NEESR-CR: Seismic Response of Landfills: In-Situ Evaluation of Dynamic Properties of Municipal Solid Waste, Comparison to Laboratory Testing, and Impact on Numerical Analyses

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

This award is an outcome of the NSF 09-524 program solicitation ''George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes the University of Michigan (lead institution), California State University in Los Angeles (subaward) and Geosyntec Consultants (subaward). This project will utilize the NEES equipment site at the University of Texas at Austin. The increasing amounts of municipal solid waste (MSW) generated every year are, in their majority, landfilled. Modern (since the 1990s) MSW landfills are environmentally sensitive, sophisticated facilities and are similar in size to large dams. Recent U.S. earthquakes (e.g. 1994 Northridge Earthquake) highlighted the potential seismic vulnerability of MSW landfills. Excessive movement during shaking may damage the landfill?s containment or cover system or cause stability failures. The impact of such failures on the environment can be devastating. The use of accurate and representative dynamic properties of Municipal Solid Waste is a requirement to reliable seismic engineering analyses and design, but our understanding of the dynamic properties of MSW is rudimentary and lacking. The intellectual merit of this project is in evaluating, for the first time, the in-situ nonlinear dynamic properties of MSW using the T-Rex mobile shaker available at NEES@UT. The mobile shaker is a truck mounted, high capacity shaker that can induce significant cyclic strains in the waste material. Accelerometers are used to record the accelerations of the waste mass at depths in the vicinity of the shaker and derive the dynamic properties of the waste material. Testing using T-Rex will be performed at four locations, at four carefully selected MSW landfills (one in Texas and three in areas of high seismicity in California) with emphasis on documenting the variability of MSW and capture factors such as effect of age, degradation and moisture content. Subsequently, test pits will be excavated and waste material will be collected and tested in large-scale laboratory testing facilities at the University of Michigan and smaller scale testing facilities at California State University in Los Angeles. The laboratory tests will allow the investigators to study the various factors (e.g. confining stress, density, composition) that affect the dynamic properties of waste and compare the results with the field testing. Numerical analyses will be performed to evaluate the seismic behavior of landfills and provide recommendations for use in seismic design. This investigation has the potential to transform seismic engineering practice in landfill design by providing a new methodology for field testing of solid waste, validating the applicability of large-scale laboratory testing of MSW, generating much needed field and laboratory data, and developing recommended methodologies for the performance of seismic analyses of MSW landfills. The broader impact of this project is the safer, more reliable, designs of Municipal Solid Waste landfills in seismic regions. The project will also be integrating research and education by actively involving undergraduate and high school students in research and mentoring activities. Outreach to a broader population of high school students and the community is planned during a demonstration and learning event at a landfill site. The research proposed will provide the basis for at least one Ph.D. dissertation (at U-M) and will promote collaboration between primarily research and primarily teaching institutions. A comprehensive plan for broad data and research results dissemination to the technical community is also outlined. Data from this project will be archived and made available to the public through the NEES data repository. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).