m a r i z e d below.

E a s y job conditions Average job conditions Difficult job conditions

feet long a t 1250 e a c h .

20 t o

15 t o

20 p e r l i n e a l foot

20 t o

25 p e r l i n e a l foot 30 p e r l i n e a l foot

25 t o

A s s u m i n g a v e r a g e t i e b a c k l e n g t h s o f a b o u t 50 25 p e r foot. t h i s r e p r e s e n t s a c o s t o f 1000 t o

C o s t s f o r i n s t a l l e d w a l l s , s u p p o r t e d b y tie·b a c k s a n d including t h e w a l e a n d connections., a r e a s f ollows:

1 Cost p er Square Foot 2 Interlocked Soldier iles and 2 Wood L agging Sheet Piles

Depth (feet)

1

2

30 - 40

17 t o

22

· 20 t o

27

4 0 - 50

21 t o

26

25 t o

32

50 - 60

24 to

30

30 t o

40

6 0 - 70

30 t o

40

35 t o

45

W h en a p p l i e d t o t h e e x p o s e d p o r t i o n o f t he wall., t h i s i n c l u d e s toe p e n e t r a t i o n t o about 25 p e r c e n t o f the e x p o s e d w a l l h e i g h t b e l o w t he b o t t o m o f

the e x c a v a t i o n . W a t e r p r e s s u r e i s a s s u m e d t o a c t o n t h e sheeting., b u t i s a b s e n t f r o m t h e soldier piles.

-13 

1. 83.

2

wale an d co n n ectio n s

Dep th feet)

I n t e r n a l B r aci n g Costs f o r i n t e r n a l l y b r a c e d w al l s , including r e a s fo.llows:

C o s t P.er S q u a r e F o o t 1 i 2 I n t e r l o c k e 42 Soldier Pil~s and Wpod .Lagging S h e e t ileis

30 - 4 0

15 t o

20

18 t o

23

4 0 - 50

20

?5

23

2~

50 - 60

to 25 t o

30

to 28 t o

60 - 70

30 t o

40

35 t o · 45

35

1

w h e n a p p l i e d t o the e x p o s e d p o r t i o n o f the wall, this includes toe p en et r at i o n t o ab o u t 25 p e r c e n t o f t h e e x p o s e d ·wall height belo\\f the b o t t o m o f the excavation. 2

w a t e r p r e s s u r e i s a s s u m e d t o a c t o n the sheeting, b u t i s a b s e n t f r o m the s o l d i er p i l es . 1.

84

Un d erp in n in g

General guidelines a.

re

C o n cr et e P i t Underpinning Installed cost is co n cr et e.

b.

a s fo llo ws:

2 75 t o

350 p e r cubic y a t d o f I

J a c k e d P i l e Un d erp in n in g I n s t a l l a t i o n c o s t i n c l u d e s c l e a n i n g o u t o f p~l s  

Soft m a t e r i a l 125 -   175 p e r l i n eal foot H a r d M a t e r i a l 150 - 25 0 p e r l i n e a l foot

-14-

 

c.

Pali Radice o r p i l e s 4 to 6 in c h e s ih d i a m e t e r :

E a s y job conditions A v e r a g e job conditions Difficult job conditions o r piles

to

percent. 1 85

Gro\,lnd

reezing

1

20 t o

2 5 p e r l i n e a l foot

25 to 35 to

3 5 p e r linea~ foot 60 p e r l i n e a l foot

i n c h e s i n d i a m e t e r , add about 25

T h e m a i n f a c t o r s affecting c o s t s a r e :

1. 2. 3.

4. 5.

Geometry of excavation. E a r t h and w a t e r p r e s s u r e s t o b e s u p p o r t e d . Amount of t i m e available for c o m p l e t i o n o f t h e excavation support system. D u r a t i o n o f t i m e f o r which the excavation i s t o b e held open a f t e r completion. Union o r n o n -u n i o n w o rk r u l e s . (Union w o r k r u l e s , which d e m a n d round-the-clock manning of c o m  pletely automated electrically powered equipment, f r e q u e n t l y s u b s t a n t i a l l y i n c r e a s e the c o s t o f g ro u n d fre e z in in g ) .

I n s t a l l a t i o n o f a cut-and-cover f r o z e n e x c a v a t i o n s u p p o r t and g ro u n d w a t e r control s y s t e m m i g h t t y p i c a l l y r a n g e f r o m 8 t o 16 p e r s q u a r e foot of e x p o se d w a l l ; M a i n t e n a n c e o f t h e s y s t e m d u ri n g su b se q u e n t e x c a v a t i o n a n d s u b s u r f a c e c o n s t r u c t i o n m i g h t c o s t b e t w e e n . 20 a n d . 80 p e r s q u a r e foot o f e x p o se d w a l l p e r week, Underpinning and tunneling c o s t s v a r y too widely to allow a n y g e n e r a l i z a t i o n , A s a r u l e , c i r c u l a r , elliptical, o r a r c h s t r u c  t u r e s i n which c o m p r e s s i o n r a t h e r t h a n s h e a r o r t e n s i o n s t r e s s e s g o v e r n a r e l e a s t e x p e n si v e t o construct. 1 . 86

Grouting

T h e s pe c ializ e d n a t u r e o f g ro u t i n g w o rk p r e v e n t s a n a c c u r a t e e s t i m a t e o f g ro u t i n g c o s t s . T h e c o s t d a t a p r e s e n t e d h e r e i n w a s o b t a i n e d f r o m H a l l i b u rt o n S e r v i c e s (1975). The c o s t o f t h e grout m a t e r i a l s c a n b e a c c u r a t e l y estimated (c e m e n t g r o u t s : 0 . 5 0 -   1 . 3 0 / f t 3 ; c h e m i c a l g r o u t s : 1 . 5 0   7 . 0 0 / £ t3 ); h o w e v e r, t h e installation costs a r e not a s w e l l known b e c a u s e

-15 

o f the v a r i a b l e s (time t o g ro u t , COl Jt o f e q u i p m e n t , e t c . ) . Only ~he grouting c o n t r a c t o r h a s a n a c c u r a t e i d e a o f t h e s e c o s t s , w h i c h will a l s o v a r y depending upon t h e amount of competition. H a l l i b u r t ( 1975) a l s o r e p o r t s r a n g e s i n c o s t s fo r fi n a l v o l u m e s o f g ro u t e d s o i l (c e m e n t grouts: 13. 5 0 -   35. OO/yd3 o f g ro u t e d soil; c h e m i c a l g ro u t s: 4 0 -   190/yd3 o f g ro u t e d so i l ).

-16 

C H A P T E R 2 - SOL DI E R P I L E W A L L S 2. IO

I NT R ODUC T I ON

H i s t o r i c a l l y , the s o l d i e r p ile and lagging m e t h o d w a s d ev elo p ed i n G e r m a n y in the l a t t e r p a r t o f the 19th c e n t u r y and is f r e q u e n t l y r e f e r r ~ d t o i n E u r o p e a s th e B e r l i n Me t hod. T h e p r o c e d u r e i s to d r i v e o r p r e . e x c a v a t e a n d s e t a v e r t i c a l m e m b e r o f s t e e l o r co:;.1crete a t s p a c i n g s n o r m a l l y i n t h e r a n g e o f a b o u t 6 t o 1 0 f e e t o n c e n t e r . T he e x c a v a t i o n p r o d e e d s i n s t a g e s o f a b o u t 1 foot t o 5 f e e t d e p e n d i n g upon t h e a b i l i t y o f th e s o i l t o stan d i n p l a c e b e f o r e lagging in i n s t a l l e d . T h e n h o r i z o n t a l s h e e t i n g , c o m m o n l y c a l l e d lagging, i s p l a c e d b e t w e e n the p r e v i o u s l y i n s t a l l e d

soldier piles. S o l d i e r p i l e s a r e e i t h e r i n s t a l l e d with p i l e d r i v i n g e q u i p m e n t o r a r e s e t in p r e - e x c a v a t e d h o les and t h e n c o n c r e t e d i n p l a c e . T he m o s t c o m m o n s o l d i e r p i l e s a r e r o l l e d s t e e l s e c t i o n s , n o r m a l l y wi de f lange o r b e a r i n g pile. But s o l d i e r p i l e s c a n b e a l m o s t a n y s t r u c t u r a l m e m b e r pipe s e c t i o n s , c a s t - i n - p l a c e c o n c r e t e , o r p r e c a s t e l e m e n t s . When s o l d i e r p i l e s a r e d r i v e n , a b e a r i n g p i l e sec,tion woul d n o r m a l l y b e u s e d b e c a u s e o f the r u g g e d n e s s o f the m e m b e r , i n p a r t i c u l a r i t s r e s i s t a n c e t o twistin g a n d be ndi ng. O n the o t h e r hand, d e e p e r wide

fl g r e a t , e r s t i f f n etshse as n n s as roel dui es re dpile. where t reenn; g t h r eaqnge u i r esde citni othe Conventionally, e da frlee x nu o rt adl r si v

iis 1

•

r a t he r they a r e s e t in p r e - e x c a v a t e d holes. F i g u r e I shows v a r i o u s t y p e s o f s t e e l s o l d i e r p i l e s . I n ad d itio n t o wi de f lange a nd b e a r i n g p i l e s e c t i o n s , b a c k - t o - b a c k c h a n n e l s o r t pe s e c t i o n s a r e a l s o u sed . B a c k - t o - b a c k c h a n n e l s a l l o w t i e b a c k s to b e i n  s t a l l e d b e t w e e n the c h a n n e l s , t h u s e l i m i n a t i n g w a l e s . Su ch a s e t u p co u ld not b e d r i v e n a n d woul d ha ve t o b e i n s t a l l e d i n a p r e - e x c a v a t e d hole a s i s the c a s e fo r the wi de fl a nge sectio n . A n i n s t a l l a t i o n o f t h i s type w a s d e s c r i b e d b y W o s s e r a n d D a r r a g h (1970). P i p e s e c t i o n s m a y b e a d a p t e d a s s o l d i e r p i l e s y welding o r b o l t  ing a T - s e c t i o n to the f r o n t o f the m e m b e r t o p e r m i t the i n s t a l l a t i o n o f the wood lagging. P i p e s e c t i o n s ha ve a l s o b e e n a d a p t e d f o r i n s t a l l a t i o n of lagging lagging along the s i d e o f the p i p e p i l e sectio n i a s d e s c r i b e d b y Donol o (1971). I n t h a t c a s e , 3 4 - i n c h d i a m e t e r pipe p i l e s w e r e i n s t a l l e d i n v e r y h a r d g r o u n d with a B e not o c a i s s o n r i g , a n d a t i e b a c k w a s d r i l l e d t h r o u g h the c e n t e r o f the p i p e s e c t i o n .

-17 

(a.) W _ SECTION ........

OR H PILE

SECTION

 --

L w E D G E D BEHIND

FRONT

FLANGE

(b) CHANNEL SECTION

I

.....

.....

.....

~

/

LAGGING C N LSO~BE ATTACHED TO RO T FLANGE, ADAPTABL OR TIEBACKS i

e.g. WOSSERatARRAGH (1970)1

d : _ TIEBACK

(c) PIPE SECT O N

LAGGING

LAGGING

TO

TO

FRONT

SIDE

t ST

SECTION

__ .. .

TIEBACK 9.

F i g u r e 1.

pONOLO 1971)

Steel soldier piles.

18  

2.20

T Y P E S O F SOLDIER PILE_WALLS

2. 21

LAGGING

Lagging i s m o s t c o m m o n l y wood, but m a y a ls o c o n s i s t p light s t e e l , sheeting, c o r r u g a t e d g u a r d r i l se c t i o n s, o r p r e c s t conc'rete. '

Wood lagging i~ m o s t c o m m o n l y i n st a l l e d e i t h e r behind o r i n fro n t o f the flange n e x t to the e x c a v a t i o n (front flange). I t i s techni¢ally This p o ssi b l e t o i n s t a l l the lagging behind the r e r flange s w e l l p r o c e d u r e i s n o t r e c o m m e n d e d , b e c a u s e t h e a r c h i n g a c t i o n i n t h e sail[ is destroyed by this process. ~_ n o t e d i n F i g u r e 1 (a), t h e t a g g i n g C&?f, e i t h e r b e a r d i r e c t l y a g a i n s t the soil si d e (back side) o f t h e f r o n t Lang~ 1

o r i t c a n b e w e d g e d t o m a k e m o r e i n t i m a t e contact w i t h the- s o i l a n d

thus r e d u c e a s s o c i a t e d l a t e r a l . d i s p l a c e m e n t . typical s o l d i e r p i l e w a l l i n s t a l l a t i o n s .

Figures 2 and 3 shaw

'

F i g u r e 4 s h o w s v a r i o u s m e t h o d s o f a t t a c h i n g lagging to the excavation side (front side) o f the fro n t flange. T h e c a s e s shown e m p l ~ y e i t h e r a bolt o r a T - s e c t i o n w e l d e d to the s o l d i e r p i l e o r a p r o p r i e t a r y m e t h o d known s u c o n t a c t Sheeting >'f I n a l l c a s e s , the v e r t i c a l p l a t e which holds the laggiag c a n e x t e n d up o v e r s e v e r a l lagging b o a r d s s o Hl-at the n u m b e r o f s p e c i a l a t t a c h m e n t s c a n b e m i n i m i z e d . One distinguishiµ.g fe a t u re o f a t t a c h i n g lagging b o a r d s to the fro n t f a c e i s that the b o a r d s ~an run c o n t i n u o u sl y c r o s s s e v e r a l s o l d i e r p i l e s . T h i s, o f c o u r s e , i s not: p o ssi b l e when_ i n s t a l l e d behind the fro n t flange.

1

S e v e r a l e x a m p l e s o f c a s t - i n - p l a c e c o n c r e t e s o l d i e r pile$ a r e shown i n F i g u r e 5. The hole i s p r e - e x c a v a t e d , a r e i n f o r c i n g c a g e :is se t , a n d c o n c r e t e i s poured. T h i s m e t h o d i s u n c o m m o n in the United S t a t e s b u t h a s b e e n u s e d i n E u r o p e . F o r i n s t a n c e , the f i g u r e s h o w s a ~ e x a m p l e o f both a c a s t - i n - p l a c e s o l d i e r J?ile a n d a n a r c h e d r e i n f o r c e d c o n c r e t e w a l l b y Gunite m e t h o d ) t h a t w a s u s e d in Sweden a n d d e s c r i b e d b y B r o m s a n d B j e r k e ( 1973 . The u se o f s p a c e r s b e t w e e n the lagging b o a r d s ( c a l l e d

" l o u v r e s " ) allows fo r t h e i n t ro d u c t i o n o f m a t e r i a l fo r b a c k p a c k i n g b o a r d s a n d f i l t e r i n g so i l to 9 r o t e c t a g a i n s t g r o u n d l o s s f r o m e r p s i o n c a u s e d b y s e e p a g e . _In groun~ that i s slow d ra i n i n g , the louvres r e filJ ed with s a l t hay. T h i s m a t e r i a l p e r m i t s w a t e r to b l e e d t h r o u g h b u t a l s d a c t s a s a f i l t e r w h i c h p r e v e n t s .loss of ground ( s e e F i g u r e 6).

,:,contact Sheeting, I n c . , Nyack, New York.

-19 

I

P I ::

I ---  - -

-

I ■

...

I •

:l

•.. .:.,-.,.

I'

''

•.

;

" . \,;-, . , ;A~ -

•.\

~...... ' ...

•.

•

I

••

N 0 I

° .

.

tar·

\

'

•, .

..

' · . · - -~ .. .. ... .

\

.

\ : ' •·}

i

-

(.-

...... ••

.

. f

,t

· •... J

-.

II

'~--

·\ .

..

PS:

-.--• Elm

 

,

Illa

-.

.

\ r~

~\ - - - . . . . . .

......

- ·.:.. ;, •

.

.

_I

'· . -

' .'~~ .~

-

:

. .

r

.,.

_..;

.

•

■

• . :-.-, C

.,

.

--·

-~

.

..

--. .•• . •,-.,~.••

-

;

•

..

;

•;

-.

r

-.

•

a• .

.

. -

...,

.

'~

'--~~~rfi:;;:.. ·· _·- ~·····

.

..·.

:i.:

-

,+

.•.

•••·

.., _

;

•~.:,a;•.,..~ w J ·  J

L ~

N o t e : 1.

2. F i g u r e 2.

··· -

,it.1-, • ,,

f _ 

,

f.

.

_r,,

•.

' ,

.-

~

..

..

.

• ..

.-

~ I - •

.... .

. .;._.

-~~;

.

. . ....;y--·_. r,

' \••

• '

~·

.,,

- :;..;..-

'w-..:'.~~ 7i"' '- · •1 (~ ,

.

,

'

.. .. .. .

\' .

..

. . . . . f- • ..

•

• .,.

~ ~-'..., 4.. -~

.

'-~

. .~.... .

,

.

'°

V

•

....-~-✓

·:

'I ' •.

,

'hflh'\~ ••

)

..

¥

' . ·' .

~ -

1 ,. '

.JI

.:,b,tr ~

4'

~

/ .

,~

..

/

..- "•. - r.,,,,_,. .-. .,_.

r;   r ~~.•_ .. I ;

-

• ·'

,....,=

..._ ...

~,,_.W

-

,,

.:? .- '

.

J.

;r.r-'-~--ri··  -ri··     ,,

I

-

.~-"' r. . .-

.

.

_

•

I

.'

~

~

..

JP..·:•· . .... ~

.

·)

··-

n

~

~

S o m e d r i v e n s o l d i e r p i l e s o u t o f p l u m b , p r o b a b l y d u e to b o u l d e r s o r ro c k . Hole s p a c e r blocks and open lagging ( s h u t t e r e d lagging).

Soldier pile w a ll (lagging behind front flanges).

(Courtesy of Urban Foundation C o . , Inc.).

 

 

N

D ep th i s a p p r o x i m a t e l y 25 f e e t i n s o i l a n d 15 f e e t d e e p in r o c k . Note upper portion of wall has lag g in g b eh in d flan g e; l o w e r p a r t o f w a l l h a s l a g g i n g a t t a c h e d to f r o n t o f f l a n g e . i g u r e 3.

S o l d i e r p i l e w all,

C ourtesy of Schnabel Foundation Co.).

 

  a)

CONTACT SHEETING

I

CONTACT SHEETING INCORJORATEO I I

NYACK, N .Y.

I

i

PASSES BETWEEN ANO PLAtE HOLDS O LAGGING B04RDS.

BOLT THE TWO LEVELS

b) BOLT

THREAD ED BOLT BOLT ATTACHED NELSON STUD

BY

OR RAM SET

. _ _ P L A T E OR

CHANNEL SECTION HOLDS TOP ANO BOTTOM LAGGING

c ) SPLIT

T - SECTION

SPLIT T

F i g u r e 4.

 

WELDED TO FACE

W o o d lagging to f r o n t flange.

22  

  a ) WOO

LAGGING , FORMED ·av STYROFOAM INSET.

b ) ARCHED REINFORCED CONCRETE

TIEB

CK

2 8 . m

__ .~~

~REINFOR

ED

GUNITE

AFTER BROMS a e j E R K E 1973)

F i g u r e 5.

Cast in place concrete soldier piles.

23  

 

s PL N

111

S

I

Lt 11

2

L GGING BO RD

 

2 :t

SO~OIER PILE

FRONT ELEV TION

F i g u r e 6.

L o u v r e e f f e c t f o r wood lag g in g .

24  

2. 22

CONCRETE WALL

E x a m p l e s o f s h o t c r e t e o r _ p o u r e d c o n c r e t e w a l l constr1i1ctcd i n conjunction w i t h s t e e l s o l d i e r p i l e s r e s how n i n F i g u r e 7 . A n a p p l i  c a t i o n with p r e c a s t c o n c r e t e s o l d i e r p i l e s i s s how n i n F i g u r e 8 . I n g e n e r  al, the t y p i c a l procedll;re i s to e x p o s e about a 5-f-oot high s e c t i o n an d to cQ ns truct the V Z a l l y p r o c e e d i n g . s e q u e n t i a l l y to the b o t t o m o f the e x c a v a  tion. I n a l l c a s e s , s o i l w ould have to h av e s u f f i c i e n t c o h e s i o n to s t a n d up while the s e c t i o n o f the w a l l i s c o m p l e t e d . F i g u r e 9 sh o w s p r e c a s t s o l d i e r p i l e s s h a p e d t o :receive e i t h e r w ood l ag g i n g o r p r e c a s t c o n c r e t e lagging.

F r e n c h l i t e r a t u r e i:efers t o the r e i n f o r c e d c o n c r e t e in£ill

b et w een s o l d i e r p i l e s a s a P a r i s i e n n e Wallll. T h e w a l l w i t h p r e c a s t c o n c r e t e o r h o r i z o n t a l w oqd s h e e t i n g i s r e f e r r e d t o a s a B e r l i n o i s e Wall · . W al l . 2. 23

SO L D I E R P I L E S A LO N E

Lagging m a y n o t b e n e c e s s a r y i n h a r d c l a y s , s oft s h a l ~ s , or other cohesive or cemented soils, if the soldier piles r e spaced

s ufficiently c l o s e t o g e t h e r an d a d e q u a t e s t e p s r e t a k e n to p r o t e c t a g a i n s t e r o s i o n an d s p a l l i n g o f the f a c e . E x a m p l e s o f this w e r e d e s c r i b e d y S h an n o n a n d S t r a z e r 1970) a n d b y Clough, e t a l (1972) f o r c a s e s i n c o h e s i v e s o i l i n S e a t t l e , Was hington. n b o t h c a s e s , s ·oldier p i l e s

were set

feet on center.

E r o s i o n o r r a v e l l i n g c a u s e d y d r y i n g o f the e x p o s e d s o i l can b e inhibited y s p r a y i n g the e x p o s e d s o i l face. Shannon a n d S t r a z e r , f o r e x a m p l e , r e p o r t e d t h e u s e of A e r o s p r a y 52 B i n d e r . n o t h e r c a s e , t a r p a u l i n s m a y b e d r a p e d o v e r s o i l to m a i n t a i n m o i s t u r e . W o r k m e n c a n b e p r o t e c t e d y w el d i n g w i r e fen ci n g o r wi.re m e s h to the s o l d i e r p i l e s t o p r e v e n t m a t e r i a l f r o m falling into t h e excavation.

-25 

(a)

CAST IN PLACE

. . . . · . . ; SOIL ' . · · . . . . . .

. .

.

...

~

.

ON S T E E L V F SE

.

RETE W

TION

(b) SHOTCRETE

,

'

.

.... ..

.

.

..

.. L

•

..

. .

t

•.

..

'

. ..

'

•

...

I

'

\.

..

•

.--.

. •

•

t

. .. . , .. •

•

•

I

•

41

'

t

, ~•

Concret e infill between s o ld ie r piles.

26  

...

I

•

'

'

F i g u r e 7.

I

LL

GROUT

GROUT

SE HORIZONTAL

SET REBARS ANO FORMS

STEEL

AS EXCAVATION -PROCEEDS DOWNWARD

 

PLACE SECTION

CAST I N

F i g u r e 8. P a r i s i e n n e w a l l . p r e c a s t s o l d i e r p i l e s w i t h f o r m e d c a s t i n p l a c e w a l l . ( a f t e r F e n o u x , 1974; X a n t h a k o s , 1974; a n d D A p p o l o n i a , e t a l , 1974).

-27 

.

.

•

. .

•

WOOD

\

·

•

OR ON RETE

PREF BRIC TED ELEMENT

F i g u r e 9. B e r l i n wall p r e c a s t s o l d i e r p i l e s w i t h w o o d o r p r e c a s t c o n c r e t e lag g in g a f t e r F e n o u x , 1974 .

-28 

2. 30

DESIGN CONSIDERATIONS 2. 31

SOL DI E R P I L E S

I n ad d itio n t o t h e i r func tion a s s u p p o r t fo r lagging, s o l d i e r piles m u s t also develop vertical flexural strength, l at eral resistance below the l e v e l o f the l a s t s t r u t o r tieb ack l e v e l , a n d in the c a s e o f i n  c l i n e d t i e b a c k s b e a r i n g t o s u p p o r t t h e v e r t i c a l c o m p o n e n t of tieback, f o r c e .

i n Volum e I I 2. 32

Desig n r e c o m m e n d a t i o n s f o r s o l d i e r p i l e s a r e p r e s e p . t e d De si gn F u n d a m e n t a l s ) . WOOD LAGGING

2 . 32. 1 Wood M a t e r i a l s

T h e m o s t c o m m o n wo o d u s e d f o r lagging in the United S t a t e s i s c o n s t r u c t i o n g r a d e , u s u a l l y r o u g h - c u t . S t r u c t u r a l s t r e s s g r a d e d l u m b e r m a y b e s p e c i f i e d though s e l d o m u s e d . P r e f e r r e d woods both o f w h i c h p r o v i d e a d e s i r a b l e b a l a n c e b e t w e e n £:lexural s t r e n g t h and d e f o r m a t i o n m o d u l u s . H.ard woods, s u c h a s oa k, a r e l e s s c o m m o n . Although they a r e s t r o n g , they a r e a h o v e r y s t i f f a n d heavy. T a b l e 1 l i s t s the p r o p e r t i e s o f s o m e woods that m a y b e u s e d f o r wood lagging. The allo wab le f l e x u r a l s t r e s s s t a t e d i n are bouglas

i r o r S o u t h e r n Ye llow P i n e ,

the tab le i s f o r n o r m a l o r r e p e t i t i v e u s e c o n s t r u c t i o n . 2 . 32. 2 A r c h i n g

E x p e r i e n c e h as shown that lagging i n s t a l l e d i ~ the co n v en tio n al m a n n e r i n m o s t r e a s o n a b l y c o m p e t e n t s o i l s d o e s not r e c e i v e the t o t a l e a r t h p r e s s u r e a c t i n g o n the wail. The l a t e r a l e a r t h p r e s s u r e c o n c e n t r a t e s on the r e l a t i v e l y s t i f f s o l d i e r p i l e s ; l e s s p r e s s u r e i s a p p l i e d t o the m o r e f lexible lagging b e t w e e n the s o l d i e r p i l e s . White i n L e ~ n a r d s , 1962) d i s c u s s e s t h i s point b a s e d upon m a n y y e a r s o f p r a c t i c a l e x p e r i e n c e o n a g r e a t n u m b e r o f j o b s u n d e r d i f f e r e n t co n d itio n s. known a s a r c h i n g , is u r esd i bauntni e o rn ooff cpornesstsruurcet i, o n i s i n h e r e n t l y r e l a t e d toT h the u iaslt rm . The lagging is s u p p o r t e d o n the f r o n t flange; a s l i g h t o v e r c u t i s m a d e behind the lagging to f a c i l i t a t e p l a c e m e n t o f the b o a r d s ; an d the inte · rve ning s p a c e behi p.d the b o a r d s i s filled with soi l . T h e s o i l s h o u l d b e p a c k e d tight; h o w e v e r , p ack in g o f the s o i l d o e s not induce f l e x u r e . F l e x u r e c o m e s ab o u t a s e a r t h p r e s s u r e b u i l d s u p o n the w a l l a s the e x c a v a t i o n d e e p e n s . T h i s f l e x u r e c a u s e s a r e d i s t r i b u t i o n o f Load r e s u l t i n g i n a d e c r e a s e o f p r e s s u r e n e a r t h e c e n t e r w h e r e f l e x u r e i s the g r e a t e s t a n d a c o r r e s ponding i n c r e a s e n e a r the en d s o t h e b o a r d n e a r the s o l d i e r p i l e .

-29 

Str ength properties for tyy_ical g_ ades o f l u m b e r .

Table I.

Allowable Wood Type and Grade

Douglas F i r - L arch, surfaced dry o r surfaced green used a t m a x . 19 M. C. Construction Select Structural

Douglas F i r

-

S o u t h2 s u r f a c e d

Flexural Stress fb p s i

Modulus bf Elasticity . E, psi

I f

; i

1200

1 , s o o , oop

2050

1 , s o o , oob

I

l

dry o r surfaced green used a t m a x . 19 M. C. Construction Select Structural

1,100,oop 1 , 4 0 0 , oob i

1150 1950

N o r t h e r n P i n e 2 s u r f a c e d a t 15% m o i s t u r e co n t en t , u s e d a t 15% max. 19%M.C. Construction Select Structural

' ' ' I I

1,200,oop 1,soo,oolo

1050

1750

I

So11thern P i n e ,

s u r f a c e d a t 15% m o i s t u r e content K. D . u s e d a t 15% m a x . M C . Construction Select Structural

1300

1 , 500, oop

2250

1 , 900, oo o I

Southern Pine, surfaced dry, u s e d a t m a x . 19% M. C. Construction Select Structural

i

I

1 , 4 0 0 , ooio 1 , s o o , oolo

1200 2050

i

'

*A m e r i c a n I n s t i t u t e o f T i m b e r C o n s t r u c t i o n ,

T i m b e r Cons trucition I

M a n u a l " , 2nd E d i t i o n , W i l e y , 1974.

-30 

A r e l a t e d p h e n o m e n o n i s t h a t the p r e s s u r e o n lagging i s r e l a t i v e l y u n a f f e c t e d b y depth. I t t h e r e f o r e follows t h a t t h e g r e a t e r

forces associated with deeper excavations m u s t be transmitted through p i l e s . A g a i n , t h i s i s a t t r i b u t e d to a r c h i n g . T o t ak e a d v a n t a g e o f arch i n , g , t h e e x c a v a t i o n s h o u l d

not b e m a d e b eh i n d the r e a r flange o f t h e s o l d i e r p i l e .

During excavation

behind the s o l d i e r pile, t h e p o i n t o f l o a d c o n c e n t r a t i o n i s r e m o v e d , _ a n d the, s t r e s s conditions for a r c h i n g a r e d e s t r o y e d . S i m p l y s t a t e d , the a b u t  m e n t o f the a r c h i s r e m o v e d . See P e c k , 1969).

2. 32, 3 G e n e r a l P r a c t i c e C o n c e r n i n g Lag g i n g T h i c k n e s s

Lag g i n g t h i c k n e s s d e s i g n i s b a s e d p r i m a r i l y u p o n e x p e r i e n c e an d / o r e m p i r i c a l r u l e s . One p r o c e d u r e i s to v a r y the a m p l i  tude o f the p r e s s u r e d i a g r a m w ith m a x i m u m p r e s s u r e a t the s o l d i e r p i l e and m i n i m u m p r e s s u r e m i d w a y b e t w e e n the s o l d i e r p i l e s s e e L a c r o i x a n d J a c k s o n , 1972). A n o t h e r p r o c e d u r e i s to r e d u c e the b a s i c p r e s s u r e d i a  g r a m u s e d in the d e s i g n o f b r a c i n g a n d / o r t i e b a c k s y applying a r e d u c t i o n f a c t o r . F o r e x a m p l e , A r m e n t o 1972) in d e s i g n i n g ragging f o r t h e BA RTD s y s t e m ; a p p l i e d a 5 0 p e r c e n t r e d u c t i o n f a c t o r t o t h e. b a s i c trapezoida.~ e a r t h p r e s s u r e d i a g r a m u s e d f o r s t r u t d e s i g n . T h e New Y o r k City T r a n s i t A u t h o r i t y u s e s the b a s i c p r e s s u r e d i a g r a m b u t a l l o w s 50 p e r c e n t

i n c r e a s e i n the a l l o w a b l e f l e x u r a l s t r e s s o f s t r e s s g r a d e d l u m b e r . S ome e x a m p l e s o f e m p i r i c a l d e s i g n r u l e s u s e d i n p r a c t i c e a r e l i s t e d below . T h e e x a m p l e s a r e p r e s e n t e d to show a r a n g e o f u s a g e and a r e n o t i n t en d ed t o b e final r e c o m m e n d a t i o n s . a . White 1973) s u g g e s t s a 3 - i n c h l a g g i n g t h i c k n e s s for e x c a v a t i o n s i n s a n d y s o i l s f o r s o l d i e r p i l e s s p a c e d f r o m a b o u t 6 . f e e t t o 10 f e e t o n c e n t e r s . H e a l s o s u g g e s t e d a t h i c k n e s s o f 4 i n c h e s wh n i n s o f t c l a y f o r s o l d i e r p i l e s s p a c e d about 5 f e e t t o 6 . 5 f e e t o n c e n t e r s .

T h e s e r e c o m m e n d a t i o n s a p p l y to d e p t h s o f a b o u t 50 f e e t . C h a p m a n , e t a l 1972) r e p o r t t h e u s e o f 3 for on in 9 D. soils Was hington, C . iTh n ceh tlagging f e e t s o l d i e r p i l e s c e n t e r s ypical soils include stiff clays and me d i u m dense sands, and the e x c a v a t i o n w a s 41 - 4 9 f e e t d e e p .

b.

c . W a r e , e t a l { I 973) d e s c r i b e r e q u i r e m e n t s f o r l ag g i n g f o r the Was hington M e t r o S y s t e m . F o r s o l d i e r p i l e s 6 to 7 f e e t o n c e n t e r , the r e q u i r e d t h i c k n e s s w a s 3 i n c h e s t o 25 f e e t a n d 4 i n c h e s belo:w 2 5 f e e t , u s i n g t i m b e r w ith a n a l l o w a b l e 1100 p s i . fl ex u ral s t r e s s .

The w a l l s w e r e p r i m a r i l y i n c o m p e t e n t g r a n u l a r soi.ls t o d e p t h s o f a b o u t 3 0 feet an d in stiff to v e r y s t i f f clay s b elo w 30 f e e t .

-31 

W o s s e r a n d D a r r a g h (1970) r e p o r t lagging thick n e s s e s f r o m 3 i n c h e s to 6 ,inches us ing D ouglas F i r w ith an al l o w ab l ~ f l e x u r a l s t r e s s a f 2000 p s i and w i t h s o l d i e r p i l e s 8 f e e t o n c e n t e r . ' t h e depth a f t h e e x c a v a t i e n w a s 60 feet, and .the s o i l s w e r e t y p i c a l l y sanely. T h i c k n e s s o f l a g g i n g w a s v a r i e d w i t h depth, a n d 8 i n c h l a g g i n g w a s . i n e a r t h e b o t t o m o f the e x c a v a t i o n i n s o m e o f t h e c l a y a r e a s use d.

e . I n a n e x c a v a t i o n i n s oft c l a y , I n s l e y (1972 I r e port-ed u s i n g l a g g i n g t h i c k n e s s e s o f 4 i n c h e s t o a depth o f 22 f e e t andj 6 in-" c h e s t o a d e p t h o f 3 0 f e e t for s o l d i e r b e a m s s p a c e d 6 f e e t o n center.'i B a s e d upon d a t a p r e s e n t e d , the c o m p u t e d r a t i o o f o v e r b u r d e n s t r e s s to undl.rained s h e a r s t r e n g t h w a s about 5 . 5 . 2 . 32. 4 R e c o m m e n d e d Lag g i n g T h i c k n e s s

B a s e d o n the above d i s c u s s i o n , upon o t h e r emjpirical r u l e s that h av e b e e n r e p o r t e d , a n d i n c o n s i d e r a t i o n o f the v a r i o u s s ~ i l conditions that m a y b e e n c o u n t e r e d , r e c o m m e n d e d t h i c k n e s s e s a r e ~iven i n T a b l e 2 . Since the table h a s b e e n d e v e l o p e d o n the b a s i s o f c o n s t r u c t i o n grade lumber, adjustments a r e required for s t r e s s graded structurail lumber. I I

The recommendations given in the table a r e x i m a r i l y f o r c a s e s w h e r e t h e r e i s a n e e d to l i m i t d i s p l a c e m e n t s t o p r o t e c t e · s t i n g facilities a d j a c e n t to a n e x c a v a tio n . T h e y a r e t h e r e f o r e , b y n e c e s s i

m o r e c o n s e r v a t i v e t h a n w h at could b e s u c c e s s f u l l y u s e d i n c a s e s w h ¢ r e t h i s c r i t e r i o n for p r o t e c t i o n d i d n o t e x i s t . · Th e s o - c a l l e d II c o m p e t e n t s o i l s " sh o w n i n the ~able a r e typically e i t h e r g r a n u l a r w ith r e l a t i v e l y high a n g l e s o f i n t e r n a l I f r i c t i o n o r stiff to v e r y s t i f f c l a y s . M e d i u m c l a y s included i n the ta~ le have a r a t i o o f o v e r b u r d e n s t r e s s t o u n d r a i n e d s t r e n g t h o f l e s s t h a n

$.

Th e c a t e g o r y o f " d i f f i c u l t s o i l s " i n c l u d e s loosei, g r a n u l a r s o i l s w i t h low a n g l e s o f i n t e r n a l f r i c t i o n , s u c h a s l o o s e sanids an d silty sands. Tne table a l s o i n c l u d e s s o i l s w hich m a y p o s e s o m e '

difficulty d u r i n g c o n s t r u c t i o n b e l o w the g r o u n d w a t e r t a b l e ,

Some a t e

clayey s a n d s , c o h e s i o n l e s s s i l t s , a n d fine s a n d s , a l l of w hich draip. s l o w l y a n d m a y h a v e a t e n d e n c y t o r u n . F i n a l l y , this g r o u p includes h e a v i l y o v e r c o n s o l i d a t e d f i s s u r e d clay. T y p i c a l l y , t h i s group o f m a t e r i a l s m a y h a v e a K 0 v a l u e i n e ~ c e s s e f 2 o r 3: H e a v y o v e r c o n  s o l i d a t e d s o i l s ha ve a t e n d e n c y t o e x p a n d l a t e r a l l y e x p e c i a l l y when a

:;1~r;iir£:wt~~it~i~¥iir:~} ~rt#~• l~i~~rr,~lf=iaef~;flrrNi~~ c r e a s e o f -effective s t r e s s -caused

y the. e x c a v a t i o n

t

-

1  

1

k?:~

1

-32 - - -·  

Ta bl e 2

R e c o m m e n d e d t h i c k n e s s e s o f woo jl l aggi n g

Uni fi e d

Soil D t c r i p t i o n

C l a ssi f i c a t i o n

S i l t s o r fine sand and s i l t above w a t e r ·table

ML SM-ML

Sands and g r a v e l s (medium dense to dense).

GW, G P , G M

Clays (stiff to v e r y stiff); n o n - f i ssu r e d .

C L , CH

C l a y s, m e d i u m c o n s i s 'l(H tency and

C L , CH

Depth

R e c o m m e n d e d Thicknesses: of Lagging (roughcut) f o r C l e a r ppans of: 5' 10' 7' 8' 6' 9

0 1 tO 25 I

?

3

25 I tO 60 1

3

3

GC, SW, SP, SM

-

3

,

3

41

4

4

41

5

Su

en :i

....

0

en

<

5.

Sands and s i l t y sa n d s, (loose).

SW, SP, SM

Clayey sands (medium d e n s e to dense) below water table.

SC

C l a y s, heavily · o v e r consolidated f i s s u r e d .

C L , CH

C o h e s i o n l e s s s i l t o r fine s a n d a nd s i l t be l ow w a t e r table.

M L; S M - M L

Soft c l a y s

C L , CH

iH Su

)

5.

-

Slightly p l a st i c s i l t s be l ow w a t e r t a b l e .

ML

Clayey sands (loose), be l ow w a t e r t a b l e .

SC

-

4

0' to 25'

3

3

3

4

25 I tO 60 1

3

3

4

4

5

0' to 15'

3

3

4

5

--

- 15' to 25'

ii

4

5

6

5

6

--

5

 

25 1 to 35 I

4

--

--

 

--

Note:

*In

the c a t e g o r y of potentially d a n g e r o u s so i l s , u s e of lagging i s questionable.

-33 

The final g r o u p i n g i n c l u d e s p o t e n t i a l l y d a n g e ro u s s o i l s , w h i c h m a y r u n and l e a d t o l o s s o f ground. N o r m a l l y , s o l d i e r p i l e w a l l s a r e the l e a s t d e s i r a b l e a l t e r n a t i v e i n t h e se s o i l s Typical problem so i l s a r e : Soft c l a y s with a ra t i o o f o v e r ~ u r d e n s t r e s s t o u n d ra i n e d s h e a r s t r e n g t h g r e a t e r than 5 . T h e c o n s e ~ u e n c e s o f e x c e s s i v e s h e a r d e f o r m a t i o n i n c r e a s e s with se n si t i v i t y o f the soil. : A s s u m  ing a n a v e r a g e ·total unit weight o f about 110 poonds p e r c u b i c foot, the a p p ro x i m a t e s h e a r s t r e n g t h value a s s o c i a t e d with the r a t i o o f 5 a t d e p t h s o f 15, 25, and 35 fe e t a r e r e s p e c t i v e l y 330, 550, and 770 psf P e c k (1969) h a s shown that a s the ra t i o o f total o v e r b u r d e n s t r e s s t o u n d r a i n e d ~ t r e n g t h a p p r o a c h e s 7 t h e r e i s m a r g i n a l safety, and the so i l m a y b e o n the y e r g e o f i n c i p i e n t fa i l u re i n tunnels without a i r p r e s s u r e M o r e o v e r t h e tu.n

a . Soft C l a y s .

neling p r o c e e d s without unusual difficulty_provided t h e r a t i o i s l e s s t h a n 5.

b. D i l a t a n t Soils o f Low P l a s t i c i t y . T h i s c a t ~ g o r y includes slightly p l a s t i c s i l t s a n d loose· c l y e y s a n d s below t h e w a t e t t a b l e : Both of t h e s e highly d i l a t a n t m a t e r i a l s and upon d i s t u r b a n c e w o u l d b b T h i s would ~ e su l t e x p e c t e d to e x p e r i e n c e a n i n c r e a s e i n p o r e p r e s s u r e i n a l o s s o f e f f e c t i v e s t r e s s a n d t h e r e f o r e a l o s s o f st re n g t h . M o r e ~ v e r , b e c a u s e o f p o o r d r a i n a g e c h a r a c t e r i s t i c s , . they m a y flow a n d l e a d to: g r o u n d l o s s . Commonly: they a r e known a s r u n n i n g so i l s.

2 . 32. 5 E q u i v a l e n t U n i f o r m P r e s s u r e

The c o n c e p t o f a n e q u i v a l e n t u n i f o r m h o r i z o n t ~ l p r e s s u r e a c t i n g o n lagging is u s e f u l . i n i l l u s t r a t i n g t h e P.ffectiven e s s o f a r c h i n g . With v e r i f i c a t i o n b y field d a t a , the e q u i v a l e n t unifrm h o ri z o n t a l p r e s s u r e could a l s o b e u s e d a s a b a s i s for c o n s i d e r a t i o n o f d i ffe re n t g r a d e s o f l u m b e r and a s a n i n d e x o f lagging d e f l e c t i o n . In F i g u r e 10 t h e f l e x u r a l s t r e s s h a s b e e n a r b i t r a r i l y a s s u m e d t o b e 50 p e r c e n t above the n o r m a l w o r k i n g s t r e s s o f ~on s t r u c t i o n g r a d e l u m b e r . T h i s r e p r e s e n t s t h e a p p r o x i m a t e u p p e r litnit o f w h a t a d e s i g n e r would al.low for t e m p o r a r y c o n st ru c t i o n . A c t u a l f l e x u r a l s t r e s s could b e m o r e o r l e s s t h a n t h e a b o v e l i m i t s , b e c a u $ e

the failure s t r e s s m a y be several times the normal working s t r e s s The p r o c e s s u s e d i n p r e p a r i n g F i g u r e 10 w a s a s

follows:

a. A family of curves was developed r e l a t i n g t h e lagging t h i c k n e s s , r e q u i r e d t o l i m i t f l e x u r a l s t r e s s (1800 p s i ) , to v a r i o u s c l e a r s p a n s . T h e 1800 p s i fi g u re i s b a s e d o n a 5 0 p e r c e n t o v e r s t r e s s v a l u e a p p l i e d t o the n o r m a l e x t r e m e fi b e r w o r k i n g s t r e s s o f about 1200 p s i for c o n s t r u c t io i o n g r a d e Douglas F i r o r So u t h e r n P i n e .

-34 

 

. I LI

:

:

SPAN

DISTANCE vs

HORIZONTAL PRESSURE

U U I LI

8: .J

z 1000

UPPER

LIMIT

FOR

DEPTHS > ~ TABLE 2

2

6

:

z

soo

:

z

I LI

.J

5 0

I LI

5

6

7

1.

R

RESSURE 2 EQUIVALENT

E

L

- - 1 t± t ± r l tt1 1__1 ~b;,drl L

G i v e n a l a g g i n g t h i c k n e s s a n d s p a n d i s t a n c e , the e q u i v a l e n t u n i f o r m h o r i z o n ta ta l p r e s s u r e c a u s e s a f l e x u r a l s t r e s s o f 1800 p s i ; e g g i v e n 4 i n c h laggb:ig a n d 8 f oot c l e a r s p a n , a

2.

u n i f o r m p r e s s u r e o f 600 p s f c a u s e s 1800 psi. 3.

1

FEET

CLEAR SPAN

~

9

8

O

4

flexural stress of

Implied range for

c o m p e t e n t ' ' s o i l s ( T a b l e 2).

Implied range for

difficult

~C

t?z/~

a

s o i l s ( T a b l e 2).

L a g g i n g t h i c k n e s s r e q u i r e d to l i ~ i t f l e x u r a l s t r e s s

F i g u r e 10.

-35 

Th e points w e r e p l o t t e d f r o m T a b l e 2.

These c o r r e s p o n d to the r e c o m m e n d e d l a g g i n g t h i c k n e s s f o r d i f f e r e n t cleajr s p a n b

va.lues.

y c o m p a r i n g t h e t h e o r e t i c a l c o m p u t a t i o n f r d m (a) w i t h w h a t work.s in p r a c t i c e , f r o m (b) o n e c a n i n f e r a n e q u i v a l e n t u n i i fo rm pressure

2. 32. 6 D i s c u s s i o n

f oot d e e p c u t i n

II

T o i l l u s t r a t e the e f f e c t o f a r c h i n g , c o m p e t e n t s o i l s g i v e n i n T a b l e 2. Let:

= 130 p c f

K a = o. 3 0

consider

ai

40

where: = unit w e i g h t K

a

= coefficient of active e a r t h p r e s s u r ~

A s s u m i n g a c t i v e e a r t h p r e s s u r e co n d i t i o n s, t~e h o r i z o n t a l p r e s s u r e a t 4 0 f e e t w o u l d b e a s follow s : Cf ' h = o. 3 0 x 130 x 4 0 = 1 5 6 0 p s f

C o m p a r e · t h i s p r e s s u r e w i t h the e q u i v a l e n t uni\form h o r i z o n t a l p r e s s u r e i n f e r r e d f r o m F i g u r e 10. A s a n e x a m p l e , cons + der a c l e a r s p a n o f 8 f e e t b e t w e e n s o l d i e r p i l e s . F r o m F i g u r e 10, the eqtj.iva l e n t h o r i z o n t a l p r e s s u r e c a u s i n g a f l e x u r a l s t r e s s o f 1800 p s i i s a b o ~ t 6 0 0 psf, which is l ss than one-half the active p r e s s u r e · T o c o n s i d e r s t r e s s g r a d e d s t r u c t u r a l l u m b e r , 1u s e the e q u i v a l e n t u n i f o r m p r e s s u r e f r o m F i g u r e 10. T o b e c o n s i s t e n t ~ i t h the b a s i c a s s u m p t i o n o f F i g u r e 10, a llow 5 0 p e r c e n t a b o v e n o r m a l working s t r e s s 1

A s a n e x a m p l e , c o n s i d e r the following: a.

Given:

I.

Sand and gravel;

2

E x c a v a t i o n 50 f e e t d e e p ; and S o l d i e r p i l e s t o b e s e t a t 10 to f eet on c e n t e r

3.

11

-36 

b.

Find:

I.

Lag g i n g t h i c k n e s s f o r s o l d i e r p i l e s a t 1 0 f e e t a n d 11 f e e t o n c e n t e r s , u s i n g

construction grade lumber.

2.

c.

Repeat for structural grade Douglas ir (normal working flexural st.ress f = 2000 p s i ) . w

F i n d l ag g i n g t h i c k n e s s lumber f r o m Table 2.

o t c o n s t r u c t i o n grade.

S o l d i e r p i l e s p a c i n g (feet) A p p ro x . c l e a r s-pan (feet) Lag g i n g t h i c k n e s s f o r 1 c o m p e t e n t soi1 (inches )  

10

11

9

10

4

5

d.

Find lagging thickness for structural grade lumber. 1. C o m p u t e m o m e n t u s i n g e q u i v a l e n t h o r i z o n t a l p r e s s u r e f r o m F i g u r e 10. where: w = u n i f o r m pressu:i-e, p s f 1 = c l e a r s pan, f e e t M = moment, foot-lbs.

M = ~

8

S o l d i e r p i l e s p a c i n g (feet) A p p ro x . c l e a r s p a n (feet) w (psf), u s i n g u p p e r lin;,it curve from Figure l 0 Moment, foot-lbs.

10

9

10

600

600

6060

7500

*N ote

that the upper curve will produce cons e r v a t i v e r e s u l t s f o r c l e a r s p a n s a t 7 an d 9 f e e t in c o m p e t e n t s o i l •  

Co mp u t e s e c t i o n m o d u l u s f o r 3 a n d 4 in~ hes

2.

y 12 inch w i d e lagging.

thick S

b h = 6

2

where: b = 12 i n c h e s h = 3 o r 4 i n ch t h i c k n e s s

3 2 3 F o r 3 .m e h th'1ck n e s s , S -- ( l )( ) -- 18 ·u 6 2 _ (12)(4) 3 F o r 4 i n ch t h i c k n e s s , S = 32 in 6

-3 7  

3.

Check s t r e s s A l l o w a b l e = 1. 5 x 2 0 0 0 = 3 0 0 0 p s i C h e c k 9 f oot c l e a r s p a n

inch l a g g i n g :

3

·

6060

x 18

M

f

S

-T h i s e x c e e d s a l l o w a b l e s t r e s s

12 .

: 4040

psi

Use 4

l a g g i n g f o r a 9 f oot c l e a r s p a n . C h e c k 1 0 foot c l e a r s p a n A

:i:

me •

h l

.

aggm0 :

T h i s i s ok. clear span.

f

7 5 0 0 x 12 . 28 00 p s i 32 l a g g i n g for a 1 0 '

M

=S

Use 4

=

e.

Summary S o l d i e r p i l e s p a c i n g (feet ) A p p r o x . c l e a r s p a n (feet ) Lagging thickness (inches) Construction grade Structural grade

f.

2.33

10

11

9

10

4

5

4

4

Adopt 1.

C o n s t r u c t i o n g r a d e : s o l d i e r p i l e s a t 10 f e e t on c e n t e r with 4 inch lagging, o r s o l d i e r p i l e s a t 11 f e e t o n c e n t e r w i t h 5 i n c h l a g g i n g .

2.

Structural grade: soldier piles at cent ers with 4 inch lagging.

11

feet on

Displacements and Loss of Ground 2 . 33. 1 G e n e r a l

During construction of soldier pile and l a g g ~ g w l l s t h e s o i l f a c e m u s t b e e x p o se d t o i n s t a U l a g g i n g a n d , i n m o s t i n s t a n c e s , the la gging a l l ow o w s d r a i n a g e o f w a t e r b e h i n d the e x c a v a t i o n . B e c a u s e o f the c h a r a c t e r i s ~ i c s o f a s o l d i e r p i l e w a l l , u n f a v o r a b l e s o i l c o n d i t i o n s c a n l e a d d i r e c t l y to g r o u n d l o s s a n d d e f o r m a t i o n .

Important factors contributing to ground l o s s a r e the s o i l i n the z o n e s i m m e d i a t e l y b e h i n d t h e l a g g i n g a n d the f l e x u r e o f the la gging b o a r d i t s e l f . T h e fo l l o w i n g d i s c u s s i o n c o n c e r n s g r o u n d l o s s c a u s e d

-38 

b y the. i n h e r e n t c h a r · a c t e r i s t i c s o f s o l d i e r p i l e w a l l s ,

t e c h n i q u e s u s e d in t h e i r c o n s t r u c t i o n .

i n p a r t i c u l a r the

T h e d i s c u s s i o n d o e s not d e a l w i t h

o v e r a l l d e f o r m a t i o n s o f the i e t a i n e d e a r t h m a s s . 2 . 33. 2 Deflectio n of L agging

T he lagging b o a r d t h i c k n e s s e s r e c o m m e n d e d i n T a b l e 2 w i l l g e n e r a l l y m a i n t a i n d e f l e c t i o n to l e s s t ha n ab o u t 1 inch. B e c a u s e o f the e m p i r i c a l n a t u r e o f T a b l e 2 and F i g u r e 10, the e q u i v a l e n t u n i f o t m p r e s s u r e develc;ped in the l a t t e r fig u re should not be· u s e d f o r a c o m p u t a  tion o f the ab so lu te v alu e o f def lection.

B e c a u s e o f a r c h i n g , i t i s p r o b a b l e that the inf luence z one f r o m lagging d e f l e c t i o n i s l i m i t e d t o the vicinity o f the s o l d i e r p i l e w a l l in the " c o m p e t e n t " s o i l s l i s t e d i n T a b l e 2 . W h en a r c h i n g is not lik ely , s u c h a s fo r the "d ifficu lt" s o i l s l i s t e d i n T a b l e 2 , the inf luence z one h o r n

lagging i s not l i m i t e d t o the l o c a l e o f the wall. 2 . 33. 3 O v e r c u t

I n o r d e r to p h y s i c a l l y i n s t a l l a lagging b o a r d , it . i s n e c e s s a r y to p r o v i d e a c l e a r s p a c e behind the b o a r d s o th at i t c a n b e fltted p r o p e r y i n p l a c e . W h e n e v e r the r e i s c o n c e r n ab o u t the e f f e c t o f d i s p i a c e  1 m e n t s on adjoining s t r u c t u r e s , t h i s s p a c e m u s t b e filled t i .... :n to d e v e l o p i n t i m a t e c o n t a c t with the so il. -·--

_

An example of movement f r o m overcut was reported b y P r a s a d , · e t a l (1972). I n t h a t c a s e , d u r i n g p r e s t r e s s i n g o f t i e b a c k s ) t h e

s o l d i e r pile and lag g in g w a l l m o v e d a b o u t I / 2 in ch t 2 i n c h e s t o w a r d the u n ex cav ated so il. S i m i l a r b e h a v i o r h as b een o b s e r v e d b y m a n y pr actif  t i o n e r s u n d e r s i m i l a r c i r c u m s t a n c e s w h i c h i s c a u s e d b y p o o r backpack(ing_ I

T he m o s t effectiv e w a y o f b ack p ack in g i s t r a m the s o i l into the spac~ f r o m the u p p e r s i d e o f the lagging b o a r d . I f t h e r e i s dif f iculty i n obtai*ing suf f icient c o h e s i o n i n the m t e r i l r a m m e d i n this m a n n e r a n d / o r t h e r b i s c o n c e r n with f u t u r e w a s h o u t f r o m g ro u n d w a t e r actio n , the s o i l c a n b e m i z e d with c e m e n t an d d r y p a c k e d . L o u v r e s r e a l s o helpful b e c a u s e t h e y allow backpacking f r o m the top o f the b o a r d a s w e l l a s f r o m the ut11ders i d e . A l s o , the p r o v i d e a n o p p o r t u n i t y t o t a k e r e m e d i a l m e a s u r e s to , i m p r o v e f i l t e r i n g o r to c o r r e c t f o r g ro u n d l o s s behind p r e v i o u s l y i n s t a p e d l a ggi ng. I

2. 33. 4 I n h e r e n t Soil P r o p e r t i e s

T h o s e s o i l s which, b y v i r t u e o f t h e i r n a t u r a l characteristics, m a y produce excessive strains during excavation re s o f t clay s a n d l o o s e s o i l s o f l o w p l a s t i c i t y b e l o w t h e w a t e r t a b l e .

-39 

T h e p h y s i c a l a c t o f exposing a fa c e b e l o w t h e l s t p l a c e d ragging b o ~r d

m a y r e s u l t i n d e f o r m a t i o n e v e n while the excavaHon i s b e i n g made.i A n e x a m p l e o f a r a t h e r d r a m a t i c f a i l u r e in soft s e n s i t i v e c l a y w a s r e p o r t e d b y B r o m s and B j e r k e (1973). T h e failmre took p l a c e a t a depth o f a p p r o x i m a t e l y 30 f e e t w h e r e soft c l a y a c t u a l l y s q u e e z e d t h ro u g h the opening b e t w e e n a d j a c e n t s o l d i e r p i l e s a f t e r the fa c e o f tth h e c l a y had b e e n e x p o se d for a p e r i o d o f 1 t o 3 d a y s . The ~atio o f total o v e r b u r d e n s t r e s s J o u n d r a i n e d s t r e n g t h was about 6 . 3 . I n ; a n o t h e r c a s e , B r o m s and, B e n n e m a r k (1967) r e p o r t e d a s h e a r failu.Jte t h ro u g h a 6. 5 foot d i a m e t e r opening i n soft c l a y about 1-1 / 2 h o u rs atfter e x p o s u r e . The s l i d e b u r i e d 3 m e n ; one of whom was killed. The rtltio o f o v e r b u r d e n s t r e s s t o u n d r a i n e d s t r e n g t h e x c e e d e d si x .

E x a m p l e s o f a G e r m a n p r o c e d u r e for dealing with 1

soft u n st a b l e s o i l

r e shown .in F i g u r e 11.

·

'

I n (a) o f t h e F i g u r e the s o i l b e t w e e n t h e soldier p i l e s i s s h a p e d i n a sl i g h t l y c u rv e d m a n n e r -using a s p e d l s t e e l f o r m . Double wedging i s u s e d behind the flange o f e a c h soldier p i l e , and the lagging b o a r d i s thus pulled tightly a g a i n s t the soil. The se c o n d ca$e shown i n (b) i s a n example o f ¢ & st -i n -p l a c e c o n c r e t e t o p r o v i d e thei stiff n e s s n e c e s s a r y t o lim it d e f o r m a t i o n and t o f o r m i n t i m a t e c o n t a c t wfth t h e excavated soil. I n ( c) o f t h e F i g u r e the p r o c e d u r e i s t o d r i v e shorti v e r t i c a l s h e e t s and to wedge behind h o r i z o n t a l w a l e s a t t a c h e d t o the;.

soldier piles

T h i s p r o c e d u r e effectively p r e s t r e s s e s t h e s o i l .

T h e e x t e n t o f s t r e s s r e l i e f f r o m a r c h i n g t h a t occurs w i t h v e r y s o f t s o i l s a n d soils s u b j e c t t o pl a s t i c c r e e p i s c e r t a i n l y itj q u e s tion. T h e r e f o r e , the p r e s s u r e u s e d for lagging d e s i g n should b e d e ~ e r m i n e d d i r e c t l y f r o m t h e b a s i c p r e s s u r e d i a g r a m u s e d for d e s i g n o f s t r u t s '-nd v e r t i c a l m e m b e r s . Such a s e v e r e d e si g n condition ·would m a k e i t h i lghly u n l i k e l y that lagging would b e s e l e c t e d i n the f i r s t p l a c e o v e r s h e e t i n g o r a •

•

-

I

1

'

d i a p h r a g m wall

I

I n d e a l i n g with i n t e r b e d d e d s i l t s and o t h e r soiils that a r e difficult t o d r a i n , one obvious p r o c e d u r e i s t o d e w a t e r long in a d  v a n c e o f excavation. A n a l t e r n a t i v e p r o c e d u r e would b e t o continuo~sly m a i n t a i n a sl o p e d b e r m f r o m the i n s i d e fa c e o f the s o l d i e r p i l e s and t o p u m p from. open s u m p s ·installe·a a t the l o w e s t p o r t i o n o t h e excavation. I~ t h e s e p ? o c e d u r e s do not p r o v e s u c c e s s f u l , t h e n i t m a y b e n e c e s s a r y t o eniploy s p e c i a l p r e c a u t i o n a r y m e t h o d s , s u c h a s the G e r m a n technique shown i n F i g u r e 11 c . I

D r y c o h e s i o n l e s s s o i l m a y a l s o l e a d t o difficulty, e s p e c i a l l y i n hot, a r i d a r e a s . Under t h e s e c i r c u m s t a n c e s , one t e d i n i q u e

-40 

·..

.. .

 ~

:;

. .· · .

·

.

•.

.

~

WE GES

(b) CONCRETE

... 7_

:-:.: ••

: . P;

..

1>·. •

:i..

.

•.

.

..... . .•. '•·p·:··.,

,P•.~:~

• ·

..

· . ... -~•

.:

...

.,•

~

·.

··:•···: I)·•·

••.• a

•

•

. .· . . . . . .·.·.

· 1>·

• .

........

· · · v . • ~ • : · • . ~ ; , - • , • ,

·

(c) VERT ICAL ST EEL

IN

SHEETS

SOFT

SOIL

SOL

IER PILE

STEEL SHEET

·.

j

::

.. I

t

. ~IE---

--

STEEL

· . · · 1·

: ·

DETAIL

SHEET

·.

: ·1

.. I ·. .

I_

. . I· ~1

. :· I . 1:: • I

F i g u r e 11.

I ·1

SECTION

A-A

G e r m a n t e c h n i q u e s to p r e v e n t d e f o r m a t i o n s

after Weissenbach,

1 9 7 2 ).

-41 

i s t o m o i s t e n the face b y s p r a y i n g while p l a c i n g t h e lagging. One :rtjay a l s o u s e a b o a r d s u c h a s plywood to hold the s o i l t e m p o r a r i l y i n p l a c e while s e t t i n g lagging. 2 . 33. 5

P r e - e x c a v a t i o n fo r Soldier P i l e s

T h e r e a r e s e v e r a l p o t e n t i a l ;cau ses o f materi~.l loss during pre-excavation. One c a u s e i s f r o m t h e s u c t i o n e f f e c t t h a t occujrs d u r i n g w i t h d r a w a l o f the a u g e r . T h i s m a y c a u s e s o i l t o s q u e e z e in to th e h ~le. One

way t o p r e v e n t t h i s i s t o p r o v i d e p o r t s with in th e a u g e r wh ich will p f o h i b i t th e s u c t i o n f r o m . d e v e l o p i n g b e l o w the au g er . An o th er i s t o ap p ly p i t e s s u r e t o the i n n e r hole of a hollow s t e m a u g e r a s i t i s with d rawn . ·

s e c o n d c a u s e o f g ro u n d l o s s i s f r o m co llap ~e o f th e soil in to th e a u g e r e d hole. T h i s can b e p r e v e n t e d b y u s i n g a c a s i n g o r a b e n   

to n ite s l u r r y s u s p e n s i o n t o s t a b i l i z e the h o le, e s p e c i a l l y when a pos,itive s l u r r y h e a d i s m a i n t a i n e d above th e g ro u n d w a t e r t a b l e . I

t h i r d p o s s i b l e c a u s e o f g ro u n d l o s s i s froml i m p r o  p e r l y fillin g the p r e - e x c a v a t e d hole. N o r m a l l y , the filling i s done i t h l e a n c o n c r e t e o r g ro u t. C a s e s h av e b e e n o b s e r v e d i n which ground· water o r s u r f a c e w a t e r c o n c e n t r a t e d alo n g i m p r o p e r l y filled h o l e s , flowed. down w a r d alongside th e hole, e m e r g e d o u t f r o m the s p a c e b e t w e e n lag g i~g b o a r d s , a n d c a r r i e d out a significant quantity o f s o i l . 2 . 33. 6

S u r f a c e W a t e r an d Gro u n d W a t e r

T h e i m p o r t a n c e o f p r o p e r l y sloping the top s ~ r f a c e s o t h a t s u r f a c e w a t e r d r a i n s a w a y f r o m , r a t h e r t h a n t o w a r d s , the er, cava tio n cannot b e o v e r e m p h a s i z e d . S u r f a c e w a t e r tends t o concentrate i n local zo n es an d b e c o m e channelized o n c e a p a t h o f flow d e v e l o p s . t h i s i n t u r n m a y l e a d t o g ro u n d l o s s . I n t h a t co n n ectio n , the G e r m a n code i DIN 4123, 1972) c a l l s fo r e x c a v a t i o n w a l l s a t l e a s t 2 i n c h e s h i g h e r t h a n § u r r o u n d i n g ground i n o r d e r t o m a i n t a i n d r a i n a g e .

O t h e r s i t u a t i o n s a.rise f r o m l e a k y o r b r o k e n

~

w

rs

o r b a c k e d - u p m u n i c i p a l s t o r m d r a i n a g e d u r i n g h e a v y r a i n . S u ch co p d itio n s a r e ·contingency i t e m s t h a t m a y o r m a y n o t b e with in t h e c o n t r a c t o r l s control. I t i s th e r esp o n s i b i l i t y o f all p a r t i e s t o i n v e s t i g a t e the p r q b a b i l i t y o f s u c h co n tin g en cies - - p a r t i c u l a r l y w h e r e s t r u c t u r e s ab u t the ex c~v atio n . •

I

I n an y w a t e r - b e a r i n g f o r m a t i o n i t i s a b s o l u t e t y el Jsential t h a t the g ro u n d b e d r a i n e d p r i o r t o ex p o sin g the face. Th e co n seq u ~n ces o f doing o t h e r w i s e could b e s u b s t a n t i a l g ro u n d l o s s . 'l'he d e p t h o f cu t l:>elow the

-42 

w a t e r t ab l e, t h e p o r o s i t y a n d p e r m e a b i l i t y o f t h e ·soil, a n d th e r s e n c e o f u n d e r l y i n g o r i n t e r b e d d e d i m p e r v i o u s Layers m u s t a l l b e c o n s i d e r e d i n devising a d e w a t e r i n g s c h e m e .

-

I n s o i l s wh ich d r a i n v e r y slo wly , t h e e x c a v a t i o n face c a n only b e a d v a n c e d ab o u t one foot a t a t i m e . T he b o t t o m o f t h e cut i s slope i n a V;.shaped f a s h i o n t o allow for s u r f a c e d r a i n a g e an d to a i d epressing t h e o h r e a t i c . s u r f a c e a t 'the s i d e o f t h e e x c a v a t i o n . S u c h DJ p r o c e d u r e s h av e b e e n u s e d s u c c e s s f u l l y i n s i l t d e p o s i t s i n New Y o r k C i t y (knawn l o c a l l y a s B u l l ' s l i v e r ) . When i m p e r m e a b l e l a y e r s a r e inter b.edded with m o r e The grouncf urn da w on p l asyteor sflow , gro o r e dpifficu fo r ealtaetri vi se l m y long e r i o dlt otfo t icm e t rj o weartveiro tuesn d u ls.t above the im  p e r v i o u s l a y e r ( o r l ay er s) o r a n i n t e r b e d d e d f o r m a t i o n . T h i s co n d itio n i s

n o r m a l l y c q n t r o l l e d b y w e l l s wh ich i n t e r c e p t flow b e f o r e i t r e a c h e s t h e excavation. I n v e r y s e v e r e i n s t a n c e s , one p o s s i b l e p r o t e c t i v e m e a s u r e would b e t o i n s t a l l a s e r i e s o f v e r t i c a l d r a i n s wh ich s u c c e s s i v e l y p e n e t r a t e the v a r i o u s · l a y e r s a n d t o i n t e r c e p t h o r i z o n t a l flow b e f o r e i t e m e r g e s t h r o u g h t h e o p e n l a g g i n g a t th e s o l d i er p i l e w~ll. O v e r a l l

t h e s e s i t u a t i o n s r e q u i r e the u s e o f j u d g m e n t t o d e t e r m i n e t h e f eas i b i l i t y o f open lagging. A l t e r n a t i v e s o f i n t er l o ck ed sheeting o r d i a p h r a g m w a l l s must be considered. P r o t e c t i o n a g a i n s t w a t e r e r o s i o n thro ll:gh lag g in g i s c o m m o n l y done b y a combination o f effective b ack p ack in g an d p l a c e m e n t o f s a l t m a r s h h a y i n the o p en s p a c e b e t w e e n t h e lag g in g b o a r d s t o f i l t e r o u t t h e soil. A n o t h e r way t o p r e v e n t e r o s i o n i s t o u s e p o r o u s c o n c r e t e a s a f i l t e r b eh in d the lag g in g . S u ch a p r o c e d u r e w a s r e p o r t e d b y M a n s u r and A l i z a d e h (1970).

F i g u r e 12 i l l u s t r a t e s a c a s e w h e r e w a t e r s e e p a g e t h r o u g h th e s o l d i e r pile w a l l c a u s e d g r o u n d l o s s b e h i n d t h e wall. T he g r o u n d l o s s w a s n o t s e v e r e an d w a s c o n t r o l l e d with o u t d a m a g e .

-43 

W a le

>it__ ~ " '

■

"I

--

"

..

'

ll(II

'(

-

C

  Bracket

I

I

..

--

--~-

-:-~-~·:\:t~ \ . , : · ~ .... \

~.~-.

..... ·_-<

-

.,...._ ~7 ': . . . . .

.. ..· ,

.•-

.

r·'·_

-.. ....... ......

-.~ a-· •·

.

~

>.

:r7i

,

ti~

I

.-;

.

. / .t JJ~•jJ,,_ •jJ,,_ .,

/,,.-;,,; :~-· -

. :-

~

_. .J:

 

.~•

;,

...

,4 . . . . .

---=

..

-:-,.,·•

~

I

~

r

. , . . ,:-;; '. .

•.""tt-"Y,;, .

;·.......,.,

·--~-

. . . .~ .

-

•

.

 / - -...~~~

. .

. . . _ . . . :.:. : . . . -.

- J ~ . ..

.. •

~

· :

•

:-~

.

-

 

/.

':·

.... .

 

  ~ ~

. . .J

;-~ ·

._-~.

.

\,;,~

:

4~... .. :·.

·r ·

....

Note:

Ill

•

_.' 'l'J,,

,..

, .

■

....... •

•. -

'•

. -~

.- . ~

  tF . _.:... . . . . ·•- ~ - , --......., ..t. ~..... -

~~

-.

If?

+

·.

~ ·

'

-·

-....

..

..... . - ~ -.... ·

-

- -. -. .. .. -

•.

.

1 tt:

~ . . . _\ . .

__ ,..

i.

.. - - • ~,..~-~-

.,,_ .,,

~~....

....._ --. .;.-;..... ....._ ____ ,.,..'"'='..:1"

~'•

\

-

.... .....

_ 1·