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- November, 1971

Journal of the

SOIL MECHANICS AND FOUNIIATIO IIIVISIOP 3 -ax

-

9 Proceedings of the American Society of Civil Engineers

HEAVE AND LATERAL MOVEMENTS DUE TO PILE DRIVING

By D. Joseph Hagerty,' A. M. ASCE and Ralph B. Peck,' F. ASCE

INTRODUCTION

Whenever pi les a r e driven, so i l i s displaced. The movements inducec the so i l itself may have severa l undesirable consequences, including the lifl o r l a te ra l displacement of those pi les that have already been driven. ' effects of pi le and so i l displacement on foundation performance depend 1 g r e a t extent upon the type of thepi lesand the way in which they t rans fe r tf load t o the surrounding ground.

If the pi les a r e designed to be end-bearing, their r i s e during the drivinj subsequently installed pi les may ser iously impai r their load carrying capac The ensuing pile set t lement may be a t l eas t a s g rea t a s the pile heave. If pi les a r e grouped in c lus te rs beneath a s tructure, differential set t lemf among the heaved p i les may be la rge and detr imental to the suppol s t ruc ture .

When pi les a r e to support loads by skin friction, the detr imental effect pile heave may be l e s s pronounced because there i s no bearing s tratum 1 which the t ip of the pile loses contact. Nevertheless, the strength and cc pressibi l i ty of the so i l a r e al tered by the displacements, with effects not fully understood (3,20,23).

Pi le driving displaces so i l and previously dr iven piles laterally a s we1 vertically. [Existing s t r u c t u r e s a l s o may be displaced by the pile d r i i (6,9,10,26)]. The tops of d r ivenpi les may bedisplaced f r o m their design 10 tions by dis tances which great ly exceed the location tolerances in the f a n tion construction specifications. Moreover, where a pile contains a w element, such as a s l i p joint in a composite pile o r a splice in a t imber P l a t e r a l s o i l displacement may produce a sharp kink and may dccrease . -

capacity of the pi le (16). Note.-Discussion open until April 1, 1972. To extend the closing dntc one mont

written request must be filed wlththe Executive Director, ASCE. I'hls pnPcr 1s p:ll thecopyrighted Journal of the Soil Mechanics and Foundations Dlvlslon, I'rocc*cdlng the American Society of Civil Engineers, Vol. 97, No. SMl1, Novcml)cr. 1071. hlnnusc was submitted for review for possible publication on Jnnunry 21, 1971.

'Asst . Prof. of Civ. Engrg., Univ. of Louisville, Louisvlllc, KY- Prof. of Foundation Engrg., Univ. of nllnols, Urbnnn, n l .

This pap 9 resents the results of astudy of heave involving case histories from priva .es and the engineering literature. Thirteen suitable cases were found. They -are:

Cases from Private Fi les . Case Al-Chicago; Steel-frame structure; insensitive soft clays over hard

clays and compact silts. Case A2-Cleveland; Bridge pier; insensitive medium to hard saturated

clays. Case A3-St. Louis; Office buildings; insensitive soft silty clays and clayey

si l ts over weathered limestone. Case A4-Chicago; Warehouse extension; insensitive saturated soft to

medium clays. Case A5-Great Britan; Power station; insensitive soft to medium clays.

Cases from Engineering Literature. Case B1-WesternCanada; Pulp mill extension (8); variable glacial deposits

over sand-gravel outwash. Case B2-Cleveland; Blast furance foundation (13); fill over sand and gravel,

overlying medium to stiff blue clay. Case B3-Backa, Sweden; Foundations at three si tes (14,27); deep deposits

of soft normally-loaded sensitive clay. Case B4-Detroit; Expressway pier (3); deep deposit of soft blue clay,

sensitive along upper 20 ft of 80-ft long piles. Case B5-Mexico City; Building foundation (30,31); deep deposit of soft

sensitive clay. Case B6-Utah; Willard Pumping Plant (5,28,29); lean insensitive soft to

medium clays with sand and silt layers. Case B7-Boston; Insurance building (1,2); deep deposit of saturated in-

sensitive soft clay. Case B8-Tokyo; Telephone building (4); loose sand layers over a deposit

of soft silty clay and medium clay. Case B9-Detroit; Pumping station (24); deep deposit of soft insensitive

clay.

The first part of the paper deals with movements of soil during pile dri;ing, and the second with movements of piles already driven. The intention herein i s to present specific aspects of heave and lateral movements due to pile driving. Recognition of the nature of such movements should suggest appro- priate preventive and remedial measures; therefore, specific remedial measures a r e not rgcommended herein.

DISPLACEMENT OF SOILS

Previous studies suggest that net soil displacement i s likely to be small when piles a r e driven into clean granular soils (7,12,19). On the other hand, significant soil dislilacement occurs during pile driving in fine-grained soil deposits.

Analysis of the collected data leads to theco~iclusion that saturated, insen- sitive clay soils behave incompressibly during pile driving; i.e., the volume of

(0 displaced soil i s equal to the volume of the inserted piles. OD? ; may i e described in some detail to support this conclusion.

v! Figs. 1 and 2 show, respectively, a plan view and a soil p r d l e for a pile foundation consisting of step-taper piles driven behind a bulkhead into a soft clay deposit. The piles nearest the bulkhead weredriven first and subsequent driving was successively farther from the water. The riverward piles were

/ € Anchored Bulkhead

........................................................ . .

FIG. 1.-PLAN. WAREHOUSE ADDITION, CASE A4

FIG. 2.-SECTION THROUGH FOUNDATION, CASE A4

displaced laterally and tilted toward the bulkhead. The measured lateral pile movements suggest that all the movement of soiland piles was directed toward the bulkhead, away from subsequent driving and toward the zone where soil support was missing. Fig. 3 shows movements of the bulkhead toward the river. If it i s assumed that al l the soil displaced by the piles moved laterally toward the r iver and that the lateral rpovement was of uniform magnitude along the bulkhead and along the depth of the piles, the movement would have

w been appro: tely 23 in. The average displacement along the en t i re bulkhead between c o l ~ .I l ines 16 and 26 was about 21-1/2 in. However, s o m e movement had occur red a t the west end of the bulkhead before the location s u r v e y s w e r e initiated. Considering only that portion of the bulkhead between column l ines 22 and 26, where the location surveys were begun before any pi les w e r e dr iven behind the bulkhead, the average measured displacement w a s about 24 in.

The movements of the various rows offoundationpiles w e r e est imated i n a s i m i l a r manner. Table 1 shows a comparison between computed and measured movements.

La te ra l movements of the so i l toward the r i v e r completely account f o r the volume of the piles. Thus it appears that the insensitive clay s o i l into which the pi les were dr iven behaved incompressibly during pi le driving.

TABLE 1.-PILE MOVEMENTS, CASE A4

PILE DRIVING >

A5, the pi les were dr iven in a fa i r ly regu la r sequence f ron , end of the v- foundation t o the other, and the ground sur face f r o m which rid piles were

dr iven was pract ical ly level. Given the conditions of a sa tura ted insensi t ive clay soil, a regular pile

driving sequence, and a level foundation ground surface, i t is concluded that the so i l su r face heave within the foundation a r e a may be est imated by the following procedure:

1. The volumetric displacement ra t io is calculated by dividing the total volume of the inser ted pi les by the volume of so i l enclosed by the pile foundation.

2. The normalized so i l heave, equal t o the so i l heave divided by the pile length, is est imated empirically. F o r the conventional types and dimensions of pi les and foundation a r rangements studied i n this investigation, the nor-

Pile row (1)

Computed movement, In inches (2 1

Measured movement, in inches (3)

1 I I I 1 I L 20 21 2 2 23 2. I 5 26

Column L4n.s Lonp#lud#n(ll SCrle ? '? ': "

FIG. 3.-DISPLACEMENT OF BULKHEAD, CASE A4

The values of heave of tlie ground sur face observed a t four o ther s i t e s where p i les were dr iven into insensitive, saturated clays indicate that approximately half the volume of displaced so i l appeared as sur face heave within the a r e a of the pile foundation, while the remaining half appearedas sur face heave outside the foundation a r e a . The data a r e shown in Fig. 4. The so i l heave in each c a s e was divided by the length of the pi les t o obtain the normalized so i l heave. T o facilitate comparison of case his tory data, a volumetr ic displacement ra t io was calculated f o r each c a s e by dividingthe total volume of the inser ted pi les by the v o l u n ~ e of soi l enclosed o r surrounded by those piles. In Fig. 4 a significant correlat ion is apparent between the normalized s o i l heave and the volumetric displacement ratio. In the four c a s e s designated A2, B4, B7, and

Volumetric Dirplocemsnl Ratlo

FIG. .. -SOIL SURFACE HEAVE SUMMARY

malized so i l heave was found to be approximately one-half the volumetric displacement ra t io obtained in s tep 1.

3. The heave of the so i l su r face is est imated t o be the product of the normalized s o i l heave and the average length of the piles.

T h i s procedure is applicable only to those situations in which a l l the con- ditions mentioned a r e satisfied. The significance of changes in these coridi- tions i s indicated in the individual c a s e .histories.

Effect of Soil Chnvacteristics.-Information f r o m two cases, B3 and B5, indicates that when pi les a r e dr iven into sensi t ive c lays the pat tern of so i l displacement may differ f r o m that produced in insensitive clays.

F i r s t , the dis turbance of the so i l may liquefy a sensi t ive clay so i l around the pile a s i t is being driven. T h e liquefied so i l may be extruded onto the ground surface around the pile. Such extrusion was noted in c a s e B5 and has been reported elsewhere (11). The effect of such extrusion appears to be to reduce the heave of the so i l su r face beyond-the l imi t s of the a r e a enclosed by the pi les themselves and t o confine the sur face heave roughly within the a r e a of the pile foundation. In both c a s e s B3 and B5 the observed heaves of the s o i l

November, 1971

sur fac the c e n t e r s of the foundations w e r e approximately equal t o those that wouluhave beenpredictedfor insensitive clay subsoils, a s shown in Fig. 4. j However, in c a s e B3, the total volume of heaved s o i l amounted t o l e s s than 40 %

i of the volume of the inser ted piles, and sur face heaye outside the foundation J

a r e a was negligible. Second, s o m e evidence was found i n c a s e s B3 and B5 that a significant

amount of consolidation occurred i n the disturbed sensi t ive clay so i l during pile driving. The effect of such consolidation is t o reduce the total volume of heaved soil. Thus, the low volume of displaced s o i l noted in c a s e B3 may have been a resul t , a t l eas t inpar t , of consolidation of the sensi t ive clay during pi le driving.

T h e data f r o m c a s e s B6 and B8 show that, when pi les penetrated al ternat ing s t r a t a of fine-grained so i l s and granula r mater ials , the observed sur face heave was much l e s s than the heave that would have occur red in insensitive clay soi ls . In these c a s e s there occur red only about one-fifth the amount of heave that would have been predicted on the bas i s of the p rocedure outlined above for insensitive clay soils.

Effect of Driving Seque~zcc and Foundation Geometry .-The cor re la t ion be- tween normalized so i l heave and volumetric displacement ra t io shown in Fig. 4 was obtainedfor foundations in which the so i l su r face was level everywhere and the pi les were dr iven in fairly regular sequence f rom one end of the foundation to the other. Data f r o m c a s e s A l , A4, and B9 suggest that when la rge differ- ences in elevation exis t within the foundation a r e a , the so i l is lateral ly dis- placed preferent ial ly toward the lower elevations and the so i l heave a t the upper elevations is correspondingly reduced.

Case B2 i l lus t ra tes that if the sequence of pile driving involves f i r s t driving piles along the per imete r of the foundation, thereby tending t o enclose the s o i l in the foundation, the heave of the so i l sur face in the cen t ra l a r e a of the foun- dation i s increased t o a value g r e a t e r thanthat obtained in the procedure out- lined above. Space limitations inconnect ionwithcaseB2 made i t necessary to d r ive H-piles f o r a blast furnace foundation in a horseshoe pat tern f r o m the outside of the a r e a toward the center . P i le heaves of a s much a s 11 in. w e r e observed. Hence, the so i l surface heave must have been equal t o o r g r e a t e r than 11 in.

The piles penetrated fill, s i l t , and sand in addition t o clay. If only the clay s o i l s a r e considered, the total so i l displacement, dis t r ibuted uniformly over the a r e a of the foundation itself, would have produced a sur face heave of about 13 in. Thus, in t e r m s of t h e p a r a m e t e r s in Fig. 4, the ra t io of normalized s o i l su r face heave t o volumetric displacement rat iowasapproximately unity. T h i s ra t io con t ras t s with the data in Fig. 4, wherein the value of the ra t io is on the o r d e r of 0.5. '

In s u m m a r y , i t may be concluded that s o i l displacements of significant magnitude occur when piles a r e dr iven into fine grained, impermeable soi ls . The principle fac tors affecting the magnitude of s o i l displacement in addition t o the charac te r i s t i cs of the subsoil, appear t o be the dr iving sequence of the pi les and the geometry of the foundation.

DISPLACEMENT O F DRIVEN PILES

The following analysis of movements of p i lesa l ready driven caused by sub- sequent dr iving is introduced with a presentat ion of a par t i cu la r c a s e wherein

pi le movements direct ly influenced the overal l succec the foundation construction. d

FIG. 5.-PLAN VIEW O F HOSPITAL FOUNDATION, CASE A1

CLpLI-Sell lo Mmlbm Clay qc :;;tlf

LL,.34% PL,-16% Sacllon A-A

FIG. 6.-SECTION THROUGH FOUNLlATION, CASE A1

Case A1 .-A l a rge s tee l - f rame s t r u c t u r e was constructed on the west s ide of Chicago. The subs t ruc ture consisted of pile-supported f r a m e s beneath r e - inforced concrete walls and columns. A s the s i t e was underlain by a thick

deposit c \ft clay, the structure was designed to be supported on cast-in- place pile. ,hich would penetrate through the soft clay and transmit the weight of the building to f irm strataatdepth. A plan of the structure i s shown in Fig. 5.

The subsoils of the Chicago area have beendescribed in general elsewhere (17).

The ground surface at the si te was located at about El. 13 with respect to Chicago City Datum. The subsoils, a s revealed by the exploratory borings, a r e shown in Fig. 6.

The piles were of a composite typeconsistingof a lower portion of 10-3/4- in. diam steel pipe a t least 15 ft long, and an upper portion of 12-in. diam, 18-

,,&A Day When Molt Ptisr 10 Cluriar Ware Urlvan

FIG. 7.-PILE CLUSTERS IN SOUTIIEASTERN WING O F HOSPITAL FOUNDATION, CASE A1

gage corrugated metal shell. They were driven inclusters of 3 to 16, beneath walls and individual columns, and were spaced a t 3 ft center-to-center, both ways, within the individual clusters. The design load was 40 tons per pile.

The f i rs t phase of construction was excavation of the foundations to the levels shown in Fig. 5. The driving of the composite piles was then begun by four pile-driving figs.

Driving proceeded without apparent difficulties for about 80 days, when it was discovered that some piles had been displaced vertically and laterally from their initial locations. At this time, approximately 80 % of the piles called for in the original foundation design had been driven. Systematic location

and elevation surveys were begun onDay 85and were conductec' 'era1 t imes after the conclusion of pile driving on Day 122. These surve) -fiowed that, in general, the piles stopped moving vertically after al l driving on the job was completed. Some piles continued to move laterally, however, for a s long a s two months. With the exception of the piles in the northern wing of the struc-

boy When Plles

-boy When Most Phles In C l u s t e r Were Driven

Scule 0 2 4 6 8 11 u

FIG. 8.-PILE LOCATION PLAN, CLUSTERS IN SOUTHEASTERN AREA O F FOUN- .DATION. CASE A1

ture, the driven piles were considered unacceptable because of the vertical and lateral displacements they had experienced. Remedial measures were undertaken on Day 178 and continued until Day 407. These measures took several forms: (1) H-piles were driven t'o adjust the position of the centers of gravity of the clusters, o r several pile clusters were tied together with

reinff h concrete beams; (2) individual piles were subjectedto static load 4 of 40 .s o r 50 tons in an effort to test their capacity and to reseat them aL- ., their original elevations; and (3) some c lus ters whichhad been capped before '1 the movement of driven piles was noticed were subjected to reseating loads a s great a s 900 tons.

I

2-b/2 1-1/11 1 .1 /2

.-Heave On Day 119

-Heave On Day 136

I / Z 4 -- - Driving Dale

109

-- Line B '

Scale: 0, f , 11

FIG. 9.-PILE HEAVE IN CLUSTERS C-6 AND C-5, CASE A1

The response of thepiles tothe reseatingloads was rather errat ic; many of the piles did not move, but some piles in the central and southern a r eas of the foundation settled a s much a s 12 in. under 50 tons. All the capped clusters in the elevator pit settled at least 2 in. under 900-ton gross loads.

In only two clusters , B-7 and D-5 (see Figs. 7 and 8), were the elevations

PILE DRIVING

of any piles established before al l the piles in those cluste. _ / e r e driven. In cluster B-7, piles 1,2,3, and 5 were driver. on Day 111 and piles 4, 6, 7, and 8 were driven on Day 112. The elevation of the top of pile 3 was f i r s t established on Day 111, those of piles 4 and 7 on Day 114. The measured changes in eleva- tion of piles 4 and 7 must, therefore, reflect the influence of pile driving after Day 114 along line A. The recorded heave of pile 7 was 1-1/4 in., but zero heave'was recorded for pile 4.

The heave of pile 3 in cluster B-7 reflects principally the influence of pile driving within cluster B-7 and in cluster B-6 and cluster B-5. The measured heave for pile 3,4-3/4 in., didnot represent the total heave of pile 3, however, since pile 5 had beendriven 3 ft away on Day 111, after pile 3 was in place, and almost certainly caused pile 3 to be heaved. The heave of pile 3 caused by driving pile 5 was probably on the order of 1 in. o r less; driving the last 4 piles in cluster B-7 and al l the piles in cluster B-6 caused only 4-3/4 in. of heave of pile 3. The total heave of pile 3 may, therefore, be estimated a s ap- proximately 5-1/2 in.

TABLE 2.-PILE HEAVES, CASE A1

Pile

(1 1

A second cluster in which total pile heave may be estimated i s D-5. The driving sequence along line D was from west to east. Pi les 1 and 2 in cluster D-5 were driven on Day 119and their elevations were determined immediately after they were driven. The remainder of the piles in cluster D-5 and piles 1 and 2 in cluster D-4 were driven on Day 120. Driving on line D was com- pleted on Day 121 with the installation of piles 3 through 9 in cluster D-4.

The elevation of pile 1 in cluster D-5 was checked on Day 121 and the pile was found to have heaved 4-1/8 in., the result of driving piles 3 through 9 within cluster D-5 and a l l the piles incluster D-4. Since pile 2 in cluster D-5 had been driven after pile 1, pile 1 would have been displaced by that driving also. The heave of pile 1 caused by the driving of pile 2 may be estimated a s less than 1 in. because driving the other 7 piles in the cluster produced only about 4 in. of heave of pile 1. The total heave of pile 1 may, therefore, be estimated a s about 5 in.

Thus, the heaves of pile 1 in cluster D-5 and pile 3 in cluster R-7 may be considered typical fo r the southeastern wing of the 'foundation and rnay be realiably estimated a t 5 in. and 5-1/2 in., respectively.

The overall cluster-to-cluster effects of the pile driving a r e evident in the

Increase in pile top e1cv:ktion through Day 120, in incllcs

(2)

Pile

(1 1 7 Increase in pile top e1cv:ktion through Day 120, in incllcs

November, 1971 -

reco heaves of the pi les in c l u s t e r s C-6, C-5, and D-6. Fig. 9 shows th pile hedves which were produced in c l u s t e r s C-6 and C-5 by driving the p i l e y in c lus te r C-4 and in the c lus te rs along l ines B and D. Moreover, in c lus te r 6 C-5 elevation surveys showed a definite set t lement over a 17-day period a f te r !! the initial heave observations. Such set t lement probably occur red in other i '

c lus te rs between the t imes when the pi les were dr iven and when they were 1

subjected to reseat ing loads but was not noticed because of the lack of continued !

extensive elevation surveys. Clus te r D-6, Fig. 8 , dr iven on Day 118 and Day 119, was heaved by adjacent

driving. The elevations of the pi les on c lus te r D-6 w e r e established f i r s t on !

Day 118 o r Day 119, immediately a f te r they w e r e driven, and w e r e checked on day 120, Day 121, and Day 136. T h e check survey on Day 120 indicated that the pi les had heaved by the amounts shown in Table 2.

Measurements w e r e a l s o made of the l a te ra l movement of var ious pi les on this project. T h e locations of the piles w e r e not established, however, until

.-Survey On Ooy 122

3 . 0 3 ' 3.20/,

7 2.99 - ---- 1 3 . 2 8 - I -Survey On Ooy 132

! -Pule Number

N 0 r-.(+.-@r-o*+:%;!?del 0, 3 '"7 0 m

I < T ' U - , -

- -- .L ..,. . - .. - C .-

A l l Oarloncer In Feel

FIG. 10.-LATERAL hlOVEFvIENTS OF PILES IN CLUSTER A7. CASE A1

a l l the pi les within a c lus te r had been driven. Fig. 10 shows movements in cluster A-7 which was the las t c lus te r in i t s vicinity t o be driven. The pi les within c l u s t e r , A-7 continued to move lateral ly a s much a s 1 in. f o r a s long a s th ree days a f t e r they were driven. The pi les were a l s o probably displaced during within-cluster driving, mos t likely away f r o m subsequent driving within the c lus te r , but no data a r e available concerning the magnitudes of such movements.

Fig. 11 shows the movements of the cen te rs of gravi ty of the c lus te rs in the southeastern wing of t h e s t r u c t u r e betweentheday on which the i r locations were f i r s t determined and Day 133. It is apparent that: (1) The magnitude of movement shown f o r any c lus te r is direct ly related to the number and proxim-

j ity of piles dr iven a f te r the f i r s t locat ionsurvey f o r that c lus te r ; (2) c l u s t e r s continued t o move f o r s o m e t ime a f te r driving had ceased i n the immediate

I I vicinity; and (3) the direct ions of pile movement s e e m t o have been governed I 1

PILE DRIVING

pr imar i ly by the location of subsequent driving. Many of the c l u s t e r s i n the cen t ra l a r e a of the f o u n d a m n s a l s o moved

lateral ly a f te r a l l nearby driving had ceased. These include the c lus te rs adja- cent t o the construction s lope which descended f r o m El. 8 to El. 0 (Fig. 5); c lus te r H-15, c lus te r 1-15, and c lus te r 5-15. ClusterH-15 was dr iven on Day 20, c lus te r 1-15 on Day 27, and c lus te r 5-15 on Day 29. The f i r s t location s u r - veys w e r e conducted on Days 25, 59, and38 f o r c lus te rs 5-15, 1-15, and H-15, respectively. These f i r s t su rveys showed that noc lus te r of the th ree was dis- placed more than 1 in. f r o m i t s design location. Then, between the days when the f i r s t su rveys were conducted and Day 83, a l l th ree c l u s t e r s moved toward the eas t even though no construction activity took place nearby during that time. Clus te r H-15 moved 17 in.; cluster1-15moved 24 in.; and c lus te r 5-15

L o s . , ~ on S v n "

DO" P11.l w.r. Dr1r.n

FIG. I%.-LATERAL MOVEMENTS OF PILE CLUSTERS, CASE A1

moved 15 in. La te r location surveys showed that these c l u s t e r s continued t o move until about Day 114, approximately 60 days a f te r a l l the pile driving i n that a r e a had been completed.

ANALYSIS O F CASE

Effect on Soil Characteristics.-The effects of pile driving on the s t rength of the clay a t this s i t e and the p r o g r e s s of subsequent consolidation within the pile c lus te rs have been discussed elsewhere (15,21,22). At many of the c lus te rs , i t i s evident that the soft clay had anopportunity to consolidate appreciably during the interval between pi le driving and reseat ing operations.

November, 1971 PILE DRIVING

E'fecc Pi le Type.-The magnitudes of ground and pi le heave were la rge because the pi les were of a type associatedwith high displacements. The heave

2

was especially s e r i o u s because of the s l i p joint between pi le sections. The ;i s l i p joint allowed concreted piles t o elongate a t the point because the tensile : i s t rength of the concrete was not sufficient to r e s i s t the upward pull of the s o i l : : on the shel l sections. If the 28-day s trength of the concrete had been equal t o ' I 3,000 psi, the tensi le capacity of the cured plain concrete a t the s l i p joint ,

would have been about 14 tons. The n ~ i n i m u m p u l l of the soft clay (completely remolded) along the she l l sect ions may be est imated as about 13 tons. Since a t least one day elapsed between driving and concreting the piles, the s t rength of the clay was g r e a t e r than the remolded s trength and the upward pull on the pile shel ls was undoubtedly g r e a t e r than 14 tons. The lower pipe sect ions of the piles remained s tat ionary s ince they probably developed a frictional r e - s is tance of a t least 15 tons in the hard clays and compact s i l ts .

Effects of Fortndntion Geometry.-Grouping of ~ i l e s in c l u s t e r s caused a buildup of s t r e s s i n the so i l a t the location of the clusters . Thus, a f te r being driven, the pi les within a c lus te r had a tendency t o move lateral ly outward f rom the cen te r of the c lus te r f o r s e v e r a l weeks a s s t r e s s relaxation took place within the soil. If the pi les had been driven a t a uniform spacing through- out the foundation a r e a , the s t r e s s e s produced by pile driving would have been r a t h e r uniform throughout the a r e a and there would have been no reason to expect fur ther so i l movement.

The existence of t h r e e levels of excavat ioninthe foundation a l s o had a n ef- fect upon the movement of the dr iven piles. In many instances, so i l was dis- placed during driving toward the open a r e a of a nearby excavation, and previously dr iven pi les were displaced in the s a m e direction. F o r instance, the location surveys conducted a f te r Day 80 showed that many pi les near the construction s lopes were displaced toward the lower excavation levels during driving. The different excavation leve l s a l s o led to delayed movements of the so i l and the piles.

The general sequence of construction operations hadanimpor tan t influence on so i l and pile aovement . Initially, t h r e e p i l e d r i v e r s were positioned in the western extremit ies of the excavation and driving proceeded eastward toward the cen t ra l a r e a of the foundation. Driven pi les were displaced t o the west, away f r 31 the cen t ra l a r e a , by the subsequent driving. The combined effects on pile movements of foundation geometry and pile driving sequence may be deduced f r o m the behavior of the pile c l u s t e r s along row 15, mentioned pre - viously. The piles along row 15, dr iven a f te r a l l the pi les to the west of that row were in place, moved eas t toward the lower excavation levels a s they w e r e driven. Then wh,en the pi les a t the lower level along rows 13 and 12 were driven, between Day 41 and Day 57, the pi les along row 1 5 were displaced to the west away f r o m the slope. The initial eastward and l a t e r westward move- ments produced litt le net displacement of the row-15 c lus te rs . The location surveys showed only smalldisplacement a s of about Day 59. After a l l the pi les i n the cen t ra l a r e a w e r e driven, no fur ther changes in the s o i l s t r e s s e s were created. After about Day 60 there existed l a r g e r l a te ra l f o r c e s in the so i l t o the west of row 15 than in the so i l to the eas t of that row because the pi les to the west penetrated a g r e a t e r depth of s o i l than did the pi les t o the east . The unbalanced applied forces in the so i l produced c r e e p movements toward the lower foundation level. The so i l c a r r i e d the pi les toward the eas t in agree- ment with the measured displacements f o r c lus te rs 5-15, H-15, and 1-15.

Bordng No. 4

1 ,- ---

5 .r1'""5'd B!!dQ.-. _ - . .. . I-- . - -- - - - - I L-- -- 7--' Baring No. 3

Boring No. I

Plan - ------I r - - - - 7

S t i f f Clay q,f 1.8 1st

I

... El. 300 - Shal l

A

I

-- --

Cloy , Er ra t ic Conslrtency

-

Elevation O 50' 100' - Hard Clay q,= 4 - 8 I r f

4 0 0

Very S t i f f Cloy qu= 2 -6 1st

E l . 4 5 0 S t t f f Clay q,, : 2 0 1st

I

FIG. 12.-SOIL PROFILE ALONG CENTER LINE O F B R D G E , CASE A2

El. 350

FIG. 13.-BALANCE O F FORCES ON PILE

~ u m m a q Case.-(1) Pi lc heaves of 5 in. o r more were produced by driving c l rs of closely-spaced displacement pi les into a deposit of soft clay overl-6 hard clay and compact s i l t ; (2) the soft clay acted a s an in- compressible mate r ia l in the lnlrnediate vicinity of any one pile c lus te r during the few days required l o r driving the pi les in that c lus te r ; (3) the pi les in a cluster heaved during driving within that c l u s t e r andduring driving of adjacent c lus te rs ; (4) the pi les moved 1;lterally away f rom a r e a s of subsequent driving during and f o r s o m e t ime a f te r driving; and (5) different excavation levels within the foundation a l s o influenced the amount and direct ion of the l a te ra l movement.

A con~prehens ive analysis 01 pile heave problems a t another s i t e is con- tained in Fig. 8 (corresponding i r ~ this study to c a s e Bl) .

ESTIMATE O F PILE HEAVE

Pi le heave data f r o m nine other c a s e h i s to r ies support the observations made in the preceding summary . However, i n only two other cases , A2, and

rould exceed that of the surrounding so i l a t that level. m here fore,? wer half of the pile would be acted on by downward forces tending tc uce the total uplift of the pile. If the consistency of the so i l va r ies with de4, a s u r - f

face a-a, Fig. 13, may be found a t which the relative movement between s o i l

I! and pile i s zero. AS anapproximation, the pile heave may be considered rough- ,

f! ly equal t o the heave of the so i l on the assumption that no heave takes place ; below a-a. T h e depth, dl is est imated by balancing the potential upward and : I downward adhesive f o r c e s on the upper and lower p a r t s of the pile, respectively. ) f The procedure i s i l lustrated f o r c a s e A2. The soil-pile adhesion is est i -

mated on the b a s i s of the relationship between so i l cohesion and soil-pile 1 adhesion proposed by Tomlinson (25). The estimated adhesionvalues a r e given

in Table 3. F o r these assumed relat ive adhesion values, the upward pull on the upper

I part of the 140-ft pi les would equal the resis tance t o movement of the r e - ; maining lower p a r t f o r a depth of about 73 f t t o the sur face of z e r o relat ive , displacement, i l lustrated a s follows:

Upward Pull TABLE 3.-ES'I'IMA'I'ED ADIIESION VALUES

Avert1 r:o Tomlinson cohesior~, in adhesion, in adhcsion per

square foot foot of pile square foot (1 1 (21 (3) (4 (5 1 (6)

Stiff clay C 1 1,800 0.75 1,350 1.35 A Very stiff clay C2 3,000 0.50 1,500 1.50 A Stiff clay C 3 2.000 0.70 1,400 1.40 A Hard clay C4 4,000 0.40 1,600 1.60 A

TABLE 4.-PII.1: HEAVES, CASES A l , A2, 07

Estimated rn:utimum Observed maimurn pile heave. In inches pile heave, in inches

(3)

B7, a r e comprehensive data available. Fig. 12 shows, f o r c a s e A2, the plan and elevation of a bridge foundation. T h e pile heave in the center of the excavation f o r each p i e r was approximately 24 in., and the so i l su r face heave was approximately 50 in. Case B7 h a s been described extensively elsewhere (1,2).

In a uniformly: heaving m a s s of c lay the upward movement would vary linearly with dis tance above the base of the clay, Inextensible vert ical pi les embedded in the clay would be lifted by the relat ive r i s e of the soi l with respect to the upper par t of the pile, but the r i s e of the lower par t of the pile

Resis tance to Movement

65 ft of soil C 1 22 ft of soil C2 i~ 65 X 1.35A = 88 A 22 X 1.50A = 33 A

8 ft of soil- C2 30 ft of soi l C3 8 X 1.50 A = 1 2 A 30 x 1.40A = 4 2 A

1 5 ft of so i l C4 To ta 1 100 A 15 x 1.60 A = 24 A

Total 99 A

The pile heave is then est imated a s about (140 - 73)/140 t i m e s the total s o i l - heave, o r about 24 in. The est imated maximum pile heave is approximately equal t o the observed pile heaves n e a r the cen te r of the foundation. F o r c a s e s A1 and B7 the maximum pile heave may be est imated in the s - m e way. Table 4 shows the r e s u l t s of such es t imates and furnishes a comparison with ob- served pile heaves.

The close agreement of the values shown i n Table 4 is fortuitous, but it would appear that the procedure i s reasonable. I t s h o u i ~ be applied only if the piles a r e t o be d r i v e n i n a r a t h e r regu la r manner f r o m one s ide of a foundation to the opposite side. A driving sequencewhich tends t o confine the so i l o r r e - s t r ic t i t s movement t o a ce r ta in direct ion may cause g r e a t e r so i l heave in certain a r e a s of a foundation than would be predicted on the bas i s of the pro- cedure, a s demonstrated by c a s e B2. The procedure should not be used if the soil may d e c r e a s e in volume significantly during driving. F o r example, in case B6 (5,32,33) the densification of granular l a y e r s during pile driving probably reduced s o i l heave, and the densifying s t r a t a a l s o acted to hold down driven piles. The average pile heave was approximately equal to 1/10 of the observed so i l heave a t this site.

In severa l o ther c a s e s the action of a v e r y stiff o r s t rong s t ra tum near the Pile tip in holding down the pi les against upward pull of heaving upper so i l s - Was apparent. Obviously, the efficacy of such holding s o i l s depends upon the character is t ics of the pi les themselves. In c a s e A3, inextensible pipe pi les

were effec*' 9 held down by a weathered rock zone into which their tips pene- trated, aL t the upward pull of heaving overlying s i l ty c lays and clayey s i l ts . -

CONCLUSIONS

1. Significant so i l displacement occurs during pi le dr iving i n fine grained so i l deposits. Saturated insensitive clay s o i l s behave incompressibly during pile driving.

2. At four s i t e s where pi les were dr iven into such clay soils, approximately half the volunle of displaced soil appeared a s sur face heave within the a r e a of the pile foundation while the remaining half a p p e a r e d a s sur face heave outside the foundation a rea .

3. Given the conditions of a saturated, insensitive clay subsoil, a regular pile driving sequence, and a level foundation ground surface, the normalized so i l surface heave within the foundation a r e a may be est imated a s half the volumetric displacement rat io f o r the s i te .

4. When pi les a r e dr iven into sensi t ive clays, the resul tant so i l displace- ment, especially beyond the l imits of the a r e a enclosed by the p i les themselves, may be l e s s than that produced during driving in insensitive clays. Remolded so i l may be extruded around the pile a t the ground surface.

5. When piles penetrate alternating s t r a t a of fine-grained so i land granular mater ials , the observed surface heave may be much l e s s than that which would have occurred in insensitive clay soils.

6. When la rge differences in elevation exist within the foundation a rea , pile driving may displace the so i l la teral ly preferent ial ly toward the a r e a s i n which the lower elevations occur. The movements maycontinuefor some t ime a f te r driving has ceased.

7. If the sequence of pile driving involves driving p i les f i r s t along the pe- r i m e t e r of the foundation, the heave of the so i l su r face i n the cen t ra l a r e a of the foundation is increased and that of the surrounding a r e a correspondingly decreased.

8. The magnitude of the dile heave in a foundation, which differs f rom the heave of the ground surface, may be est imated by a s imple procedure. P i le heaves estimated by this procedure a g r e e quite well with the values observed.

9. Lateral move] ents of so i l and pi les may occur during pile driving and for a considerable length of t ime thereafter . In general, dr iven pi les tend to be displaced away f rom subsequent driving.

I. Avery. S. B.. and Wilson, S . D., discussion of "Effect of Driving Piles into Soft Clay," by Cummings. et al., Tr?n.racrions, ASCE, Vol. 1 15, 1950, pp. 322-331.

2.Casagrande. Arthur. "The Pile Foundation for the New John Hancock Building in Boston," Joirrnol. Boston Society of Civil Engineers, Vol. 34, No. 4. Oct., 1947.

3.Cumrnings. A . E.. Kerkhoff, G. 0 . . and Peck, R. B.. "Effect of Driving Piles Into Soft Clay," Trr i t tsu~i iot i~ . ASCE. VJI. l IS. 1950, pp. 275 285.

3 Hokugo. Hisash,. "Observation of Soil Movement Due to Y~le Dr~v~ng," B u r l d ~ t ~ ,a9 itrg News. Nippon Telegraph and Telephone Public Corporation (in Japaneie). 1964. ',

-T' 5. Holtz. W. G.. and 1-owitz. C. A.. "Effects of Driving Displacement Piles in ~ e a n d v . " Jorrr- '?

. - no1 o/ rhe soi l Mechanics and Foundarions ~)ivisioti. A ~ E . Vol. 91, No. SMS. Yric. Paper 4476. S ~ p t . , 1965. pp. 1-13.

: 6. Ireland, El. O., "Settlement Due to Building Construction in Chicago." thesis presented to the University of Illinois, a t Urbana, Ill., in 1955, in p;~rtial fulfillment of the requirements for the degree of Doctor of Philosophy.

7. Kerisel. J.. "Fondations profondes en milieu sableux." Proceedings. 5th International Con- ference on Soil Mechanics and Foundations Engineering. Vol. 2. 1961.

8. Klohn, Earle J., "Pile Heave and Redriving." Transactio~u. ASCE, Vol. 128. 1963, pp. 557- 577.

9. Koizumi, Yasunori, and Ito, Kojiro. "Field.Tests with Regard to Pile Driving and Bearing Capacity of Piled Foundations," Soil and Formdarion, (Japanese Society of Soil Mechanics and Foundation Engineering. Vol. VII, No. 3, August 1967.

10. Lambe, T. W.. and Horn, H. M., "The Influence on an Adjacent Building of Pile Driving for the M.I.T. Materials Center," Proceedings, 6th International Conference of Soil Mechanics and Foundations Engineering, 1965, Vol. 2, pp. 280-284.

I I . Legget. R. F., discussion of "Effect of Driving Piles into Soft Clay," by Cummings, et al., Transacriom, ASCE, Vol. l 15, 1950, pp. 319-322.

12. Meyerhof. G . G., "Compaction of Sands and Bearing Capacity of Piles." Jorirnal o/ rhe Soil Mechanics and Forrndarions Division. ASCE. Vol. 85, No. SM6. Proc. Paper, pp. 1-29.

13. Olko. S . M.. discussion of "Pole Heave and Redriving," by Klohn, Tronsacrions. ASCE. Vol. 128, 1963, pp. 578--587.

14. Orrje, 0 . . and Broms. B.. "Effects of Pile Driving on Soil Properties." Proceedings. ASCE, Vol. 93, 1967, No. SM5, Proc. Paper5415, Sept., 1967, pp. 59-73.

IS. Parsons, J . D., and Peck, R. B., discussion of "The Action of Soft Clay Along Friction Piles," by Seed and Reese, Tramacrions. ASCE, Voi. 122. 1957, p. 758.

16. Peck, Ralph B.. Lecture notes on "Problems of Installation," for Seminar on Proh1en1.r in the Evoluarion oJPile Foutrdarions. Metropolitan Section. ASCE, New York, 1966.

17. Peck, R. 0.. and Reed, W. C., "Engineering Properties of Chicago Subsoil," University of Illinois Engineering Experiment Station Bulletin N o . 423, Urbana, Illinois. 1954.

18. Peck, Ralph B.. and Berman. S . . "Recent Practice for Foundations of High Buildings in Chi- cago," The Design o j High Building. Symposium, University of Hong Kong, Golden Jubilee Congress. Sept., 1961.

19. Plantema. G., and Nolet, C. A., "Influence of Pile Driving on the Sounding Resistance in a Deep Sand Layer." Proceedings. 4th International Conference on Soil Mechanics and Founda- tions Engineering, Vol. 2, 1957.

20. Reese. L. C., and Seed, ti. B., "Pressure Distribution Along Friction Piles," Proceedings. American Society for Testing and Materials, Vol. 55, 1955, pp. 1156-1 182.

21. Rutledge, P. C., Soil Mechanics Fact Finding Survey Progress Report, U.S. Waterways Exper- iment Station, 1947.

22. Rutledge, P. C., discussion of "Effect o f Driving Piles Into Soft Clays." by Cummings, et al.. Trimsactiom, ASCE, Vol. 115, 1950, pp. 301-304.

23. Seed. H. B. and Reese, L. C., "The Action of Soft Clay Along Friction Piles," Trun.tuc.rions. ASCE. Vul. 122, 1957, pp. 73 1-754.

24. Thornlcy. J. H.. "The Mystery of the Restless Substratum," Engineeririg Newr-Record. hlarch 19. 1953.

25.Tomlinson. M. J. , "The Adhesion of Pile Driven in Clay Soils," Proceedings. 4th Internation- al Conference on Soil Mechanics and Foundations Engineering, 1957, Vol. 2, pp. 66-7 1 .

26. Vargas, M., "Pruebas y Observaciones de Compo Relativas a 10s Cimientos Profundos," Pro- ceedings. Congreso Solere Cimientos Profundo>. Mexico C ~ t y , 1964. pp. 573--575.

?7."Examensarbete I Geoteknik" "1963- 1964" Institution 1'0i Geoteknik Kungl. Tekniska ttijg- skolan.

?g."Keport of Pile Testing Program for Willard Pumping Plants No. I and 2 Weber Basin Proj- ect. Utah." Earrh 1.ahorurory Ri,porr Mo. Edf-622. Div. of Engrg. ~ a b o r a t o r i e s U.S. Dept. of the Interior, Bureau of Reclamation, 1961.

.""U A..'. L..."...' , ." . - -..- - .w

29. "Pile Sul d Structures in Lake Deposits," IYarrr Rcso~rrces Teclrnicol Publicarions Re- seurch Rrc. _ _ (Vo. I ! . U.S. Dept. of the Intcriot, Bureau of Reclamation. 1968.

30. Zeevacrt. L., "An Investigation of llle I'nginecring Characteristics of the Volcanic Lacustrine Clay Deposit Beneath Mexico City." tl~esis presented to the University of Illinois, at Urbana, I l l . . in 1949, in partial fulfnllrlrent of t l ~ requirements for the dcgree of Doctor of Philosophy.

31. Zeevaert. L.. discussjon of "Effect of Driving Piles into Soft Clay." by Cummings. et al., 'f'rrltrvrrcriofrs, ASCE, VuI. 1 IS. 1950. 11p. 286-292.

November, 1971

Y

!I- I! Journal of the

'I SOIL MECIfANICS AND FOUNDATIONS DIVISION ,

Proceedings of the American Society of Civil Engineers

SCALE AND BOUNDARY EFFECTS IN FOUNDATION ANALYSIS

By J a m e s Graham' and John Gordon Stuart2

INTRODUCTION

Although much experimental and theoret ical effort has recent ly gone into investigation of the fai lure loads of footings placed initially on the sur face of uniformly dense sand, there a r e s t i l l s o m e features which requi re fur ther attention. In the f i r s t place, most cur ren t theories u s e contact s t r e s s and friction assumptions whichproduce sharply discontinuous v e r t i c a l s t r e s s dis- tributions a t the center of the footing base. Secondly, the fai lure loads of model footings a r e strongly influenced by the set t lements which a r e required to mobilize the full s h e a r s t rength in the fai lure zones. T h i s i s usually t reated enlpirically by superposition of solutions obtained separa te ly for z e r o s u r - charge and for z e r o self-weight. Finally, althou,h it i s usually possible to obtain f a i r agreement between theoretical and laboratory r e s u l t s by using triaxial t es t s to descr ibe the average s h e a r s t rength of the sand, it i s generally accepted that model t es t s overest imate '+e bearing capacity of full sca le footings by an undetermined amount. Density changes observed beneath model foundations (15) show that the so i l s t reng th var ies considerably in fai lure zones, and the usual assumption of constant angle of shear ing res i s tance i s therefore a major simplification of sand behavior.

Solutions to the smooth footing problem using the numerical techniques of plasticity analysis have been presented by, e.g., Sokolovskii (20) and Larkin (14). In pract ice, however, footings a r e not perfectly smooth and the influence on bearing capacity of s h e a r s t r e s s e s n ~ o b i l i z e d a c r o s s the base of the footing has been outlined by Gorbunov-Possadov(S), Hansen and Chris tensen (1 I ) , and Karafiath (13). T h e purpose of this paper i s to examine the effects of various

Note.-Discussion open until April 1, 1972. T o extend t h e closing date one month, a written request must be filed with the Executive Di rec tor , ASCE. This paper is par t of the copyrighted Journal of the Soil hZechmics and Foundations Division, Proceedings of the American Society of Civil Engineers. Vol. 97, No. S h l l l . November, 1971. Manu- Script was submitted for review for possible putdication'on March 26, 1971. ' Lecturer , Dept. of Civ. Engrg., Queen's Univ., Belfast, Northern lrcland.

Sr . Lec turer , Dept. of Civ. En@-g., Queen's Univ., Belfast. Northern Ireland.