TxDOT In-House SS 25.1

A STUDY OF DRILLED SHAFTS CONSTRUCTED BY THE SLURRY

DISPLACEMENT METHOD

BRIDGE DIVISION TEXAS HIGHWAY DEPARTMENT

February 1973

A STUDY OF DRILLED SHAFTS CONSTRUCTED BY THE SLURRY

DISPLACEMENT METHOD

by

H. D. Butler Senior Designing Engineer

Conducted by

Bridge Division Texas Highway Department

in cooperation with the United States Department of Transportation

Federal Highway Administration

The op~n~ons, findings, and conclusions expressed in this publication are those of the author and not

necessarily those of the Federal Highway Administration.

TABLE OF CONTENTS Page No.

PREFACE • • • • • • • • ABSTRACT ••••••••• LIST OF FIGURES AND TABLES

· . . • • • • • •

· . . . . . . · . . . . . . · . . . . . . CHAPTER I.

CHAPTER II.

CHAPTER III.

CHAPTER IV.

CHAPTER V.

CHAPTER VI ..

CHAPTER VII.

INTRODUCTION • . . • • • • • 1

DESCRIPTION OF TEST SITES • • • 4 Location • • • .. • • • • • • • • 4 Soil Exploration • • • • • • • .. 4 Shear Strength Profiles •••• 6

TEST SYSTEMS • • • · . . . . . . Test Shafts · . . . . . . . . . Reaction System Loading System • Instrumentation

· . . . . . . . · . . . . . · . . . . . . . Data Acquisition • • • · . · . ..

CONSTRUCTION OF TEST SHAFTS. • •

10 10 10 12 12 17

19 Equipment. • • • • • • • • • •• 19 Site G2. • • • • • • • • • • •• 19 Site G1 •••• 0 • • • • • • •• 22 Site BB. • • • • • • • • •• 24 Concrete Placement • • · . . LOAD TESTS •• . . . . · . . . . EXTRACTION AND INSPECTION · . . Shaft Gl Shaft G2 • Shaft BB •

• Q • • • • • • • • • . . . . . . . . . . . BOND TESTS .. · . · .. .. . .. .. .. .

25

31

41 41 45 46

52

CHAPTER VIII. CONCLUSIONS AND RECOMMENDATIONS. 55

CHAPTER IX. IMPLEMENTATION • · . . . . . . . 58

APPENDIX A DETERMINATION OF SOIL REDUCTION FACTOR · .. . · . . . . 59

Page No.

APPENDIX B BORING LOGS. • • . . . • • • · · 64

APPENDIX C PLOTS OF ACCUMULATED SOIL SHEAR STRENGTHS. . • . • .. • · · 71

APPENDIX D SPECIAL PROVISION TO ITEM 416 (416---002) OF TEXAS HIGHWAY DEPARTMENT STANDARD SPECIFICATIONS.z 1972. • • 0 • • 78

ii

Figure No.

2.1

2.2

2.3

2.4

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

4.1

4.2

4 .. 3

4.4

4.5

5.1

5.2

5.3

LIST OF FIGURES AND TABLES

Location of Test Sites

Shear Strength Profile for Site Gl

Shear Strength Profile for Site G2

Shear Strength Profile for Site BB

Details of Anchor Shafts and Test Shafts

Details of Reaction Beam and Anchor Posts

Reaction System

Loading System

Soil Profiles and Location of Shaft Instrumentation

Mustran Cell Attached to Reinforcing Steel

Settlement Gage

Honeywell Data Logging System

Clean-Out Bucket

Tremie Guide

Installing Temporary Tremie Seal

Concrete Placing Operation

Drilling Slurry Being Displaced by Fluid Concrete

Load-Settlement Curves, Shaft Gl

Load-Settlement Curves, Shaft G2

Load-Settlement Curves, Shaft BB

iii

Page No.

5

7

8

9

11

13

14

14

15

16

16

18

21

26

28

29

30

35

36

37

LIST OF FIGURES AND TABLES

Figure No. Page No.

5.4 Load Distribution Curves, Shaft Gl, Test No. 1 38

5.5 Load Distribution Curves, Shaft G2, Test No. 1 39

5.6 Load Distribution Curves, Shaft BB, Test No. 1 40

6.1 Drilling Around Shaft Prior to Extraction 43

6.2 Lifting Device in Place 43

6.3 Removal Shaft 44

6.4 Inspection Shaft 45

6.5 Tip of Shaft Gl 48

6.6 Shaft Gl 48

6.7 Tip of Shaft G2 49

6.8 Shaft G2 49

6.9 Close-up of Shaft G2 50

6.10 Tip of Shaft BB 50

6.11 Shaft BB 51

iv

Table No.

5.1

5.2

A.l

A.2

Dates and General Information on Load Tests

Percent of Applied Load Carried by Frictional Resistance

Frictional Load Transfer and SR Values For Test Sites Gl, G2, and BB

Frictional Load Transfer and SR Values For Load Tests at SH 225 Site Located Approximately 2.5 Miles East of Sites Gl and G2.

v

Page No.

33

34

62

63

PREFACE

This report presents a detailed description of all work

done relative to the construction and test loading of three

drilled shafts constructed in Houston, Texas, using a

"slurry displacement" method of construction. It is hoped

that the information contained herein will be useful to

others who choose to use this method for drilled shaft con­

struction.

This report is the result of the combined efforts of

many people. The design and construction of the test

shafts were under the general supervision of Mr. A. C. Kyser,

former Engineer-Manager of the Houston Urban Office. The

design work was supervised by Mr. W. V. Ward and construc­

tion was supervised by Mr. R. A. Vansickle and Mr. F. W. Geron.

The soils investigations and load tests were under the super­

vision of Mr. G. P. Berthelot. Mr. Horace Hoy made signifi­

cant contributions toward developing and implementing the

design procedures which resulted from these tests.

Major contributions were made by Professor L. C. Reese

and Mr. Fadlo Touma of the University of Texas Center for

Highway Research. They were responsible for constructing

and installing the instrumentation, collecting and analyzing

the test data, and reporting the results to the Texas Highway

vi

Department. Much of the material in this report was taken

from that reported to the Texas Highway Department by

Messrs. Reese and Touma and from field notes taken on the

job by Mr. Touma.

Farmer Foundation Co. of Houston, Texas, was the

contractor for this work and the fine cooperation of

Mr. Glyen Farmer and his personnel is greatly appreciated.

vii

ABSTRACT

A "slurry disp1acement ll method for constructing drilled

shafts in water bearing and/or caving soils without the use

of casing was proposed by foundation drilling contractors

for use in the Houston~ Texas area. This is a method

whereby the sides of the excavation are supported by a mud

slurry which is subsequently displaced by the fluid concrete

that forms the completed drilled shaft. Three instrumented

full-size shafts were constructed in Houston to evaluate

this method of construction. The shafts were then test

loaded to determine the maximum load capacity and load trans­

fer characteristics of each shaft. Upon completion of the

load tests~ the shafts were removed from the ground~ in­

spected~ and pull-out tests performed on two reinforcing

bars.

Results of the tests and inspections performed indicate

the following:

1. Drilled shafts can safely be constructed

using the "slurry displacement" method of

construction.

2. For the design of drilled shafts in the

Houston area, it can safely be assumed that

the shear strength developed is 0.7 times

viii

the shear strength of the soil as determined

from Triaxial and/or THD Cone Penetrometer

Tests.

3. A significant portion of the load applied to

a drilled shaft is transferred to the sur­

rounding soil through skin friction: 88% for

shaft Gl, 95% for shaft G2, and 61% for shaft

BB.

4. The frictional load capacity of drilled shafts

constructed in the Houston area is independent

of the construction method used.

ix

CHAPTER I

INTRODUCTION

The use of drilled shafts as foundations for highway

structures has experienced a rapid and unprecedented growth

during the past two decades. Through several years experi­

ence, the Texas Highway Department has demonstrated that

the use of drilled shafts offers a significant economic

advantage over the use of driven piles in soils where holes

can be drilled without the use of specialized drilling

techniques. These soils, generally referred to as well­

behaved soils, are mostly stiff clays, shales, and cemented

sands.

Results of a comprehensive research study of the load

transfer characteristics of drilled shafts, Research Study

No. 3-5-65-89, revealed that further economic benefits could

be realized through utilization of the ability of a drilled

shaft to transfer load to the surrounding soil by skin

friction as well as through point bearing. This resulted

in two major benefits: (1) the belled footings required for

point bearing design can be eliminated in many cases, and

(2) drilled shafts may be used in areas where soil conditions

are not suitable for drilling and therefore require the use

of driven piles.

Early in 1971, the Texas Highway Department began in­

vestigating the feasibility of using straight drilled shafts

in other soils, not so well-behaved, such as sands, silts,

and soft clays. One promising method suggested by Houston

area foundation contractors for constructing shafts in

these materials was a "slurry displacement" method. This

is a construction method whereby the sides of the excava­

tion are supported by a mud slurry which is subsequently

displaced by the fluid concrete that forms the completed

drilled shaft. Similar methods have been used in the

United States to construct cofferdams, retaining walls, and

building foundations.

A series of load tests on full-size shafts constructed

by the "slurry displacement" method was planned to evaluate

the method. Specific objectives of the tests were as

follows:

1. Verify the calculated load capacity for

straight shafts constructed by this method.

2. Obtain information necessary for the prep­

aration of construction specifications for

this method.

3. Establish a relationship between the measured

frictional load capacity of a shaft constructed

2

by this method and the frictional load

capacity calculated from soils data.

The test shafts were to be loaded to failure and then ex­

tracted from the ground for inspection.

Methods for instrumenting drilled shafts were developed

by the Center for Highway Research of the University of Texas

as a part of Research Study No. 3-5-65-89. Through an Inter­

agency Cooperation Contract the Center for Highway Research

furnished personnel under the supervision of Professor

L. C. Reese to fabricate and install instrumentation in

the three test shafts, collect data during load tests,

analyze the data, and report the results to the Texas High­

way Department.

A contract was awarded Farmer Foundation Co. of

Houston, Texas in July, 1971, for construction of the

three test systems and extraction of the test shafts after

all load tests were completed.

3

Location

CHAPTER II

DESCRIPTION OF TEST SITES

Three locations in Houston, Texas, were selected for

the construction of the test shafts (Fig. 2.1). Two of

these sites, Gland G 2, are located in the area of a

proposed interchange at the intersection of Interstate

Highways 45 and 610 (South Loop). The third site, BE, is

located on the north bank of Brays Bayou at the proposed

crossing of State High·t.1ay 288. These sites were chosen

because soil conditions prohibited the use of drilled shafts

designed to carry load in point bearing only_ Successful

completion of these tests would permit the use of straight

drilled shafts rather than the more expensive driven piles.

Furthermore, the caving conditio:1s expected at these sites

would provide a good test for the "slurry displacement"

method of construction.

Soil E~loration

Three test borings were drilled very near the location

of the test shafts. THO cone penetrometer data were taken

from one ho1er undisturbed samples for triaxial testing,

supplemented by THO cone penetro~eter data, were taken

in one hole" and standard penetration tests were run in

4

N

610

,-0 nG [W=====-ROSEN6E" __

Figure 2.1. . f Test Sites Locat1on 0

5

the other hole for other work being done at the University

of Texas Center for Highway Research. Appendix B contains

the boring logs for the holes drilled for the THD cone

penetroml'9ter and triaxial tests, the two methods presently

used by the Texas Highway Department.

Shear Strength Profiles

Profiles of shear stren9th were develop.2d for each

test site using soils data obtained from triaxial tests

and/or THD cone penetration tests. Th2se profiles are

shm-om plotted in Figures 2.2 - 2.4.

6

.j..l 4-1

..c;

.j..l 0.. OJ

o

10

20

30

40

Q 50

60

70

80

o Shear Strength (tons/sq ft)

1 0 1 5 2.0

~-----.,.. .­

< .... ..... -­.--...:::----

<

.--

---,-- :-.:;>

<:;:. ---THD Penetrometer Test

.-'

<.'­-- --- ---

Triaxial Test Supplemented by THD Penetrometer Test

... '" < ...... -...... --- .....

-----<.---- -~~ -- ~-

'-. , >

\ \

-)

Figure 2.2. Shear Strength Profile for Site G 1

.. .. -. .. " . . .. "' .... · . , " ., .... .. .. : I •

: : .f

.. " . '" .... iii·

.' · .. , .... .. , . ..... .. ..

t."' ..

......... .,: ....

".. . ... ". ,,, .. . ' . .. ...".

. . . . . . · ." :

· '.

· " ., . ·

7

o

10

20

30

40

50

60

70

80

~­<:---- ---

".----

---

-,. <

-:--..:.-::.-

...... , , , )

~-\

.... __ -.J '-- ------:..-"'-----

-> <-... --;>

,,) (

Shear Strength (tons/sq ft)

2.0 2.5

<J THD Penetrometer Test '>

----:;::"> ----l-:~aXia 1 Te s t S upplemen ted ott::...-.. __ _

--I by THD Penetrometer Test

-- ---:. -::-----,-----90 ~ ______ U_ ______ L_ ______ ~ ______ ~~ ____ ~ ______ ~ ____ ~

Figure 2.3. Shear Strength Profile for Site G 2

8

Shear Strength (tons/sq ft)

1

10

20 ..........

....... _-------- ....... --'> ---

-----~ ---30 - -- - - - - ---7

40

THD Penetrometer Test

50

60 -----\ \

70

Figure 2.4. Shear Strength Profiie for Site BB

• to •• . ' . , .. .. ..' .. " " . · · . f • .. ..

'''. :# . .. : . • {l4. · . · .. " .. · . .. .... .. · . .. ...... , ... .. 'I .. · .. . ., ...... .... .: : :. "I: -. ,. .. .. to .' .' , # .. " .. · . , ..... ' .. . ... · . .. "' ... · ., ." .. ,_.-r ..

9

Test Shafts

CHAPTER III

TEST SYSTEMS

Two shaft sizes were constructed for testing. The

shafts at sites G 2 and BB were 2'-6 11 in diameter and the

shaft at site G 1 had a diameter of 3'-0". The size and

length of shafts to be test loaded are generally designed

to fail at a load equal to, or slightly in excess of, two

times the required service load on the shaft; however., the

design of these shafts had to take into consideration the

additional requirement of extraction of the shafts after

testing. Data obtained from testing the two diameters

selected would be used for scaling up to the required size

should one or more of the test shafts fail to prove out

the required design load. Details of the test shafts are

shown in Figure 3.1.

Reaction Sx;stem

The reaction system for these tests was :made up of a

reaction beam, two anchor posts, and two an::hor shafts

designed to become part of the permanent structures.

Details of the anchor shafts are sho~n in Figure 3.1. The

reaction beam, designed to be used for a variety of load

10

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Not" Z dnchor posl' re'1Ulrt!d for ~h I,sl 1oc411Dn. FurnIsh t?OO·~-tiI'l.S bolts'" ASTM A·~Z:S

with nuts dnd Z ~sh.!!~ 'or 'dCh bell' .. I' t!<!JCh ;",sr s.dup.

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&"ncrtl;e Tor cdstlol dr7chor shdft-s shdl/ b~ CldSS C .

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ANCHOR SHAFT

Figure 3.1.

ANCHOR SHAFT SECTION A- A

SECTION B-B ' (loCdt'lons .!~~)

--(I t3ars

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SECTION B-B (Locdtion I)

TEST SHAFT

TABLE OF ELEVATIONS

TLST LOCATIONS

1'0 -.$6.0 ="0 -3.z.0

locdtion I' South "'iolcl/~ bd'l of "'n; It! of / ·610 LdSfbound.

Locdfion Z' Soufh bay of 8"nt.?7 of / ' 610 edstbound.

Locdhem ~, W~st bd'l of Ben t 5 "f l~ft Fronfd9' Str. 5.H. -!~8.

t80tJ'r:vn of ~II ~/,,_rlons n'>dt;I b" ~5ft.

ESTIMATED QUANTITIES _I..t"m ~Jt IOUdnfl'""s

Drill Shaf;(.50In.) L~7.0 QaJ£$ii ... ftr3G!n.l- ~L- I Glt!.O

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Co"frdcfor shall proyid#l ntf~5$."r", prof~tion durin9 fIst 'or d",...I • ..... t'nd,ng .. boYt! shdft.

No laps will b" d//oH<t!d in the fr:>p ~;o, f~ Y~rTICd/ r~/"lbrc/~ in t-he Tesl- ShoI,r.

TEXAS HIGHWAY DEPARTMENT HOUSTON URBAN PROJECT

DRILLED SHAFT TEST

APPARATUS

... , ... M.G."' . ~ .. ( C,,[o £ .1 w.

r ..... r · Z '. Z ' ''I '~

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Details of Anchor Shafts and Test Shafts

I-' I-'

tests, has a load capacity of 1000 tons and a span length

which can be varied from 14 to 25 feet. Details of the

reaction beam and anchor posts are shown in Figures 3.2

and 3.3.

Loading System

Load was applied to the test shafts with hydraulic

rams jacked against the above reaction system. Two 400-

ton-capacity double-acting Bayou Industries· jacks coupled

in tandem with a cornmon pressure supply were used. Pressure

was applied to the jacks by an SC Hydraulic Engineering

Corporation Model 10-600 hydraulic pump. This pump is

air-operated and requires an air pressure of 90 psi.

loading system is pictured in Figure 3.4.

Instrumentation

This

Instrumentation was installed in the test shafts to

determine the load transferred from the shaft to the

surrounding soil. This instrumentation consisted of Mustran

load cells which were developed by the University of Texas

Center for Highway Research under Research Study No. 3-5-

65-89. Load cells were located at several levels in the

shafts with four cells in the top and bottom levels and

two cells per level in each of the intermediate levels.

12

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.... ~

<t; \.~ ~ " ~ ~'.' .. ~ ~! .~ bid lor Slrvcl 511 (NoS)

DRILLED SHAFT TEST APPAR ATUS

, · .s"9",..n/~III~J:'f 1 LIi.b6'(J 'KJ" (NTC) (lfrc),

" t ""-1'0'5 (NYC,) rn-,-,. -. -, -, .. ---,.~ __ s"''''--l_=Of-,Z'''''''''-r---,,--t

TYPE "A" TIE (I R .. ,d)

TYPE "B" TIE (6 R,-,'d')

Fig ure 3 . 2. De t a ils of Reaction Beam and Anchor Pos ts

S·l' Dlf'tJdlNAl IKC'. ". C.J.M.. C . .J·'

I~1/~"'.C_ 7

IZ il4M IS :J0l J 7:1 ~ ~~

J--I LV

14

Figure 3.3. Reaction System

Figure 3.4 . Loading System

I

I 7 I ....::/" T ~

'~~ I 8 I W 30 :k{~ --

~ , #~

II 9 I ~b7

1'1 I ~ 10 40 ~ . . -- : ,~.~. ; .. , .. '~ . .. ".

~

I I II ,

I

T . . ;

• 121 50 ' . -- .

I 13 "

.: 'O'

" . ' "

I 14 1 ' . " . , .. , ,115 I T 60

" , I

, : ..

. , , .

I

, "', ..

.. I" I , 0' . \ . '

( a ) Gl Sit e

"* T = Thermocouple

I 2 I ,,­

I 3 I T

I 4 I

I 5 I T

I 6 I

1 7 I T

I 8 •

I 9 I

1 10 t

I II I

I 12 1 T

O(feet)

10

20

40

50

60

70

80

., ,o. I

.. 0, ... • • I ••

: .. '.' 0° :

. ' .', ", ' , ' ' 0 I

, , '

I 8 I

I 9 I

I .10 I

' I II I I

: I l2 I T

( c ) B

(b) G2 Site

Figure 3. 5 . Soil Profiles and Locatiop of Shaft I nstrumentation

1 5

30 ' ' --

" .

;

,

40 I"

-- I

, , . . ,

I.

. . , .

.' ,;".;'," 50 , .

, .

. , " " , ..

' . .' . .'

B Sit e

Figure 3.6. Mustran Cell Attached to Rein­forcing steel

Figure 3.7. Settlement Gage

16

The location of the load cells was based on the following

considerations:

1. To provide an accurate measure of the load

reaching the tip of each shaft.

2. To provide a good calibration level at the

top of each shaft.

3. To gain information about the load transfer

characteristics of the various soil strata.

The location of the instrumentation levels, along with soil

profiles, for each test shaft is shown in Figure 3.5. A

typical Mustran cell installation is shown in Figure 3.6.

In addition to the Mustran load cells, dial gages were

used to measure the settlement of the top of each test

shaft. Two dial gages, mounted on the shaft and referenced

to four-by-four wooden beams, were used at each test shaft.

The gages were located on opposite sides of the shaft to

detect nonuniform settlement should any occur. The method

used for mounting these gages can be seen in Figure 3.7.

Data Acguisition

Data from the Mustran load cells were acquired digitally

with a Honeywell Model 620 Data Logging System. This system,

a portable modular unit shown in Figure 3.8, was housed in

a van adjacent to the test shaft. Power was supplied by

17

a 3 KV a.c. generator. When the ambient temperature ex­

ceeds 95° F. some means of cooling is required for proper

operation of the data acquisition equipment. The ambient

temperature during these tests was such that no cooling was

required; however, air-conditioning has been required during

some previous tests.

Figure 3.8. Honeywell Data Logging System

18

Equipment

CHAPTER IV

CONSTRUCTION OF TEST SHAFTS

Construction of the test shafts using the "slurry dis­

placement" method required no specialized equipment, only

that which is required for any drilled shaft construction.

Maj.or equipment used on this job included a crawler crane

with drilling equipment mounted, water tank, and a holding

tank for the mud slurry. A second crawler crane was gen­

erally available to handle casing, reinforcing steel, etc.,

and to serve as a back-up crane during concrete placement.

_Site G 2

The test shaft at this site was 2'6" in diameter with

its tip 75.1 feet below the ground surface. The contractor

elected to construct this shaft first and construction

began August 17, 1971.

The first significant ground water was encountered at

an approximate depth of 56 feet. The soil above this

level was a fairly stiff clay and it was relatively easy

to drill the smooth round hole desired for a test shaft.

Just prior to introducing the first slurry into the hole,

a 39-foot length of surface casing, with an inside diameter

19

of 30 inches, was set in place to prevent wallowing of the

hole while drilling in the slurry.

The slurry used in this hole was mixed in the hole and

consisted of water and Baroid Quick-Gel, described as a high

yield Bentonite clay. Water was allowed to flow into the

hole until the water level was about four feet above the

bottom of the casing, making the water depth about 21 feet.

Two sacks (50 pounds/sack) of Bentonite were then mixed

into the water. When the drilling reached a depth of 64 feet

another sack of Bentonite was added and the water level

brought up to its original level where it was maintained

until drilling reached a depth slightly less than plan

depth. At this time the surface casing was removed and the

hole was enlarged to a diameter of 30 inches. When drilling

reached a depth of 75 feet two more sacks of Bentonite were

added, making a total of five sacks, and the water level

was brought up to 25 feet below the ground surface. Ex­

cavation continued for two more feet using a clean-out

bucket in lieu of an auger (Figure 4.1). Use of the clean­

out bucket permitted a detailed examination of the material

on which the tip of the shaft would rest.

Approximately one and one-half hours after the removal

of the surface casing the sides of the hole near the water

20

Figure 4.1. Clean-out Bucket

level began caving. The water level was then raised to a

level approximately 17 feet below the ground surface in an

attempt to stop the caving. About one hour later, two and

one-half hours after removal of casing, concrete arrived.

Just prior to setting the reinforcement cage in place, and

while making the final clean-out of the hole, sUbstantial

cavi ng was discovered near the water level. Examination

revealed that the area of caving was much too large for a

test shaft, therefore this hole was abandoned and filled

with concrete.

21

The location for this test shaft was moved to the

adjacent bay in the same bent and the shaft installed

August 19, 1971. It was believed that the previous failure

resulted from leaving the upper portion of the hole open

for too long a period of time. To preclude the possibility

of another failure the hole was drilled in the'dry

until the water bearing stratum was reached and then com­

pletely filled with slurry. Drilling was then completed in

the slurry and without the use of surface casing. The slurry

used for drilling this hole was mixed one day before it was

used and stored in an open-top tank. Twelve sacks of

Baroid Quick-Gel were mixed with approximately 2900 gallons

of water to form the slurry.

The total time required for construction of this shaft

was approximately five hours. Three hours of this time

were used for drilling the hole and about one and one-half

hours were used in placing the concrete. The remaining

one-half hour was used in placing and aligning a section

of Sonotube used to form the portion of the shaft extending

above ground.

Site G 1

The test shaft at this site was 3'-0" in diameter with

its tip 58.7 feet below the ground surface. Construction of

22

this shaft was completed September 3, 1971.

A water bearing sandy silt was encountered at an

approximate depth of 17 feet. At this point, the hole-was

filled with slurry to a level three feet below the ground

surface. Slurry was maintained at that level throughout

the remainder of the drilling operation.

The slurry used for this shaft came from two sources:

One was a mixture of Baroid Quick-Gel used the previous day

in the drilling for an anchor shaft, and saved for re-use.

Additional slurry was provided by mixing Macogel bentonite

and water in a jet-cone mixer and pumping directly into

the hole.

An auge~ was used for the final clean-out of this hole

because a clean-out bucket of the correct size was not

available. Use of an auger in lieu of a bucket has the

disadvantage of cuttings tending to wash off during removal

and falling back into the hole. This creates a weak found­

ation for the tip of the shaft and reduces the bearing

capacity of the shaft. An indication that weak material

had fallen into this shaft occurred when the tremie settled

approximately six inches when the first bucket of concrete

was dumped into it.

23

Installation of this test shaft was completed approx­

imately four and one-half hours after drilling began.

Site BB

The test shaft at this site was the third and final

one constructed. It was 2'-6" in diameter with the tip

44.3 feet below the ground surface and was installed

September 21, 1971.

A water bearing sand was encountered at an approximate

depth of 20 feet. A slurry was then mixed in the hole using

four sacks (100 pounds/sack) of Macogel bentonite and water

pumped from Brays Bayou. One more sack of bentonite was

added when the hole was 40 feet deep.

Interpolation between known locations of sandstone on

each side of the test shaft indicated that sanqstone should

be found at or near the planned tip elevation, however none

was encountered at this elevation. The soil below the

bottom of the hole was probed to locate the expected sand­

stone: first with a three-foot long chisel, and then with

a 10-inch diameter auger. A layer of sandstone was located

at an approximate depth of 47 feet below the ground surface.

Final clean-out of this hole was made approximately

four hours after drilling had been completed. During this

time an estimated two feet of sediments had settled in the

24

bottom of the hole. Final tip elevation was 44.3 feet

below the ground surface, or approximately 2.7 feet above

the sandstone.

The depth of slurry in this hole decreased about ten

feet during the four hours the hole was open. A similar

loss in slurry depth occurred in an adjacent hole drilled

for an anchor shaft the previous day and left open through

the night. One probable cause for these losses is the

steep gradient towards the bayou of the area in which these

holes were drilled.

25

Approximately seven and one-half hours elapsed between

the start of drilling and completion of concrete placement;

however, concrete placement required only one and one-half

hours. There was a delay of approximately four hours between

completion of the drilling and beginning of the concrete

placement.

Concrete Placement

A 10-inch diameter steel pipe tremie was used to place

the concrete in the three test shafts. Steel guides were

used to hold the tremie in the center of the reinforc-

ing steel cage: one temporarily attached at the top of the

cage and another permanently attached to the cage approx­

imately 20 feet below the top (Figure 4.2). At site BB

Figure 4.2. Tremie Guide

the short length of shaft did not require these guides.

When first inserted into the mud slurry the lower end

of the tremie was sealed to prevent slurry entering it.

This seal was temporary in nature and consisted of a ply­

wood plug in the pipe with the end of the tremie covered

with polyethylene sheeting held in place by rubber bands

(Figure 4.3). This seal was broken by vigorously bouncing

the tremie full of concrete.

At site BB some difficulty was experienced in getting

the concrete flow initiated. The first attempt failed and

the tremie had to be removed and emptied of concrete.

There were two possible reasons for this happening: (1) The

tremie was not clean on the inside, and (2) it was not

wetted before using. The flow of concrete in this shaft,

as well as in the other two, could have been improved by

using a tremie with a larger diamete~.

Once the tremie seal has been broken and concrete

begins to flow, the bottom of the tremie must remain sub­

merged In the concrete; otherwise the slurry will contaminate

the fresh concrete. The procedure used for placing concrete

in these test shafts was to fill a one-cubic-yard dumping

bucket with concrete from a Transit Mix truck, attach

bucket to top of tremie, then slowly raise the tremie until

a good flow of concrete was obtained while dumping concrete

from the bucket into the tremie. After a bucket was emptied

the tremie was lowered to the bottom of the hole and the

above procedure repeated until good clean concrete was ob­

served to flow from the excavation. Pictures of the concrete

placing operation are shown in Figures 4.4 and 4.5.

27

(a) Wooden Plug (b) Polyethylene Sheet

Figure 4.3. Installing Temporary Tremie Seal N

(X)

29

(a) Firs t Appearance of concrete

(b) Good Flow of Concrete

Figure 4. 5 . Dr illing Slurry Being Displaced by Concrete

30

CHAPTER V

LOAD TESTS

Load tests were performed on all three of the test

shafts. Shaft BB was tested at an age of 16 days while

Gland G 2 were tested at ages of 45 days and 52 days re­

spectively. BB was tested at the earlier age to ascertain

the effect, if any, of testing at an early age.

All but one of the tests were performed using the

IIquick-test" procedure described in the Texas Highway De­

partment "Special Provisions to Specification, Item 405,"

dated July, 1965. The exception was the third and final

test on shaft G 1 when a "cyclic" procedure was used.

Dates of the load tests, maximum applied load, and other

general information are shown in Table 5.1. Table 5.2

shows the amount of load, as a percent of maximum applied

load, carried by frictional resistance.

Top of shaft load-settlement curves for Test Nos. 1

and 2 plus the tip load-settlement curve for Test No. 1

are shown in Figures 5.1 through 5.3. Load-distribution

curves for the first load test performed on each shaft are

shown in Figures 5.4 through 5.6. Two curves are shown in

each figure; one is the distribution for the Plunging Fail­

ure Load and the other is for the Double Tangent Failure

31

Load. The Double Tangent Failure Load is the load indicated

by the intersection of two lines drawn on a load-settlement

curve~ one tangent to the initial flat portion of the curve

and the other tangent to the steep portion.

32

33

TABLE 5.1 DATES AND GENERAL INFORMATION ON LOAD TESTS

Shaft Test

BB 1

Cast 9-21-71 2

Extracted 3 10-13-71

G2 1

Cast 8-19-71 2

Extracted 10-26-71

G1 1

Cast 9-3-71 2

Extracted 3 (Cyclic) 11-5-71

Date of Test

10-7-71

10-8-71

10-8-71

10-12-71

10-12-71

10-19-71

10-19-71

10-19-71

Load Incr.

2ST

SOT

lOOT

2ST

SOT

2ST

SOT

7ST

Unloading Incr.

--* 7ST

300T

SOT

lOOT

SOT

lOOT

one incr.

Maximum Load

Applied

7S0T

7S0T

600T

700T

680T

480T

4S0T

4S0T

*Hydrau1ic system broke and an unloading curve could not be obtained.

34

TABLE 5.2 PERCENT OF APPLIED LOAD CARRIED BY FRICTIONAL RESISTANCE

Site

Gl

G2

BB

Ultimate Plunging Load (Tons)

480

700

750

Frictional Load Transfer (Tons)

425

665

460

Frictional Load Transfer (%)

91

95

88

-~ -,.,

.j.J ~ Q)

E: Q) .-l .j.J .j.J Q)

U)

Load (tons)

Ie!:::: jll '~I!I I pit .t:.vv 250 300 350 400 450

01 ~ • I. • • := == I I I I ~ .

0.2

0.4

0.6

0.8

" " '\ \ Tip Settlement V (Test No.1) ,

-0--_____ .,

I \

\ I

---- \. \ ---- ---4-0--- ---- --- Test No.2 2 ~

\ --- --0--_ ---------- \ ---G-_ I 1 - - - - - - - ... ~..o i --~----~

~

"''0.- -J Test No. 1

1.OL, ________ -4 ________ -L ________ ~ ______ ~~ ________ ~ ________ ~ ________ ~ ________ ~ ________ ~ ______ ~

Figure 5.1. Load-Settlement Curves, Shaft G 1

w U1

-. ~

-.-I

0.1

0.2

0.3

0.4

0.5

"-' 0.6

0.9

1.0

1.1

1.2

1.3

\ \ \ \ YZ-- Tip Settlement \ (Test No.1)

\ \ \ \ I

" I -J

--- --"'"0...._

Load (tons)

. ---- ..... v--_ ---0-----0- __

---0....

----0,. \

\.

36

\ \ \ \ \ \ \ \ \ \

~ I

I I I I

Test No. 1 7 ----'---o. __ ~_4J

-- - i ---0.. __

------0-._____ Test No. 2] J ---.0.-._____ .,."'.1"

- ---0- " . ---------0"'-'

Figure 5.2. Load-Settlement Curves~ Shaft G 2

Load (tons)

o 50 100 150 ___ ___ ___ ___ ~_~ ~__ ___ ___ ___ ___ ,__ , __

o K· • • .' • .1 • .1 :::L_ _ I I I I I I I I I I 0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

2.0

\ \ \

------""'0-_\ - ----0- __ _ -----0-

Test No. 2

----- --0---- ----0-

, '\ , ,

\ /I /Tip Settlement ~~~:~::)--- ---~-- --0---_ ----0---- - __ -b

\ \

(Test No.1)

Estimated

Test No. 1

Figure 5.3. Load-Settlement Curves, Shaft BB '-',

W -...J

o

10

20

-+> 30 ~ -,c: +> 0.. Q)

t:l 40

50

60

Load (tons)

200 300

Double TangentFailure Load

Plunging Failure Load

Figure 5.4. Load Distribution Curves, Shaft G 1, Test No. 1

38

....... 0, .

00' . , 0 .. .

." . . ' . .

. . . . . " .. .

-

o

10

20

30

40

50

60

70

Load (tons)

Double Tangent Failure Load

o

• Plunging Failure Load

39

.. " . . " . . : ..

80 ~ ____ ~ ______ ~ ______ ~ ______ ~ ______ ~ ______ ~ ______ ~~

Figure 5.5. Load Distribution Curves, Shaft G 2, Test No.1

1

2

3

40

50

Load (tons)

200 400 600

Double Tangent -Failure Load

800

40

"'.' ":. . . Plunging Failure Load' ,",'

" , "w ~

, " " . , '

" . '': . . '

. -.. t , ,

" . , ' '. #'

......

60 '

Figure 5.6. Load Distribution Curves, Shaft BB, Test No. 1

CHAPTER VI

EXTRACTION AND INSPECTION

After load testing was completed, all test shafts were

extracted and inspected. The procedure used for extraction

was (1) drill an annular opening around the shaft for its

full depth, (2) loosen the shaft from the soil using a

specially constructed pulling device, and (3) lift shaft

from hole with a crane (Figures 6.1 - 6.4). After removal

41

of the shafts, the shaft .diameter was measured at each in­

strumentation level and a careful examination of the concrete

soil interface was made. Additionally, several gages were

removed to inspect their seating in the concrete and the

concrete inspected for slurry contamination. Results from

the inspections are discussed below for each test shaft and

photographs of the extracted shafts are shown in Figures 6.5-

6.11 at the end of this chapter.

Shaft G 1

The shape of shaft G 1 was generally cylindrical and

straight. Slight enlargements were found at the bottom of

the section formed with the Sonotube and in the areas of

sand strata. The small size of these enlargements indicated

that no significant caving had occurred in the sand strata.

The tip of the shaft was irregular in shape with some re­

inforcing steel exposed. The wooden plug used as a temp­

orary tremie seal was located to one side of the shaft and

the polyethylene used for the same purpose had covered most

of the tip and a portion of the sides near the tip.

A coating of discolored material which had the appear­

ance of sand stabilized with cement and drilling slurry

covered the entire length of the shaft. The thickness of

this coating varied from ~" to ~II in the portion of the

shaft in the sand with a lesser thickness over the remain­

der of the shaft. Examination of the soil adherred to the

sides of the extracted shaft indicated that failure had

occurred in the surrounding soil and not in this coating.

Removal of concrete around some of the load cells pro­

vided an opportunity to inspect the interior of the shaft

concrete. In the upper levels of the shaft evidence of

entrapped sand and bentonite was found around the in­

strumentation cables and where the spiral steel and rein­

forcing bars were joined. The,bottoms of some load cells

also had trapped some mud. Some evidence of contamination,

which appeared to be a stabilized mixture, was also found

approximately six inches from the surface, however, this

contamination did not appear to be widespread.

42

Figure 6.1. Drilling Around Shaft Prior to Extraction

Figure 6.2. Lifting Device in Place

43

44

Figure 6.3 . Removal of Shaft

Figure 6.4. Inspection of Shaft

The texture of the concrete surface was somewhat

roughened but there was no indication of any weak or bad

concrete except at the tip where turbulent flow of the

fluid concrete may have caused some mixing with sediments

in the bottom of the hole. Soil attached to the tip in­

dicated the tip had been founded in a relatively soft mix­

ture of clays which had fallen into the hole during

construction. The color of these clays matched that of the

clay layers in the upper portions of the hole. A low tip

resistance was measured during load testing further confirm­

ing the presence of soft material at the tip of this shaft.

The shape of the shaft tip suggested that the tremie

might have been in an off-center position when the first

fluid concrete was introduced into the hole.

Shaft G 2

45

Extraction of this shaft was considerably more difficult

than the other two due to caving conditions in the upper

soil layers. A large casing was required around the shaft

and the shaft was broken several times during extraction.

This shaft was generally cylindrical in shape with slight

enlargements at depths of 18 feet, 32 feet, and two feet

above the tip. These enlargements, approximately two

feet in length, increased the shaft diameter by no more than

three inches, and corresponded to the depths of silt strata.

The shaft appeared to be out of plumb in the lower 10-20

feet, however, no attempt was made to measure the alignment

of shaft. The tip of this shaft was well formed with the

tremie plug in the center of the shaft and there was

46

evidence of a good concentric flow of fluid concrete with

good scouring action at the bottom of the shaft (Figure 6.6).

There was no coating of sand or drilling mud on this

shaft as on the other two test shafts. The concrete had

been in contact with the clay soil and no evidence of

significant entrapped mud was found.

Shaft BB

This shaft was straight with a relatively smooth surface

and had a near constant diameter. Slight enlargements were

found near the tip and at the bottom of the section formed

with the Sonotube.

The upper sections of the shaft contained small pockets

of sand~rich mud at the junction of the spiral and reinforcing.

steel, along instrumentation wires, and around the load cells.

Except at the tip, no contamination was found in the lower

portion of the shaft. No significant amount of entrapped

mud was found between the concrete and adjacent soil.

A coating of slightly clayey sand covered the en-

tire length of the shaft. This coating was 1/16" - 1/4"

thick, depending on the roughness of the concrete surface,

and failure apparently took place in this layer. The sand

adjacent to the concrete appeared to be somewhat stabilized.

The bottom five feet of this shaft had layers of clay

clinging to it but they were separated from the concrete by

the clayey sand layer. The different colors of the clay

indicated that it had come from the strata near the ground

surface. It is likely that this clay had fallen into the

hole during drilling and then pushed to the sides of the

hole by the fluid concrete. A smooth flow of concrete at

the bottom of this shaft had apparently been prevented by

the temporary tremie seal just as in Shaft G 1. The tip

of Shaft BB is pictured in Figure 6.7.

47

48

Figure 6.5. Tip of Shaft Gl

Figure 6.6. Shaft Gl

49

Figure 6.7. Tip of Shaft G2

Fi gure 6.8. Shaft G2

50

Figure 6.9. Close -up o f Shaft G2

Figure 6 .10 . Tip of Shaf t BB

51

Figure 6.11. Shaft BB

CHAPTER VII

BOND TESTS

A limited number of pull-out tests were performed to

determine if the bond strength of the concrete was signifi­

cantly affected by the II s 1urry displacement" method of

placing concrete.

Two tests were performed using a section of shaft G 2

from a level approximately 65 feet below the ground surface.

This section was 2'-6" in diameter and 5'-6" long. Concrete

was removed and the No. 8 reinforcing bars cut to form two

test specimens: one with a bar embedment length of 13 inches

and one with an embedment length of 9 inches. Concrete

cover was 2-5/8 inches on the 13-inch length and 2-1/4 inches

on the 9-inch length.

The concrete over the 13-inch length did not fail by

bond splitting. The direction of the applied load was not

parallel to the axis of the bar and this caused a portion

of the concrete cover to spall off. This failure occurred

at an applied load of 55,500 pounds and a calculated bond

stress of 1360 psi. The concrete over the 9-inch length

failed by bond splitting at an applied load of 61,000 pounds

and a calculated bond stress of 2160 psi.

52

Inspection of the concrete removed for the above tests

did not reveal any significant slurry contamination in the

concrete or around the reinforcing steel.

Additional pull-out tests were performed on 12 concrete

specimens 12 inches in diameter, 14 inches long, and pre­

pared as follows:

1. Three with No.8 deformed bars coated with a

mud slurry before casting in concrete.

2. Three with No. 8 deformed bars cast without

.a mud slurry coating.

3. Three with one-inch diameter smooth bars coated

with a mud slurry before casting in concrete.

4. Three with one-inch diameter smooth bars cast

without a mud slurry casting.

Two of the deformed bars cast with the slurry coating

failed in a threaded area before concrete failure. These

failed at loads of 54,000 and 56,000 pounds which represents

an approximate bond stress of 1230 psi and 1275 psi. Using

a different method for applying load, the third specimen with

a slurry-coated deformed bar was loaded until the concrete

failed by bond splitting. This occurred at a load of

61,500 pounds and a calculated bond stress of 1400 psi. The

three specimens made·with deformed bars without the slurry

53

coating all failed by bond splitting. The average of the

failure loads was 60~500 pounds with an average calculated

bond stress of 1375 psi.

54

All of the specimens with smooth bars failed by slippage

of the bars. The average of the failure loads for the

specimens with slurry-coated bars was 5,800 pounds with an

average calculated bond stress of 133 psi. The average of

the failure loads for the specimens with un-coated bars was

10~700 pounds with an average calculated bond stress of

242 psi.

CHAPTER VIII

CONCLUSIONS

55

Load tests were conducted on three straight drilled

shafts of constant diameter constructed using the "slurry

displacement" method. The primary reasons for these load

tests were: (1) to obtain a proven load capacity for design

verification, (2) to evaluate the II s 1urry displacement"

method of construction, and (3) to determine the load trans­

fer characteristics of drilled shafts constructed by this

method. Based on the results of these tests and the in­

spection of the extracted shafts, the following conclusions

and recommendations are presented.

Conclusions

1. Straight drilled shafts designed to carry load by

frictional resistance can safely be used in the

areas tested. Results of the load tests indicated

that a significant portion of the applied axial load

was carried by frictional resistance.

2. Drilled shafts can safely be constructed in water

bearing and caving soils using the "slurry

displacement" method of construction. Con-

struction techniques have a significant influ­

ence on the condition of shafts constructed using

this method and care should be exercised to

prevent contamination of the concrete by the

drilling slurry.

3. The values of load transfer developed in the soils

surrounding the shafts constructed by the IIslurry

displacement ll method were found to be comparable

to those developed from previous research when

shafts were constructed in the dry.

56

4. The tip resistance of shafts constructed by the

"slurry displacement ll method can be substantially

reduced by loose materials falling into the hole

and not being completely removed before placing

concrete. This apparently occurred at shaft GI

where a low ultimate tip resistance was measured

and material from upper levels of the hole were

found clinging to the tip of the extracted shaft.

This likely was the result of making the final

clean-out of the hole with an auger rather than

with a clean-out bucket. When an auger is used the

soil cuttings have a tendency to wash off during

withdrawl o"f the auger.

57

5. The "slurry displacement" method of placing concrete

has no significant affect on the bond strength of

the concrete when deformed bars are used and the

load is applied axially. When smooth bars are

used, the slurry will cause a reduction in bond

strength. The average bond strength for the slurry

coated smooth bars was 133 psi compared with 242

psi for the uncoated bars.

CHAPTER IX

IMPLEMENTATION

Based on the results from these tests and those con­

ducted under Research Study No. 3-5-65-89~ the following

procedure has been adopted for utilization of frictional

design for drilled shafts in the Houston area:

1. Use a Soil Reduction Factor* of 0.7 based on a

shear strength obtained from THO Triaxial and/or

THO cone penetrometer data.

2. Disregard the frictional capacity of the soil for

the upper 10 feet of a single shaft.

3. Assume that frictional load transfer is inde­

pendent of the shaft construction method used.

Evaluation of the "slurry displacement" method used

58

to construct these test shafts resulted in approval of this

method for construction of any straight shafts used in the

I-45/I-610 (So. LOOp) Interchange structures. The specifi­

cations governing this type of construction are included as

Appendix C.

* See Appendix A for definition.

59

APPENDIX A

DETERMINATION OF SOIL REDUCTION FACTOR, SR

RELATIONSHIP BETWEEN MEASURED AND

CALCULATED LOAD TRANSFER

60

Previous research has shown that the load transferred

from a drilled shaft to the surrounding soil is related to

the shear strength of the soil. This relationship, even

though sometimes greater than unity, is herein defined

Soil Reduction Factor (SR) and was determined using the

following procedure:

1. Calculate for each soil stratum, a unit shear

strength (tons/sq ft) based on Triaxial Test data

and/or THD Cone Penetrometer data.

2. Multiply the unit shear strength from Step 1 by

the stratum thickness to obtain a shear strength

in tons per foot of shaft perimeter.

3. Make an accumulative total of the shear strengths

from Step 2.

4. Calculate the potential ultimate load transfer

for each soil type from the accumulative total

shear strength in Step 3.

5. Prepare a load distribution curve (load vs. depth)

for the IIdouble-tangent" failure load obtained

from load test data.

6. The ratio of measured load transfer from Step 5

to the calculated load transfer from Step 4 is

the Soil Reduction Factor, SR.

61

Values of measured unit load transfer, calculated

total load transfer based on Triaxial Test Data and THO

Cone Penetrometer Data, total load transfer measured

during load tests, and SR are shown tabulated in Table A.l.

Values of SR' based on data taken from Research Study

3-5-65-89 Reports, for a site approximately 2.5 miles east

of Test Sites Gl and G2, are shown in Table A.2.

Site Soil

Clay G-l

-' Sand

Clay 1 G-2

Clay 2

Sand

BB Clay

Sand

Table A.l. Frictional Load Transfer and SR Values for

Test Sites Gl, G2, and BB

Frictional Load Transfer "

Per Soil Type (Tons) Average Measured Calculated Ult. Soil Reduction Unit Load Transfer

Measured Factor, SR (TSF) THD Pen. Triaxia] THD Pen. Triaxia]

Test Test Test Test

0.52 139 135 145 1.04 1.07

1.05 400 280 0.70 --

0.81 230 272 320 1.39 1.17

1.62 128 123 220 1.72 1.78

1.79 74 125 1.69 --

0.94 132 198 170 1.29 0.86 -

1.53 378 290 0.77 --

(j\ tv

-

Test

Sl Tl

S2 Tl

S3 Tl

S4 Tl

Table A.2. Frictional Load Transfer and SR Values for

Soil

Clay

Clay

Clay

Clay

Load Tests at SH 225 Site Located Approximately

2.5 Miles East of Sites Gl and G2

Frictional Load Transfer(Tons

Soil Reduction Calculated Factor (SR)

Measured THD Pen. Triaxial THD Pen. Triaxial

Test Test Test Test

88 110 97 1.10 0.87

65 87 86 1.32 0.99

88 110 121 1.37 1.08

237 259 191 0.81 0.74 ..

O"l W

APPENDIX B

BORING LOGS

64

DATE

..I

LABORATORY LOG OF BORING ffG-1-2

FOR

M~ 21--,- 1971 1-610 & 1-45 INTERCHANGE N 695,995 . TYPE p~rPeWrometer LOCATION -..!.. 3.177 .460

IIII.~ ;..,: POINT BEARING T.S.F.

65

CI) w ~ DESCRIPTION

:1:1- 0 ~w CD o...w a

PER z >- "" --0 0 0 FOOT ~~~~ ~~. 1.0 2.0 3.0 4.0 S.O

~ui~~ 0 W.&L o·

~O ~

. 1--0-~

- ~O'"

~

>-CI)

r-I" I" 1"",

I" ~ I" ~ I"

r--~ fI!

u J. ELEVATION'" 41.6 . Dk. gray tan silty clay

Tan It. gray w/calc. @ 8'

Lt. gray t an w/o calc. @ 12'

Tan It. gray clayey ~ silt w/calc.

I-~~'tn", w/o calc.@20' r-=- I" r-- I"

r--

'It 2nd ~a;!~:; ~~ MOISTURE CONTENT S- 6- ts IE ~ ~ I 0 • 20 ' 3·0 40· SO

4 2

3 4

7 8

7 9

8 7

12 17

- I"

Tan It. gray siltr clay Red It. gray @ 26 9 12

r--..:Ill'\. ~ f~ ~I"

r-~ -9 12

pill

r-- ~ 9 12

Tan It. gray silty sand 27 26

8" layer clay @ 40'

~ · · ~.r.: ..... "" . r. , ..... -: : . - . -.. 19 21

· · · . . 31 36 r--- · ·

~ · · · Lt. gray tan @ 49'

Tan It. gray @ 52' . 35 32 - · · F ;. ~.~:

26 34 . :t-. - · · · - · . · . 4.}:1! 34; , · . : · ·

~'. · · 6" 2!t' · ~.::

~ · . ~ : ,

4.}:" 3~' r-' r-.: : ~ ,

5" 3!' ~ · , · . · ,

2~"'1 II · - · · · · · -----< .

1------4 ........... - - - - - - - - - - - - ..l.~ .ll ~ - - t- - ++-t-H++t+t++t+t-t+t+tof-tot+"-t-T-t-t-H

W A T E R

LA BORATO RY LOG OF BORING G-l·3

FOR N 69.5.9H

~TION &3.11L440

66

POINT BEARING T.S.F. ~ 0 0

1.0 2.0 3.0 4.0 5.0

MOISTURE CONTE~T

10· 203·0 ~o 50

W A T ! It

• • •

• • • • • • • • • • • • • • • • • • • • • •

• • • • • • • • •

OATE

-' XI- 0 1-&&.1 CD 0. &&.1 a &&.I Ll. > 0 en

~ ------~o .. t---

f--r--t--t· r--~

f--t---

f--f--

~ ~ t---t---r--I I .

~ t---

f--I--

f--f--

~ I r--r--

~ . I · ... f--I-- · '.

~'UII .. · . I · . . " I · . · .

· : . ~ : .

---~ ~

~

~:..::. f--f--

~ :=: Ii--f--

LABORATORY LOG OF BORING G -2 -2

FOR 1-610 & 1-45 Interchange

696 ,375 Ma v 18 1971 TYPE 3" Shelby LOCATION ~ 3 ,1 78 500

8WWS ~..,: Pat NT BEAR ING T.S .F. PER z

~i >IA.. ~ 0 0--en FOOT 0 12:. 1.0 2.0 3.0 4.0 S.O &&.I ~;; ~~ 12: DESCRIPTION t40ISTURE CONTENT 0 'It 2nd ~Q. t:en u g • • • ELEVATION + 39 . 6 6- 6- ~ ~~ 10 20 3 a 40 50

Ok. gray tan silty clay Tan It. gray @ 4' 96 W/silt pockets @ 6'

Tan It. ~ray clarey silt wi ayers 0 clay 106

Tan lt. gray nlti clay Lt. ~ray tan @ 14 Tan t. gray @ 15' Red 1 t. g ray @ 17' 104

Re~ It. ¥ra y clayey f'. w clay ayers

silt 99

Tan It. gray silty clay w/ calc. 96

wlo ca lc. @ 24' Red It. ~ray @ 27' W/calc. 29' 108 3" layer silt ~ 31' 2" layer silt 32'

98

95

If 94

Ie Tan lt. gray (9 50' 88 Ok. gray tan @ 52'

81

Gray tan silty sand 8" 1 3~er very sandy clay ~ 62 94

7 la¥er very sandy clay @ 63

Ok. gray tan silty clay 7/l

Gray tan silty sand

102

4" laye r clay @ 76'

Red 1 t . g ray s ilty cl ay 100

I" l a yer sil t @ 85' 2" layer sil t @ 86' 101 1" layer sil t @ 88'

Red 1 t. gray clayey r---- -- -- ,.. 11 '1 '_sJ.l£ ______________ ,

• S lickens ided

.

l. :~.

T E R

67

OATE

I--I--

~O" I I-- ~ I--

~ ~ ---F L-== I--

~ ~ I---I---I--~

I ........ ru-I f--

I

iM:;; = -I--I--

~ ' . . ~.:-.. · .

· . ~ .:. ,"- ' -;== · . I-- · .' f-- :

~ · .' I--I . . .. I · . · . · . bu:::: ~ -r----I--

~

~ I--F--I I

Ma v 19

LABORATORY lOG OF BORI NG #C- 2-3

FOR

1971 1- 610 & 1-45 INTERCHAN GE N 696,3 75

TI-ID TYPE Pene tromet e r LOCATION E 3 178 525

DESCRIPTION

7 5

W/ca1e. @ 10' 3 4

. wiD silt layer s @ 13' 5 6

Red 1t. gra y @ 18' 8 10

11 10

10 11

10 12

8" layer silt @ 32' 20 18

12 13

12 12

13 13

14 14 Lt. gray @ 50 '

Dk . gray @ 54' 10 12

Dk. gray tan silty sand 16 f,

30 34

20 15

14 14

20 19

3:);" 6"

Red 1 t. gray silty clay 13 18

13 12 81

19 ~ Red 1t. gray clayey silt

\ Red 1 t. gray silty clay W-i La ~-\ _____________ _ I

68

I W A T E

Y

.

DATE

LABORATORY LOG OF BORING #B-B-2

FOR STATE HIGHWAY 288 N 700,96S

Mav 27 1971 TYPI 3" Stlel IV LOCATiON E _l~,205 ,kOWS ~ POINT BEARING T.S.F •

69

.J PER Z )00 t: ~ 0 0 I~ti ~ : FOOT 0 !~~ I!i ;; 1.0 2.0 5 .0 4.0 5.0 I ~"~ :: e DESCRIPTION lit 2nd ~:Iti~ -i MOISTURE CONTE~T ~O~~~=EL~E~~=~~T~~N~+ __ ~50~.~o ____ ~6_·~6~·~~~~c-~!~~-~+'nO~·~n20Tnri3~~~ri40~~5~0Tr' n1

',-

Gray tan silty clay w/ calc.

Lt. gray tan @ 5'

Tan It . gray silty sand

8" l aye r sand stone @ 53'

- ----------• Slickensided

32 4S

2" ~tl

I

2" 3"

3~" U;" ,

4~" ~"

1" ~t'

5-t" 2t"

~~ t\: --~- ~ -

"

W A T E R

DATE

...J %~ 0 ~ W CD (L.W ~ W,'" > 0 ' U)

~O

---... 0 <111 ~

0..-, I""":'-

l1li'" ~

r1IU"'I ~~ , -

--~ .

~~

~ : I-~ -.-~ ~ I" · · "

· . ...... ' · · ~. · . · . r--- . ~:. · - · · . - · .

· . ~ · . -',.

· . - : . I- . · . · . ~ , . ~.'. ~ .. ~ r---10-~ ~ ~ --~ '--:'-:;:: ---1-~ r.-----

LABORATORY LOG OF BORING B-B-3

FOR STATE HIGHWAY 288 N 700,960

Ms,y_ 28_. 1971 TYP! THD Penetrometer LOCATJON, E 3.149.215 IU,~ ;..,: POINT BEARING T.S.F. - .,.

'PER ' ~ 0 0-U) Z ZItoi >-a&. 3.0 4.0 5;0 FOOT 0 !i~ 1.0 2.0 w ~Ui ~~ ~ DESCRIPTION

i~ t40ISTURE CONTENT lit 2nd ,,!a: u e • • • ELEVATION + 50.1 ,- ,II IE 10 20 30 40 SO

Gr,y ran silty clay w ca c.

Lt. gray tan @ 4'

13 14

11 9 ' Tan 1to gray clayey

silt 14 14

Lt. gray tan silty 9 12 clay. w/vertica1 silt seams

16 21 , " ' ,

9 19 Lt. ~ray tan Clayey

san 141 4 ~

Lt. gray tan silty sand ' 24 29

48 52 -5~"

2" 1"

2\" 1\'

,3\" 2"

1;;;" 1;;;' .

--- ---------- ~'~3.i' -- - --

70

.

W A j.'

E R

APPENDIX C

PLOTS OF ACCUMULATED

SOIL SHEAR STRENGTHS

71

)

•

q ex)

2 __ •

72

•

-

I I

I I

n rTi1 -f ,1 r -t

r r r

tiii~ 1 H­I II n

M r

J -l j1 J:J u -t-+t K-H-H -r-, " I I ' ; II I HtIt"Q1nIHl-1..+ t++++ttttU=mri-1H- ' -: rt , P~

q -t-U H 'T-l tf-l ", ± N " n rr ;'+

; J H-+rr. l-rut1=: ~ ' tt

r

U

+-t-4iT I I n r-t- U + -t -l--l- -t tt ++U'"'hTlIII U U. ...j. -++-t-TT I ,4~ i ,. J

74

q (\I

0 . -

. C

.

r J I

I I

I

r

] , "T T

t""' T"

~

r-

t-

a..

---------75 ~--------------

:n

. ,

, ' -.l ..l -!,..,_ ,

I I I I

I "

.' , I ,

L.L

j

1

T

J

t-

T .1

H

-.l ..LH­J 1

I-

f­I-

I-

T .ll.J

-

H-± H-H-L ..1 T T I; ~ ffWTIT tt ct.j. + H f+I r-tl.--t--l-Ll I r:rr:C

O

LL" u..u. -H -rl J-+ ..... J ~ T J T FfH+r.-r.,.j....l.....lU

"" c Il I .,... -r-n-rl-H-+ J. . NiLLR=. 1-+ ] T u..LL H- + 1'+ iii 1 '1 f en -r-t-+.+-LJ

1

IRi H +- r-rt+-+-1-I+-I I- +TI' +-1--+-1-1 '+t+++H+ 1

r-r-+-W--II -I. H H-~H ., .lL Ii-T'" H+ff-J- + ++, ~ l ' I ri-1 -f-tJ--l-H-t ~ ~ '. I T +P-+ T' -rrr II TJ+ .. ~i , ' +,~ 11 -Hj , -r ,,4-t+++ T ....... l=-J

n-t-4-Ll. 1T' t-t+-fR-i i ' ,i- 1

T 1

•

..

i

i

i r

rr..l

APPENDIX D

SPECIAL PROVISION TO ITEM 416

(416---002) OF TEXAS HIGHWAY

DEPARTMENT STANDARD SPECIFICATIONS, 1972

78

79

TEXAS HIGHWAY DEPARTMENT

SPECIAL PROVISION . ~TO

ITEM 416

DRILLED SHAFT FOUNDATIONS

For this project the Item, "Drilled Shaft Foundations" is hereby amended with respect to the clauses cited herein. No other clauses or requirements of this Item are waived or changed hereby.

Article 416.1. Description is supplemented by the following:

The "Slurry Displacement ll method is defined as a cUlstruction pro­cedure whereby the sides of the excavation are supported, all or in part, by a mud slurry and the slurry displaced by concrete, to form a continuous concrete shaft.

The "Slurry Displacement" method may be used, at the Contractor's option, to construct any drilled shaft not requiring bell footings. Regardless of the method of shaft construction, the length shown on the plans will be the minimum length placed and the length to be paid for, unless modified by design change.

One interior drilled shaft in Bent 11, Structure 37, will be in­strumented with strain gages, mustran cells and other incidentals, installed on the reinforcing steel cage. The instrumentation cables for the gages will be brought out at the construction joint at the top of the shaft. Lead wires will pe collected into a bun­dle at the top of the shaft in such a manner to not interfere with the placing of column forms. The instrumentation, installation and the completion of the instrumentation setup for long-term read­ings will be handled by State forces.

Article 416.2. Materials. This article is sUpplemented by the following:

concrete for the "Slurry Displacement" method shall be Class liEn, modified to contain a minimum of 7 sacks of cement per cubic yard, and a maximum grade 3 Coarse Aggregate. The slump shall be as re­quired for use in a cased drilled shaft.

1-3 416---002 8-72

Article 416.3. Construction Methods. S1,lba~ticle (1) Excava-• t, _ _. ,_ _ ,

tJ.on, is supplemented by the follow,in9 when the IISlurry Displace-ment" method is used:

The shaft excavation, during ~nd after drilling operations, shall be completely filled with slurry.· When a surface casing is used, the slurry shall fill the excavation to at least 2 feet above the bottom of the casing. The casing shall not be extracted until after the concrete placing operations have been completed.

A good grade commercial bentonite of the type commonly used in the drilling of oil wells shall be mixed with water and excavation cut­tings to produce a viscous slurry capable of supporting the sides of the excavation and to hold· the excavation cuttings in suspen­sion. A minimum of 30 pounds of bentonite per cubic yard of slurry will be required. If sufficient groundwater is not available to produce the required slurrYJ additional water shall be supplied by the Contractor.

Just prior to placement of concrete, the drilling auger and/or other acceptable tools shall be passed down and up the excavation to free it of any large obstruction that may have fallen from its sides between the cessation of drilling operations and the placing of concrete.

If the mud slurry 'sets up' or forms a gel prior to concrete place­ment, the gelled slurry shall be agitated to liquification just prior to concrete placement and at other times when directed by the Engineer.

A sump pit adjacent to and connected with the shaft excavation, or a pump and portable container may be used to collect the slurry displaced by the concrete. The displaced slurry, if not contam­inated, may be re-used in subsequent drilling operations.

Article 416.3. Construction Methods. Subarticle (2) Rein­forcing Stee~, is supplemented by the following:

The reinforcing cage may be positioned before or after concrete placement. However, should difficulty arise in sUbmerging and positioning the reinforcing cage after concrete placement, the Engineer may direct that on subsequent drilled shafts the rein­forcing cage be installed prior to the concrete placing opera­tion. Suitable guides will be required at the lower end of the reinforcing cage to assist in centering it in the excavation.

2-3

416---002 8-72

80

The entire cage of reinforcing steel for the instrumented shaft shall be the full shaft length and shall be completely assembled and available to the State two days prior to installation in the shaft to allow the p1acemen~ of instrumentation. The Contractor shall use utmost care in handling the steel cage and placing concrete. The instrumented reinforcing cage shall be installed prior to the placing of concrete. Suitable guides will be in­stalled on the reinforcing steel to keep the tremie from damaging the instrumentation.

81

Article 416.3. Construction Methods. Subarticle (3) Concrete, is supplemented by the following:

For the "Slurry Displacement" method, the concrete shall be placed by the tremie method in accordance with Article 420.14, "Placing Concrete in Water".

If it appears that the continuity of concreting has beencompro­mised due to withdrawal of the submerged end of the tremie tube prior to completion of concrete placement, the tremie shall be removed, resealed at the bottom, forced well into the concrete already placed and recharged prior to progressing further, and the Contractor will be required to core the entire length of the completed shaft or otherwise prove that the shaft is free from inclusions or contamination unless this requirement is specifically waived in writing by the Engineer.

3-3

416---002 8-72