Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. FHWA/TX-14/0-6792-1 4. Title and Subtitle 5. Report Date GEOSYNTHETIC REINFORCED STEEP SLOPES Published: March 2016 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Yoo Jae Kim, Jiong Hu, Soon Jae Lee, Ashley Russell Kotwal, and Report 0-6792-1 Justin Wayne Dickey 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Texas State University Department of Engineering Technology 11. Contract or Grant No. 601 University Drive Project 0-6792 San Marcos, Texas 78666 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Texas Department of Transportation Technical Report: Research and Technology Implementation Office September 2012–November 2013 125 E. 11th Street 14. Sponsoring Agency Code Austin, Texas 78701-2483 15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation: Project Title: Synthesis on Geosynthetic Reinforced Steep Slopes URL: 16. Abstract Geosynthetics provide a means to mechanically stabilize earth structures by improving strength through tensile reinforcement. When incorporating these polymeric materials in the application of stabilizing steep slopes, geosynthetic reinforcement can accommodate budgetary restrictions and alleviate space constraints. TxDOT currently has limited use of geosynthetics in steep slope construction. Therefore, a synthesis study of geosynthetic reinforced steep slopes has been conducted to enhance the present understanding of this technology. The study summarized the benefits and limitations of utilizing geosynthetic reinforcement and investigated current design and construction methods in order to determine best practices. Additionally, the cost effectiveness of geosynthetic reinforced steep slopes was examined. Case studies were also identified and assessed to determine optimal soil conditions, geometry of the slope, design criteria, construction specifications, and performance measures. The synthesis study summarized best practices, existing methodologies, and recommendations for the use of geosynthetic reinforced steep slopes in Texas. 17. Key Words 18. Distribution Statement Geosynthetic, Geogrid, Geotextile, Reinforced Soil, No restrictions. This document is available to the Slope, Embankment public through NTIS: National Technical Information Service Alexandria, VA 22312 http://www.ntis.gov 19. Security Classif.(of this report) 20. Security Classif.(of this page) 21. No. of Pages 22. Price Unclassified Unclassified 184 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized. GEOSYNTHETIC REINFORCED STEEP SLOPES by Yoo Jae Kim Assistant Professor Texas State University Jiong Hu Associate Professor Texas State University Soon Jae Lee Associate Professor Texas State University Ashley Russell Kotwal Doctoral Research Assistant Texas State University and Justin Wayne Dickey Graduate Research Assistant Texas State University Report 0-6792-1 Project 0-6792 Project Title: Synthesis on Geosynthetic Reinforced Steep Slopes Performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration Published: March 2016 TEXAS STATE UNIVERSITY Department of Engineering Technology 601 University Drive San Marcos, TX 78666 DISCLAIMER This research was performed in cooperation with the Texas Department of Transportation (TxDOT). 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 view or policies of TxDOT. This report does not constitute a standard, specification, or regulation. This report is not intended for construction, bidding, or permit purposes. The researcher in charge of the project was Dr. Yoo Jae Kim. v ACKNOWLEDGEMENTS The authors are grateful for the support and guidance of Kevin Pete, Project Manager of Research and Technology Implementation. In addition, the authors thank Marie Fisk for her valuable comments during the project. The authors also acknowledge ADAMA Engineering for providing software that was essential for completing the design example. vi TABLE OF CONTENTS Page List of Figures ............................................................................................................................... ix List of Tables ................................................................................................................................ xi Chapter I: Introduction ................................................................................................................ 1 Scope ........................................................................................................................................... 1 Research Significance ................................................................................................................. 2 Definition .................................................................................................................................... 2 Background and History ............................................................................................................. 3 Geosynthetics .............................................................................................................................. 4 Chapter II: Design Methods and Materials ................................................................................ 7 Design Methods .......................................................................................................................... 7 FHWA Design Guidelines ........................................................................................................ 22 Design Software ........................................................................................................................ 37 Foundation and Backfill Materials ........................................................................................... 38 Geosynthetic Materials ............................................................................................................. 42 Chapter III: Construction Practices ......................................................................................... 45 Construction Sequence ............................................................................................................. 45 Transportation Agency Specifications ...................................................................................... 47 Weak Foundation Soil .............................................................................................................. 48 Contracting Methods ................................................................................................................. 49 Site Evaluation .......................................................................................................................... 50 Additional Considerations ........................................................................................................ 51 Chapter IV: Performance Measures and Cost Effectiveness ................................................. 53 Quality Control ......................................................................................................................... 53 Field Inspection ......................................................................................................................... 54 Performance Monitoring ........................................................................................................... 54 Lifespan .................................................................................................................................... 55 Failure Modes ........................................................................................................................... 56 Cost Effectiveness ..................................................................................................................... 57 Additional Considerations ........................................................................................................ 58 Chapter V: Case Studies ............................................................................................................ 61 Purpose ...................................................................................................................................... 61 Geosynthetic Material ............................................................................................................... 61 Foundation and Backfill Material ............................................................................................. 62 Slope Geometry ........................................................................................................................ 63 Design Methods ........................................................................................................................ 64 Construction Practices .............................................................................................................. 64 Performance .............................................................................................................................. 65 Cost Effectiveness ..................................................................................................................... 65 vii Chapter VI: Conclusions and Recommendations ...................................................................