Rock-Socketed Shafts for Highway Structure Foundations (2006)

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TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2006 www.TRB.org NAT IONAL COOPERAT IVE H IGHWAY RESEARCH PROGRAM NCHRP SYNTHESIS 360 Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration SUBJECT AREAS Bridges, Other Structures, and Hydraulics and Hydrology and Soils, Geology, and Foundations Rock-Socketed Shafts for Highway Structure Foundations A Synthesis of Highway Practice CONSULTANT JOHN TURNER University of Wyoming Laramie, Wyoming

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board’s recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state, and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. 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, however, is intended to complement rather than to substitute for or duplicate other highway research programs. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP SYNTHESIS 360 Price $39.00 Project 20-5 (Topic 36-12) ISSN 0547-5570 ISBN 0-309-09768-1 Library of Congress Control No. 2006925246 © 2006 Transportation Research Board COPYRIGHT PERMISSION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. Such approval reflects the Governing Board’s judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council. NOTE: The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway 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.

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 techni- cal 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 achieve- ments of engineers. Dr. William A. Wulf 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 initiative, 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 Acad- emy, the Council has become the principal operating agency of both the National Academy of Sciences 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 the Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. William A. Wulf are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is a division of the National Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board’s mission is to promote innovation and progress in transportation through research. In an objective and interdisciplinary setting, the Board facilitates the sharing of information on transportation practice and policy by researchers and practitioners; stimulates research and offers research management services that promote technical excellence; provides expert advice on transportation policy and programs; and disseminates research results broadly and encourages their implementation. The Board’s varied activities annually engage more than 5,000 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 departments, 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

NCHRP COMMITTEE FOR PROJECT 20-5 CHAIR GARY D. TAYLOR, CTE Engineers MEMBERS THOMAS R. BOHUSLAV, Texas DOT DONN E. HANCHER, University of Kentucky DWIGHT HORNE, Federal Highway Administration YSELA LLORT, Florida DOT WESLEY S.C. LUM, California DOT JAMES W. MARCH, Federal Highway Administration JOHN M. MASON, JR., Pennsylvania State University CATHERINE NELSON, Oregon DOT LARRY VELASQUEZ, New Mexico DOT PAUL T. WELLS, New York State DOT FHWA LIAISON WILLIAM ZACCAGNINO TRB LIAISON STEPHEN F. MAHER COOPERATIVE RESEARCH PROGRAM STAFF ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP EILEEN DELANEY, Director of Publications NCHRP SYNTHESIS STAFF STEPHEN R. GODWIN, Director for Studies and Information Services JON WILLIAMS, Manager, Synthesis Studies DONNA L. VLASAK, Senior Program Officer DON TIPPMAN, Editor CHERYL KEITH, Senior Secretary TOPIC PANEL DAN A. BROWN, Auburn University JOHN G. DELPHIA, Texas Department of Transportation LEO FONTAINE, Connecticut Department of Transportation G.P. JAYAPRAKASH, Transportation Research Board PAUL PASSE, PSI, Inc. TOM SHANTZ, California Department of Transportation DARIN SJOBLOM, Utah Department of Transportation JERRY A. DIMAGGIO, Federal Highway Administration (Liaison) BEN RIVERS, Federal Highway Administration (Liaison) Cover photograph: Bridge with surface exposures of foundation rock.

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 eval- uating such useful information and to make it available to the entire highway community, 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 Proj- ect 20-5, “Synthesis of Information Related to Highway Problems,” searches out and syn- thesizes 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. FOREWORD By Staff Transportation Research Board During the past 25 years, much knowledge and experience has been acquired by the engi- neering and construction industries on the use of rock-socketed shafts for support of trans- portation structures. This synthesis collected, reviewed, and organized the most salient aspects of this knowledge and experience to present it in a form useful to foundation design- ers, researchers, contractors, and transportation officials. The objectives of this report were to collect and summarize information on current practices pertaining to each step of the design process, along with the limitations; identify emerging and promising technologies; determine the principal challenges in advancing the state of the practice; and provide sug- gestions for future developments and improvements in the use and design of rock-socketed shafts. For this TRB synthesis report a literature review was conducted on all topics related to drilled shaft in rock or intermediate geomaterials. A questionnaire was developed and dis- tributed to the principal geotechnical and structural engineers of U.S. state and Canadian provincial transportation agencies. Questions were grouped into the following categories: use of rock-socketed shafts by the agency, evaluation of rock and intermediate geomateri- als, design methods for axial loading, design methods for lateral loading, structural design, construction, and field load and integrity testing. John Turner, Professor of Civil and Architectural Engineering, University of Wyoming, Laramie, collected and synthesized the information and wrote the report, under the guid- ance of a panel of experts in the subject area. The members of the topic panel are acknowl- edged 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. PREFACE

CONTENTS 1 SUMMARY 3 CHAPTER ONE INTRODUCTION Background, 3 Problem Definition, 3 Scope and Objectives, 3 Methodology, 4 Organization of Synthesis, 4 Design Process, 5 8 CHAPTER TWO SITE AND GEOMATERIAL CHARACTERIZATION Scope, 8 Site Geology, 8 Field Investigations, 10 Geologic and Index Properties of Rock, 16 Engineering Properties of Rock, 20 Intermediate Geomaterials, 29 Summary, 31 33 CHAPTER THREE DESIGN FOR AXIAL LOADING Scope, 33 Relationship to Geomaterial Characterization, 33 Load Transfer Behavior of Rock Sockets, 33 Capacity Under Axial Loading, 37 Axial Load-Displacement Behavior, 47 Current AASHTO Practice, 51 Summary, 52 54 CHAPTER FOUR DESIGN FOR LATERAL LOADING Scope, 54 Design Process, 54 Rock-Socketed Foundations for Lateral Loading, 54 Analytical Methods, 55 Structural Issues, 66 Summary, 70 71 CHAPTER FIVE CONSTRUCTION AND FIELD TESTING Scope, 71 Construction of Rock Sockets, 71 Field Load Testing, 74 Constructability, Inspection, and Quality Assurance, 88 Examples of Difficult Geologic Conditions, 93 Summary, 95

97 CHAPTER SIX CONCLUSIONS Site and Geomaterial Characterization, 97 Design for Axial Load, 98 Design for Lateral Load, 99 Load Testing, 99 Constructability and Inspection, 99 Research Needed to Advance State of Practice, 100 102 EQUATION SYMBOLS 104 REFERENCES 110 APPENDIX A SURVEY RESPONDENTS 111 APPENDIX B SURVEY QUESTIONNAIRE AND RESPONSES