ARCHIVED REPORTS_2008_19 - Laserfiche WebLink

Home Browse Search

Results of Static and Pseuodostatic Slo a Stability Analyses For the section analyzed, the static factor of safety for slip surfaces through the liner system varied between 1.79 and 3.43. The yield accelerations varied between 0.16g and 0.17g. Output from the stability analyses are attached. Earthquake Modeling The generally accepted seismic deformations under a design earthquake for the final slopes of a composite-lined landfill are between 6 inches and 12 inches (Seed and Bonaparte, 1992; Sharma and Lewis, 1994). An average seismic deformation of 12 inches or less was used as the acceptance criterion for the stability of the final slopes of the WMU D-01. Design Earthquake GeoSyntec performed a seismic hazard analysis for the Forward Landfill. The seismic hazard analysis is attached. Based on GeoSyntec's evaluation, the MCE is a magnitude (M) of 7.9 on the San Andreas and a M of 6.7 on the Great Valley Fault. GeoSyntec developed three time histories for the M=6.7 MCE and one time history for the M=7.9 MCE. These time histories were used for the one-dimensional seismic response analyses (i.e., SHAKE). To match the spectral content, GeoSyntec recommended that the bedrock time histories for the =6.7 MCE be adjusted to a AW bedrock acceleration of 0.19g and the time history for the =7.9 MCE be adjusted to a bedrock acceleration of 0.10g. Seismic Response Analyses The one-dimensional analysis was completed using the SHAKE computer program (Schnabel et al., 1972; Sun, 1988; Idriss and Sun, 1992) to predict the res landfill mass to the input base rock motionsp. The program uses the equivalent linearonse of the method to model the seismic shaking of a deposit and predict seismic response. Inputs for SHAKE include unit weight, shear-wave velocity, and shear modulus and damping characteristics for each soil layer. Design earthquake motion is input as an acceleration-versus-time record. The design earthquake time histories developed by GeoSyntec were used for these analyses. To model the dynamic response analysis of the East-West cross.section, the following columns were used: • 80 feet of soil overlying bedrock/stiff soil. This column was used to calibrate the ' shear wave velocities assumed for the soil. After the results at ground surface were considered to be reasonable, refuse was modeled above the soil for the remaining analyses.