9416261 Bray Federal regulations required that municipal solid waste landfills located in seismic impact zones be designed to resist earthquake hazards. The seismic response of waste repositories is of concern because dynamic loads may produce relative movements within the waste, liner and cover systems, foundation and their interfaces. These movements could damage the liner systems, with a consequent loss of sealing, and/or disrupt the function of the leachate and gas collection systems. There is a relative lack of field data regarding landfill performance during earthquake shaking, particularly with respect to seismic performance of waste fills constructed with composite liner systems containing geosynthetics. The 1994 Northridge Earthquake provides important observational data on the response of landfills to strong levels of earthquake shaking. Landfills which experienced strong levels of shaking (peak bedrock accelerations of 0.2 g to over 0.5g), including two with geosynthetic liner systems, were inspected by the research team immediately after the event. None of these landfills showed any signs of major instability, but several experienced damage due to cracking. Because of the difficulties associated with laboratory evaluation of the dynamic properties of waster materials, these field observations present an invaluable opportunity to back-calculate dynamic strength and deformation properties. One of the landfills (OII) is well instrumented with survey monuments, inclinometers and a pair of strong motion recording stations. The objectives of the project are to: 1. Gather observational data documenting the seismic performance of solid waste landfills strongly shaken by the 1994 Northridge earthquake. 2. Organize existing landfill characterization data, including characterization of the waste fill properties (composition, age, unit weight, moisture content, strength, and shear wave velocity) and landfill geometry. 3. Perf orm preliminary one-dimensional (1-D) equivalent linear and nonlinear dynamic response analyses of five important landfill case records and 2-D equivalent linear dynamic response analyses of the OII landfill. Perform pseudo-static limit equilibrium and Newmark-type seismic deformation analyses to back-calculate minimum dynamic strength values and to calibrate prevalent seismic design procedures. ***
