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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 587 Subject Areas Design ⢠Materials, Construction, and Maintenance Countermeasures to Protect Bridge Abutments from Scour Brian D. Barkdoll MICHIGAN TECHNOLOGICAL UNIVERSITY Houghton, MI Robert Ettema UNIVERSITY OF IOWA Iowa City, IA Bruce W. Melville UNIVERSITY OF AUCKLAND Auckland, New Zealand 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 Boardâs 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 587 Project 24-18A ISSN 0077-5614 ISBN: 978-0-309-09895-3 Library of Congress Control Number 2007932422 © 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 Boardâs 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. 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 manufacturersâ names appear herein solely because they are considered essential to the object of this report.
CRP STAFF FOR NCHRP REPORT 587 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Robert E. David, Senior Program Officer Eileen P. Delaney, Director of Publications Beth Hatch, Editor NCHRP PROJECT 24-18A PANEL Area of Soils and GeologyâField of Mechanics and Foundations Harry A. Capers, Jr., Arora and Associates, P.C., Lawrenceville, NJ (Chair) Daniel G. Ghere, Federal Highway Administration Jon E. Bischoff, Utah DOT Rebecca S. Burns, Pennsylvania DOT J. Sterling Jones, Annandale, VA Jorge E. Pagán-Ortiz, Federal Highway Administration Patricia Schriner, St. Johns, MI Paul Sharp, Federal Highway Administration David B. Thompson, Texas Tech University, Lubbock, TX Kornel Kerenyi, FHWA Liaison G.P. Jayaprakash, TRB Liaison AUTHOR ACKNOWLEDGMENTS The authors would like to thank the others who worked laboriously on the project: Roger Kuhnle and Carlos Alonso from the USDA-ARS National Sedimentation Laboratory, who, along with Brian Barkdoll, guided doctoral student Hua Li in the experiments on parallel rock walls, spur dikes, and abutment col- lars; University of Iowa graduate students Recep Korkut, who worked on geobag and riprap apron at wing-wall abutments, Emelio Martinez, who worked on countermeasure concepts for wing-wall abut- ments, and Reinaldo Morales, who performed experiments on large-scale apron performance at a spill- through abutment; Art Parola of Riverine, Inc., who performed the 2D modeling; and Sjoerd van Balle- gooy, who performed the work on riprap and cable-tied blocks at both wing-wall and spill-through abutments. In addition, the authors would like to thank Timothy Hess, the Project Manager for NCHRP on this project, and the Review Panel. Thanks also to the staff at all the institutions who also contributed to the organization and facilitation of the work. 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
NCHRP Report 587: Countermeasures to Protect Bridge Abutments from Scour will be of interest to transportation departments that are responsible for constructing and maintain- ing bridges that span waterways. This report provides selection criteria and guidelines for the design and construction of countermeasures to protect bridge abutments and approach embankments from scour damage. Typical approaches for protecting bridge abutments from scour are to mechanically sta- bilize the abutment slopes or realign the upstream flow. The slopes are often stabilized with riprap, gabions, cable-tied blocks, or grout-filled bags, while the upstream flow is realigned with guidebanks, dikes, spurs, or in-channel devices such as vanes and bendway weirs. Nei- ther of these approaches has been totally successfulâbridge abutments and their approach embankments are the most commonly damaged bridge components during floods. The objective of this research was to develop and validate selection criteria and guidelines for the design and construction of countermeasures to protect bridge abutments and approach embankments from scour damage. Two common forms of bridge abutments are addressed in this report: wing-wall (vertical face with angled walls into the bank) and spill- through (angled face). Conditions of scour that affect these two types of abutments include abutments threatened by main channel flow (in the cases of single and compound chan- nels), failure of the bank, failure of the floodplain, and failure of the embankment. Coun- termeasures were tested under both clear-water scour (when the water velocity is slightly below the velocity at which bed sediment is in motion) and live-bed scour (when the bed sediment is in motion), the two most critical conditions for abutment scour. Tests were con- ducted in compound-channel flow in which the flow has overtopped the main channel and is flowing on the over-bank floodplain area as well. The selection process identifies the countermeasure concepts that may be appropriate for addressing a scour concern, indicates possible construction options, and then provides design relationships associated with the layout and dimensioning of countermeasures developed in the course of this project. Guide- lines are provided for the following abutment countermeasures: riprap, cable-tied blocks, geobags (permeable bags filled with gravel), parallel walls (guidebanks with no elliptical end), spur dikes located locally to the abutment, and abutment collars (a horizontal plate attached to the abutment). The research was performed under NCHRP Project 24-18A by Dr. Brian D. Barkdoll of the Michigan Technological University in cooperation with Dr. Robert Ettema of the Uni- versity of Iowa, Dr. Bruce W. Melville of the University of Auckland, Arthur Parola of the University of Louisville, Roger Kuhnle and Carlos Alonso of the USDA National Sedimen- tation Laboratory. F O R E W O R D By Robert E. David Staff Officer Transportation Research Board
C O N T E N T S 1 Summary 4 Chapter 1 Introduction 4 1.1 Introduction 4 1.2 Problem Statement 5 1.3 Objective and Scope 5 1.4 Relationship to Prior NCHRP Studies 6 1.5 Abutment Forms 6 1.6 Countermeasure Concepts 6 1.7 Research Approach 6 1.8 Overview of Report 7 Chapter 2 Abutment Forms and Scour 7 2.1 Common Forms of Abutments 7 2.2 Abutment Setting 9 2.3 Proximity of First Pier 9 2.4 New Versus Existing Abutments 10 2.5 Scour Processes and Abutment Failure Mechanisms 10 2.6 Channel and Bank Scour Processes 15 2.7 Need for Countermeasures 19 Chapter 3 Countermeasure Concepts and Criteria 19 3.1 Introduction 19 3.2 Approach-Flow Control 20 3.3 Criteria 21 3.4 Technical Effectiveness 21 3.5 Constructability 21 3.6 Durability and Maintainability 22 3.7 Aesthetics and Environmental Issues 22 3.8 Cost 23 3.9 Bridges over Narrow Versus Wide Channels 24 Chapter 4 Practitioner Survey 24 4.1 Introduction 24 4.2 Summary of State DOT Responses 36 4.3 Summary of Responses 38 Chapter 5 Literature Review 38 5.1 Introduction 38 5.2 Approach-Channel Alignment 41 5.3 Vanes 43 5.4 Guidebanks 43 5.5 Grade-Control Structures 46 5.6 Riprap
63 5.7 Cable-Tied Blocks 66 5.8 Geobags 67 5.9 Other Forms of Armoring 68 Chapter 6 Lab Results I: Preliminary Experiments 68 6.1 Introduction 68 6.2 Program of Experiments 69 6.3 Use of Large Blocks 72 6.4 Use of Large Geobags 73 6.5 Wing-Wall Abutment and Geobags 75 6.6 Influence of Wing-Wall Angle 75 6.7 Influence of Abutment Alignment 78 6.8 Summary of Findings from Preliminary Experiments 79 Chapter 7 Lab Results II: Aprons at Wing-Wall Abutments 79 7.1 Introduction 80 7.2 Experiments on Aprons of Riprap or Cable-Tied Blocks 103 7.3 Experiments on Aprons of Geobags and Riprap 115 7.4 Summary of Results from Riprap, Cable-Tied Blocks, and Geobags 118 Chapter 8 Lab Results III: Aprons at Spill-Through Abutments 118 8.1 Experimental Work 123 8.2 Bridge Abutment Flow Fields 132 8.3 Spill-Through Abutment Clear-Water Study 143 8.4 Two-Dimensional Modelling of Flow Around a Small-Scale Model Abutment 150 8.5 Large-Scale Tests of Riprap Apron Performance 161 Chapter 9 Lab Results IV: Flow Modification 161 9.1 Experimental Apparatus and Procedure 164 9.2 Baseline Experiment 169 9.3 Parallel-Wall Countermeasure 178 9.4 Spur Dike Countermeasure 185 9.5 Abutment Collar Countermeasure 190 9.6 Summary 191 Chapter 10 Design Guidelines 191 10.1 Introduction 191 10.2 Countermeasure Selection and Construction Options 192 10.3 Channel Bed Degradation 195 10.4 Channel Control 198 10.5 Design Guidelines for Localized Abutment Armoring 205 10.6 Design Guidelines for Localized Flow Field Modification 207 10.7 Relation to Existing HEC Guidelines 208 Chapter 11 Conclusions 208 11.1 Wing-Wall Abutments 209 11.2 Spill-Through Abutments 210 11.3 Flow Guidance 212 References 217 Notation
