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Job No. XXXX _ NCHRP# XXX Pantone 202 CV 96+ pages; Perfect Bind with Spine COPY = 14 pts Washington, DC 20001 500 Fifth Street, NW Tra NCHRP Synthesis 382 nspo rtation R Address S er vi ce Req NCHRP esea National cooperative rch Boa rd uested Highway Research Program Synthesis 382 Estimating Stiffness of Subgrade and Unbound Materials for Pavement Design Estimating Stiffness of Subgrade and Unbound Materials for Pavement Design A Synthesis of Highway Practice TRB Need Spine Width
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TRANSPORTATION RESEARCH BOARD 2008 EXECUTIVE COMMITTEE* Abbreviations used without deﬁnitions in TRB publications: OFFICERS AAAE American Association of Airport Executives AASHO American Association of State Highway Officials Chair: Debra L. Miller, Secretary, Kansas DOT, Topeka AASHTO American Association of State Highway and Transportation Officials Vice Chair: Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley ACI–NA Airports Council International–North America Executive Director: Robert E. Skinner, Jr., Transportation Research Board ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act MEMBERS APTA American Public Transportation Association ASCE American Society of Civil Engineers J. BARRY BARKER, Executive Director, Transit Authority of River City, Louisville, KY ASME American Society of Mechanical Engineers ALLEN D. BIEHLER, Secretary, Pennsylvania DOT, Harrisburg ASTM American Society for Testing and Materials JOHN D. BOWE, President, Americas Region, APL Limited, Oakland, CA ATA Air Transport Association ATA American Trucking Associations LARRY L. BROWN, SR., Executive Director, Mississippi DOT, Jackson CTAA Community Transportation Association of America DEBORAH H. BUTLER, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA CTBSSP Commercial Truck and Bus Safety Synthesis Program WILLIAM A.V. CLARK, Professor, Department of Geography, University of California, Los Angeles DHS Department of Homeland Security DAVID S. EKERN, Commissioner, Virginia DOT, Richmond DOE Department of Energy NICHOLAS J. GARBER, Henry L. Kinnier Professor, Department of Civil Engineering, University of Virginia, Charlottesville EPA Environmental Protection Agency FAA Federal Aviation Administration JEFFREY W. HAMIEL, Executive Director, Metropolitan Airports Commission, Minneapolis, MN FHWA Federal Highway Administration EDWARD A. (NED) HELME, President, Center for Clean Air Policy, Washington, DC FMCSA Federal Motor Carrier Safety Administration WILL KEMPTON, Director, California DOT, Sacramento FRA Federal Railroad Administration SUSAN MARTINOVICH, Director, Nevada DOT, Carson City FTA Federal Transit Administration IEEE Institute of Electrical and Electronics Engineers MICHAEL D. MEYER, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta ISTEA Intermodal Surface Transportation Efficiency Act of 1991 MICHAEL R. MORRIS, Director of Transportation, North Central Texas Council of Governments, Arlington ITE Institute of Transportation Engineers NEIL J. PEDERSEN, Administrator, Maryland State Highway Administration, Baltimore NASA National Aeronautics and Space Administration PETE K. RAHN, Director, Missouri DOT, Jefferson City NASAO National Association of State Aviation Officials SANDRA ROSENBLOOM, Professor of Planning, University of Arizona, Tucson NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program TRACY L. ROSSER, Vice President, Corporate Traffic, Wal-Mart Stores, Inc., Bentonville, AR NHTSA National Highway Traffic Safety Administration ROSA CLAUSELL ROUNTREE, Executive Director, Georgia State Road and Tollway Authority, Atlanta NTSB National Transportation Safety Board HENRY G. (GERRY) SCHWARTZ, JR., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO SAE Society of Automotive Engineers C. MICHAEL WALTON, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) LINDA S. WATSON, CEO, LYNX–Central Florida Regional Transportation Authority, Orlando TCRP Transit Cooperative Research Program STEVE WILLIAMS, Chairman and CEO, Maverick Transportation, Inc., Little Rock, AR TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board EX OFFICIO MEMBERS TSA Transportation Security Administration U.S.DOT United States Department of Transportation THAD ALLEN (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, Washington, DC JOSEPH H. BOARDMAN, Federal Railroad Administrator, U.S.DOT REBECCA M. BREWSTER, President and COO, American Transportation Research Institute, Smyrna, GA PAUL R. BRUBAKER, Research and Innovative Technology Administrator, U.S.DOT GEORGE BUGLIARELLO, Chancellor, Polytechnic University of New York, Brooklyn, and Foreign Secretary, National Academy of Engineering, Washington, DC SEAN T. CONNAUGHTON, Maritime Administrator, U.S.DOT LEROY GISHI, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, DC EDWARD R. HAMBERGER, President and CEO, Association of American Railroads, Washington, DC JOHN H. HILL, Federal Motor Carrier Safety Administrator, U.S.DOT JOHN C. HORSLEY, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC CARL T. JOHNSON, Pipeline and Hazardous Materials Safety Administrator, U.S.DOT J. EDWARD JOHNSON, Director, Applied Science Directorate, National Aeronautics and Space Administration, John C. Stennis Space Center, MS WILLIAM W. MILLAR, President, American Public Transportation Association, Washington, DC NICOLE R. NASON, National Highway Traffic Safety Administrator, U.S.DOT JAMES RAY, Acting Administrator, Federal Highway Administration, U.S.DOT JAMES S. SIMPSON, Federal Transit Administrator, U.S.DOT ROBERT A. STURGELL, Acting Administrator, Federal Aviation Administration, U.S.DOT ROBERT L. VAN ANTWERP (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC *Membership as of May 2008. Need Spine Width
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National cooperative Highway Research Program NCHRP Synthesis 382 Estimating Stiffness of Subgrade and Unbound Materials for Pavement Design A Synthesis of Highway Practice Consultant Anand J. Puppala The University of Texas at Arlington S ubject A reas Soils, Geology, and Foundations Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration Transportation Research Board Washington, D.C. 2008 www.TRB.org
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP SYNTHESIS 382 Systematic, well-designed research provides the most effective Project 20-5 (Topic 38-09) approach to the solution of many problems facing highway admin- ISSN 0547-5570 istrators and engineers. Often, highway problems are of local inter- ISBN 978-0-309-09811-3 Library of Congress Control No. 2008906008 est and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the © 2008 Transportation Research Board accelerating growth of highway transportation develops increas- ingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. COPYRIGHT PERMISSION In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Authors herein are responsible for the authenticity of their manuscripts Officials initiated in 1962 an objective national highway research and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used program employing modern scientific techniques. This program herein. is supported on a continuing basis by funds from participating Cooperative Research Programs (CRP) grants permission to reproduce member states of the Association and it receives the full coopera- material in this publication for classroom and not-for-profit purposes. tion and support of the Federal Highway Administration, United Permission is given with the understanding that non of the material will be States Department of Transportation. used to imply TRB, AASHTO, FAA, FHWA, FMSCA, FTA, or Transit development Corporation endorsement of a particular product, method, or The Transportation Research Board of the National Research practice. It is expected that those reproducing the material in this document Council was requested by the Association to administer the for educational and not-for-profit uses will give appropriate acknowledg- research program because of the Board’s recognized objectiv- ment of the source of any development or reproduced material. For other ity and understanding of modern research practices. The Board uses of the material, request permission from CRP. is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway NOTICE transportation subject may be drawn; it possesses avenues of communication and cooperation with federal, state, and local The project that is the subject of this report was a part of the National governmental agencies, universities, and industry; its relationship Cooperative Highway Research Program conducted by the Transpor- tation Research Board with the approval of the Governing Board of the to the National Research Council is an insurance of objectivity; National Research Council. Such approval reflects the Governing Board’s it maintains a full-time research correlation staff of specialists in judgment that the program concerned is of national importance and appro- highway transportation matters to bring the findings of research priate with respect to both the purposes and resources of the National directly to those who are in a position to use them. Research Council. The members of the technical committee selected to monitor this proj- The program is developed on the basis of research needs ect and to review this report were chosen for recognized scholarly compe- identified by chief administrators of the highway and transporta- tence and with due consideration for the balance of disciplines appropri- tion departments and by committees of AASHTO. Each year, ate to the project. The opinions and conclusions expressed or implied are specific areas of research needs to be included in the program those of the research agency that performed the research, and, while they are proposed to the National Research Council and the Board have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National by the American Association of State Highway and Transporta- Research Council, the American Association of State Highway and Trans- tion Officials. Research projects to fulfill these needs are defined portation Officials, or the Federal Highway Administration of the U.S. by the Board, and qualified research agencies are selected from Department of Transportation. those that have submitted proposals. Administration and surveil- Each report is reviewed and accepted for publication by the techni- cal committee according to procedures established and monitored by the lance of research contracts are the responsibilities of the National Transportation Research Board Executive Committee and the Governing Research Council and the Transportation Research Board. Board of the National Research Council. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, Published reports of the however, is intended to complement rather than to substitute for or duplicate other highway research programs. NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 NOTE: The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the and can be ordered through the Internet at: American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway http://www.national-academies.org/trb/bookstore Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of this report. Printed in the United States of America
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THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Acad- emy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initia- tive, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sci- ences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transportation Research Board is to provide leadership in transportation innovation and prog- ress through research and information exchange, conducted within a setting that is objective, interdis- ciplinary, and multimodal. The Board’s varied activities annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation depart- ments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org
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NCHRP COMMITTEE FOR PROJECT 20-5 COOPERATIVE RESEARCH PROGRAMS STAFF CHRISTOPHER W. JENKS, Director, Cooperative Research CHAIR Programs GARY D. TAYLOR, CTE Engineers CRAWFORD F. JENCKS, Deputy Director, Cooperative Research Programs MEMBERS NANDA SRINIVASAN, Senior Program Officer THOMAS R. BOHUSLAV, Texas DOT EILEEN DELANEY, Director of Publications DWIGHT HORNE, Federal Highway Administration YSELA LLORT, Florida DOT NCHRP SYNTHESIS STAFF WESLEY S.C. LUM, California DOT STEPHEN R. GODWIN, Director for Studies and Special JAMES W. MARCH, Federal Highway Administration Programs JOHN M. MASON, JR., Pennsylvania State University JON M. WILLIAMS, Associate Director, IDEA and Synthesis CATHERINE NELSON, Oregon DOT Studies LARRY VELASQUEZ, New Mexico DOT GAIL STABA, Senior Program Officer PAUL T. WELLS, New York State DOT DONNA L. VLASAK, Senior Program Officer DON TIPPMAN, Editor CHERYL KEITH, Senior Program Assistant FHWA LIAISON WILLIAM ZACCAGNINO TOPIC PANEL JUDITH B. CORLEY-LAY, North Carolina Department of TRB LIAISON Transportation STEPHEN F. MAHER LEO FONTAINE, Connecticut Department of Transportation G.P. JAYAPRAKASH, Transportation Research Board ANDREW M. JOHNSON, South Carolina Department of Transportation JOHN A. SIEKMEIER, Minnesota Department of Transportation BRUCE STEVEN, University of California–Davis ZHONGJIE “DOC” ZHANG, Louisiana Department of Trans- portation and Development MICHAEL MORAVEC, Federal Highway Administration (Liaison) CHERYL ALLEN RICHTER, Federal Highway Administration (Liaison) Cover: LWD devices in field operation (White et al. 2007).
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FOREWORD Highway administrators, engineers, and researchers often face problems for which infor- mation already exists, either in documented form or as undocumented experience and prac- tice. This information may be fragmented, scattered, and unevaluated. As a consequence, full knowledge of what has been learned about a problem may not be brought to bear on its solution. Costly research findings may go unused, valuable experience may be overlooked, and due consideration may not be given to recommended practices for solving or alleviat- ing the problem. There is information on nearly every subject of concern to highway administrators and engineers. Much of it derives from research or from the work of practitioners faced with problems in their day-to-day work. To provide a systematic means for assembling and evaluating such useful information and to make it available to the entire highway commu- nity, the American Association of State Highway and Transportation Officials—through the mechanism of the National Cooperative Highway Research Program—authorized the Transportation Research Board to undertake a continuing study. This study, NCHRP Project 20-5, “Synthesis of Information Related to Highway Problems,” searches out and synthesizes useful knowledge from all available sources and prepares concise, documented reports on specific topics. Reports from this endeavor constitute an NCHRP report series, Synthesis of Highway Practice. This synthesis series reports on current knowledge and practice, in a compact format, without the detailed directions usually found in handbooks or design manuals. Each report in the series provides a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. PREFACE The new Mechanistic Empirical Pavement Design Guide (MEPDG) and other existing By Jon M. Williams pavement design guides use resilient modulus (MR) as the primary input parameter when characterizing stiffness of subsoils and unbound bases. Resilient modulus of soils is typi- Program Officer cally determined either by using laboratory tests or field tests. This report was prepared to Transportation describe the significance of the resilient modulus property, various methods of determin- Research Board ing this property of subsoils and unbound bases, and the application of this parameter in the mechanistic empirical pavement design guide. The report will be of interest to design, geotechnical and materials engineers and technicians. Information collected in this synthesis was based on a comprehensive literature review, surveys of pavement design, materials and geotechnical engineers from state DOTs, and selected interviews. Information collected also included research reports from studies con- ducted by several state DOTs. The consultant, Anand J. Puppala, collected and synthesized the information and wrote the report. The members of the topic panel are acknowledged on the preceding page. This synthesis is an immediately useful document that records the practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new knowledge will be added to that now at hand.
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CONTENTS 3 CHAPTERONE INTRODUCTION Introduction a4d Definitions, 3 Synthesis Objectives and Overview, 5 Outline of ChaPters, 5 6 CTTAPTER TWO SUMMARY OF SURVEY RESPONSES Introduction, ó Survey Questionnaire, 6 Survey Procedure StePs, 6 Survey Results, 6 Summary,21 22 CHAPTER THREE LABORATORY METHODS FOR MATERIAL STIFFNESS MEASUREMENT Introduction, 22 Laboratory Tests Used for Resilient Modulus, 22 Labor atory M p Tests-Summary, 24 Intemational PersPectives, 40 Summary,41 42 CHAPTER FOUR FIELD METHODS FOR MATERIAL STIFFNESS MEASUREMENT Field Tests, 42 Synthesized Information-Nondestructive Tests, 45 Final Summary on Nondestructive Methods, 56 Intrusive Methods, 57 Summary,65 66 CHAPTERFIVE CORRELATIONSANDMATRIXTABLES Resilient Moduli Correlations, 66 Direct Resilient Moduli Conelations, 66 ' Indirect Models, 7l Correlations Development and Evaluation, 74 Matrix Tables, 78 Resilient Moduli Magnitudes, 80 Summary,82 83 CHAPTER SIX USEFUL PRACTICES, CONCLUSIONS, AND FUTURE RESEARCH NEEDS Useful Practices for Determining Resilient Properties, 83 Useful Approaches to Pavement Design, 84 Conclusion, 84 Future Research Needs, 85 87 REFERENCES 95 APPENDIX A SURVEY QUESTIONNAIRE 109 APPENDIX B SURVEY RESPONDENT INFORMATION 111 APPENDIX C SUMMARY OF SURVEY RESULTS 124 APPENDIX D MODULI OF VARIOUS SOILS AND AGGREGATES