TA

.W34no.3-398

tC

CORPS OF ENGINEERS. U. S. ARMY

ANALYSIS OF SETTLEMENT DATA

WAPPAPELLO DAM, MISSOURI

CWI ITEM NO. 505

PROTOTYPE ANALYSIS (SOILS)

nICI lil

li00~ 0 011

TECHNICAL MEMORANDUM NO. 3-398

PREPARED FOR

OFFICE OF THE CHIEF OF ENGINEERS

BY

WATERWAYS EXPERIMENT STATION

VICKSBURG, MISSISSIPPI

ARMY-MRC VICKSBURG. MISS.

FEBRUARY 1955

_ -- -

i

PREFACE

The Waterways Experiment Station was authorized to undertake the

analysis presented in this report by 1st Ind, dated 14 September 1950,

from the Office, Chief of Engineers, to letter from the Waterways

Experiment Station, dated 7 July 1950, subject "Minutes of Conference

Held 27-28 June 1950." Settlement studies at Wappapello Dam were

approved as a part of the Office, Chief of Engineers, Civil Works

Investigation Program Item 903-B, which was subsequently changed to

Item 505, "Prototype Testing and Analysis, Soils."

The program of prototype tests to study the performance of earth

dams and foundations originally was divided into 14 categories. Of these,

four were selected for initial analytical study: (a) relief well systems,

(b) compaction, (c) pressures in and under dams, and (d) settlement under

dams. Certain test facilities were installed in a number of structures

to provide data on these four items from the behavior during and after

construction of the structures. Considerable data on various phases of

their performance have been obtained.*

One of the structures for which performance data have been obtained

is the Wappapello Dam, Missouri. These data were obtained through the

cooperation of the Memphis District, CE. The Wappapello Dam project was

constructed under the inmediate direction of the District Engineer,

Memphis District, CE, Memphis, Tennessee, and the supervision of the

* A series of reports, entitled "Analysis of Piezometer and Relief-WellData," presenting data obtained under this phase of the prototype testprogram, was initiated with the publication in February 1954 of TM3-:79, Report No. 1, "Data from Sardis Dam, Missiasippi."

t

Prei~et, Missisipit River Co lission, C, ViOcksburg, Missistpp, ean

the ie of egns, U. S. Ar, washits D. C.

1raat of ti Sols Di vision o tn as es aere Station

actively onnected with studB y erw s besrs. V. J. Turnbull, W. 0.

Sbookley, A. A. Uexltl, J. L. McCal, G. V. Leens, a) a rs. Marile M.

Leaster. hs repofl was prepared by Mr. KcCafl.

iii

CONTENTS

PREFACE . . . . . . . . . . . . 9 . . . . . . . . . . . . . .

PART I: INVESTIGATIONS OF PERFORMAICE OF EARTH DAM

Objective . . . . . . . . . . . . . . . . .Selection of Wappapello Dam for Analysis . . .

PART II: DESCRIPTION OF PROJECT . . . . . . . .

General Features . . . . . . . . . . . . . . .

Prototype Test Facilities . . . . . . . . .

PART III PREDICTED AND ACTUAL SETTLEMENTS. . . .

Prototype Test Facilities Used in Analysis . .Methods of Computation . . . . . . . . . .

Comparison of Predicted and Actual Settlement

PART IV: ANALYSIS OF PROTOTYPE DATA . . . . . .

Ultimate Settlement . . . . . . . . . . . . .Time Rate of Settlement.. . . . . . . . .

PART V: DISCUSSIO. . . .... .........

PART VI: CONCLUSIONS AND RECO{EDATIOS . . . . .

Conclusions . . . . . . . . . . . . . .. . .Recommendations . . .. .. . . . .. .

ASSOCIATED REPORTS

TABLES 12-4

PLATES 1-22

S

Is 9 0 9 . 9

. . 9 . 9 9 .

" " " "

" " " " "

" " s "

iv

I

12

3

37

9

91012

15

1521

25

28

2828

iv

SU *ARY

Data obtained from observations of settlement plates at Wappappapello

Dam, Missouri, are analyzed in this report in furtherance of a Corps of

Engineers program to study the performance of earth dams and foundations.

The data derived from these studies are to be used to assist in solution

of problems encountered in the design of future, similar structures.

Review is made of assumptions and the method of computation used

in the original settlement predictions together with new assumptions and

methods of computations of settlement. The results of the various compu-

tations are then compared with measured settlement of the foundation. It

was found that the agreement between theoretical and measured settlements

was measurably improved when consideration was given to certain factors

affecting settlement at the site that had not originally been considered.

ANALYSIS OF SETI 4AENT DATA

DATA FROM WAPFAPPAPELLO DAMt MISSOURI

PART I: INVESTIGATIONS OF PERFORMANCE OF EARTH DAMS

Objective

1. A large number of dams built by the Corps of Engineers during

recent years consist wholly or partly of earthen materials and rest on

soil foundations. The design of such structures is based on soil

mechanics theories which in many cases are complex and their application

to specific problems is not always fully understood. Furthermore, soil

conditions at the sites are often very complicated and impractical to

explore in detail. Therefore, certain simplifying assumptions are made

so that generalized soil conditions may be established which will permit

the application of the theories of soil mechanics in the design analysis.

2. Because of these uncertainties in the design of earth structures

and foundations, the Office, Chief of Engineers, has inaugurated a program

of investigations to provide information on the performance of such

structures in operation. This information is intended to assist in the

design of future, similar projects. Specifically, data on the actual

behavior of engineering structures built of earthen materials and on soil

foundations, and which have been in operation long enough to permit a

reasonable evaluation of their performance, are compared with the design

requirements. Valuable information as to the prototype behavior of

structures of this type is thus made available for future use.

2

Selection of Wapapello Dam for Analysis

3. Wappapello Dam was selected for study of foundation settlements

because the foundation of the dam is composed of compressible soils and

the dam is of sufficient height to impose enough load on these soils to

result in substantial settlements. In addition, design data and a com-

plete record of prototype settlement data for the dam were available.

PART II: DESCRIPTION OF PROJECT

General Features

4. Wappapello Dam, built for flood-control purposes, is located

on the St. Francis River at the edge of the Ozark foothills. It is about

one-quarter mile southwest of the town of Wappapello, which is located

in. southeast Missouri. The project consists of a rolled earth dam,

approximately 2700 ft in length, across the river valley; three small

auxiliary dikes north of the dam site; an outlet structure located in

the right abutment, and an outlet channel; a spillway also located in

the right abutment, and a spillway outlet channel. The main embankment

has a crown width of 30 ft at elev 420 mG1 and symmetrical upstream and

downstream composite slopes, as shown on the typical cross section,

plate 1. The maximum section is between sta 19+00 and 19+50, where the

dam crosses the St. Francis River bed, and has a height of approximately

110 ft above the stream bed. The stream bed was filled with compacted

earth for 500 ft upstream and downstream from the axis of the dam.

Topography

5. The main embankment is constructed across the valley of the

St. Francis River at a point where the flanking hills converge to narrow

the valley to approximately 2400 ft at elev 350 mrG1. The flanking hills,

which form the right and left abutments to the dam, rise on an average

slope of I on 2.2 to slightly above crown elevation and then flatten to

gentler slopes. The valley floor was traversed by the St. Francis River,

located nearly in the center of the valley, and by two small streams,

4

Redman Creek and Peoples Creek. Redman Creek was located adjacent to

the south abutment at sta 6+00 and emptied into the St. Francis River

approximately 2000 ft downstream from the axis of the dam. Peoples Creek

was located on the valley floor near the north abutment and crossed

obliquely under the dam in a meandering pattern, emptying into the St.

Francis River about midway between the axis and downstream toe of the

dam (see plate 2).

Subsurface explorations

6. Soil conditions existing in the foundation for the main embank-

ment were explored during the latter part of 1935. Explorations were

extended by means of 34 auger, 29 core, and 5 undisturbed sample borings

as the design of the various component parts of the structure progressed.

The soils data obtained from the borings were further supplemented by

data obtained by excavating 10 test pits, numbered TP U-14 to TP U-23,

inclusive, and two test trenches, numbered 6 and 7. The auger borings,

test pits and trenches were limited in depth to ground-water level,

except for a few test pits in which the ground-water level was lowered

by pumping. Ground water was encountered 10 to 25 ft below the ground

surface. The core borings were carried well into the underlying bedrock.

The undisturbed sample borings varied from 44 to 70 ft in depth. Locations

of subsurface explorations, except auger borings, are shown on plate 2.

Foundation conditions

7. A log of borings along the center line of the dam is shown on

5

plate 3.* It may be noted that the foundation of the dam consists of

alluvial soils of variable thickness which are underlain by limestone

bedrock. The soil types vary considerably, both horizontally and

vertically along the axis of the dam. Fine-grained top stratum soils

averaging approximately 50 ft in thickness are encountered adjacent to

the right and left abutments of the dam and extend from the right abutment

to sta 11+00 and from the left bank of the St. Francis River (sta 20+00)

to the left abutment of the dam. These fine-grained soils are underlain

by strata of sandy soils, some of which contain gravel. Generally sandy

soils averaging 100 ft in thickness extend from sta 11+00 to the right

bank of the St. Francis River and from natural ground to the limestone.

These soils also contain strata of gravelly sandy soils.

8. A deep stratum of silty clay extends from approximately sta

8+00 across the valley to the left abutment (see plate 3). A weathered

zone approximately 10 ft deep tops the underlying limestone, The lime-

stone rises sharply under both abutments and is covered with a soil

mantle which generally contains broken stone, boulders, gravel, and

strata of weather porous limestone. A generalized soil profile * is

shown in the upper part of plate 3.

Sanpling and testing

9. Samples taken from the foundation beneath the main embankment

were subjected to tests according to their types and the purposes for

* The upper portion of plate 3 is a reproduction of plate 97, and thelower portion is a reproduction of plate 65 of St. Francis River Proj-ect, "Wappapello Dam, Analysis of Design, Appendix II, Report on SoilInvestigations," Memphis District, CE.

6

which they were obtained. Samples taken by auger, drive tube, and cores

were subjected to water content and mechanical analysis tests. Samples

recovered from the 6 undisturbed sample holes were tested for shear

strength and Atterberg limits in addition to the above-mentioned tests.

The samples recovered from test pits TP U-14 and TP U-23, inclusive, were

tested for consolidation characteristics, shear strength, Atterberg

limits, and specific gravity,

Design of embankment

10. The selection of rolled-fill construction for the embankment

of the dam was based on investigations that indicated that the materials

to be excavated for the appurtenant structures were suitable for compacted

fill. The design of the embankment section was based on a thorough in-

vestigation of the stability of the foundation, which contained strata

of plastic materials of considerable thickness in some areas as may be

noted from plate 3. The crest elevation initially selected was 416 ft

mraG1 and was subsequently changed to 420 ft mGl.

Construction

11. Construction work was started in August 1938 with clearing and

stripping of unsuitable top stratum materials in the foundation. The

amount of stripping found necessary varied from 1 to 4 ft. The stripped

foundation was thoroughly scarified prior to fill placement. The toe

drain was completed and rolled fill placed to elev 390 ft mCG1 on both

sides of the river, with only a few interruptions occasioned by inclement

weather. Upstream and downstream cofferdams were then constructed across

the St. Francis River and the river bed was dewatered and stripped of

unsuitable materials prior to construction of the closure section. The

toe drain across the river bed was of similar design to that placed

elsewhere, except that a rocky fill was placed in the old channel up to

elev 336 ft mGl. The entire embankment was completed to project grade

of 420 ft mG1 by May 1941.

Prototype Test Facilities

Settlement plates

12. Eighteen settlement plates, located as shown on plate 2, were

placed in the foundation in order to observe the amount and rate of

settlement. The location and original elevation of the plates are

tabulated below:

Plate ElevationNo. Station Location ft, mGl

1 6+37 Center line 327.492 8+06 250 ft upstream 348.393 7+53 Center line 349.124 10+50 Center line 345.495 8+98 250 ft downstream 347.666 15+25 Center line 346.077 25+68 200 ft downstream 348.498 283+05 250 ft upstream 342.669 25+65 Center line 343.78

10 22+55 Center line 348.7411 21+05 250 ft downstream 339.6112 18+00 250 ft downstream 315.6813 19+00 Center line 312.7014 16+03 480 ft downstream 308.9915 19+50 250 ft upstream 312.3516 19+50 480 ft upstream 313.8317 21+55 250 ft upstream 350.2118 15+07 250 ft downstream - 345.68

The settlement plates were made of 3/4-in.thick steel plate, 3 ft by

3 ft square, and were placed on the first or second layer of compacted

fill. A vertical l-t/2-in, steel riser pipe was welded to the center

of each plate and lengthened in 5-ft sections as the height of the

embankment increased. These vertical riser pipes were not cased.

Present engineering practice usually provides for casing such riser

pipes in order to eliminate friction between the pipe and the

surrounding compacted fill and provide freedom of movement as the plates

settle.

Hydrostatic pressure gages

13. Twenty-eight hydrostatic pressure gages of the Goldbeck,

Foxboro, and Wilson types were installed at various locations and

depths in the foundation for the purpose of observing the pore-water

pressure resulting from construction of the embankment and the progress

of consolidation of the compressible material.

PART III: PREDICTED AND ACTUAL SETTLMBENTS

Protot ye Test Facilities Used in Analysis

14. The highly stratified nature of the foundation is apparent

from a study of plate 3. The continuity between borings of the various

strata was generally indeterminate. In many cases, samples of fine-

grained soils contained silt and sand partings and samples of sandy

soils contained clay lumps.

15. Settlement predictions were made, for inclusion in the analysis

of design, at 11 locations based on the results of consolidation tests

of samples from 10 test pits, TP U-14 to TP U-23, inclusive, and on

an embankment height extending to elev 416 mGl. Of the 11 locations

selected for settlement computations, only 7 were close enough to

settlement plates to warrant comparisons of the predicted and measured

settlement in this report. Thus, predicted and measured settlements

are compared by means of data obtained from

Settlement plate 3 and TP U-20

Settlement plate 4 and TP U-20

Settlement plate 6 and TP U-16

Settlement plate 10 and TP U-22

Settlement plate 9 and TP U-23

Settlement plate 13 and TP U-17

Settlement plate 18 and TP U-19

the following:

32

265

10

10

10

95

50

Settlement plate 4, located at eta 10+50, was compared with test pit TP

U-20 because the original estimate of settlement at this location was

based on soil conditions encountered in test pit TP U-20 even though

ft

ft

ft

ft

ft

ft

ft

apart

apart

apart

apart

apart

apart

apart

10

test pit TP U-21 was located at a distance of only 125 ft from the

settlement plate.

Methods of Conputation

Ultimate settlement

16. The amount of consolidation of a given stratum in the

foundation was determined from the pressure-void ratio diagram for

a sample representative of that stratum. The ultimate settlement, S,

was determined from the following expression:

el - e$ l+e 1 h ,

where in:

el = void ratio corresponding to overburden pressure,

e 2 = void ratio corresponding to total pressure afterconstruction of embankment, and

h = thickness of stratum.

The total settlement is equal to the summation of ultimate settlement S

for each stratum encountered under the settlement plate. An average

overburden load of 110 lb per cu ft, based on laboratory test data, was

used. A submerged unit weight of 64 lb per cu ft was used for strata

below the water table. The added load due to the embankment was taken

simply as the weight of the embankment above the point in question, using

a unit weight of 130 lb per cu ft. Void ratios el and e2 corresponding

to the pressures before and after the addition of load were taken

directly from the laboratory pressure-void ratio curve for a sample

representative of the stratum under consideration.

11

Settlement during construction

17. Settlements that would occur during the construction period

were computed, using Terzaghi' s method, based on the assumption that the

settlement at the end of construction would be the same as that which

would have occurred in one-half the construction time had the entire load

been acting. A construction period of 9 months was used in the settlement

predictions and the loading during the construction period was presumed

to be accomplished at a uniform rate.

Depth of foundation considered

18. Consolidation tests were made only on samples taken from the

10 test pits, and settlement predictions were not made for strata

located below the bottom of the test pits. Depths of the test pits

(TP U-14 through TP U-23) are listed in table 1. It thus appears that

settlement was assumed to be the result of compression in the soil

strata above the bottom of the test pits, although no statement to this

effect has been found in the available reports.

19. There is one exception to the above implied assumption. The

"Analysis of Design Report, Appendix II," paragraph 7-08, states in

part: "A greater thickness, 90 feet of compressible material was found

along the center line in the vicinity of sta 27+50.* Assuming identical

conditions (with test pit TP U-20), the maximum settlement will occur at

this point and will equal approximately 5 feet of which approximately

50 per cent will occur during the construction period."

* Stationing has changed since publication of report so that oldstation 27+50 is now station 10+50.

12

Comparison of Predicted and Actual Settlement

Predicted ultimate settlement

20. A study of the computations for the original settlement

predictions showed that the loads were computed from the top of the

fill down to the stripping line and from the original ground surface

downward, thereby introducing a small error in that the weight of the

soil between natural ground surface and the stripping line entered the

computations twice. This error was generally small and its magnitude

of occurrence depended on the depth of stripping at the location of

the settlement prediction. In order to provide a basis for comparison,

the original computations have been corrected in this report to eliminate

the overlap in weight of the soil between the original ground surface and

the stripping line. In making-the correction, the computations are based

on a net embankment load and assume that the net effect of the rebound and

recompression of the foundation because of stripping is negligible.

21. The settlement was then recomputed to take into account the

change in project grade from elev 416 to 420 mG1 using the same assump-

tions and methods as were employed in the original computations. The

originally predicted settlement and the corrected originally predicted

settlement for project grade at elev 416 ft mGL, and the recomputed

originally predicted settlement for project grade at elev 420 ft mG1

are summarized in table 1. The latter values will be used in this report

for "predicted settlement."

22. The per cent of settlement occurring at the end of the construc-

tion period, as originally predicted, was assumed not to be affected by

13

the computations described abve so that settlement at the end of the

construction period was determined in each case frox the ultimate

settlement on a percentage basis. Table I shovs that it was predicted

that the ultimate settlements would take place during the construction

period at stations betveen eta 11+60 and 18+05 where the compressible

strata were relatively thin. At the ends of the dam, where the compres*

sible strata were relatively thicker, only about 50 to 60 per cent of

the ultimate settlement ase predicted to occur during construction.

Actual settlement

23. The amount and rate of actual settlement ocurring within the

foundation were obtained by running precise levels at given periods of

time on the settlement plate riser pipes. The periods of time varied

from daily during construction to semiannually sometime after completion

of the structure. The measured settlement taking place to 30 June 1953

at the settlement plates listed in paragraph 15, together with predicted

ultimate settlements and settlement at end of construction, is plotted

on plates 4 through 10. The progress of embankment construction also is

shown on these plates. Reference to these plates shows that practically

all settlement had taken place at every location by 30 June 1953 and that

only a small amount of additional settlement may be expected. The actual

settlement that had occurred by 30 June 1953 is presented on table 2

together with the predicted ultimate settlement for the 420-ft mC1 proj-

ect grade., Plate 1U shovs the measured settlement along the center line

of the Asm on 30 June 1953 compared with ultimate gpredicted settlement for

projceot grade of 420 ft mC. Plate 12 shows a cross section of the dam

at approximately sta 22+00, the predicted settlement on the center line

14

at sta 22+45, and the settlement measured by settlement plates 10, 11,

and 17 at the end of construction and on 30 June 1953. It may be noted

on plate 12 that the measured settlement at the center line had exceeded

the ultimate predicted settlement by the end of the construction period.

A comparison between the per cent predicted settlement and the per cent

measured settlem ent at the end of the construction period is shown in

table 2.

15

PART IV ANALYSIS OF PROTOTYPE DATA

Ultimate Settlement

24. Comparison of measured versus predicted settlements after

adjustments were made for stripping and actual height of dam showed that

good agreement obtained only in the case of settlement plate 3. Other

settlement plates showed measured settlements considerably in excess of

the predicted values. It is the purpose of this portion of the analysis

to determine the reason for these differences. Settlements at plates 4

and 13 were eliminated from further analysis because the distances

between the settlement plates and the nearest test pits were considered

too great to permit a reliable comparison between computed and measured

settlements.

Depth of compressible material

25. Apparently the predicted settlement was computed on the basis

of compression of the soil strata above the bottom of the test pits, as

stated in paragraph 18. Plate 3 shows that compressible soil strata are

also encountered between the bottom of the test pits and the underlying

bedrock. A computation of settlement based on the full depth of conpres-

sible material, but otherwise using the same assumptions as were used in

the original computations, was made and the results are listed in

table 3 under Case I.

26. Available consolidation test data were limited to test pit

samples. In lieu of actual consolidation test data for the compressible

soil strata below the bottom of the test pits, correlated data obtained

from a study of all soil data were used in the analysis. A chart was

prepared (see plate 13) on which the soil profiles were plotted together

with available soils data for the five test pits and settlement plates

under consideration. Soil conditions below the depth of the test pits

were taken from the nearest borings. The soil profiles were then divided

into strata and the available data for each strata were recorded on the

chart. Silty material encountered immediately below the bottoms of test

pits TP 22 and U-22 and TU-23 was assumed to be essentially the samn as that

sampled near the bottom of each of these two test pits. Accordingly,

consolidation characteristics of the silty material at the bottom of

each test pit were assigned to similar strata immediately beneath it in

each case. Consolidation test data obtained for sample 47, test pit TP

U-20, recovered at a depth of 48 ft, were assumed to be representative of

the lower clay strata in this test pit. Since this stratum was the

deepest actually tested, the data were also assumed to be representative

of all the clay strata encountered below the bottom of the test pits.

Properties of sandy soils were assumed on the basis of an initial void

ratio of 0.550, a compression index (Cc) of 0.40, and a saturated condi-

tion. These properties of sandy material are fairly typical of similar

materials encountered in the alluvial valley of the Mississippi River.

27. Settlement values obtained for Case I conditions again compared

favorably with measured settlement for settlement plate 3, and reasonably

well with the measured value at settlement plate 18 (see table 3). The

settlement values obtained for other settlement plates were larger than

the measured settlement but showed better agreement at settlement plates

9 and 10 than did the predicted settlement.

16

17

Other factors affectingsettlement computations

28. Other factors which may affect settlement computations for this

site aret the method of determination of vertical stress, the effect of

preconsolidation of the soil strata, the use of an assumed embankment

density vwhich was not obtained in the field, and variations in ground-

water elevation. These factors and their effects on the settlement

ccputations will be considered in subsequent zaragraphs.

29. Vertical stress determination. Vertical stresses for the

canputation of predicted settlement were determined as the weight of the

embankment directly over the point in question, using a density of 130 lb

per on ft. Vertical stresses may also be computed by the elastic method.

In the theory of elasticity, the vertical stress distribution imposed on

a foundation by the construction of an embankment is dependent on the

size and shape of the embankment section in addition to the unit weight

of the embankment material. The accuracy of the stress computations is

limited to a certain extent by the fact the soils do not behave as per-

fectly elastic bodies, Vertical stresses, based on the elastic theory

method, were computed by means of a chart based on the Carothers-Terzaghi

formula* for strip loads of infinite length, Computations were made for

vertical stresses at depths corresponding to the mid-height of the vari-

ous strata encountered under each of the five settlement plates con-

sidered. An egbankment density of 130 lb per cu ft was used, as in the

computations for predicted settlement. The depth-vertical stress

* Leo Jurgenson, The Aplication of Theories of Elasticity andPlasticity to Foundation Problems, 8$S, 1934.

18

variation under the five settlement plates caused by the embankment

surcharge load is shown on plate 14. It may be noted on this plate that

considerable reduction of vertical stress is indicated as the depth in-

creases at settlement plates located under the axis of the dam, and a

slight increase in vertical stress is shomw as depth increases at settle-

ment plate 18 which is located 250 ft downstream from the axis. This

effect is to be expected because, according to the elastic theory, the

stres intensity under areas subjected to triangular loading is dissipated

in an outward direction from the center as the depth increases. Thus,

vertical stresses below the surface near the outer edge of the loaded area

may equal or slightly exceed the stress caused by imposed load directly

above. The ultimate settlements computed on the basis of the entire depth

of compressible material and using vertical stresses determined by the

elastic theory method are tabulated in table 3 under Case II.

30. Settlement values obtained for Case II conditions generally

compared slightly more favorably with the measured settlement than those

obtained originally or for Case I conditions; however, the differences

were numerically quite small between Cases I and II. Settlement values

for all settlement plates except plate 18 were lover than those obtained

for Case I conditions.

31. Effect of preconsolidation. The concept of preconsolidation of

soil strata and its relationship to settlement problems was not generally

considered when the settlement analysis, cu ~:bich the predicted settle-

meants were based, was made. A study of the pressure-void ratio curves

obtained from consolidation tests showed that the soils at this site have

19

been preconsolidated to varying pressures in excess of the overburden

pressure at the beginning of construction. A number of methods for

adjusting the pressure-void ratio curves to take preconsolidation into

account have been proposed and are in current use. In this analysis the

adjustments were made in accordance with the method proposed by

Terzaghi*,: which is illustrated on plate 15.

32. Eb~_bankment density. In the laboratory compaction test when

gravelly soils are being tested it is standard practice to remove the

material retained on the 3/4-in. sieve. The wasted material is then

replaced on a parcentage basis with material retained on the No. 4

(0.18-n.) sieve. In placing the embankment, however, stones up to 6 in.

in diamoter were allotced in the fill. Under these conditions it is dif-

ficult to obtain field compacte densities that agree closely with the

laboratory values. The overa-ll compacted density obtained for the

embankmnt on this da amounted to approximately 88 per cent of that

obtained in the laboratory. Actual average densities of the erbnlkment

material ere determined from available field control data, and are

included in table 3.

33. Vaiations in roundr-xater elevtion. A factor which has

coniderable bearing on settlement comrutations is the determination of

a reliable average ground-ater elevation for any particular point. A

review of the exploratory data showled that ground-wter elevations

determined in the test pits varied only3 4 ft in the 10 test pits, with

an average elevation of 325 ft rl. However, 11 core borings showing an

* K. Terzaghi, ' Relation of Undisturbed Sampling to Laboratory T'sting."Discussion, Proc ASCE, JUne 1943.

20

extreme variation of 16 ft in water elevation gave an average ground-water

elevation of 335 ft mGi, which is 10 ft higher than that shown by the

test pits. It was decided to use the ground-water elevation from the core

borings as shown on the lower part of plate 3, because the plotted ground-

water table conformed more nearly to natural conditions and therefore

appeared to be more reasonable.

34. Overburden weight. The overburden weights were computed for

each test pit from the available laboratory and correlated soils data

(see plate 13) using the relationships

S 7

m 1 t"e

wherein ym = unit moist weight

o'm = unit submerged weight

7w = unit weight of water

S = 6specific gravity

a = void ratio

w = water content

The overburden load-depth diagrams for the five test pit locations are

show on plate 16.

35. A computation of settlement was made based op the full depth

of cozressible material, vertical stresses computed by the elastic

method, and considering factors described in the preceding paragraph

(31 to 34). Results of the computations are shown in table 3 under

Case III. Settlement values obtained for Case III conditions compare

2

very favorably with the measured values for the five settlement plates

under consideration.

Time Rate of Settlement

Method of Computation

36. Tie-settlement rates were recomputed for instantaneous loading

conditions based on ultimate settlement computations for Case III. The

following relationships were used:

t90OL

and

-T---t t

wherein

tg F = time for 90 per cent consolidation in field stratum

t90L = time for 90 per cent consolidation in laboratory specimen

= height of longest drainage path in field specimen

=L = one-half height of laboratory specimen

tuF = time for u per cent consolidation in field stratum

T = time factor for corresponding u per cent consolidation

(Case I as tabulated by Tersaghi and Frbhlich*)

Values of t w0L vere obtained for the portion of the compressible soils

above the bottom of the test pitse and for silty soil imuediately below

the bottom of the test pits by averaging values of tg90 L, for all

* Theorie der Setzung von Tonschickten, Vienna: Deutische, 1936.

22

consolidation tests performed on the nearest test pit samples. For clay

soils below the bottom of the test pits an average value of t90L Vas

obtained from all consolidation tests performed on silty clay soil from

test pit TP O-20. Instantaneous settlement was assumed for all coarse-

grained soil strata. Computed time-consolidation data obtained for the

instantaneous loading condition under settlement plate 3, located near

test pit TP U-20, are tabulated below. Strata are numbered as shown on

plate 13. Actual drainage conditions at the site were difficult to deter-

mine because of the highly stratified nature of the foundation soils. It

was assumed that a free drainage surface exists between the top of stratum

I and the embankmnnt. It was also assumed that the combined strata I, II

and III, combined strata IV and V, and stratum VI would be drained from

the top and bottom. Instantaneous settlement equal to 0.15 ft was assumed

to occur in stratum VI which consisted of gravelly sandy soil. Also, 30 per

cent of the settlement occurring in strata I, II and III or 0.28 ft was

estimated to be instantaneous, making a total of 0.43 ft of instantaneous

settlement which would occur under the settlement plate. The remaining

70 per cent or 0.64 ft of the settlement occurring in strata I, II and III,

and all of the settlement or 2.16 ft occurring in strata IV and V were

subject to time effects.

Strata I, II, III Strata I , V

StuF Settlement F SettlementT Days ft Days ft

10 0.0077 1.6 0.06 81 0.22o20 0.031 6.3 0.13 326 0.4340 0.l426 26 0.26 1,310 0.8760 0.287 58 0.39 2,980 1.3080 0.565 115 0.51 5,880 1.7390 0.848 171 0.58 8,830 1.9595 1.129 230 0.61 11,900 2.06

23

Time-settlement curves forconstruction rate of loadi

37. Data similar to those tabulated above were utilized to construct

the tipe-settlement curves for the construction rate of loading which are

shown on plates 17 through 21 for the five settlement plates (3, 18, 6,

10, and 9) under consideration. The time rate of construction was divided

into stages which conformed as nearly as practicable to the actual con-

struction rate. Computations for the time-settlement for the construction

rate of loading were made on the basis of conditions for Case III as

described in table 3.

38. The method used to determine the adjusted time-settlement curve

is described in paragraph 4 04, part CXIXJ chapter 4 of the "Engineering

Manual for Civil Works Construction.. The following is an application of

this method to the specific case The theoretical and measured time-

settlement curves for the construction rate of loading at settlement plate

3 are shown on plate 17. It may be noted that the rate of construction was

divided into two stages which conform fairly well with the actual construc-

tion rate. Stage I represents a period of uniform loading for 379 days dur-

ing which time 79 per cent of the total embankent load was applied.

Stage 2 represents a period of uniform loading for 161 days during which

time 21 per cent of the total embankment load was applied. There vas also

a period of 320 days between stages 1 and 2 when no embankment load was

applied.

39. in order to obtain the theoretical time-settlement curve for

eonstruction loading, plate 17, the settlements obtained for instantaneous,

canbined strata I, IIU, and III, and ccmbined strata IV and V vere propor-

tioned on a percentage basis vith 79 per cent allotted to stage 1 and

24

21 per cent allotted to stage 2. For stae , the instantaneous settle..

meat as applied uniformly over the construction period. The settlements

subject to time effects (strata I, fI, and II, and strata I1 and V)

vere applied starting at the halt-time for stage I period. Thus, three

settlement urves for assumedt. instan s loading conditions were drMawn

instantaneous settlements for all strata cbined, time settlements for

strata I, U, and I and time settlements for strata V and VI. The

toretical settlement urve for construction loading, stage 1I was ob-

tasned by adding the ordlnates for the three curves. In a similar man.

nero settlements for stage 2 constructton were applied to the theoretical

cIrve obtained for stage 1 construction. The theoretical settlement

curves were developed in a similar manner for the other settlement plates

as shoa on plates 18 through 21.

40. A cazparmison between the actual and reocpted settlaemnts at

the end of the construction period ts shon on table 4. The individual

settlemet curves for instantaneous loaditn coditions that were used to

obtain the theoretial tie-stleent curves are not shown on plates 17

25

PART V: DISCUSSION

41. The predicted settlement and settlement computed on the basis

of Cases I and II as given in table 3 did not compare favorably with the

measured settlement except at settlement plate 3. Settlement computed on

the basis of Case III conditions as given in table 3 compared favorably

with the measured settlement. Computations for Case III conditions had

the advantage of the use of actual average embankment densities and the

refinement of adjusted pressure-void ratio curves to take preconsolidation

into account, factors which were not available for the original

computations.

42. Discrepancies between the originally predicted and measured

settlements can be attributed largely to the fact that the compressible

soil strata below the bottom of the test pits was not considered. The

close agreement between predicted and measured settlement at settlesettlement

plate 3 supports this statement, because the depth of test pit TP U-20,

on which the computations were based, was closest of all the test pits

considered to the actual bedrock. However, when the full depth of the

compressible soil strata is considered, Case I computations result in

settlement values which somewhat exceed the measured values. Case II

computations, which utilize vertical stresses determined by the elastic

method, result in settlement values that agree more favorably with the

measured values and thus demonstrate the advantage of the elastic method

for vertical stress determination when compressible soil strata extend

to considerable depths as at this site.

43. Consideration was given to the various factors affecting settle-

ment described in paragraphs 31 to 34 in the Case III computations. The

effect of the individual factors on the computations was not separately

demonstrated. The combined effect of considering these factors is shown

by the close agreement obtained between the coputed and measured settle-

eint values. It is believed that the factor effecting the major improve-

ment in the results was use of the actual embankment densities, although

consideration of the other factors may have materially contributed.

44. Some of the discrepancy between the theoretical and measured

settlements may be attributed to the fact that settlement plates were

usually located at some distance from the test pits. Soil conditions at

the site were heterogeneous, as previously stated, so that computation of

settlement at the test pit may not be valid for couparison with measured

settlement at the nearest settlement plate. These circumstances are

inescapable when test pits are employed for obtaining samples for con-

solidazion tests and subsequent settlement analysis, because the settle-

ment plate ast be located at a sufficient distance from the test pit to

avoid disturbed soil conditions attendant to excavation and backfilling

of the test pit.

45. The recomputed theoretical time-settlement curves for construc-

tion loading based on conditions for Case III comared very favorably

with the measured settlements at settlement plate 18 (plate 18) and fairly

well with the measured settlements at settlement plate 6 (plate 19). The

comparison at other settlement plates was not good. Several factors may

have influenced the results of these computations. They are: sample

disturbance, selection of a representative value of t9oL , and the

27

occurrence of thin strata or lenses of fine sand or silt in the founda-

tion soil. It is believed that the largest error in the time-settlement

computations for this site was introduced by the lenticular nature of

the fourndaton soila which contained innumerable fine sand and silt

lenses. These lenses, if continuous or interconnected, provide drainage

paths for pore water dissipation and thus introduce additional drainage

boundaries which may greatly speed up the rate of consolidation over that

predicted on the assumption of a homogeneous stratum. A careful examina-

tion of the undisturbed samples in conjunction with a study of the boring

logs may provide a basis for establishing mr e realistic drainage condi-

tions than is apparent from an inspection of the boring logs alone.

28

PART VI COIUSIONS AND RECIOWIATIONS

Conclusions

6E. On the basis of the preceding analysis, the following conclu-

sions are believed warranted,

a. A reasonable estimate of ultimate settlement for a struc-ture of this type may be made, as evidenced by results ofCase III cmputations, if factors influencing settlementat the site are carefully evaluated.

b. Reliable time-settlement predictions are difficult to makeVhen lnticular ecapressible soil strata are encounteredin the foundation, as at this site. Under these conditions,predicted settlement values at the end of construction areusually less than measured values. A careful examinationof undisturbed samples and boring logs is required to revealdraage conditions in such foundations that may in turnresult in more favorable time.settlement predictions.

Recommendations

47. The following procedures are reomsded for use in explorations

and settlement analyses, and in installation of prototype test facilities

in connection with future studies of this type.

a. Foundation explorations for the purpose of settlementanalyses should be made by means of borings of a type anddiameter suitable for the recovery of undisturbed samplesfor consolidation tests. The required depth of borings forsettlement analyses should be detemined on the basis of afew deep preiminary borings. If soils subject to consider-able consolidation are encountered in the preliminaryborings, the borings for settlement analyses should eitherpenetrate the compressible strata or extend to such depththat the stress increase for still deeper strata is reducedto values so small that the corresponding consolidation ofthese strata will not materially influence the settlement ofthe proposed structure. Plate 22 shows a diagram of a pro-posed method for determining the required depth of boringsfor settlement analyses .*

* M. Jul v-orsle, Subsurface.: Exploration and S-mplirq- of Soils forCivil Engineerinjg Purposes. iES, lovember 198, age 18.

29

b. Consolidation test data should be examined to determinewhether the soils are preconsolidated. If preconsolida-tion is indicated, the pressure-void ratio curves shouldbe adjusted as described in paragraph 31, or by othermethods, before use.

. A preliminary computation of vertical stresses should bemade by the elastic theory method. If compressible soilstrata extend to depths below bich the vertical stressestend to decrease with depth, the settlement analyses shouldbe based on vertical stresses determined by the elastictheory method. The preliminary computations will alsoserve as a guide to determining the required depth of boringsas described in a above.

d. Bettlement plates installed for the purpose of comparingpredicted settlement with measured settlement should belocated within a few feet of the boring on which thesettlement prediction is based.

ASSOCIATED REPORTS

St. Francis River Project - The Wappapello Dam, Analysis of Design,Appendix II, Report on Soil Investigations.

St. Francis River Project - The Wappapello Dam, Plans for Constructionof Dam and Appurtenant Structures.

St. Francis River Project - The Wappapello Dam, Completion Report(unpublished).

Test PitDepth

Station Location No. ft

7+85

10+50*

11+60

11+75

15+15

15+35

15+35

18+05

18+05

22+45

25+55

Centerline

Centerline

300 ftDS

Centerline

300 ftDS

225 ftUS

Centerline

225 ftUS

Centerline

Centerline

Centerline

TP U-20

TP U-20

TP U-18

TP U-21

TP U-19

TP U-14

TP U-16

TP U-15

TP U-17

TP U-22

TP U-23

68.5

68.5

24.3

24.4

26.2

28.0

26.2

24.3

20.5

43.3

42.4

Table 1

SUMMARY OF PREDICTED SETTLEMENT

Predicted SettlementOriginal Project Grade, Corrected Original Project

416 ft mGl Grade, 416 ft mGlAt End

Ultimate Constructionft ft Per Cent

3.29

5.00

0.19

0.96

0.32

0.23

1.17

0.45

1.84

1.70

2.78

1.71

2.50

0.19

0.91

0.32

0.23

1.17

0.45

1.84

1.04

1.53

52

50

100

95

100

100

100

100

100

61

55

At EndUltimate Construction

ft ft Per Cent

3.04

5.00

0.14

0.96

0.21

0.20

1.15

0.38

1.84

1.67

2.78

1.57

2.50

0.14

0.91

0.21

0.20

1.15

0.38

1.84

1.02

1.53

52

50

100

95

100

100

100

100

61

55

Recomputed Original ProjectGrade, 420 ft mG1

At EndUltimate Construction

ft ft Per Cent

3.24

5.00

0.14

1.01

0.21

0.20

1.20

0.38

2.02

1.76

2.91

1.68

2.50

0.14

0.96

0.21

0.20

1.20

0.38

2.02

1.07

1.60

52

50

100

95

100

100

100

100

100

61

55

* Estimate based on 90 ft of compressible material. Refinement not considered warranted.

Table 2

COMPARISON OF PREDICTED AND MEASURED SETTLEMENT

Predicted*At

Ultimate

3.24

5.00

0.21

1.20

2.02

1.76

2.91

EndCon-

struc-tion

1.68

2.50

0.21

1.20

2.02

1.07

1.60

Settlement in Feet

PerCent

52

50

100

100

100

61

55

Ultimateas of30 June1953

3.35

3.76

0.50

2.09

1.58

5.14

5.79

Measured

AtEndCon-

struc -tion

2.50

3.03

0.25

1.60

1.00

3.25

4.13

Settlements computed on basis of** Settlement recomputed for 250 ft

*** Estimate

420-ft mGl project grade and 9-monthsDS, while prediction was computed for

construction period.

300 ft DS,

Settle-mentPlate

3

4

18*

6

13

10

9

Station

7+53

10+50***

15+07

15+25

19+00

22+55

25+65

Loca -tion

CL

CL

250 ftDS

CL

CL

CL

CL

TestPitNo.

TP U-20

TP U-20

TP U-19

TP U-16

TP U-17

TP U-22

TP U-23

OriginalElev ofPlateft mGl

349.12

345.49

345.68

346.07

312.70

348.74

343.78

Con-struc-tion

Periodin

Months

26

25

5

25

9

19

19

PerCent

75

81

50

76

63

63

71

Table 3

MEASURED AND COMPUTED SETTLEMENTS

Project Grade, 420 ft mGl

Measured

30 JuneStation Location 1953

SettLement in FeetRecomputed

DesignPredicted Case I Case II Case III

Assumed Depth ofCompressible MaterialGround Surface in FeetPredicted Recomputed

Density ofEmbankmentCase IIIlb/cu ft

7+53 Centerline

18 15+07 250 ftDS

6 15+25 Centerline

10 22+55 Centerline

9 25+65 Centerline

3.35

0.50

2.09

5.14

5.79

3.24

0.21

1.20

1.76

2.91

3.38 3.26

0.63 0.80

3.14 2.65

6.64 6.26

7.37 6.60

Case I: Full depth of compressibledirectly above.

Case II: Full depth of compressibleCase III: Full depth of compressible

consolidation of foundationutilized.

material with vertical stresses equal to the weight of embankment

material with vertical stresses determined by the elastic method.material, vertical stresses determined by the elastic method, pre-materials considered and the actual coverage embankment densities

LSette -mentPlateNo.

3.24

0.44

2.19

5.31

5.77

68. 4

24.5

38.0

29.3

42.3

82

125

122

122

126.2

119.7

121.0

120.5

121.0

i r rr - r r r i -

lAl _ _ 1.7 i '7 t T

--

- -- ~~ ~-~~-~-~ -~-

TABLE 4

COEARISON F COF C'UTED AND MEASURED SETIIENETEND OF CCNSTRUC~ TIN PERIOD

SettlementPlate

3

6

10

9

Station

7+53

15+07

15+25

25+65

Location

CL

250 ft DS

CL

CL

CL

Settlement in ft atEnd of Construction

PeriodMeasured Recomuted

2.50 i.66

0.25 0.27

1.6o 1.73

3.25 2.10

4.13 2.26

Error

Feet Per Cent

0,84 34

0.02 8

0.13 8

1.15 35

1.87 45

- UL IL - - --

J - -U - L-L-L i . L ..-

.___~~~_~______ _~______ _ _~ __~ _ ~_ _ _____~ __~~____~ _~~~~_~___~ ~~__ _~~_______ _~__~__ _~_ ______~

UPSTREAM

3'- O"DUMPED 4SLOPE O/V 5S_ EL 378.

CROWN OF ROAD EL 420.0'

SLOPE /ON 2 SLOPE ON 2

SLOPE ON 4 EL 405S.0 ..3' " EL 405.O SLOPE / ON 4 DOWNSTREAM

/PRAP ':MA" T'E . < .: 3'-O" DUMPED RIPRAP

5IS" .' COMPACTED • "EL_378.75 SLOPE I ON 5S- IMPERVIOUS MATERIAL - 3787 EL 3670

/&6"SAND & GRAVEL ! r I'- O"SAND GRAVEL " .C.,

APPROX ORIGINAL GROUND AVERAGE DEPTH OF STRIPPING APPROX STRIPPING LI

APPROX 3'- 0"

SCALE IN FEET

50 0 50 100

13I

rTYPICAL CROSS SECTION

.. '"

v .0

LEGEND

O SP SETTLEMENT PLATE

® U UNDISTURBED BORING

* CORE BORINGo TP TEST PITIL- TRENCH LOCATIONS OF EXPLORATIONS

AND SETTLEMENT PLATES

T3r

*1rn

N

I

LEGEND

CLAY

L SILT

SAND OR

SAND AND GRAVEL

TEST PIT

CENTER LINE PROFILESTATIONING ALONG CENTER LINE OF DAM

270 , 0 GENERALIZED SOIL250 -250 PROFILE AND BORINGS230. -230 ALONG CENTER LINE210 o210 OF DAM

PROFILE ALONG CENTER LINE

STATIONING ALONG CENTER LINE OF DAM

3600

- 340

Z 320

300

W 2a0

260

!-or

rriCo

J

U

wHLLz

z

7

0H

w

w

w

UL

z

Li

H

Li

2w

wU,

1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954

O PREDICTED SETTLEMENT - END OF CONSTRUCTION0 PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENT

SETTLEMENT PLATE 3STATION 7+53 CENTER LINE

420 - --

TOP OF FILL!400

380

360 --

ORIGINAL PLATE ELEV

320

300

0.0

1.0

2.0

SETTLEMENT--------

4.0

5.0

6.0

7.0

r-

H-

e w

420i ==..=.TOP OF FILL -

400

380

360

340ORIGINAL PLATE ELEV.

320

300

1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954

O PREDICTED SETTLEMENT - END OF CONSTRUCTIONO PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENT

SETTLEMENT PLATE 4STATION 10+50 CENTER LINE

Jl

WLLU-

z

z0

w

J

w

F-

Ut-I

z

F-

w

2U

F-HH

VI)

-Ur

440 l- IT I I -- i

J 421C,

420

401W

w

a

L 38

z

36

w 32

30

0.

6.

w 2.

zL

Z 3.1

Z 4.1

w

I

w .

u} 6

7.

8.1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 195

0

0

0

STOP O F FL

ORIGINAL PLATE ELEV

0

0 SE T TL EMEN T

I I

0 I

0

I I

0 i_ _ i I i IL i _ _ 1

O PREDICTED SETTLEMENT - END OF CONSTRUCTION0 PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENT

SETTLEMENT PLATE 18STATION 15+07 250 FT D.S.

54

'Dr

rn0)

J 420C,

2400

Hw

w

L 380

z

z 360360

OS340

w 320

0.0 T T [ 1 - T - T I

I.

2.

n I -i - I TS . .. ___ L 4 _ _ - 4 1 4 £4I 1 ; T 1 1 4 1 1 4 I--- 4-

01 -I I I- rzrftt-r'r-rA Li ISET TL EMi

I I I[ IFIT I4.0 11

7.0

7.0-

a.0

1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 J950 1951 1952 1953 1954

O PREDICTED SETTLEMENT - END OF CONSTRUCTIONO PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENT

SETTLEMENT PLATE 6STATION 15+25 CENTER LINE

ENT---wWL-

z

Hzi2w

JF-H-Liu}

I-

-m

vu

v.v

440

420

I-2 TOP OF FILL-

400wL 3 C80

z

360

340

ORIGINAL PLATE ELEV.

O PREDICTED SETTLEMENT - END OF CONSTRUCTIONO PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENT

SETTLEMENT PLATE 13STATION 19+00 CENTER LINECDI

Ir1

cx,

J

HwWUL-

z

z2HUI-

w

w

w

w

F-

w

U I7.0 zi8.0

1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954

O PREDICTED SETTLEMENT - END OF CONSTRUCTION

0 PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENTSETTLEMENT PLATE 10

STATION 22+55 CENTER LINE

4404

420

TOP OF FILL

400

380-------------------- - - _ - --

360

0.0

3. -

4.0

SE T TL EMENT -

- ---

T1

-uJ"O

r

co

_ -

F-WIUU

z

zz0

J

w

U

zH

z

J

F-w

Hul

O PREDICTED SETTLEMENT - END OF CONSTRUCTION

O PREDICTED ULTIMATE SETTLEMENT FOUNDATION SETTLEMENT

SETTLEMENT PLATE 9STATION 25+65 CENTER LINE

-4rP__0

0

w

zI-

tR3

J

5

60+00

LEGEND

0 PREDICTED SETTLEMENT AT

0 MEASURED SETTLEMENT ATJUNE 30,1953

* ESTIMATED

10+00 20+00CENTER LINE STATIONING

30+00

UNDATION SETTLEMENT

)NG CENTER LINE OF DAM

-r-

m

DISTANCE IN FEET DOWNSTREAM

0 160

DISTANCE IN FEET UPSTREAM

160 241

LO

w 2.0

z

r-Z 3.0w

-J

4.0u

5.0

6.0

DATE EMBANKMENT WAS COMPLETE TOPROJECT GRADE OVER SETTLEMENTPLATE.

wwLzI -zw

Lii

LIn

FOUNDATION SETTLEMENTAPPROX STATION 22 +00

r

r

I

a_

PLATE 3F TP U-20

cy 0N

l

So _ c--

°~ .d -

II my oa -- N

.. N

-Oqflnc

0 jenc P2 F.

0a:

0

20

40

I-

Ls 60L

.la

100

PLATE 18TP U-19

250 03

oo 00

1 0o0

Iv

Vl -IO, nI N

o 00

I o I -

• 0I 0 0 IVIII co -t

v

0

PLATE 6TP U- 16

, o lo u ,-Evieo12r=

F

Il-

iv

V

VI

&-

I

PLATE 10TP U-22

Su

N r o -

l0I O N l

SF -,F -o

1 01 i I0

VIIl j 144vP I

VII1

SX

LEGEND

SETTLEMENT PLATE POSITIONGROUND WATER DEPTHWATER CONTENTCOMPRESSION INDEXSWELLING INDEXEXISTING OVERBURDEN PRESSUREPRECONSOLIDATION PRESSUREINITIAL VOID RATIO AT EAISTING OVERBURDEN PRESSUREHEIGHT OF STRATA IN FEET

UNDERSCORED FIGURES ARE ASSIGNED VALUES BASEDON TEST RESULTS ON TEST PIT SAMPLES

IO

F

cr

:,

IV

Y

VI

VII

VIII

Li X

PLATE 9TP U-23

o

o c, o a u r

•ONNf -noi 'N0

.NI OJ -

Im l l o

o1 r

nI

tooI

I

III

1

I

cI

0

20

40

I--60 w

z

I

80 w

120

140

GENERALIZED DATA FOR FIVE

SETTLEMENT PLATES

oI'I onI - NNI° ..

1I 1

i t I -

NO 'q.

1 pj CMNO O

120

140

F

I-a

w

F

u

z

U.ODm '

2w

CcCtPoPceoH

-u,r

-1mrN

- ----- --- ------- -- ----------- --- -- --- ------------ ------ - --- --

4

F

I i

0

20

wwF-iI-

z 40

hJ

F-J

C-n

- 601-4LUWz

w

hi

ED3:80I-0WQ

100

120

AP IN TONS PER SQ FT

VERTICAL STRESSES DETERMINEDBY ELASTIC METHODEMBANKMENT LOADING

CURVE LOCATION DENSITY SETTLEMENTCURVE LOCATION LB/CU FT PLATE

I _ 13 3,6,9 & 10 /2 k 126 33 C121 9&10

4 120 6

- -- 5 250' DS 130 18-6 250o' DS 120 18

-ur

-rli

N d n co -03- N m3 1 o a I- 0 - N at

I I I I l

eo " B I. DRAW HORIZONTAL LINE AB THROUGH

POINT OF INITIAL VOID RATIO , .

2. DETERMINE P AND PC.

AF - LABORATORY CONSOLI- 3. DRAW VERTICAL LINES THROUGH P AND

DATION CURVE Pc INTERSECTING AB AT C AND DCG - CONSTRUCTED CONSOLI- RESPECTIVELY.

DATION CURVE

Po - EXISTING OVERBURDENPRESSURE 4. DRAW LINE DG PARALLEL TO EF (STRAIGHT

P - PRECONSOLIDATION - - - - - - - - - LINE PORTION OF LABORATORY CURVE)

PRESSURE THROUGH D.

5. STARTING AT C. SKETCH A PRESSURE-

VOID RATIO CURVE OF SIMILAR TREND

AND CURVATURE TO LABORATORY CURVE

AND TANGENT TO DG.

Po PCLOG OF PRESSURE

METHOD OF ADJUSTINGPRESSURE-VOID RATIO CURVE

PRECONSOLIDATED SOILS

0

Ia

-Dr

-Imn

_ ~ _~___~

F G

OVERBURDEN CURVES20 -- WAPPAPELLO DAM

TP U-20TP U-19

"--- T P U-2 2

40 ------ TP U-23

-- TP U-16

60

80

20

LI I I [ i - 1 [1 1 [ l J -1 II I I I I IAII I i -J-I Ili I.i - I-2 3

Po - OVERBURDEN PRESSURE IN TONS PER SQ FT4

VERTICAL STRESSES FOREXISTING OVERBURDEN LOAD

I-UwLL-

z

I

a-UWO=

0

I

-I

0)

I

- I 4Il I I -

____ - _ _ - --i-- -I--

0 -

--. THEORETICAL SETTLEMENT FOR1.5 CONSTRUCTION LOADING

25 - MEASURED SETTLEMENT

3.0 4 - -0 16uuTIME IN DAYS

TIME IN DAYS

SETTLEMENT-TIME FORCONSTRUCTION LOADING

SETTLEMENT PLATE 3

-0hozJ

J 50

L0

t.,0

-0

I-rn-IiT

00

100I1 1 / j i

r' 1 i 1 I 1 I I ! i I 1 _

I u IW%600 10U00 [200o200 400

IL0<NLO

zJ

w.-hi

0

800TIME IN DAYSTIME IN DAYS

1000 1200 1400 1600

SETTLEMENT-TIME FORCONSTRUCTION LOADING

SETTLEMENT PLATE 18

02

0.3

-- I M EASURED SE r TL EMEN --

THEORETICAL SETTLEMENT FOR.- CONS TRUC TION LOADING

0.6 2400 200AAA

nA IAA n .w

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W

i

hiZ

hI2W

W-JF-I-hiCI}

>t

m

v LV~ 44,UU00

=

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0<-0

I-

U.

z

I-

z

U

z

I

JI-I-U

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600 TIE N DAYSTIME IN DAYS

1000

SETTLEMENT-TIME FORCONSTRUCTION LOADING

SETTLEMENT PLATE 6

100

0.4THEORETICAL SETTLEMENT FOR

CONSTRUCTION LOADING

0.0

1.2

MEASURED SETTLEMENT

2.0

0~ 9 rt/- dA e., ,., ............... ...

_Q[-r-t

rV 400 1200 1400 1600I -

LL a0<

F-Oz-Ju0

aJ-

r

w0

z

I-WW

zw

z

HZW

J

HHi

400 600 800

TIME IN DAYS

1000 1200 1400

SETTLEMENT-TIME FORCONSTRUCTION LOADING

SETTLEMENT PLATE 10

100

THEORETICAL SETTLEMENT FOR

cONsRUCTION LOADING

1

S- _ - MEASURED SETTLEMENT

6 ~ ~~~ _ _ _ j__ _ __

~_00 500

r-I

to

1600

_~__~_~~_

20 0

- i

w ----- k----.-0-

w\

U

-- - ........ _ THEORETICAL SET TLEMEN T FOR3-- CONSTRUCT/ON LOADING

1--w J -_-

MEASURED SETTLEMENT

TIME IN DAYS

SETTLEMENT-TIME FORr

CONSTRUCTION LOADINGSSETTLE . SETTLEMENT PLATE 9

0 F 0 00')t0 20 4010

VERTICAL STRESSGROUND LEVEL

z0

O_C '

SQ I

w /NNCREASE IN VERTICAL SOIL STRESS

O CAUSED BY PROPOSED STRUCTURE

I C:-J

w

owC

rIO 10/o OF ORIGINAL VERTICALI- STRESS IN SOIL

0,

STRESS DISTRIBUTION DIAGRAMS

METHOD FOR DETERMININGr

SREQUIRED DEPTH OF-I

fl BORING

N