Shear Strength of Clay and Silt Embankments Teruhisa Masada, Ph.D. ORITE, Ohio University for the Ohio Department of Transportation Office of Research and Development and the U.S. Department of Transportation Federal Highway Administration State Job Number 134319 (0) September 2009 Ohio Research Institute for Transportation and the Environment (ORITE) 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA/OH-2009/7 4. Title and Subtitle 5. Report Date Shear Strength of Clay and Silt Embankments September 2009 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report Dr. Teruhisa Masada 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Ohio Research Institute for Transportation and the Environment 11. Contract or Grant No. 141 Stocker Center 134319 Ohio University Athens OH 45701-2979 12. Sponsoring Agency Name and Address Ohio Department of Transportation 13. Type of Report and Period 1980 West Broad St. Covered Columbus OH 43223 Technical Report 14. Sponsoring Agency Code 15. Supplementary Notes Prepared in cooperation with the Ohio Department of Transportation (ODOT) and the U.S. Department of Transportation, Federal Highway Administration 16. Abstract Highway embankment is one of the most common large-scale geotechnical facilities constructed in Ohio. In the past, the design of these embankments was largely based on soil shear strength properties that had been estimated from previously published empirical correlations and/or crude soil test results. This is because either the actual soil fill material is not available for testing at the time of embankment design or detailed shear strength determination of soil samples in the laboratory tends to be time-consuming and expensive. Structural stability of these embankments is vital to the state economy and public safety. There is a strong need to conduct a study to examine whether the empirical correlations are truly applicable to Ohio soils and to develop comprehensive geotechnical guidelines concerning the shear strength properties of cohesive soils typically used in Ohio. In this study, soil samples from nine highway embankment sites scattered across Ohio were tested both in the field and laboratory to establish comprehensive geotechnical properties of cohesive soil fills, which represent a wide range of geological features existing in the state. The large volume of soil data produced in the study was then analyzed to evaluate reliability of the empirical correlations and derive statistically strong correlations for shear strength properties of cohesive soil fill materials found in Ohio. Based on the outcome of these analyses, multi-level guidelines are proposed by the author for estimating shear strength properties of Ohio cohesive soils more confidently. 17. Key Words 18. Distribution Statement shear strength, embankment, highway, soils, cohesive, No Restrictions. This document is available to slope stability, trixial test, statistical analysis, geotechnical the public through the National Technical guidelines Information Service, Springfield, Virginia 22161 19. Security Classif. (of this report) 20. Security Classif. (of this 21. No. of Pages 22. Price Unclassified page) 300+ Unclassified Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized Shear Strength of Clay and Silt Embankments Final Report Prepared in cooperation with the Ohio Department of Transportation and the U.S. Department of Transportation, Federal Highway Administration by Teruhisa Masada, Ph.D. (Professor of Civil Engineering) Leading Research Agency: Ohio Research Institute for Transportation and the Environment Russ College of Engineering and Technology Ohio University Athens, Ohio 45701-2979 and Sub-Contractor: BBC & M Engineering Inc. 6190 Enterprise Ct. Dublin, Ohio 43016-7297 Disclaimer Statement: 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 Ohio Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification or regulation. September 2009 Acknowledgements The author would like to acknowledge the support of the Ohio Department of Transportation (ODOT) technical liaison, Gene Geiger and Steve Sommers (both from the Office of Geotechnical Engineering) as well as the ODOT Director of R & D Office Monique Evans. The author is also grateful to his graduate research assistants Jeffrey Holko and Xiao Han, who spent long hours performing triaxial compression tests and statistical data analysis. i TABLE OF CONTENTS Page No. ACKNOWLEDGEMENTS ……………………………………..……... i TABLE OF CONTENTS ……………………………………………..……... ii LIST OF TABLES ………………………………………………….………… vi LIST OF FIGURES ……………………………………………………..…..…. xii CHAPTER 1: INTRODUCTION …………………………………….……… 1 1.1 Background ………………………………………………….………… 1 1.2 Objectives of Study ………………………………………….………… 2 1.3 Outlines of Report ………………………………………….………… 3 CHAPTER 2: LITERATURE REVIEW ………………………….………... 6 2.1 General …………………………………………………………… 6 2.1.1 Shear Strength of Soil …………………………………………… 6 2.1.2 Pore Water Pressure in Soil …………………………………… 7 2.1.3 Consolidation …………………………………………………… 9 2.1.4 Stability of Highway Embankments …………………………… 10 2.1.5 Soil Classification …………………………………………… 11 2.2 Review of Literature in Ohio …………………………………………… 13 2.2.1 Glaciers …………………………………………………… 13 2.2.2 Soil and Bedrock …………………………………………… 13 2.3 Standard Penetration Test (SPT) …………………………………… 15 2.3.1 SPT General …………………………………………………… 15 2.3.2 SPT Equipment …………………………………………… 15 2.3.3 SPT Procedure …………………………………………… 17 2.3.4 SPT Energy Corrections …………………………………… 18 2.3.5 Normalization of SPT-N Values …………………………… 19 2.3.6 Static Forces and Stresses in SPT …………………………… 20 2.4 Empirical SPT Correlations …………………………………………… 24 2.5 Triaxial Compression Test …………………………………………… 27 2.5.1 Test Set-up and Equipment …………………………………… 27 2.5.2 Back Pressure Saturation …………………………………… 27 2.5.3 Consolidated-Drained (C-D) Test …………………………… 28 2.5.4 Consolidated-Undrained (C-U) Test …………………………… 28 2.5.5 Unconsolidated-Undrained (U-U) Test …………………… 31 2.6 Unconfined Compression (UC) Test …………………………………… 31 2.7 Additional Information on Soil Shear Strength …………………… 32 2.8 Statistical Analysis of Geotechnical Data …………………………… 33 CHAPTER 3: RESEARCH METHODOLOGY …………………………... 35 3.1 General …………………………………………………………… 35 3.2 Site Selection Criteria …………………………………………………… 35 3.3 Subsurface Exploration Protocol …………………………………… 38 ii 3.3.1 SPT Hammer Calibration ………………………………..….. 38 3.3.2 SPT Protocol and Soil Sampling ………………………..….. 39 3.4 Laboratory Soil Testing Protocol ………………………………..….. 42 3.4.1 Soil Index Property Testing ………………………………..….. 43 3.4.2 Unconfined Compression Strength Test ………………..….. 44 3.4.3 C-U Triaxial Compression Test ………………………..….. 45 3.4.3.1 C-U Triaxial Test Equipment ………………………..….. 46 3.4.3.2 C-U Triaxial Test Procedure ………………………..….. 48 3.5 Statistical Analysis Protocol ………………………………………..….. 52 CHAPTER 4: RESEARCH DATA AND RESULTS ………….……..…. 56 4.1 Introduction ………………………………………………………..….. 56 4.2 Embankment Sites Selected ………………………………………..….. 57 4.3 Subsurface Exploration Work ………………………………………..….. 58 4.3.1 Calibration Test Result for SPT Automatic Hammer ………..….. 58 4.3.2 Subsurface Exploration Data for I-275 Site in Hamilton County ………………………………………………….... 58 4.3.3 Subsurface Exploration Data for USR-35 Site in Fayette County ………………………………………………….... 62 4.3.4 Subsurface Exploration Data for SR-2 Site in Lake County ….... 65 4.3.5 Subsurface Exploration Data for USR-33 Site in Athens County ………………………………………………..….. 67 4.3.6 Subsurface Exploration Data for I-71 Site in Morrow County ………………………………………………..….. 69 4.3.7 Subsurface Exploration Data for SR-2 Site in Erie County ….... 72 4.3.8 Subsurface Exploration Data for I-75 Site in Hancock County ………………………………………………….... 73 4.3.9 Subsurface Exploration Data for I-70 Site in Muskingum County ………………………………………………….... 75 4.3.10 Subsurface Exploration Data for I-77 Site in Noble County ….... 77 4.4 Laboratory Index Properties and Sieve Analysis ………………..….. 79 4.4.1 Soil Index Properties for Site No. 1 (Hamilton County) ….... 80 4.4.2 Soil Index Properties for Site No. 2 (Fayette County) ….... 80 4.4.3 Soil Index Properties for Site No. 3 (Lake County) ………..….. 81 4.4.4 Soil Index Properties for Site No. 4 (Athens County) ….... 82 4.4.5 Soil Index Properties for Site No. 5 (Morrow County) ….... 83 4.4.6 Soil Index Properties for Site No. 6 (Erie County) ………….... 84 4.4.7 Soil Index Properties for Site No. 7 (Hancock County) ….... 84 4.4.8 Soil Index Properties for Site No. 8 (Muskingum County) ….... 85 4.4.9 Soil Index Properties for Site No. 9 (Noble County) ………..….. 86 4.5 Soil Shear Strength Properties ………………………………..….. 86 4.5.1 Shear Strength Properties for Site No. 1 (Hamilton County) ….... 87 4.4.2 Shear Strength Properties for Site No. 2 (Fayette County) ….... 88 4.4.3 Shear Strength Properties for Site No. 3 (Lake County) ….... 89 4.4.4 Shear Strength Properties for Site No. 4 (Athens County) ….... 91 4.4.5 Shear Strength Properties for Site No. 5 (Morrow County) ….... 92 iii 4.4.6 Shear Strength Properties for Site No. 6 (Erie County) ….... 94 4.4.7 Shear Strength Properties for Site No. 7 (Hancock County) ….... 95 4.4.8 Shear Strength Properties for Site No. 8 (Muskingum County) ………………………………………………..….. 96 4.4.9 Shear Strength Properties for Site No. 9 (Noble County) ….... 98