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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
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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.
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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-
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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-
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The members of the technical committee selected to monitor this proj-
The program is developed on the basis of research needs
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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.
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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
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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
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tive, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the
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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
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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
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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,
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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
