Phát triển quy trình đánh giá tính chất đất không bão hòa - Natalia Perez

DEVELOPMENT OF A PROTOCOL FOR THE ASSESSMENT OF UNSATURATED SOIL PROPERTIES by Natalia Perez A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy ARIZONA STATE UNIVERSITY December 2006 UMI Number: 3241336 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.

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Box 1346 Ann Arbor, MI 48106-1346 DEVELOPMENT OF A PROTOCOL FOR THE ASSESSMENT OF UNSATURATED SOIL PROPERTIES by Natalia Perez has been approved November 2006 APPROVED: SS LZ. Lb a<< $— _ Chair VLIW We x— 2⁄2 auclis ££ “| pa h0 Supervisory Committee. Department Chair Deasinison of Graduate Studies ABSTRACT In this study, shear strength and volume change behavior of unsaturated soils 1s evaluated using axis-translation test methods and advanced testing equipment designed to provide accurate volume change determination during specimen shearing. Tests were performed on a wide range of soil types with net normal stress from 20 to 250 kPa and matric suction from 20 to 700 kPa.

This data set adds significantly to the existing database of unsaturated soil properties. The triaxial test data was analyzed using the extended Mohr-Coulomb equation proposed by Fredlund et al (1978). A hyperbolic curve was fit to the o° versus suction relationship, and a correlation between the hyperbolic curve parameters and soil index properties was developed. Volume change behavior for the soils was related to soil suction, and it was found that for a given suction, the test soils exhibited greater tendency to dilate as soil suction is increased.

For a given suction, soils exhibited higher compressive strains as the net normal stress was increased, as expected. A new oedometer device for soil water characteristic curve (SWCC) determination was evaluated by testing a wide range of soil types, and recommendations for best practices for use of this device have been made. The new device allows application of overburden stress to the specimen, measurement of specimen volume change due to suction and overburden pressure changes, and the use of a single specimen for determination of the SWCC. The evaluation includes issues of temperature control, overburden stress, air diffusion through high air entry disks, and a study of potential sources of error in water content determination for SWCC’s.

It was concluded that the new oedometer device can be used to obtain accurate SWCC determinations on a single 11 specimen up to 1500 kPa. General recommendations for appropriate corrections to SWCC data obtained using axis translation pressure plate-type devices are made. 1V DEDICATION To my family and husband ACKNOWLEDGEMENTS This work was supported by the National Science Foundation under the grant No. The author is truly indebted to Dr.

Sandra Houston and Dr. Houston who contributed so much to the completion of this dissertation, most the ideas that were followed during the testing came from them. The innumerably meetings and phone conversations in which they spent so much time explaining the advantages and disadvantages of using different testing procedures and data analysis will never be forgotten. Acknowledgements are given to Dr.

Delwyn Fredlund who has given so many ideas during the development of this research project. The author also appreciates the time that he took to answer some of her questions even when he was traveling overseas. Acknowledgments are also for Dr. Claudia Zapata who is always willing to share her knowledge of unsaturated soil mechanics and data analysis.

This research work was also greatly supported by Dr. Manuel Padilla, Dr. Lawrence, and Peter Goguen, no words exist to show them the appreciation for their help. Thanks are also given to the Mexican Transport Institute that provided support to the author to continue studying postgraduate studies.

vi TABLE OF CONTENTS Page ¡0/9002. EEE EOE XV NOMENCLATURE. ccccccc cece eee ene E EERE EEE TERETE ES XXVI ò.- 2c nhu 1 1tr CHAPTER 1 INTRODUCTIƠN.a 1 CHAPTER 2_ HIERARCHICAL APPROACH TO UNSATURATED SOIL I›);19)2)5701A@.2 Unsaturated soil property functions .3 Assessment ofunsaturated soil property funcfIO'S. an Level côn.

16 CHAPTER 3 SHEAR STRENGTH AND VOLUME CHANGE OF UNSATURATED 10. 20 cm eo Š ees.2_ Shear strength equations for saturated and unsaturated SOIÌS.3 Models for the shear strength prediCtion.1 se 23 Models for the shear strength prediction using SWCC.2 Shear strength prediction based on empirical models.4 Historical review on the volume change measurements and negative pore water pressure on unsaturated SOIÏS.--c-creererererrierrrrrtrrtrrrrtrrrtrrrrree 38 CHAPTER 4 EXPERIMENTAL PROGRAM, EQUIPMENT AND PROCEDURES. 81 "Ho on Š naaaa 81 .3 Soil water characteristic CUIVe tEStING .1 Pressure plate apparafUS. Tempe celÌ testing.3 Testing ofthe specimen.

Traditional syst€mS.1 Pore wafter controÌ mneasuremenI-. nh nhe nh .2 Pore air controÏ meaSurem€nt.3 De-airing the high air entry stone.4 Compaction of the specimen.5 Setting up the sample in the system.-re 98 hhnhhhhhritm cà nền 4.6 Shearing of specimen. ‹ 99 he hen Hong .3 Advanced triaxial sySf€ITS.- ch HH thư 100 «+ ch 4.1 Triaxial system and modIfications.2 Modifñed triax1al celÏ. hy nh 101 nh nh nh kh.

he nhe HH 104 cà cà nen.3 Total volume change cOrr€CfIOPS.4 Pore-water controÏ sySf€m. - 106 nh nhe nh nh nhớ sec sàn nh nh .5 Pore air contro] sySfem. -- 108 nh nh khe Hinh nhe «+ 4.6 Volume change measuremenf sysfem.8 Electronic software and hardWar€. ngng ng Ki Ki kh th nón Bà th ng 114 4.4 Testing procedure for advanced triaxial sySt€IS.1 Preparation of specimen for saturated and unsaturated I E .2 De-airing of the system and saturation of the high air entry ceramic mẻ AEE REESE 114 4.3 Compaction of specimen outside of the triaxial 1 EO OEOOCESEEOOSOOOS 115 hé nhnheh 117 4.1 — Suction control testing sDeCImeH.2 ----: 117 Pre-equilibrated sample or suction adjustmeni.3 Specimen compacted at a desired water content which corresponds to a desired matric suction VAÌU©.

no SH HT n nh n Kế BH nh nh cá nh ch 120 4.4 Assembling and filling the pressure ceÌÏ. HH» nh nh BE ng km hà Khen kề kn n th kh bu 122 nh nh nh nh kh nhe 4.6 Isotropic consolidation SfaØ€.1 Specimens tested under sucfion control.2 Pre-equilibrated specImens.3 Specimen compacted at a desired water content which corresponds to a đesired matric suctlon vaÏUe.« «cà cà se 124 ch nh nh nh nh HH kh te 125 4. nen kề nh kh nhe hinh 126 4.8 Reliability of the resuÏfS.-- cà ieeHhee 128 CHAPTER 5 DESCRIPTION OF TEST SOILS.---cc ho on e6 .2 Án * nh nh HH 0 1H k3 tt Index DTOP€FẨI€S.6- 129 CHAPTER6 SOIL WATER CHARACTERISTIC CURVE TESTING.1 cọ nh nh nh n kh HH nh nh 135 Introduction.2_ Initial observations when performing SWCC testing.1 Evaluation of moisture content losses during direct water content determination and impact on degree of saturation. Evaluation of leaks from the SWCC system.

Temperature control during SWCC testing.4 Recommendation for correction to SWCC.àc che 159 Page 6.3 Other important aspects for determination of soil water characteristic curves 162 6. Correction of the soil water characteristic curve for 100 % saturation.2 Measurement ofmatric suction at very low vaÌues. Tmportance ofmatching ceramic stone to suction range/soil type. Diffused air through the high air entry ceramic stones during SWCC (505207.5 Effect of overburden pressure on the SWCC.6 Shrinkage during suction appliCatiOn.7 Effect of contact between the specimen and ceramic stone.4 Final soil water charaCf€TISẨICS.

uc ng HH Hi it 193 6.5 Correlation of air entry value with basic soil properties. cesses 202 CHAPTER 7 TRIAXIAL TESTING. SATURATED AND UNSATURATED SHEAR S126. Sensitivity ofthe $° at low matric suction.2 ASU east soil (SM|.

SH Hà HH Hàn HH HH tà Hà th 221 7.2 Unsaturated shear strength (Traditional triaxial system)-ASU east soil.3 Unsaturated shear strength (Advanced triaxial system) —ASU east soil. Price Club soil (CL-ML). HH nhau the 237 7.4 Sheely soil r€SUÏ(S. cà nh HH.1 cuc nhìn nh.

nh tk ng 245 HH nàn kh bề kh nh .2 co HH HH Unsaturated t€StInE. kh HH k HH 245 nh nh nh.5 cv Volume change m€aSUT€Tm€TS. HH Hi ha nhi .1 «cà Calibration ofthe double walled cell.2 Volume change measurements for ASU east soil (SM). Price Club soil -Volume change measurernens.4 +: 262 Sheely soil -Volume change measuremenfS.6 Comparison of suction control procedure, “pre-equilibrated” procedure and specimen compacted at a đesired wafer content/suction vaÌue.-- 265 CHAPTER 8 MODEL FOR THE PREDICTION OF ð? VALUE .2 Hyperbolic fit to the ©” VerSUS (Wg-Uw) CULVES.3 Published literature on shear strength for unsaturated solls.1 Data from literature and placed into hyperbolic ¡10 278 CHAPTER 9 CONCLUSIONS AND RECOMMENDATIONS.1 Conclusions with respect to soil water characteristic curve testing.2 Unsaturated triaxial testing COMCIUSIONS.cssseseresreeteeteeeeeteeeeseneretereenees 293 PS NN:(cuou oi ae.ỐỐ 299 APPENDIX A OPERATING PROCEDURES FOR THE ADVANCED TRIAXIAL SYSTEMS ¬.

319 xH Page CHARACTERISTICS OF SAMPLES FOR SOIL WATER CHARACTERISTIC CURVE TESTING. HH HH HH KH TH HH HH HH nhiệt 342 UNSATURATED SHEAR STRENGTH RESULTS FOR YUMA SAND. TRADITIONAL TRIAXLAL SYSTEM. che 344 UNSATURATED SHEAR STRENGTH RESULTS FOR ASU EAST SOIL.

TRADITIONAL TRIAXLAL SYSTEM.-- St nnehhhhiHrhreree 351 UNSATURATED SHEAR STRENGTH AND VOLUME CHANGE FOR ASU EAST SOIL. PRE EQUILIBRATED SAMPLES. ADVANCED TRIAXIAL SQYSTEMS. ung Ho HH Hư TH KH HH g0 1011101510111 101801001110 357 UNSATURATED SHEAR STRENGTH RESULTS FOR PRICE CLUB SOIL.

TRADITIONAL TRIAXIAL SYSTEM. cà chui 375 UNSATURATED SHEAR STRENGTH RESULTS FOR PRICE CLUB SOIL. TRADITIONAL TRIAXIAL SYSTEM. ceccccescesesseessesecseeeteenessesneeneeeenaeees 381 UNSATURATED SHEAR STRENGTH RESULTS FOR SHEELY SOIL.

ADVANCED TRIAXIAL SYSTEM.cccccescesseeeseessecseeseeeesssesssessessessenees 392 xII LIST OF TABLES Table Page 2.1 Properties needed at level 1 of the hierarchical level .2 Hierarchy of laboratory testing for unsaturated soil properties.1 Summary of indeX DTOP€Fi€S. HH0 11101 HH HH TH TH ưu 130 5.3 Gradation Of SOI SapÏ€S. th nh ng nryếu 131 6.1 Selection OÝ C€TaTnIC SỈOTIS. th TH TT HT TT ng no 172 6.2 Soils to be used in the air entry value correlation.1 Summary of shear strength at failure for Yuma sand and corresponding o° 214 7.2 Computation of o° based upon the total cohesion intercepfs .3 Characteristics of samples tested under saturated conditions.4 o° values for ASU east SOiL .5 Computations of 6° based upon the total cohesion InferCepfsS.6 Water content of samples after shearing (samples tested on modified triaxial SYSCOM) oo.1 Summary of soils for which a and b parameters were obtained.2 Summary of a and Ð paTaIn€f€FS.

TT ng ng. tren 286 XIV LIST OF FIGURES Figure Page 2.1 Approaches that can be used to determine unsaturated soil property functions (From Fredlund, Houston and Houston, 2002) 2.2 Predicted SWCC based on the Dạo and wPI (Zapata, 1999).3 Comparison of a soil water characteristic curve obtained in laboratory versus soil water characteristic curve predicted with Zapata”s mođel. se cs se srsea 14 2.4 Yuma sand soil water characteristic curves versus predicted curve.5 Flow chart for hierarchical approach (From Fredlund, Houston, and Houston, 2002). HH11111111 TH HH HH Họ ty 18 3.1 Typical relationship between the shear strength and matric suction (From Gan et al 1988, cited by Khalili and Kabbaz 1988) .2 Definition for a and b parameters .3 Small volume of soil considered to derive the equation (From Brahtz, Zanger and Bruggeman, 1939) oo csscssssesssesssssssesscscscesscsvscssssecsesscsssceseevaceeavevsvarscacseseas 39 3.4 Layout of the apparatus for triaxial compression tests with pressure measurement (HHHẾ, 1956).

HH Han HH HH Hiệp 41 3.5 Layout of the apparatus for the direct measurement of pore water pressure using null indicator (Bishop et al, 1960) .6 Modification of triaxial cell to surround membrane with mercury (Bishop and Donald, 1 96 Ï) .