CONSOLIDATION CHARACTERISTICS DETERMINATION FOR …report together with the results of the seepage induced consolidation tests ... The soil used in this test is designated as “Scientific

The Florida Institute of Phosphate Research was created in 1978 bythe Florida Legislature (Chapter 378.101, Florida Statutes) andempowered to conduct research supportive to the responsibledevelopment of the state's phosphate resources. The Institute hastargeted areas of research responsibility. These are: reclamationalternatives in mining and processing, including wetlandsreclamation, phosphogypsum storage areas and phosphatic claycontainment areas; methods for more efficient, economical andenvironmentally balanced phosphate recovery and processing;disposal and utilization of phosphatic clay; and environmentaleffects involving the health and welfare of the people, includingthose effects related to radiation and water consumption.

FIPR is located in Polk County, in the heart of the central Floridaphosphate district. The Institute seeks to serve as an informationcenter on phosphate-related topics and welcomes informationrequests made in person, by mail, or by telephone.

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Executive DirectorRichard F. McFarlin

Research Directors

G. Michael Lloyd Jr. -Chemical ProcessingJinrong P. Zhang -BeneficiationSteven G. Richardson -ReclamationRobert S. Akins -MiningGordon D. Nifong -Environmental Services

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(863) 534-7160Fax: (863) 534-7165

CONSOLIDATION CHARACTERISTICSDETERMINATION FOR PHOSPHATIC CLAYS

Final Report(FIPR contract No. 90-02-084)

VOLUME 3 : Results of Seepage-Induced ConsolidationTests on Phosphatic Clays

Prepared forFLORIDA INSTITUTE OF PHOSPHATE

1855 West Main StreetBartow, FL 33830

RESEARCH

Submitted by

A. Naser Abu-Hejleh, Dobroslav Znidarcicand Amy Robertson

Department of Civil, Environmentaland Architectural Engineering

University of ColoradoBoulder, CO 80309-0428

October 1992

DISCLAIMER

The contents of this report are reproduced herein as receivedfrom the contractor.

The opinions, findings and conclusions expressed herein are notnecessarily those of the Florida Institute of Phosphate Research,nor does mention of company names or products constitute endorse-ment by the Florida Institute of Phosphate Research.

Contents

1 Introduction 7

2 Tests on samples from C.F Industries ISA 102.1 Experimental results of seepage induced consolidation test . . 102.2 Parameter estimation of the constitutive parameters . . . . . 16

3 Tests on samples from Seminole H2B 193.1 Experimental results of seepage induced consolidation test . . 193.2 Parameter estimation of the constitutive parameters . . . . . 28

4 Tests on samples from Agrico SA-9 384.1 Seepage Induced Consolidation Test . . . . . . . . . . . . . . 384.2 Restricted Flow Consolidation Test . . . . . . . . . . . . . . . 394.3 Self Weight Consolidation Test . . . . . . . . . . . . . . . . . 434.4 Transient Consolidation Test . . . . . . . . . . . . . . . . . . 50

5 Tests on samples from Agrico SA-North 545.1 Seepage Induced Consolidation Test . . . . . . . . . . . . . . 545.2 Transient Consolidation Test . . . . . . . . . . . . . . . . . . 55

6 Tests on samples from Occidental 646.1 Seepage Induced Consolidation Tests . . . . . . . . . . . . . . 656.2 Transient Consolidation Test . . . . . . . . . . . . . . . . . . 65

7 Conclusions 75

8 References 77

1

3

5

Chapter 1

Introduction

This report contains results of the seepage induced consolidation tests on

phosphatic clay samples as well as results of verification tests performed on

the same material. The testing program was executed as a part of a research

project sponsored by FIPR in which the seepage induced consolidation test-

ing and analysis procedures have been implemented for the determination of

consolidation characteristics of phosphatic clays.

A total of five samples were tested in the program with multiple seepage

induced consolidation and verification tests performed on each sample. The

samples are identified by the mine names:

l C.F. Industries ISA

l Seminole H2B

l Agrico SA-9

7

l Agrico SA-North

l Occidental

The results presented here do not necessarily present “typical” properties

for the clays from stated mines since many factors will affect the particular

sample’s consolidation characteristics. A detailed discussion of these factors

is beyond the scope of the research project reported here. The purpose of the

tests presented here is to demonstrate the applicability of the seepage induced

consolidation test for the determination of consolidation characteristics of

phosphatic clays. The verification tests are used as an independent way of

evaluating that the results obtained from the seepage induced consolidation

test indeed represent reliable consolidation characteristics.

The details of the seepage induced consolidation testing and analysis pro-

cedures are given in separate reports that were prepared as a part of this

research project (Abu-Hejleh and Znidarcic, 1992; Znidarcic et al., 1992).

All the seepage induced consolidation tests reported here were performed

and analyzed following procedures described in the stated reports. Details

of these procedures will not be repeated here.

Field work in collecting the samples and some of the laboratory tests were

performed by Bromwell & Carrier, Inc. from Lakeland, Florida who were the

subcontractor in this project. The results of these tests are integrated in this

8

report together with the results of the seepage induced consolidation tests

performed at the University of Colorado at Boulder.

Tests on samples from C.F. Industries ISA and Seminole H2B were used

to determine the optimal testing parameters for the seepage induced consol-

idation tests while the other three samples (Agrico SA-9, Agrico SA-North

and Occidental) were tested with the developed “routine” procedure. For this

to be accomplished multiple tests were performed on the first two samples

while only a single test was performed on each of the other three samples.

Tests on the last three samples were also used in the process of verifying

that the parameters obtained in the seepage induced consolidation test are

the appropriate parameters for the numerical modeling of a consolidation

process in the given soil.

The testing results and analysis for each sample are given in separate

chapters together with the discussion of the results and the verification ex-

periments where appropriate. In the last chapter an overall discussion and

appropriate conclusions are given.

9

Chapter 2

Tests on samples from C.FIndustries ISA

The soil used in this test is designated as “Scientific Mineral Specimen, Sam-

ple C- 1 , Sampling Area 1.” The unit weight of the soil solid particles is

28.65KN and the unit weight of water is 9.81KN . The water used in this test

in designated as "Scientific Mineral Specimen, Sample W- 1 , Sampling Area

1". Liquid limit is 114% and plastic limit is 33%.

2.1 Experimental results of seepage inducedconsolidation test

Prior to performing a seepage-induced consolidation test, the following data

were determined :

l the top effective stress was determined as .392 kPa.

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l The calibration coefficient was determined for transducer No. 1 as .227

kPa/Volt and for transducer No.2 as .853 kPa/volt.

l A dial reference reading was determined as 511; the sample height

which corresponds to this value is zero.

l The area of the sample container was determined as 82.2 cm2.

l Once the soft clay in the bucket was stirred up completely, the water

content of three samples were determined as 445.3%, 447.8%, 446.4%;

hence the initial void ratio is 13.07. This value also represents the void

ratio at zero effective stress.

11

Figure 2.1: Pressure Difference-Time from Seepage-Induced ConsolidationNo. 1.

All the experimental results of the seepage tests and the loading tests are

listed in Table 2.1. The bottom effective stress due to the self weight and

top effective stress is listed in the first row of the seepage test results. The

dial reference readings which corresponds to zero height is listed in the last

row of step loading test data.

In the seepage tests, the pressure difference response history for different

flow rates are shown in Figures 2.1 and 2.2. The pressure difference response

due to seepage flow under different vertical effective stress are shown in Fig-

ures 2.3 and 2.4.

12

Figure 2.2: Pressure Difference-Time from Seepage-Induced ConsolidationNo. 1.

13

Figure 2.3: Pressure Difference-Time from Seepage-Induced ConsolidationNo. 1. Effective stress=10 kPa.

14

Figure 2.4: Pressure Difference-Time from Seepage-Induced ConsolidationNo. 1. Effective Stress=29.2 kPa.

15

2.2 Parameter estimation of the constitu-tive parameters

The compressibility and permeability characteristics were obtained from pro-

gram SICTA using the following combinations of flow rates and levels of

loading :

l Run No. 1 : in this run the results of seepage induced-consolidation

under flow rate #7 and the step loading test under effective stress of

10 kPa were used.



29.2 kPa were used.



10 kPa were used.



29.2 kPa were used.

Program SICTA results for these combinations are shown in Appendix

A.1.1. The estimated compressibility and permeability relationships for these

16

EFFECTIVE STRESS vs. VOID RATIOTEST NO. 1

Figure 2.5: Compressibility Characteristics of Phosphatic Clay Sample fromC.F Industries ISA.

combinations are shown in graphical form in Figures 2.5 and 2.6, respectively.

17

Figure 2.6: Permeability Characteristics of Phosphatic Clay Sample fromC.F Industries ISA.

18

Chapter 3

Tests on samples fromSeminole H2B

The soil used in this test is designated as “Seminole 7705 Top Slime 1”. The

unit weight of the soil solid particles is 26.6 KN and the unit weight of water

is 9.81 KN . The water used in this test in designated as “Seminole Surface

Water 1”. Liquid limit is 198% and plastic limit is 50%.

3.1 Experimental results of seepage inducedconsolidation test

Three seepage-induced consolidation tests were conducted on top slime semi-

nole soil. The average initial void ratio was measured as 35.8. The average

void ratio at zero effective stress was determined as 32.5. Using the value

of void ratio at zero effective stress and the mass of solid of each sample,

the initial height for each sample was determined and are listed in Tables

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3.1, 3.2, 3.3. Also listed in these tables, the height of solid, Hs , the bottom

effective stress due to the top effective stress and self weight of the sample

and the results of the seepage and step loading tests.

The transducer used in the first test has a calibration coefficient of .207

kPa/volt and the transducer used in the second and the third test has a

calibration coefficient of .494 kPa/volt.

In the second test, the seepage induced consolidation was triggered with

v = #10 under top effective stress of .034 kPa and the pressure difference

response is shown in Figure 3.1. This figure shows that channelling has

occurred. Hence, the top effective stress was increased to .406 kPa. The

pressure difference under v = 95%#8 is shown in Figure 3.2. The pressure

difference due to different flow rates under different vertical effective stresses

are shown in Figures 3.3, 3.4.

20

Figure 3.1: Pressure Difference-Time Response from Seepage-Induced Con-solidation Test No. 2, Top Effective Stress=.034 kPa

21

Figure 3.2: Pressure Difference-Time Response from Seepage-Induced Con-solidation Test No. 2, Top Effective Stress=.406 kPa

22

Figure 3.3: Pressure Difference-Time Response from Seepage-Induced Con-solidation Test No. 2, Effective Stress=10.34 kPa

23

Figure 3.4: Pressure Difference-Time Response from Seepage-Induced Con-solidation Test No. 2, Effective Stress=95.36 kPa

24

Figure 3.5: Pressure Difference-Time Response from Seepage-Induced Con-solidation Test No. 3

In the third test, the seepage induced consolidation was triggered with

v = #9 and v = #8 under top effective stress of .034 kPa and the obtained

pressure difference response is shown in Figure 3.5. The pressure difference

due to different flow rates under different effective stresses are shown in Fig-

ures 3.6, 3.7.

In the fourth test, the seepage induced consolidation was triggered with

v = #8 and v = #7 under top effective stress of .1 kPa and the obtained

pressure difference response is shown in Figures 3.8, 3.9. The pressure dif-

ference due to different flow rates under different effective stresses are shown

25

Figure 3.6: Pressure Difference-Time Response from Seepage-Induced Con- solidation Test No. 3. Effective Stress=7.85 kPa

26

Figure 3.7: Pressure Difference-Time Response from Seepage-Induced Con-solidation Test No. 3. Effective Stress=100.25 kPa

27

3.2 Parameter estimation of the constitu-tive parameters

The compressibility and permeability characteristics were obtained from pro-

gram SICTA using the experimental data of Tests No. 1, No. 2 No. 3 and No. 4

for different combinations of flow rates and levels of loading:

l Run No. 1 : in this run the results of seepage induced-consolidation Test

No. 2 under flow rate 95%#8 and the step loading test under effective

stress of 10.34 kPa were used.


No. 2 under flow rate 95%#8 and the step loading test under effective

28


29


30


31


32



No. 3 under flow rate #8 and the step loading test under effective stress

of 7.85 kPa were used.


Test No. 3 under flow rate #8 and the step loading test under effective














33

Figure 3.12: Compressibility Characteristics of Phosphatic Clay Sample fromSeminole H2B Using the Results of Tests No. 2, No. 3

Program SICTA results for these combinations are shown in Appendix

A.1.2 The estimated compressibility and permeability relationships in graph-

ical form for the four first combinations are shown in Figure 3.12 and Figure

3.14, respectively, and for the second four combinations are shown in Figure

3.13 and Figure 3.15, respectively.

34

Figure 3.13: Compressibility Characteristics of Phosphatic Clay Sample fromSeminole H2B Using the Results of Test No. 4

35

Figure 3.14: Permeability Characteristics of Phosphatic Clay Sample fromSeminole H2B Using the Results of Tests No. 2, No. 3

36

Figure 3.15: Permeability Characteristics of Phosphatic Clay Sample fromSeminole H2B Using the Results of Test No. 4

37

Chapter 4

Tests on samples from AgricoSA-9

Several tests were performed on this sample in order to verify that the ma-

terial characteristics obtained from the seepage induced consolidation test

properly represent consolidation properties of the material. The tests in-

cluded seepage induced consolidation, restricted flow consolidation and self

weight consolidation tests. Unit weight of solids for this sample is 27.66

kN/m3, liquid limit is 233% and plastic limit is 49%.

4.1 Seepage Induced Consolidation Test

One seepage induced consolidation test was performed on the soil sample

using the routine procedure developed in this project. Table 4.1 contains

the output of the analysis procedure using SICTA program. The table also

summarizes the essential testing variables. The consolidation characteristics

38

are presented in the form of void ratio - effective stress and void ratio -

permeability relationships in Figures 4.1 and 4.2.

4.2 Restricted Flow Consolidation Test

One restricted flow consolidation test was performed at the BCI laboratory

in Lakeland, Florida on a sample of the same material. The testing tech-

nique and analysis procedure for the restricted flow consolidation test are

documented in the reports by Lee and Sills (1981) and Sills et al (1984). The,

data from this test together with the fitted exponential curves are presented

in Figures 4.3 and 4.4. The compressibility and permeability curves obtained

from the seepage induced consolidation and the restricted flow consolidation

tests are replotted in Figures 4.5 and 4.6 in the same units for an easy com-

parison. A good agreement between the two sets of results is noted with only

notable deviation in the low effective stress range. For that range the data

reported for the restricted flow consolidation test show substantial scatter in-

dicating that the procedure may not be as reliable in the low effective stress

range as it is for higher stress level. This observation is particularly clear in

the void ratio - permeability relationship where for the void ratio of about

20 the permeability varies over more than one order of magnitude for a small

change in the void ratio. A simple power function was fitted to compress-

ibility data from the restricted flow consolidation test while an expanded

39

40

Figure 4.1: Void Ratio - Effective Stress Relationship from SICTA for AgricoSA-9 Sample.

41

Figure 4.2: Void RatioSA-9 Sample.

Permeability Relationship from SICTA for Agrico

42

power function was used in the analysis of the seepage induced consolidation

test. Since the simple function does not recognize the maximum void ratio

for a given sample it extrapolates to the low effective stress from the data

obtained at higher stress level leading to a further disagreement between the

two techniques.

In conclusion it can be stated that despite the noted differences the two

testing techniques, restricted flow consolidation and seepage induced con-

solidation, yield essentially the same consolidation characteristics for soft

phosphatic clays with the seepage induced consolidation test producing less

ambiguous results in the low effective stress range. This statement will be

supported with the additional evidence in the following sections of the report.

4.3 Self Weight Consolidation Test

One self weight consolidation test was performed on a sample of this material.

In the test a column of phosphatic slurry 0.328 m high and initially at a

uniform void ratio of 18.4 was allowed to settle under its own weight for a

month and the slurry height was measured regularly during that time. The

obtained data are plotted in Figure 4.7 together with the prediction from a

consolidation analysis using the soil parameters obtained from the seepage

induced consolidation test. A good agreement between the experiment and

the analysis is noted up to 400 hours of elapsed time while in the later stage

43

Figure 4.3: Void Ratio - Effective Stress Relationship from Restricted FlowTest for Agrico SA-9 Sample.

44

Figure 4.4: Void Ratio - Permeability Relationship from Restricted Flow Testfor Agrico SA-9 Sample.

45

Figure 4.5: Void Ratio - Effective Stress Relationship Comparison for AgricoSA-9 Sample.

46

Figure 4.6: Void Ratio - Permeability Relationship Comparison for AgricoSA-9 Sample.

47

the experimental settlement rate is slower than the numerical prediction.

The height difference at 800 hours is 5 mm. This discrepancy is possibly

caused by the side friction between the soil and the column container. The

height to diameter ratio for this sample was 1.7 which could affect the results

especially in the later part of the experiment when higher effective stresses

develop in the sample and at the soil - container interface.

The presented results clearly demonstrate that the seepage induced con-

solidation test yields reliable consolidation characteristics for phosphatic clays

and especially that the permeability values obtained at the highest void ra-

tio is accurate. Namely, in the self weight consolidation of a slurry with a

uniform initial void ratio the settlement rate is initially constant and it can

be calculated as:

(4.1)

where ST is settlement rate; Gs is specific gravity; eo is the initial void

ratio; and k is the hydraulic conductivity at the initial void ratio. A dotted

line with this slope is indicated in Figure 4.7. This comparison is the only

direct and independent verification of permeability measurement at high void

ratios.

48

Figure 4.7: Self Weight Consolidation Test and Analysis Results.

49

4.4 Transient Consolidation Test

A further verification of the constitutive properties obtained from the seep-

age induced consolidation test can be achieved by modeling any consolidation

process in the soil. In the seepage induced consolidation test the steady state

condition is used as the basis for determining the soil parameters through

the solution of the appropriate inverse problem. However, in order to reach

this steady state the sample initially passes through a transient phase of

consolidation. This phase is routinely monitored in the experiment and the

generated pore pressure is recorded. This consolidation process gives the

opportunity for an independent verification of the obtained parameters. Fig-

ures 4.8 and 4.9 show the measured pore pressure record during the transient

phase of the seepage induced consolidation test as well as the results of the

numerical simulation with the parameters obtained from the steady state

analysis. In Figure 4.8 the seepage induced consolidation process was in-

terrupted several times in order to reset the flow pump that controlled the

induced flow rate. The cumulative time of these interruptions should be sub-

tracted prior to comparing the numerical analysis to the recorded data. This

is accomplished in Figure 4.9 where a good agreement is noted between the

experimental data and the analysis. Again it is emphasized that only the

ultimate pressure difference was used in the analysis and the agreement of

50

the transient portion of the experiment presents an independent verification

of the seepage induced consolidation test.

51

Figure 4.8: Seepage Induced Consolidation Data and Analysis for AgricoSA-9 Sample.

52

Figure 4.9: Corrected Seepage Induced Consolidation Data and Analysis forAgrico SA-9 Sample.

53

Chapter 5

Tests on samples from AgricoSA-North

One seepage induced consolidation test was performed on this sample and the

transient portion of the test was used to verify that the material characteris-

tics obtained from the seepage induced consolidation test properly represent

consolidation properties of the material. Unit weight of solids for this sample

is 25.51 kN/m3, liquid limit is 318 % and plastic limit is 74%.

5.1 Seepage Induced Consolidation Test

The seepage induced consolidation test performed on the soil sample fol-

lowed the routine procedure developed in this project. Table 5.1 contains

the output of the analysis procedure using SICTA program. The table also

summarizes the essential testing variables. The consolidation characteris-

tics are presented in the form of void ratio - effective stress and void ratio -

54

permeability relationships in Figures 5.1 and 5.2.


Again in this test the transient portion of the seepage induced consolidation

test was used for an independent verification of the obtained parameters.

Figures 5.3, 5.4 and 5.5 show the measured pore pressure record during the

transient phase of the seepage induced consolidation test as well as the results

of the numerical simulation with the parameters obtained from the steady

state analysis. The seepage induced consolidation process shown in Figure 5.3

was interrupted several times in order to reset the flow pump that controlled

the induced flow rate. The cumulative time of these interruptions should be

subtracted prior to comparing the numerical analysis to the recorded data.

The experimental data in this figure also show an initial curvature concave

downwards while the analysis indicates that it should be concave upwards

or at best the pore pressure should be represented by a straight line. The

discrepancy is a consequence of assuming in the analysis that the sample

reached a fully consolidated state under the self weight prior to the initiation

of the seepage induced consolidation phase. This is demonstrated in Figure

5.4 in which in addition to subtracting the cumulative time of the flow in-

terruptions the second numerical prediction was added. In this prediction it

was assumed that the sample did not consolidate at all under its own weight

55

56

Figure 5.1: Void Ratio - Effective Stress Relationship from SICTA for AgricoSA-North Sample.

57

Figure 5.2: Void Ratio -SA-North Sample.

Permeability Relationship from SICTA for Agrico

58

prior to the initiation of the flow process i.e. that the seepage induced consol-

idation test started immediately after placing the specimen in the apparatus.

This second prediction shows a downward concave pore pressure response of

the sample confirming that in the test some excess pore pressure existed prior

to the initiation of the seepage induced consolidation. The two limiting anal-

yses nicely bracket the test results. The seepage induced consolidation test

started after an overnight self weight consolidation that lasted for 16 hours.

A new analysis was performed in which a self weight consolidation lasting 16

hours was followed by the seepage induced consolidation process. The results

of the analysis are compared to the experimental results in Figure 5.5 show-

ing a very good agreement an verifying that parameters obtained from the

seepage consolidation test and analysis accurately represent the consolidation

characteristics of phosphatic clays

This example nicely demonstrates that the complete self weight consolida-

tion of the sample is not needed for a reliable determination of consolidation

characteristics in the seepage induced consolidation test. Thus, irrespectively

of the consolidation characteristics of the sample the seepage induced consol-

idation phase can be started immediately after a full saturation of the system

is assured by an overnight back pressure application. Note that the steady

state was reached in this sample after a substantially longer period of time

than for the sample Agrico 9 presented in Chapter 4. While Agrico - North

59

Figure 5.3: Seepage Induced Consolidation Data and Analysis for AgricoSA-North Sample.

60

Figure 5.4: Corrected Seepage Induced Consolidation Data and Analysis forAgrico SA-North Sample.

61

Figure 5.5: Adjusted Seepage Induced Consolidation Data and Analysis forAgrico SA-9 Sample.

62

sample has somewhat lower permeability the main reason for the large differ-

ence in the consolidation time comes from a much higher initial void ratio of

this sample. The same arguments explain why the self weight consolidation

was completed prior to the seepage induced consolidation test on the Agrico

9 sample, though the elapsed time between the specimen preparation and

the beginning of the test was roughly equal for both samples.

63

Chapter 6

Tests on samples fromOccidental

Two seepage induced consolidation tests were performed on this sample and

the transient portion of the test was used to verify that the material char-

acteristics obtained from the seepage induced consolidation test properly

represent consolidation properties of the material. This sample was received

as a bulk clay with the water content of around 120%. The consistency of

the soil was such that in order to prepare a slurry sample additional water

had to be added to the soil. For the two samples, designated Occidental 1

and Occidental 2 the initial water content was 290% and 342%, respectively.

Unit weight of solids for this sample is 26.78 kN/m3, liquid limit is 174% and

plastic limit is 44%.

64

6.1 Seepage Induced Consolidation Tests

The seepage induced consolidation tests performed on the two soil specimens

followed the routine procedure developed in this project. Tables 6.1 and

6.2 contain the outputs of the analysis procedure using SICTA program.

The tables also summarize the essential testing variables for each test. The

consolidation characteristics are presented in the form of void ratio - effective

stress and void ratio - permeability relationships in Figures 6.1, 6.2, 6.3 and

6.4.

The two tests on the Occidental sample demonstrate the variation of

material properties for phosphatic clays that could be expected when two

samples of the same material have different initial void ratios.


Again in these tests the transient portion of the seepage induced consolida-

tion tests was used for an independent verification of the obtained param-

eters. Figures 6.5 and 6.6 show the measured pore pressure record during

the transient phase of the seepage induced consolidation test as well as the

results of the numerical simulation with the parameters obtained from the

steady state analysis. A good agreement between the data and the analysis

prediction is noted for both experiments verifying again that parameters ob-

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Figure 6.1: Void Ratio - Effective Stress Relationship from SICTA for Occi-dental 1 Sample.

68

Figure 6.2: Void Ratio - Permeability Relationship from SICTA for Occiden-tal 1 Sample.

69

Figure 6.3: Void Ratio - Effective Stress Relationship from SICTA for Occi-dental 2 Sample.

70

Figure 6.4: Void Ratio - Permeability Relationship from SICTA for Occiden-tal 2 Sample.

71

tained from the seepage consolidation test and analysis accurately represent

the consolidation characteristics of phosphatic clays.

72

Figure 6.5: Seepage Induced Consolidation Data and Analysis for Occidental1 Sample.

73

Figure 6.6: Seepage Induced Consolidation Data and Analysis for Occidental2 Sample.

74

Chapter 7

Conclusions

The experiments reported here clearly demonstrate that the new testing tech-

nique and analysis procedure based on the seepage induced consolidation test-

ing produce reliable consolidation characteristics for phosphatic clays. The

testing technique does not require significant interventions of the operator

during testing and the analysis is implemented in a user friendly computer

program. The data from the independent experiments further demonstrate

the advantages of the new methodology as well as the level of accuracy of

the new technique.

While all the objectives of the research project have been accomplished

with the experiments reported here, a carefully planned additional test-

ing program could provide valuable information on the influence of vari-

ous factors on the consolidation characteristics of phosphatic clays. The

new methodology provides a convenient and reliable method for evaluating

75

material characteristics necessary for predicting field behavior of potential

reclamation schemes without huge investments required for their field imple-

mentation. Analyses based on the obtained material characteristics could be

used to screen the potential methods and only the most promising one could

then be implemented in the field for the final verification.

76

Chapter 8

References

1. Abu-Hejleh, A. N. and Znidarcic, D., 1992, User Manual for Computer

Program SICTA, Report prepared for FIPR, University of Colorado,

Boulder

2. Lee, K. and Sills, G.C., 1981, One Dimensional Consolidation with

Restricted Drainage, Oxford University Engineering Report

3. Sills, G.C., Hoare, S. D. L. and Baker, N., 1984, An Experimental As-

sessment of the Restricted Flow Consolidation Test, Oxford University

Engineering Report SM052/84

4. Znidarcic, D., Abu-Hejleh, A.N., Fairbanks, T. and Robertson, A.,

1992, Seepage Induced Consolidation Test, Equipment Description and

Users Manual, Report prepared for FIPR, University of Colorado, Boul-

der

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Chapter 9

Appendix A : Estimation ofthe Compressibility andPermeability Parameters usingthe Results of Seepage Testsand Program SICTA

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Documents

CONSOLIDATION CHARACTERISTICS DETERMINATION FOR …report together with the results of the seepage induced consolidation tests ... The soil used in this test is designated as “Scientific