SCHOOL OF CIVIL ENGINEERING JOINT HIGHWAY RESEARCH PROJECT FHWA/IN/JHRP-79-7 THE EFFECT OF LABORATORY COMPACTION ON THE SHEAR BEHAVIOR OF A HIGHLY PLASTIC CLAY AFTER SATURATION AND CONSOLIDATION J. M. Johnson C. W. Lovell PURDUE UNIVERSITY INDIANA STATE HIGHWAY COMMISSION Digitized by the Internet Archive in 2011 with funding from LYRASIS members and Sloan Foundation; Indiana Department of Transportation http://www.archive.org/details/effectoflaboratoOOjohn Interim Report THE EFFECT OF LABORATORY COMPACTION ON THE SHEAR BEHAVIOR OF A HIGHLY PLASTIC CLAY AFTER SATURATION AND CONSOLIDATION TO: H. L. Michael, Director July 11, 1979 Joint Highway Research Project Project: C-36-5M FROM: C. W. Lovell, Research Engineer Joint Highway Research Project File: 6-6-13 Attached is an Interim Report on the HPR Part II Study titled "Improving Embankment Design and Performance". This is Interim Report No. 6 and is titled "The Effect of Laboratory Compaction on the Shear Behavior of a Highly Plastic Clay After Saturation and Consolidation". It is authored by J. M. Johnson and C. W. Lovell of our staff. The report describes the experimental program on the effective stress strength behavior of laboratory compacted St. Croix clay. The effects of compaction water content and effort level were evaluated for the clay after it had been saturated and consolidated under confining pressures simulating various embankment positions. Prediction equations were developed for the effective stress parameters, for the pore pressure parameter at failure, and for the volumetric strain during saturation and consolidation. These equations are largely in terms of the compaction variables. Research on these relation- ships for field compacted soil continues. The Report is submitted for review, comment and acceptance as partial fulfillment of the objectives of the approved study. Respectfully submitted, C.P.-Lu^M/^;Wai C. W. Lovell Research Engineer CWL : ms A. G. Altschaeffl D. E. Hancher C. F. Scholer W. L. Dolch K. R. Hoover M. B. Scott R. L. Eskew J. F. McLaughlin K. C. Sinha G. D. Gibson R. F. Marsh C. A. Venable W. H. Goetz R. D. Miles L. E. Wood M. J. Gutzwiller P. L. Owens E. J. Yoder G. K. Hallock G. T. Satterly S. R. Yoder Interim Report THE EFFECT OF LABORATORY COMPACTION ON THE SHEAR BEHAVIOR OF A HIGHLY PLASTIC CLAY AFTER SATURATION AND CONSOLIDATION by James M. Johnson Graduate Instructor in Research and C. W. Lovell Research Engineer Joint Highway Research Project Project No. : C-36-5M File No. : 6-6-13 Prepared as a Part of an Investigation Conducted by Joint Highway Research Project Engineering Experiment Station Purdue University in cooperation with the Indiana State Highway Commission and the U.S. Department of Transportation Federal Highway Administration The contents of this report reflect the views of the author who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Federal Highway Administration, This report does not constitute a standard, specification, or regulation. Purdue University West Lafayette, Indiana July 11, 1979 TECHNICAL REPORT STANDARD TITLE PAGE Cotolog No. 1 . Report No. ?. Government Accession No. 3. Recipient! FHWA/IN/JHRP-79/7 Title and Subtitle 5. Report Date THE EFFECT OF LABORATORY COMPACTION ON THE SHEAR July 1979 BEHAVIOR OF A HIGHLY PLASTIC CLAY AFTER SATURATION Organiiotiort Code AND CONSOLIDATION s Author' s 8. Pet-forming 0'gan. zoti on Report No. J . M. Johnson and C . W. Love 11 JHRP-79-7 Performing Organization Nome and Addrell 10. Wort Unit No Joint Highway Research Project Civil Engineering Building 11. Contract or Grant No. Purdue University HPR-K17) Part II West Lafayette, Indiana 47907 13. Type of Report ond Period Covered Sponsoring Agency Name ond Addret" Indiana State Highway Commission Interim Report State Office Building 100 North Senate Avenue 14. Sponsoring Agency Code Indianapolis, Indiana 4 6204 Soppiementory Note. p reparecj ^ COO p erat ion w ith the U.S. Department of Transportation, Federal Highway Administration. Part of the Study titled "Improving Embankment Design and Performance". The effective stress strength behavior of the plastic St. Croix clay is to be studied for both laboratory and field compaction. This interim report deals with the laboratory -compacted phase. Shearing parameters were evaluated in the (CU) triaxial test after saturation and consolidation under confinements simulating a range of embankment positions. The friction angle, <j)', was found to be essentially invariant for the range of compaction conditions. The shearing intercept, c', and the pore pressure parameter at failure, Ac, depended upon the final void ratio achieved for a selected consolidation pressure. Statistical analysis were performed to construct prediction equations for c' , Af, and the volumetric strain on saturation and consolidation. These equations will aid efforts to predict and control the long term shear behavior of compacted clay embankments. 17. Key Word. 18. Distribution Statement No restrictions. This document is Laboratory Compaction; Effective available to the public through the Stress Shear Parameters National Technical Information Service, Springfield, Virginia 22161 19. Security Clai.if. (of thi. report) 20. Security Cloosii (of thi . page) 21. No. of Page. 22. Price Unclassified Unclassified 271 Form DOT F 1700.7 (e-ssi . ACKNOWLEDGMENTS Special thanks go to Professors R. D. Holtz and T. R. West for reviewing the report and providing valuable counsel. The authors are grateful for the laboratory assistance provided by Mr. Alan Lux. The secretarial and drafting work provided by Mrs. Edith Vanderwerp, Mrs. Sue Cary and Mr. David Brewer is much appreciated The Indiana State Highway Commission and the Federal Highway Administration provided the financial support for this study. The Joint Highway Research Project, Purdue University, West Lafayette, Indiana, administered the project. Tilt authors thank Mr. Albert DiBernardo, Mr. David Weitzel and Mr. Carv Witsman for their help and encouragement. Mrs. Carole Montgomery typed the manuscript. Ill TABLE OF CONTENTS Page LIST OF TABLES , vi LIST OF FIGURES ix LIST OF ABBREVIATIONS AND SYMBOLS xiv HIGHLIGHT SUMMARY xvii INTRODUCTION 1 1 - LITERATURE REVIEW 4 1-1 Saturation of Compacted Soil 4 1-1.1 Introduction 4 1-1.2 Saturation by Percolation 5 1-1.3 Back Pressure Saturation 6 1-1.4 Methods for Checking Degree of Saturation 10 1-2 Strain Rates for Triaxial Testing 14 1-2.1 Effects of Strain Rate 14 1-2.2 Drained Triaxial Testing 16 1-2.3 Undrained Triaxial Testing 16 1-3 Fabric of Compacted Fine Grained Soils ... 21 1-3.1 Introduction 21 1-3.2 Particle Level Model 23 1-3.3 Aggregate Level Model ..: 2 5 1-3.4 Changes During Swell and Consolidation 28 1-4 Long Term Behavior of Compacted Fine Grained Soils 30 1-4.1 Volume and Moisture Content Modifications 30 1-4.2 Effective Stress Strength Parameters 32 1-4.2.1 Drained Versus Undrained Testing 32 1-4.2.2 Variation of c' and <$> ' with Compaction Conditions .... 35 1-4.3 Stress-Strain Behavior 40 1-4.4 Pore Pressure Response During Undrained Shear 41 1-4.5 Consolidation to Anisotropic Versus Isotropic States of Stress 45 IV Page 49 2 - APPARATUS AND PROCEDURE 2-1 Soil Processing and Classification 49 2-2 Moisture Addition and Curing 51 2-3 Compaction 53 2-3.1 Apparatus 53 2-3.2 Procedure 56 2-4 Sampling 60 2-4.1 High and Intermediate Sample Densities 60 2-4.2 Low Sample Densities 62 2-5 Sample Set-up 64 2-6 Back Pressure Saturation 67 2-7 Consolidation 71 2-8 Undrained Shear 72 2-9 Final Void Ratio Determination 74 . 75 2-10 Summary Listing of Independent Variables . 3 - RESULTS AND DISCUSSION OF RESULTS 77 3-1 Compaction 77 3-1.1 Dry Density Versus Moisture Content Relationships 77 3-1.2 Definition of Compaction Variables. 80 3-1.3 Sample Nomenclature 83 3-2 Saturation 84 3-3 Volume Change Due to Saturation and Consolidation 94 3-4 Stress-Strain and Pore Water Pressure Response 1"3 3-5 Effective Stress Strength Parameters .... 119 3-6 Statistical Analysis I 29 3-6.1 Linear Regression Analysis 129 3-6.2 Dependent and Independent Variables . 133 3-6.3 Prediction Model for Volume Change due to Saturation and Consolidation . 141 3-6.4 Prediction Model for Skempton's A Parameter at Failure 152 3-6.5 Prediction Model for the Effective Stress Friction Angle, <j>' 163 3-6.6 Prediction Model for the Effective . 164 Stress Strength Intercept, c* . 3-7 Comparison of Strength Behavior of Samples Consolidated to Anisotropic and Isotropic States of Stress !69 4 - CONCLUSIONS AND RECOMMENDATIONS 176 4-1 Conclusions 1 7 6 4-2 Recommendations for Future Research 180 Page BIBLIOGRAPHY 182 APPENDICES Appendix A - Impact Compaction Data 192 Appendix B - Compaction, Saturation and Consolidation Data 194 Appendix C - Undraincd Shear Data 198 Appendix D - Supplementary Figures 253 Appendix E - Purdue University Negative Numbers for Photographs , 270 VI LIST OF TABLES Table Page 1. EFFECTIVE STRESS STRENGTH PARAMETERS OF COMPACTED SOILS 37 2. CLASSIFICATION TEST RESULTS FOR SAINT CROIX CLAY 51 SPECIFICATIONS FOR IMPACT COMPACTION TESTS. ... 73 BACK PRESSURES REQUIRED TO ATTAIN THE EXPERIMENTALLY OBSERVED DEGREES OF SATURATION . 85 VOLUME CHANGE DUE TO SATURATION AND CONSOLIDATION 10 ° FAILURE CONDITIONS FOR CONSOLIDATED UNDRAINED TRIAXIAL TESTS 114 MEASURED VALUES Or THE EFFECTIVE STRESS STRENGTH PARAMETERS 126 BASIC COMPACTION VARIABLES FOR PERCENT VOLUME 134 CHANGE DUE TO SATURATION AND CONSOLIDATION. BASIC COMPACTION VARIABLES FOR SKEMPTON'S A PARAMETER AT FAILURE 137 10. BASIC COMPACTION VARIABLES FOR THE EFFECTIVE STRESS STRENGTH PARAMETERS 139 11. STATISTICAL DATA OF THE PREDICTION EQUATION FOR PERCENT VOLUME CHANGE DUE TO SATURATION AND AV/V 142 CONSOLIDATION, Q(%) 12.