Countermeasures to Protect Bridge Piers from Scour (2007)

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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2007 www.TRB.org N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 593 Subject Areas Planning and Administration • Bridges, Other Structures, and Hydraulics and Hydrology • Materials, Construction, and Maintenance Countermeasures to Protect Bridge Piers from Scour P. F. Lagasse P. E. Clopper L. W. Zevenbergen L. G. Girard AYRES ASSOCIATES INC. Fort Collins, CO Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

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 REPORT 593 Project 24-07(2) ISSN 0077-5614 ISBN: 978-0-309-09909-7 Library of Congress Control Number 2007939324 © 2007 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. 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CRP STAFF FOR NCHRP REPORT 593 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Eileen P. Delaney, Director of Publications Natalie Barnes, Editor NCHRP PROJECT 24-07(2) PANEL Field of Soil and Geology—Area of Mechanics and Foundations Arunprakash M. Shirole, Arora and Associates, P.C., Robbinsdale, MN (Chair) Catherine Crossett Avila, Avila and Associates Consulting Engineers, Inc., Walnut Creek, CA Brooks V. Booher, Arkansas SHTD, Little Rock, AR Michael J. Loftus, New York State Thruway Authority, Albany, NY J. Alex McCorquodale, University of New Orleans, New Orleans, LA A. Jacob Odgaard, University of Iowa, Iowa City, IA Jorge E. Pagán-Ortiz, Federal Highway Administration, Washington, DC Kornel Kerenyi, FHWA Liaison G. P. Jayaprakash, TRB Liaison C O O P E R A T I V E R E S E A R C H P R O G R A M S

This report documents research on local scour at bridge piers resulting in the development and recommendation of a practical selection criteria for bridge-pier scour countermeasures, guidelines and specifications for design and construction of those countermeasures, and guidelines for their inspection, maintenance, and performance evaluation. Because of their critical role in ensuring bridge integrity and potentially high cost of these countermeasures, it is important that the most appropriate countermeasures be selected, designed, and con- structed. The contents of this report are, therefore, of immediate interest to highway professionals responsible for planning, administrating, evaluating, designing, constructing, inspecting and maintaining bridges and other structures founded in erosive areas. The report is also of interest to those charged with specifying materials testing procedures and accept- able results, setting budget goals, and making policy. Scour at bridges is a potential safety hazard to the traveling public. Because of the critical role of countermeasures in ensuring bridge integrity, as well as their potential high cost, scour countermeasures must be selected, designed, and constructed based on site conditions and other factors. NCHRP Project 24-07, completed in October 1998 by the University of Minnesota, was undertaken to research the performance of various countermeasures for pier protection. Under NCHRP Project 24-07(2), Ayres Associates Inc. was contracted to extend the results and applicability of the earlier project by developing and recommending practical selection criteria for bridge pier scour countermeasures; guidelines and specifications for design and construction of the suitable countermeasures; and guidelines for inspection, maintenance, and performance evaluation of the countermeasures. The countermeasures addressed include riprap, partially grouted riprap, articulating concrete block systems, gabions, grout-filled mattresses, and geotextile sand containers (used as a filter). Because some of the addressed countermeasures have had limited field application, the specifications contained within this report are based in part on laboratory testing using small- and prototype-scale models. These controlled experiments cannot duplicate all of the possible field conditions; consequently, frequent monitoring must be included in the coun- termeasure programs that use the new guidelines presented in this report. The selection methodology defining the proper conditions for the use of each specific coun- termeasure is presented in Appendix B. The selection methodology is also available on the TRB website (http://www.trb.org/news/blurb_detail.asp?id=7998) as an interactive Microsoft‚ Excel spreadsheet. Appendixes C through G consist of stand-alone documents containing all the necessary information on each individual countermeasure. To develop the guidelines and recommendations for partially grouted riprap, three German documents were translated into English. These translations are available in the Reference Document on the TRB website. F O R E W O R D By Crawford F. Jencks Deputy Director, Cooperative Research Programs Transportation Research Board

C O N T E N T S 1 Summary 6 Chapter 1 Introduction and Research Approach 6 1.1 Scope and Research Objectives 6 1.1.1 Background 6 1.1.2 Scope of Research 7 1.2 Research Approach 7 1.2.1 Overview 8 1.2.2 Transition from Project 24-07 8 1.2.3 Integration of European Technology 9 1.2.4 Continuation Funding 9 1.3 Research Tasks 9 1.3.1 Task 1—Review Literature 9 1.3.2 Task 2—Analyze Performance at Existing Installations 9 1.3.3 Task 3—Identify Merits and Deficiencies 10 1.3.4 Task 4—Develop Draft Recommendations 10 1.3.5 Task 5—Identify Bridge Owners 10 1.3.6 Task 6—Submit Interim Report 10 1.3.7 Task 7—Perform Laboratory Studies 10 1.3.8 Task 7C—Perform Laboratory Studies (Continuation Funding) 10 1.3.9 Task 8—Perform Field Evaluation 10 1.3.10 Task 9—Finalize Draft Recommendations 10 1.3.11 Task 10—Submit Final Report 10 1.4 Report Organization 11 Chapter 2 Findings 11 2.1 Review of Current Practice 11 2.1.1 Introduction 11 2.1.2 Scour at Bridge Piers 12 2.1.3 Riprap as a Pier Scour Countermeasure 23 2.1.4 Alternatives to Riprap 33 2.1.5 Federal Waterways Engineering and Research Institute (BAW) Guidelines and Codes 34 2.2 Performance Evaluation at Existing Sites 34 2.2.1 Introduction 34 2.2.2 Key Findings: Phase 1 Site Visits 35 2.2.3 Key Findings: Phase 2 Site Visits 39 2.3 Merits and Deficiencies of Pier Scour Countermeasures 39 2.3.1 Life-Cycle Factors 41 2.3.2 Merits and Deficiencies by Life-Cycle Factors 42 2.3.3 Summary

47 Chapter 3 Testing, Interpretation, Appraisal, and Results 47 3.1 Introduction 47 3.2 Laboratory Studies 47 3.2.1 Overview 49 3.2.2 Research Approach 50 3.2.3 Laboratory Test Plan 50 3.3 Unprotected Runs 50 3.3.1 Materials 50 3.3.2 Testing 51 3.4 Riprap 53 3.4.1 Materials 54 3.4.2 Testing Program 58 3.5 Partially Grouted Riprap 59 3.5.1 Materials 60 3.5.2 Small-Scale Testing Program 61 3.5.3 Prototype-Scale Tests of Partially Grouted Riprap 71 3.6 Articulating Concrete Block Systems 72 3.6.1 Materials 74 3.6.2 Testing Program 76 3.7 Gabion Mattresses 77 3.7.1 Materials 78 3.7.2 Testing Program 80 3.8 Grout-Filled Mattresses 80 3.8.1 Materials 82 3.8.2 Testing Program 83 3.9 Design and Specification 83 3.9.1 Riprap 85 3.9.2 Partially Grouted Riprap 86 3.9.3 Articulating Concrete Blocks 87 3.9.4 Gabion Mattresses 88 3.9.5 Grout-Filled Mattresses 89 3.10 Construction 89 3.10.1 Overview 89 3.10.2 General Guidelines 89 3.10.3 Filters 90 3.10.4 Installation 90 3.11 Inspection, Maintenance, and Performance Evaluation 90 3.11.1 Inspection During Construction 91 3.11.2 Periodic and Post-Flood Inspection 91 3.11.3 Maintenance 91 3.11.4 Performance Evaluation 92 3.12 Filter Requirements 92 3.12.1 Filter Design 94 3.12.2 Base Soil Properties 94 3.12.3 Geotextile Filter Properties 95 3.12.4 Granular Filter Properties 96 3.12.5 Placing Geotextiles Under Water 98 3.13 Pier Scour Countermeasure Selection 98 3.14 Implementation Plan 98 3.14.1 The Product

99 3.14.2 The Market 99 3.14.3 Impediments to Implementation 99 3.14.4 Leadership in Application 99 3.14.5 Activities for Implementation 100 3.14.6 Criteria for Success 101 Chapter 4 Conclusions and Suggested Research 101 4.1 Applicability of Results to Highway Practice 101 4.2 Conclusions and Recommendations 101 4.2.1 Overview 102 4.2.2 Riprap 102 4.2.3 Partially Grouted Riprap and Geocontainers 103 4.2.4 Articulating Concrete Block Systems 104 4.2.5 Gabion Mattresses 105 4.2.6 Grout-Filled Mattresses 105 4.2.7 Additional Observations on Pier Scour Protection Systems 106 4.2.8 Countermeasure Selection 107 4.2.9 Design Guidelines 107 4.3 Suggested Research 109 Chapter 5 References A-1 Appendix A Bibliography of Current Practice B-1 Appendix B Countermeasure Selection Methodology C-1 Appendix C Guidelines for Pier Scour Countermeasures Using Rock Riprap D-1 Appendix D Guidelines for Pier Scour Countermeasures Using Partially Grouted Riprap E-1 Appendix E Guidelines for Pier Scour Countermeasures Using Articulating Concrete Block (ACB) Systems F-1 Appendix F Guidelines for Pier Scour Countermeasures Using Gabion Mattresses G-1 Appendix G Guidelines for Pier Scour Countermeasures Using Grout-Filled Mattresses H-1 Appendix H Summary of Laboratory Testing Program

AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 24-07(2) by Ayres Associates Inc., Fort Collins, Colorado. Dr. P.F. Lagasse, Senior Vice President, served as Principal Investigator, and Mr. P.E. Clopper, Senior Water Resources Engineer, served as Co-Principal Investigator. They were assisted by Dr. L.W. Zevenbergen, Manager, River Engineering, and Ms. L.G. Girard, Hydraulic Engineer. Two research team members from Germany supported the team on several tasks. Dr. M.H. Heibaum, a geotechnical engineer from the German Federal Waterways Engineering and Research Institute (Bundes- anstalt für Wasserbau, or BAW), assisted in the translation of BAW “Code of Practice” documents and provided guidance on the design and installation of partially grouted riprap and sand-filled geocon- tainers as implemented along Germany’s extensive inland waterway system. Mr. Justus Trentmann of Gewatech-Soil and Hydraulic Engineering (Gewatech Grund- und Wasserbau GmbH & Co. KG) of Osnabrück, Germany, provided his unique expertise with the formulation and installation of partially grouted riprap. Both hosted a field trip to various field sites in Germany for two research team members and a Federal Highway Administration representative, providing insights on partially grouted riprap technology, which were invaluable in the development of an appropriate laboratory test plan. Dr. Heibaum and Mr. Trent- mann also participated in a prototype-scale installation in the United States, which demonstrated the adaptability of this technique as a pier scour protection countermeasure. All laboratory testing was performed at the Colorado State University Engineering Research Center Hydraulics Laboratory under the direction of Dr. C. Thornton and Mr. M. Robeson. The assistance of Ms. L.G. Girard and Mr. D. Varyu, graduate students, is also acknowledged. Mr. S.A. Sabol of Vermont Technical College assisted in the formulation of an appropriate format for the design guidelines in the appendixes of this report. Mr. J. Early served as an Ayres Associate project engineer during the initial phase of the project. A special acknowledgment is made to Mr. M. Miles, Alaska DOT; Mr. S. Ng, Caltrans; Mr. J. Matthews, Virginia DOT; and the NCHRP Project 24-07(2) panel members who participated in the beta test of the countermeasure selection methodology. We also wish to acknowledge Lucht’s Concrete Pumping, Inc. and LaFarge North America, Inc. of Fort Collins, Colorado, who provided equipment and expertise for batching, delivery, and pumping of the spe- cialty grout mix for field scale installation of partially grouted riprap.