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Assessment and Mitigation of Liquefaction Hazards to Bridge Approach Embankments in Oregon

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Assessment and Mitigation of Liquefaction Hazards to Bridge Approach Embankments in Oregon ASSESSMENT AND MITIGATION OF LIQUEFACTION HAZARDS TO BRIDGE APPROACH EMBANKMENTS IN OREGON Final Report SPR 361 by Dr. Stephen E. Dickenson Associate Professor and Nason J. McCullough Mark G. Barkau Bryan J. Wavra Graduate Research Assistants Dept. of Civil Construction and Environmental Engineering Oregon State University Corvallis, OR 97331 for Oregon Department of Transportation Research Group 200 Hawthorne Ave. SE Salem, OR 97301-5192 and Federal Highway Administration Washington, D.C. 20590 November 2002 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-OR-RD-03-04 4. Title and Subtitle 5. Report Date November 2002 Assessment and Mitigation of Liquefaction Hazards to Bridge Approach Embankments 6. Performing Organization Code in Oregon 7. Author(s) 8. Performing Organization Report Stephen E. Dickenson, Nason J. McCullough, Mark G. Barkau, and Bryan J. Wavra No. 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Oregon State University Department of Civil, Construction, and Environmental Engineering 202 Apperson Hall Contract or Grant No. K5010A Corvallis, Oregon 97331 SPR 361 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Oregon Department of Transportation Research Group and Federal Highway Administration Final Report 1994- 2001 200 Hawthorne Ave SE Washington, D.C. 20590 Salem, Oregon 97301-5192 14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract The seismic performance of bridge structures and appurtenant components (i.e., approach spans, abutments and foundations) has been well documented following recent earthquakes worldwide. This experience demonstrates that bridges are highly vulnerable to earthquake-induced damages and loss of serviceability. These damages are commonly due to soil liquefaction and the associated impact of ground failures on abutments and pile foundations. Current design methods for evaluating permanent, seismically-induced deformations of earth structures are based on rigid body, limit equilibrium and “sliding-block” procedures that are poorly suited for modeling soil liquefaction and establishing the pattern of embankment-abutment-foundation deformations. Recent advances in the seismic design of bridges have addressed some of the limitations of the current design procedures; however practice-oriented methods for estimating permanent deformations at sites that contain liquefiable soils and/or where soil improvement strategies have been employed to mitigate liquefaction hazards are still at an early stage of development. In Oregon, the evaluation of soil liquefaction and abutment performance are complicated by the rather unique seismo-tectonic setting and the prevalence of silty soils along the primary transportation corridors in the Portland/Willamette Valley region and along the Columbia River. This study has focused on numerical dynamic, effective stress modeling to determine the seismic performance of sloping abutments and the effectiveness of soil improvement for reducing permanent ground deformations. Recommendations are provided for evaluating the dynamic behavior of regional silty soils, the application of soil improvement at bridge sites, and comparisons have been made between the deformations computed using the advanced numerical model and the rigid-block methods used in practice. The results have been presented in the form of design charts, where possible, that can be readily used by design engineers in preliminary design and incorporated into the ODOT Liquefaction Mitigation Policy. This study has demonstrated the utility, and limitations, of soil improvement solely by densification techniques. In some cases soil densification techniques for mitigating seismic hazards may not be adequate in limiting deformations to allowable limits, indicating that other methods of soil improvement (e.g., cementation, stone columns, drainage) or structural improvements may also be required. 17. Key Words 18. Distribution Statement liquefaction, bridge abutment, ground failure, soil improvement, Copies available from NTIS. seismic design 19. Security Classif. (of this report) 20. Security Classif. (of this page) 20. No. of Pages 22. Price Unclassified Unclassified Technical Report Form DOT F 1700.7 (8-72) Reproduction of completed page authorized i ACKNOWLEDGMENTS The authors would like to express their sincere gratitude to those individuals who provided valuable assistance throughout the duration of this investigation. Significant contributions were made during several key stages of the project. The silt liquefaction studies reported herein are based in large part on the collection of data contained in numerous personal and proprietary files. This portion of the report has been enhanced by the significant contributions of regional data provided by Mr. Jason Brown of GeoEngineers (formerly Graduate Research Assistant at OSU), Mr. Andrew Vessely of Cornforth Consultants, and Dr. Michael Riemer of the Department of Civil and Environmental Engineering at the University of California, Berkeley. We are grateful to Dr. Wolfgang Roth of URS Corporation (Dames & Moore) and Mr. Douglas Schwarm of GeoEngineers for their assistance with the numerical modeling and for providing valuable insights on the pore pressure generation routines. Reference material was provided from the personal files of several individuals. We are indebted to the following people: Yumei Wang of the Oregon Department of Geology and Mineral Industries, Mr. Ian Austin of URS Corporation (Dames & Moore) for sharing photographs from Kobe, Japan, and Professor Masanori Hamada of Waseda University, Tokyo, Japan for providing a copy of his outstanding report on liquefaction and ground displacements resulting from the 1995 Kobe Earthquake. Project guidance and peer review was provided by the Technical Advisory Committee (TAC), which was convened by the Oregon Department of Transportation (ODOT). Active committee members included: Messrs. Jan Six and Dave Vournas (Geo-Hydro Section), Mr. Bruce Johnson of the Federal Highway Administration, and Ms. Elizabeth Hunt of the Research Group at ODOT. These TAC members provided reference material, ODOT bridge foundation plans and geotechnical reports, and thoughtful advice throughout the project. The TAC was assisted in the review of the final project report by Ms. Sarah Skeen of the Federal Highway Administration. This assistance is greatly appreciated. Finally, we are especially grateful to Ms. Elizabeth Hunt for her valuable assistance with the administration of the research project and organization of the TAC. iii DISCLAIMER This document is disseminated under the sponsorship of the Oregon Department of Transportation and the United States Department of Transportation in the interest of information exchange. The State of Oregon and the United States Government assume no liability of its contents or use thereof. The contents of this report reflect the views of the author(s) who are solely responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official policies of the Oregon Department of Transportation or the United States Department of Transportation. The State of Oregon and the United States Government do not endorse products of manufacturers. Trademarks or manufacturers’ names appear herein only because they are considered essential to the object of this document. This report does not constitute a standard, specification, or regulation. iv ASSESSMENT AND MITIGATION OF LIQUEFACTION HAZARDS TO BRIDGE APPROACH EMBANKMENTS IN OREGON TABLE OF CONTENTS 1.0 INTRODUCTION................................................................................................................. 1 1.1 BACKGROUND.................................................................................................................. 1 1.2 STATEMENT OF OBJECTIVES AND SCOPE OF WORK ......................................................... 3 1.2.1 Objectives.................................................................................................................... 3 1.2.2 Scope of Work .............................................................................................................5 1.2.3 Report Organization................................................................................................... 6 2.0 OVERVIEW OF LIQUEFACTION-INDUCED DAMAGE TO BRIDGE APPROACH EMBANKMENTS AND FOUNDATIONS ............................................ 9 2.1 INTRODUCTION ................................................................................................................ 9 2.2 LIQUEFACTION-INDUCED BRIDGE DAMAGE .................................................................. 10 2.3 OVERVIEW OF HISTORIC DAMAGE TO BRIDGE FOUNDATIONS ....................................... 12 2.3.1 1964 Alaska Earthquake........................................................................................... 12 2.3.2 1964 Niigata Earthquake.......................................................................................... 19 2.3.3 1989 Loma Prieta Earthquake.................................................................................. 23 2.3.4 1991 Costa Rica Earthquake .................................................................................... 28 2.3.5 1995 Hyogo-Ken-Nanbu (Kobe) Earthquake ........................................................... 30 2.4 CONCLUSIONS...............................................................................................................
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