U.S. Department of Transportation Publication No. FHWA-NHI-00-043 Federal Highway Administration NHI Course No. 132042 MECHANICALLY STABILIZED EARTH WALLS AND REINFORCED SOIL SLOPES DESIGN & CONSTRUCTION GUIDELINES NHI – National Highway Institute Office of Bridge Technology March 2001 NOTICE 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 policy of the Department of Transportation. This report does not constitute a standard, specification, or regulation. The United States Government does not endorse products or manufacturers. Trade or manufacturer's names appear herein only because they are considered essential to the objective of this document. Technical Report Documentation Page 1. REPORT NO. 2. GOVERNMENT 3. RECIPIENT'S CATALOG NO. FHWA-NHI-00-043 ACCESSION NO. 4. TITLE AND SUBTITLE 5. REPORT DATE March 2001 Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and 6. PERFORMING ORGANIZATION CODE Construction Guidelines 7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO. Victor Elias, P.E.; Barry R. Christopher, Ph.D., P.E. and Ryan R. Berg, P.E. 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. WORK UNIT NO. Ryan R. Berg & Associates, Inc. 2190 Leyland Alcove 11. CONTRACT OR GRANT NO. Woodbury, MN 55125 DTFH61-99-T-25041 12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT & PERIOD COVERED National Highway Institute Federal Highway Administration U.S. Department of Transportation 14. SPONSORING AGENCY CODE Washington, D.C. 15. SUPPLEMENTARY NOTES FHWA Technical Consultant: J.A. DiMaggio, P.E. (HIBT-20) This manual is the updated version of FHWA SA96-071 prepared by E2Si. 16. ABSTRACT This manual is the reference text used for the FHWA NHI course No. 132042 on Mechanically Stabilized Earth Walls and Reinforced Soil Slopes and reflects current practice for the design, construction and monitoring of these structures. This manual was prepared to enable the engineer to identify and evaluate potential applications of MSEW and RSS as an alternative to other construction methods and as a means to solve construction problems. The scope is sufficiently broad to be of value for specifications specialists, construction and contracting personnel responsible for construction inspection, development of material specifications and contracting methods. With the aid of this text, the engineer should be able to properly select, design, specify, monitor and contract for the construction of MSE walls and RSS embankments. 17. KEY WORDS 18. DISTRIBUTION STATEMENT Design, analysis, performance criteria, Mechanically Stabilized Earth Walls No restrictions. (MSEW), Reinforced Soil Slopes (RSS), soil reinforcement, geosynthetics, geotextiles, geogrids, specifications, contracting methods 19. SECURITY CLASSIF. 20. SECURITY CLASSIF. 21. NO. OF PAGES 22 Unclassified Unclassified 394 i SI CONVERSION FACTORS APPROXIMATE CONVERSIONS FROM SI UNITS Symbol When You Know Multiply By To Find Symbol LENGTH mm millimeters 0.039 inches in m meters 3.28 feet ft m meters 1.09 yards yd km kilometers 0.621 miles mi AREA mm2 square millimeters 0.0016 square inches in2 m2 square meters 10.764 square feet ft2 m2 square meters 1.195 square yards yd2 ha hectares 2.47 acres ac km2 square kilometers 0.386 square miles mi2 VOLUME ml millimeters 0.034 fluid ounces fl oz l liters 0.264 gallons gal m3 cubic meters 35.71 cubic feet ft3 m3 cubic meters 1.307 cubic yards yd3 MASS g grams 0.035 ounces oz kg kilograms 2.202 pounds lb TEMPERATURE ?C Celsius 1.8 C + 32 Fahrenheit ?F WEIGHT DENSITY kN/m3 kilonewton / cubic meter 6.36 poundforce / cubic foot pcf FORCE and PRESSURE or STRESS N newtons 0.225 poundforce lbf kN kilonewtons 225 poundforce lbf kPa kilopascals 0.145 poundforce / square inch psi kPa kilopascals 20.9 poundforce / square foot psf ii PREFACE Engineers and specialty material suppliers have been designing reinforced soil structures for the past 25 years. During the last decade significant improvements have been made to design methods and in the understanding of factors affecting the durability of reinforcements. In order to take advantage of these new developments the FHWA developed a manual (in connection with Demonstration Project No. 82, Ground Improvement), FHWA SA96-071, which is the basis for this updated version. The primary purpose of this manual is to support educational programs conducted by FHWA for transportation agencies. A second purpose of equal importance is to serve as the FHWA standard reference for highway projects involving reinforced soil structures. This Mechanically Stabilized Earth Walls (MSE) and Reinforced Soil Slopes (RSS), Design and Construction Guidelines Manual which is a current update of FHWA SA-96-071, has evolved from the following AASHTO and FHWA references: ! Reinforced Soil Structures - Volume I, Design and Construction Guidelines - Volume II, Summary of Research and Systems Information, by B.R. Christopher, S.A. Gill, J.P. Giroud, J.K. Mitchell, F. Schlosser, and J. Dunnicliff, FHWA RD 89-043. ! Geosynthetic Design and Construction Guidelines, by R.D. Holtz, B.R. Christopher, and R.R. Berg, FHWA HI-95-038. ! AASHTO, 1992, 1996, 1997, 1998 and 1999 Interims, Section 5.8. ! Design and Construction Monitoring of Mechanically Stabilized Earth Structures, by J.A. DiMaggio, FHWA, March 1994. ! Guidelines for Design, Specification, and Contracting of Geosynthetic Mechanically Stabilized Earth Slopes on Firm Foundations, by R.R. Berg, FHWA-SA-93-025, January 1993. ! AASHTO Bridge T-15 Technical Committee unpublished working drafts for the update of Section 5.8 of the AASHTO Bridge Design Specifications. The authors recognize the efforts of Mr. Jerry A. DiMaggio, P.E. who was the FHWA Technical Consultant for this work, and served in the same capacity for most of the above referenced publications. Mr. DiMaggio's guidance and input to this and the previous works has been invaluable. The authors further acknowledge the efforts of Mr. Tony Allen, Washington DOT, members of the AASHTO T-15 committee and the following Technical Working Group members who served as a review panel listed in alphabetical order: iii Dr. Donald Bruce - ECO Geosystems Inc. Dr. James Collin - The Collin Group Mr. Albert DiMillio - FHWA Mr. Richard Endres - Michigan DOT Mr. John Hooks - FHWA Dr. John Horvath - Manhattan College Mr. Richard Sheffield - Mississippi DOT Mr. Michael Simac - Ground Improvement Technologies Mr. Ed Tavera - Louisiana DOT Lastly, the authors wish to thank the clerical and computer graphics staff of Earth Engineering and Sciences, Inc. for their vital contributions and significant effort in preparing the earlier version of this manual. iv TABLE OF CONTENTS CHAPTER 1 INTRODUCTION ................................................ -1- 1.1 OBJECTIVES ................................................... -1- a. Scope ................................................... -1- b. Source Documents .......................................... -2- c. Terminology ............................................... -2- 1.2 HISTORICAL DEVELOPMENT .................................... -4- CHAPTER 2 SYSTEMS AND PROJECT EVALUATION ............................ -9- 2.1 APPLICATIONS ................................................ -9- 2.2 ADVANTAGES AND DISADVANTAGES .......................... -15- a. Advantages of Mechanically Stabilized Earth (MSE) Walls ........... -15- b. Advantages of Reinforced Soil Slopes .......................... -15- c. Disadvantages ............................................ -16- 2.3 RELATIVE COSTS ............................................. -17- 2.4 DESCRIPTION OF MSE/RSS SYSTEMS ........................... -20- a. Systems Differentiation ...................................... -20- b. Types of Systems .......................................... -20- c. Facing Systems ........................................... -21- d. Reinforcement Types ....................................... -25- e. Reinforced Backfill Materials ................................. -26- f. Miscellaneous Materials of Construction ......................... -26- 2.5 SITE EVALUATION ............................................ -27- a. Site Exploration ........................................... -27- b. Field Reconnaissance ....................................... -27- c. Subsurface Exploration ...................................... -28- d. Laboratory Testing ......................................... -29- 2.6 PROJECT EVALUATION ........................................ -30- a. Structure Selection Factors ................................... -30- b. Geologic and Topographic Conditions .......................... -31- c. Environmental Conditions .................................... -32- d. Size and nature of structure ................................... -33- e. Aesthetics ............................................... -33- f. Questionable Applications ................................... -34- 2.7 ESTABLISHMENT OF PROJECT CRITERIA ........................ -34- a. Alternates ............................................... -35- b. Facing Considerations ...................................... -35- c. Performance Criteria ....................................... -36- d. Design Life ............................................... -40- 2.8 CONSTRUCTION SEQUENCE ................................... -40- a. Construction of MSEW systems with precast facings ............... -41- b. Construction of MSE systems with Flexible Facings ...............