Identification of Kentucky Shales

Research Report UKTRP-81-16 IDENTIFICATION OF KENTUCKY SHALES by Tommy C. Hopkins Research Engineer Chief and Brian C. Gilpin Geologist Kentucky Transportation Research Program College of Engineering University of Kentucky Lexington, Kentucky in cooperation with Department of Transportation Commonwealth of Kentucky and Federal Highway Administration US Department of Transportation The contents of this report reflect the views of the authors who are 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 Kentucky Department of Transportation, of the Federal Highway Administration nor of the University of Kentucky. This report does not constitute a standard, specification, or regulation. August 1981 Technical Report Documentation Page Report No. Government Accession No, Recipient's Catolog No. 1. 2. 3. Title and Subtitle Report Date 4. 5. August 1981 Identification of Kentucky Shales 6. Performing Organization Code Performing Organization Report No. 8. Author's) 7. UKTRP-81-16 Tommy c. Hopkins and Brian C. Gilpin Performing Organization Name and Address Work Unit No. (TRAIS) 9. 10. Kentucky Transportation Research Program College of Engineering Contract or Gront No. 11. University of Kentucky KYP-76-79; KYHPR-82-91 Lexington, Kentucky 40506-0043 13. Type of Report and Period Cove.red 12. Sponsoring Agency Name and Address Interim Report Kentucky Department of Transportation State Office Building Sponsoring Agency Code Frankfort, Kentucky 40622 14. Supplementary Notes 15. Prepared in cooperation with the U.S. Department of Transportation, Federal Highway Administration Study Title: Engineering Properties and Uses of Kentucky Shales Abstract 16. Results obtained from a series of engineering tests performed on 40 different types of shales are summarized and discussed. Both hard and soft shales, as well as shales having well-documented histories of involvement in highway embankment failures and shales having little kuown involvement, were tested. A major portion of the report examines the suitability of the slake-durability tests, originally devised by Franklin-Chandra of England, as a means of broadly characterizing the engineering properties of Kentucky shales. Results obtained from ten different slake-durability testing procedures, which include procedures proposed by Franklin and Chandra and others as well as procedures devised during the study, were compared. Two procedures devised during the study appear to better characterize slake-durability properties of shales than procedures previously proposed. Natural water contents and jar slake tests were performed to determine if such tests might provide a fairly rapid means of identifying troublesome shales. The natural water content of a shale is a strong indicator of the slake-durability properties. Comprehensive mineral analyses were performed. Only a slight relationship between engineering performance and mineral composition was found. Most notably, montmorillonite was not present in any of the selected shales. Swelling properties of ten shale types were examined. A good correlation was obtained between a newly devised slake-durability index and the water content of a shale after swelling was completed. When exposed to water, most of the shales exhibited high swell pressures. Particle-size determinations, specific gravity tests, and Atterberg limits were performed. Correlations obtained from these tests and slake- durability indices are described. Hardness characteristics of the shales were studied using the Shore scleroscope. Key Words . Distribution Statement 17. 18 Shales Hardness Slake-Durability lvater content Mineral Analysis Evaluation Tech ,dques Swelling Physical Properties tests Security Classif. (of this report) Security Classif. (of this page) No. of Pages Price 19. 20. 21. 22. Form DOT F 1700.7 18-721 Reproduction of completed page authorized E TA RRA Research Report UKTRP-81-16 IDENTIFICATION OF KENTUCKY SHALES August 1981 Table of Contents and page 95 Title of Appendix C should read as follows: SLAKE-D BILITY INDEX - TIME CURVES URA Table of Contents and page 101 Title of Appendix D should re�d as follows: LOSS OF WATER - TIME CURVES Table of Contents and page 115 Title of Appendix F should read as follows: SWELL DEFLECTION AND SWELL PRESSURE AS FUNCTIONS OF LOGARITHM SQUARE ROOT OF TIME AND Table of Contents and page 171 Title of Appendix G should read as follows: MINERAL ANALYSES List of Figures Page Figure 1. A massive embankment failure on 64,milepost 118,in Bath County, Both embankment I and foundation contained shales (Crab Orchard Formation) of low shear strength 1 Figure 2. Accumulation of shale materials in a highway drainage ditch 2 Figure 3. Rock failures caused by the weathering of weak shales . 2 Figure 4. Uneven pavement caused by the swelling of subgrade shales 3 Figure 5. Geologic map of Kentucky 3 Figure 6. Slake�durability indices plotted as a function of lift thicknesses for various shale embankments 5 Figure 7. Schematic of an embankment and foundation showing typical conditions commonly encountered in Kentucky . 6 Figure 8. Back-computed shear strength as a function of peak shear strength from triaxial tests 8 Figure 9. Back�computed shear strength as a function of residual shear strength 8 Figure 10. Schematic illustrating "damming" effect of shale embankments 8 Figure 11. Slake�durability classification and the variation in durability of rocks of differing age 10 Figure 12. Suggested durability�plasticity classification 11 Figure 13. Proposed classification of shales for embankment construction 12 Figure 14. Classification in terms of slaking characteristics . 13 Figure 15. Engineering classification of argillaceous materials 13 Figure 16. Map of Kentucky showing sampling sites 15 Figure 17. Slake�durability apparatus 17 Figure 18. Slake�durability drum 18 Figure 19. Definition of proposed slake�durability decay index, D1 19 Figure 20. Model D Shore Scleroscope 20 Figure 21. Particle�size distribution curve 23 Figure 22. Equipment used to perform swell�deflection tests on selected shales 23 Figure 23. Equipment used to perform swell�pressure tests on selected shales 23 Figure 24. Distribution of indices from slake�durability decay tests 25 Figure 25. Indices from the Franklin�Chandra slake�durability test 26 Figure 26. Slake�durability indices from a modified procedure (modification of the Franklin�Chandra procedure) suggested by Deo 27 Figure 27.·slake�durability indices from a modified procedure (modification of the Franklin�Chandra procedure) suggested by Gamble 27 Figure 28. Slake�durability indices from a test procedure using two 25-minute cycles 27 Figure 29. Slake�durability indices from a procedure using air-dried shale and one 60�minute cycle 28 Figure 30. Slake-durability indices from a procedure using oven-dried shale and one 60-minute cycle 28 Figure 31. Slake-durability indices from a procedure using oven-dried shale and one 120-minute cycle 28 Figure 32. Comparison of slake-durability indices from a one-cycle, 10-minute test using air-dried shale and a one-cycle 10-minute test using oven-dried shale . 29 Figure 33. Comparison of slake-durability indices from a one�cycle, 25-minute test using air-dried shale and a one-cycle,25-minute test using oven-dried shale 29 Table of Contents Page Introduction . 1 Previous Work 4 Site and Shale Descriptions 15 Sampling Procedure 16 Testing Equipment and Procedures 17 Slake-Durability Test 17 Jar-Slake Test 20 In Situ Water Contents 20 Air-Drying Tests . 20 Shore Scleroscope 20 Atterberg Limits . 21 Mineralogy 21 Hydrometer Analysis 22 Specific Gravity . 22 Swell Test . 22 Test Results and Analyses 24 Slake Durability . 24 Jar-Slake Test . 30 Routine Soils Tests 31 Swell Tests 35 Shore Scleroscope 38 Mineralogy 38 Conclusions 42 References . 43 Appendix A. Detailed Descriptions of Hand Specimens, Geologic Formations, and Sampling Sites 45 Appendix B. Computer Program for Calculating the Slake-Durability Decay Index, 87 01 Appendix C. Mineral Analyses 95 Appendix D. Slake-Durability Index-Time Curves 101 Appendix E. Conditions of Shales Before and After Soaking in the Jar-Slake Test 107 Appendix F. Conditions of Shales Before and After Soaking in the Jar-Slake Test 115 Appendix G. Swell Deflection and Swell Pressure as Functions of Logarithm and Square Root of Time 171 List of Figures Page Figure 34. Comparison of slake-durability indices from a one-cycle, 60-minute test using air-dried shale and a one-cycle, 60-minute test using oven-dried shale 29 Figure 35. Comparison of slake-durability indices from a one-cycle, 60-minute test using air-dried shale and a two-cycle, 25-minute test using oven-dried shale 29 Figure 36. Square root of the slake-durability decay index plotted as a function of jar slake number 30 Figure 37. Variation of clay content (percent finer than 0.002 mm) and jar slake number 31 Figure 38. Slake-durability index (10-minute, two-cycle, oven-dried) plotted as a function of natural water content 32 Figure 39. Slake-durability index (25-minute, one-cycle, oven-dried) plotted as a function of natural water content 32 Figure 40. Slake-durability index (60-minute, one-cycle, air-dried) plotted as a function of natural water content 32 Figure 41. Variation of the square root of the slake-durability decay index, Dp with natural water content 32 Figure 42. Clay fraction (percent finer than 0.002 mm) from mineral analysis plotted as a function of natural water content 33 Figure 43. Clay fraction (percent finer than 0.002 mm) from hydrometer analysis plotted as a function of natural water content 34 Figure 44. Variation of plasticity index with slake-durability index from Gamble's procedure and proposed durability-plasticity classification of shales and other argillaceous rocks 34 Figure 45. Variation of plasticity index with slake-durability index from the proposed slake-durability test (one-cycle, 60-minute, air-dried material) and the proposed durability-plasticity classification of shales and other argillaceous rocks . 35 Figure 46.

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