G. Michael Lloyd Jr. -Chemical Processing Jinrong P. Zhang. -Beneficiation Steven G. Richardson -Reclamation Robert S. Akins

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2 The Florida Institute of Phosphate Research was created in 1978 by the Florida Legislature (Chapter , Florida Statutes) and empowered to conduct research supportive to the responsible development of the state's phosphate resources. The Institute has targeted areas of research responsibility. These are: reclamation alternatives in mining and processing, including wetlands reclamation, phosphogypsum storage areas and phosphatic clay containment areas; methods for more efficient, economical and environmentally balanced phosphate recovery and processing; disposal and utilization of phosphatic clay; and environmental effects involving the health and welfare of the people, including those effects related to radiation and water consumption. FIPR is located in Polk County, in the heart of the central Florida phosphate district. The Institute seeks to serve as an information center on phosphate-related topics and welcomes information requests made in person, by mail, or by telephone. Executive Director Richard F. McFarlin Research Staff Research Directors G. Michael Lloyd Jr. -Chemical Processing Jinrong P. Zhang -Beneficiation Steven G. Richardson -Reclamation Robert S. Akins -Mining Gordon D. Nifong -Environmental Services Florida Institute of Phosphate Research 1855 West Main Street Bartow, Florida (863) Fax: (863)

3 CONSOLIDATION CHARACTERISTICS DETERMINATION FOR PHOSPHATIC CLAYS Final Report (FIPR contract No ) VOLUME 3 : Results of Seepage-Induced Consolidation Tests on Phosphatic Clays Prepared for FLORIDA INSTITUTE OF PHOSPHATE 1855 West Main Street Bartow, FL RESEARCH Submitted by A. Naser Abu-Hejleh, Dobroslav Znidarcic and Amy Robertson Department of Civil, Environmental and Architectural Engineering University of Colorado Boulder, CO October 1992

4 DISCLAIMER The contents of this report are reproduced herein as received from the contractor. The opinions, findings and conclusions expressed herein are not necessarily those of the Florida Institute of Phosphate Research, nor does mention of company names or products constitute endorsement by the Florida Institute of Phosphate Research.

5 Contents 1 Introduction 7 2 Tests on samples from C.F Industries ISA Experimental results of seepage induced consolidation test Parameter estimation of the constitutive parameters Tests on samples from Seminole H2B Experimental results of seepage induced consolidation test Parameter estimation of the constitutive parameters Tests on samples from Agrico SA Seepage Induced Consolidation Test Restricted Flow Consolidation Test Self Weight Consolidation Test Transient Consolidation Test Tests on samples from Agrico SA-North Seepage Induced Consolidation Test Transient Consolidation Test Tests on samples from Occidental Seepage Induced Consolidation Tests Transient Consolidation Test Conclusions 75 8 References 77 1

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10 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 testing 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: C.F. Industries ISA Seminole H2B Agrico SA-9 7

11 Agrico SA-North 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 procedures 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

12 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 consolidation 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 experiments where appropriate. In the last chapter an overall discussion and appropriate conclusions are given. 9

13 Chapter 2 Tests on samples from C.F Industries ISA The soil used in this test is designated as Scientific Mineral Specimen, Sample C- 1, Sampling Area 1. The unit weight of the soil solid particles is KN and the unit weight of water is 9.81 KN. The water used in this test m 3 m 3 in designated as "Scientific Mineral Specimen, Sample W- 1". Liquid limit is 114% and plastic limit is 33%. 2.1 Experimental results of seepage induced consolidation test Prior to performing a seepage-induced consolidation test, the following data were determined : the top effective stress was determined as.392 kpa. 10

14 The calibration coefficient was determined for transducer No. 1 as.227 kpa/volt and for transducer No.2 as.853 kpa/volt. A dial reference reading was determined as 511; the sample height which corresponds to this value is zero. The area of the sample container was determined as 82.2 cm 2. 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 This value also represents the void ratio at zero effective stress. 11

15 Figure 2.1: Pressure Difference-Time from Seepage-Induced Consolidation No. 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 Figures 2.3 and

16 Figure 2.2: Pressure Difference-Time from Seepage-Induced Consolidation No

17 Figure 2.3: Pressure Difference-Time from Seepage-Induced Consolidation No. 1. Effective stress=10 kpa. 14

18 Figure 2.4: Pressure Difference-Time from Seepage-Induced Consolidation No. 1. Effective Stress=29.2 kpa. 15

19 2.2 Parameter estimation of the constitutive parameters The compressibility and permeability characteristics were obtained from program SICTA using the following combinations of flow rates and levels of loading : 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. Run No. 2 : in this run the results of seepage induced-consolidation under flow rate #7 and the step loading test under effective stress of 29.2 kpa were used. Run No. 3 : in this run the results of seepage induced-consolidation under flow rate #8 and the step loading test under effective stress of 10 kpa were used. Run No. 4 : in this run the results of seepage induced-consolidation under flow rate #8 and the step loading test under effective stress of 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

20 EFFECTIVE STRESS vs. VOID RATIO TEST NO. 1 Figure 2.5: Compressibility Characteristics of Phosphatic Clay Sample from C.F Industries ISA. combinations are shown in graphical form in Figures 2.5 and 2.6, respectively. 17

21 Figure 2.6: Permeability Characteristics of Phosphatic Clay Sample from C.F Industries ISA. 18

22 Chapter 3 Tests on samples from Seminole 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 m 3 m 3 Water 1. Liquid limit is 198% and plastic limit is 50%. 3.1 Experimental results of seepage induced consolidation test Three seepage-induced consolidation tests were conducted on top slime seminole soil. The average initial void ratio was measured as The average void ratio at zero effective stress was determined as 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 19

23 3.1, 3.2, 3.3. Also listed in these tables, the height of solid, H s, 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,

24 Figure 3.1: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 2, Top Effective Stress=.034 kpa 21

25 Figure 3.2: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 2, Top Effective Stress=.406 kpa 22

26 Figure 3.3: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 2, Effective Stress=10.34 kpa 23

27 Figure 3.4: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 2, Effective Stress=95.36 kpa 24

28 Figure 3.5: Pressure Difference-Time Response from Seepage-Induced Consolidation 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 Figures 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 difference due to different flow rates under different effective stresses are shown 25

29 Figure 3.6: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 3. Effective Stress=7.85 kpa 26

30 Figure 3.7: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 3. Effective Stress= kpa 27

31 3.2 Parameter estimation of the constitutive parameters The compressibility and permeability characteristics were obtained from program 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: 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 kpa were used. Run No. 2 : in this run the results of seepage induced-consolidation Test No. 2 under flow rate 95%#8 and the step loading test under effective 28

32 Figure 3.8: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 4 29

33 Figure 3.9: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 4 30

34 Figure 3.10: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 4. Effective Stress=9.02 kpa 31

35 Figure 3.11: Pressure Difference-Time Response from Seepage-Induced Consolidation Test No. 4. Effective Stress=99.47 kpa 32

36 stress of kpa were used. Run No. 3 : in this run the results of seepage induced-consolidation Test No. 3 under flow rate #8 and the step loading test under effective stress of 7.85 kpa were used. Run No. 4 : in this run the results of seepage induced-consolidation Test No. 3 under flow rate #8 and the step loading test under effective stress of kpa were used. Run No. 5 : in this run the results of seepage induced-consolidation Test No. 4 under flow rate #7 and the step loading test under effective stress of 9.02 kpa were used. Run No. 6 : in this run the results of seepage induced-consolidation Test No. 4 under flow rate #7 and the step loading test under effective stress of kpa were used. Run No. 7 : in this run the results of seepage induced-consolidation Test No. 4 under flow rate #8 and the step loading test under effective stress of 9.02 kpa were used. Run No. 8 : in this run the results of seepage induced-consolidation Test No. 4 under flow rate #8 and the step loading test under effective stress of kpa were used. 33

37 Figure 3.12: Compressibility Characteristics of Phosphatic Clay Sample from Seminole 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 graphical 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

38 Figure 3.13: Compressibility Characteristics of Phosphatic Clay Sample from Seminole H2B Using the Results of Test No. 4 35

39 Figure 3.14: Permeability Characteristics of Phosphatic Clay Sample from Seminole H2B Using the Results of Tests No. 2, No. 3 36

40 Figure 3.15: Permeability Characteristics of Phosphatic Clay Sample from Seminole H2B Using the Results of Test No. 4 37

41 Chapter 4 Tests on samples from Agrico SA-9 Several tests were performed on this sample in order to verify that the material characteristics obtained from the seepage induced consolidation test properly represent consolidation properties of the material. The tests included seepage induced consolidation, restricted flow consolidation and self weight consolidation tests. Unit weight of solids for this sample is 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

42 are presented in the form of void ratio - effective stress and void ratio - permeability relationships in Figures 4.1 and 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 technique 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 comparison. 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 indicating 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 compressibility data from the restricted flow consolidation test while an expanded 39

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44 Figure 4.1: Void Ratio - Effective Stress Relationship from SICTA for Agrico SA-9 Sample. 41

45 Figure 4.2: Void Ratio SA-9 Sample. Permeability Relationship from SICTA for Agrico 42

46 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 consolidation, 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 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

47 Figure 4.3: Void Ratio - Effective Stress Relationship from Restricted Flow Test for Agrico SA-9 Sample. 44

48 Figure 4.4: Void Ratio - Permeability Relationship from Restricted Flow Test for Agrico SA-9 Sample. 45

49 Figure 4.5: Void Ratio - Effective Stress Relationship Comparison for Agrico SA-9 Sample. 46

50 Figure 4.6: Void Ratio - Permeability Relationship Comparison for Agrico SA-9 Sample. 47

51 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 consolidation test yields reliable consolidation characteristics for phosphatic clays and especially that the permeability values obtained at the highest void ratio 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; G s is specific gravity; e o 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

52 Figure 4.7: Self Weight Consolidation Test and Analysis Results. 49

53 4.4 Transient Consolidation Test A further verification of the constitutive properties obtained from the seepage 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. Figures 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 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. 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

54 the transient portion of the experiment presents an independent verification of the seepage induced consolidation test. 51

55 Figure 4.8: Seepage Induced Consolidation Data and Analysis for Agrico SA-9 Sample. 52

56 Figure 4.9: Corrected Seepage Induced Consolidation Data and Analysis for Agrico SA-9 Sample. 53

57 Chapter 5 Tests on samples from Agrico SA-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 characteristics obtained from the seepage induced consolidation test properly represent consolidation properties of the material. Unit weight of solids for this sample is 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 followed 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 characteristics are presented in the form of void ratio - effective stress and void ratio - 54

58 permeability relationships in Figures 5.1 and Transient Consolidation Test 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 interruptions 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

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60 Figure 5.1: Void Ratio - Effective Stress Relationship from SICTA for Agrico SA-North Sample. 57

61 Figure 5.2: Void Ratio - SA-North Sample. Permeability Relationship from SICTA for Agrico 58

62 prior to the initiation of the flow process i.e. that the seepage induced consolidation 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 analyses 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 showing 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 consolidation 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 consolidation 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

63 Figure 5.3: Seepage Induced Consolidation Data and Analysis for Agrico SA-North Sample. 60

64 Figure 5.4: Corrected Seepage Induced Consolidation Data and Analysis for Agrico SA-North Sample. 61

65 Figure 5.5: Adjusted Seepage Induced Consolidation Data and Analysis for Agrico SA-9 Sample. 62

66 sample has somewhat lower permeability the main reason for the large difference 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

67 Chapter 6 Tests on samples from Occidental Two seepage induced consolidation tests were performed on this sample and the transient portion of the test was used to verify that the material characteristics 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 kn/m3, liquid limit is 174% and plastic limit is 44%. 64

68 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. 6.2 Transient Consolidation Test Again in these tests the transient portion of the seepage induced consolidation tests was used for an independent verification of the obtained parameters. 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- 65

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71 Figure 6.1: Void Ratio - Effective Stress Relationship from SICTA for Occidental 1 Sample. 68

72 Figure 6.2: Void Ratio - Permeability Relationship from SICTA for Occidental 1 Sample. 69

73 Figure 6.3: Void Ratio - Effective Stress Relationship from SICTA for Occidental 2 Sample. 70

74 Figure 6.4: Void Ratio - Permeability Relationship from SICTA for Occidental 2 Sample. 71

75 tained from the seepage consolidation test and analysis accurately represent the consolidation characteristics of phosphatic clays. 72

76 Figure 6.5: Seepage Induced Consolidation Data and Analysis for Occidental 1 Sample. 73

77 Figure 6.6: Seepage Induced Consolidation Data and Analysis for Occidental 2 Sample. 74

78 Chapter 7 Conclusions The experiments reported here clearly demonstrate that the new testing technique and analysis procedure based on the seepage induced consolidation testing 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 testing program could provide valuable information on the influence of various factors on the consolidation characteristics of phosphatic clays. The new methodology provides a convenient and reliable method for evaluating 75

79 material characteristics necessary for predicting field behavior of potential reclamation schemes without huge investments required for their field implementation. 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

80 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 Assessment 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, Boulder 77

81 Chapter 9 Appendix A : Estimation of the Compressibility and Permeability Parameters using the Results of Seepage Tests and Program SICTA 78

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