SCHOOL OF CIVIL ENGINEERING JOINT HIGHWAY RESEARCH PROJECT JHRP-77-24 STRESS-DEFORMATION AND STRENGTH CHARACTERISTICS OF A COMPACTED SHALE R. Aubrey Abeyesekera 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/stressdeformatioOOabey Interim Report STRESS-DEFORMATION AND STRENGTH CHARACTERISTICS OF A COMPACTED SHALE TO: J. F. McLaughlin, Director December 27, 1977 Joint Highway Research Project Project: C-36-51 FROM: H. L. Michael, Associate Director Joint Highway Research Project File: 6-6-12 The Interim Report titled "Stress-Deformation and Strength Characteristics of a Compacted Shale" is submitted for acceptance as partial fulfillment of the objectives of Phase II of the HPR Project C-36-51 titled "Design and Construction Guidelines for Shale Embankments". The research and report were performed by Mr. R. Aubrey Abeyesekera, Graduate Instructor in Research on our staff under the direction of Professors C. W. Lovell and L. E. Wood on our staff and W. J. Sisiliano, Soils Engineer of the ISHC. The report includes the results of laboratory testing of a mechanically hard but non-durable shale from the New Providence Formation in Indiana. The compaction, consolidation and shearing characteristics of the shale are presented, as well as the testing procedures used. The report should be an aid to ISHC engineers in evaluating the stress-deformation characteristics and effective stress strength parameters of compacted shales. The report is submitted as partial fulfillment of the overall objectives of the research project. Copies of the report will also be submitted to the ISHC and the FHWA for their review, comment and similar acceptance. Respectfully submitted, Harold L. Michael Associate Director HLM:ms cc: A. G. Altschaeffl G. K. Hallock C. F. Scholer 0. M. Bevilacqua D. E. Hancher M. B. Scott W. L. Dolch K. R. Hoover K. C. Sinha R. L. Eskew R. F. Marsh C. A. Venable G. D. Gibson R. D. Miles L. E. Wood W. H. Goetz P. L. Owens E. J. Yoder M. J. Gutzwiller G. T. Satterly S. R. Yoder Interim Report STRESS-DEFORMATION AND STRENGTH CHARACTERISTICS OF A COMPACTED SHALE by R. Aubrey Abeyesekera Graduate Instructor in Research Joint Highway Research Project Project No.: C- 36-51 File No. : 6-6-12 Prepared as 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 December 27, 1977 TECHNICAL REPORT STANDARD TITLE PAGE 1 . Report No. 2. Government Accession No. 3. Recipient's Catalog No. JHRP-77-24 4. Title ond Subtitle 5. Report Date STRESS-DEFORMATION AND STRENGTH CHARACTERISTICS OF December 27, 1977 A COMPACTED SHALE 6. Performing Organization Code 7. Author's) 8. Performing Organization Report No. R. Aubrey Abeyesekera JHRP-77- 24 Performing Organization Name and Address 10. Worlc Unit No. Joint Highway Research Project Civil Engineering Building 1 1 . Contract or Grant No. Purdue University HPR-1(14) Part II West Lafayette, Indiana 47907 13. Type of Report ond Period Covered 12. Sponsoring Agency Name and Addres* Indiana State Highway Commission Interim Report State Office Building 100 North Senate Avenue '4. Sponsoring Agency Code Indianapolis, Indiana 46204 15. Supp lementary Notes Prepared in cooperation with the U. S. Department of Transportation, Federal Highway Administration. Research Study titled "Design and Construction Guidelines for Shale Embankments". 16. Abstroct vThen shales are encountered in road cuts, economic and environmental consider- ations usually dictate that they be used in adjoining embankments. However, unless special precautions are taken, the stability of a shale embankment can deteriorate with time on account of the non-durable nature of some shales in the presence of water. Various tests have been developed to classify shales. This report presents the results of a laboratory investigation to determine the influence of compaction and confining pressure on the stress-deformation and strength characteristics of a mechanically hard but non-durable shale from the New Providence Formation. Some construction guidelines are also recommended. Cylindrical specimens formed by kneading compaction were saturated under a low effective confining pressure, consolidated to the desired effective stress and sheared at a constant rate of strain. The compaction characteristics, the volume changes after saturation, the consolidation characteristics, and the undrained shearing response including pore water pressure changes are reported for triaxial tests, The initial gradation of crushed shale aggregate, the molding water content, the compaction pressure, and the pre-shear consolidation pressure were adopted as the test variables. The effective stress strength parameters were found to be essentially in- dependent of the initial conditions when they were evaluated at maximum deviator stress, except for loose uncompacted aggregate. The volume change characteristics, the induced pore water pressures, and the consolidated undrained strength were found to be greatly dependent on the initial conditions. 17. Key Words 18. Distribution Statement Shale, Argillaceous Rocks, Embank- No restrictions. This document is ments, Compaction, Stress-Deformation, available to the public through the Pore Water Pressures, Strength, Effect- National Technical Information Service, ive Stresses, Strength Parameters, Tri- Springfield, Virginia 22161 axial Tests, Construction Guidelines 19. Security Classlf. (of this report) 20. Security Closslf. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 417 Form DOT F 1700.7 (8-69) ill ACKNOWLEDGEMENTS The author wishes to express his deep appreciation to his major professors, Dr. C. W. Lovell and Dr. L. E. Wood, for their advice, guidance and encouragement throughout the course of the research, and for their patient reviewing of the manuscript. Thanks are also due to Dr. W. R. Judd, Dr. G. A. Leonards, Dr. A. G. Altschaeffl and Dr. R. D. Holtz for their valuable comments and suggestions. Thanks are extended to the Federal Highway Administration and the Indiana State Highway Commission for financial support of the research, and for valuable discussion at several Advisory Committee meetings. Special thanks are extended to Mr. W. J. Sisiliano, Soils Engineer, Division of Materials and Tests, ISHC, who not only served on the said committee but also made arrangements through his staff for the collection of shale samples, visits to construction sites, etc. Willard DeGroff and Dr. John Scully helped in ordering and setting in up the triaxial testing equipment. James Lambrechts helped developing the computer program used for analysing the triaxial test Carol data. Janet Lovell assisted in the X-ray diffraction analyses. Latowski and Peter Massa helped in the preparation of shale aggregate. John Mundell, John Titrington and Peggy McFarren prepared the figures, and the draft was typed by Janice Bollinger and Edith Vanderwerp. to Janice Bollinger typed the final manuscript. Thanks are extended all of them. iv Special thanks are due to Dr. G. A. Leonards who helped the author gain re-admission to Purdue University. The author's trip to the United States was made possible by a U. S. Fullbright Travel Grant and by the award of no-pay study leave by the Government of Sri-Lanka. Finally, the love, prayers, patience and devotion of the author's wife, Manel, are gratefully acknowledged. 21 TABLE OF CONTENTS Page LIST OF TABLES viii LIST OF FIGURES xii LIST OF NOTATIONS xvii HIGHLIGHT SUMMARY xxl CHAPTER 1 INTRODUCTION I CHAPTER 2 LITERATURE REVIEW 8 2. Occurrence of Shale 8 2.2 Formation and Composition of Shale 9 2.3 Weathering of Shale 12 2.4 Engineering Classification of Shale 16 2.5 Compacted Shale Strength 20 CHAPTER 3 PURPOSE AND SCOPE 22 3. Test Procedure 23 3.2 Rationale for Selection of Test Variables 23 3.3 Summary of Independent Variables and Levels 24 CHAPTER 4 DESCRIPTION OF TEST SHALE 26 4 . General 26 4 . Geology 26 4.3 Engineering Tests on the Sample 28 4.4 Mineralogy 31 4.5 Scleroscope Hardness 35 4.6 Point Load Strength 36 4.7 Soaking Degradation and Absorption 36 4.8 Comparison Among New Providence Shale Samples 38 CHAPTER 5 APPARATUS AND PROCEDURE 42 5.1 Preparation of Size Fractions 42 5.2 Formation of Compacted Specimens 46 5.3 Saturation and Consolidation 52 5.4 Undrained Shearing 56 1 vi TABLE OF CONTENTS (continued) Page CHAPTER 6 RESULTS 59 6 . Compaction Characteristics 60 6.2 Volume Change Characteristics 66 6.3 Undrained Shearing Response 70 CHAPTER 7 DISCUSSION OF RESULTS 94 7.1 Compaction Characteristics 94 7.2 Consolidation Characteristics 99 7. 3 Stress-Strain Response 102 7.4 Pore Water Pressure Response Ill 7.5 Effective Stress Paths 133 7.6 Choice of Failure Criterion 140 7.7 Effective Stress Strength Parameters 147 7.8 Critical States in p', q, e,, Space 152 7.9 Consolidated Undrained Strength 155 CHAPTER 8 DESIGN AND CONSTRUCTION GUIDELINES 162 8.1 State-of-the-Art