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The theory of one-dimensional wave propagation through layered media can be used to model the response of the landfill mass to the rock motions associated with the design earthquake at the site. The SHAKE computer program (Schnabel et al., 1972; Idriss and Sun, 1992) was used to predict the response of the landfill mass to the input base rock motions. SHAKE models the one-dimensional response of individual vertical columns of material(s) that are representative of actual field conditions. The vertical column can consist of different layers of materials or one material. Accordingly,the modeling for a landfill consists of columns with layers of waste and soil. The shear-wave velocities are used to compute the maximum dynamic shear modulus of each layer of the vertical column. The strain-dependent modulus and damping relationships are entered into the SHAKE program for each layer in the modeled column. Because the modulus and damping values are strain-dependent and are not known at the outset, an iterative procedure is required to estimate these values for each layer. The strain in each layer of the vertical column is estimated, and the strain-dependent values of modulus and damping are calculated for that layer. Based on the computed strains in each iteration, new values of modulus and damping are obtained. The iterative analysis is continued until the values of modulus and damping are compatible with the strain developed in each layer. After the strain-compatible shear modulus and damping for each layer are determined, horizontal displacements at each layer are calculated using the closed-form wave equation. The SHAKE computer program uses these displacements to calculate the accelerations at the top of each layer. The ground accelerations at the top of the refuse-soil columns were then equated to umax in the Makdisi and Seed (1977) procedure. Deformations are estimated using the "Newmark" chart developed by Makdisi and Seed (1977). SHAKE requires unit weight, shear-wave velocity, and shear modulus and damping characteristics to be input for each soil layer. Design earthquake motion is input as an acceleration-versus-time record. When evaluating the results of a seismic deformation analysis, the effect of the net slope movement qW should be considered. The most severe consequence of slope movement would be damage to the composite base lining or LCRS of the landfill. While it is difficult to assess what deformation would damage a composite base lining system,the current practice is to limit deformations to 30 cm (1 foot) or less(Sharma and Lewis, 1994). 3.3 Stability Analysis WMU FU-03 will ultimately be filled with designated wastes up to a maximum elevation of 170 feet MSL. Due to geometrical constraints, this ultimate waste elevation can only be achieved once adjacent WMUs are developed. The maximum elevation of wastes in WMU FU-03 prior to the construction of adjacent WMUs is approximately 80 feet. As discussed earlier in this section, the ultimate fill configuration is the critical section for stability considerations. 3.3.1 Material Properties The single-composite lining system for the WMU FU-03 base will consist of a 2-foot thick clay liner overlain by an HDPE geomembrane, cushion geotextile, and granular blanket LCRS. The lining system on the excavated southern and western slopes will consist of a geosynthetic clay liner (GCL) overlain by an HDPE geomembrane and a geocomposite drainage net (GDN). The HDPE geomembrane will be double sided textured on the base and single-sided textured on the slope, with the textured side placed against the GCL. The GDN will have a nonwoven geotextile bonded to one side of the geonet. The geonet side will be placed against the smooth side of the HDPE geomembrane. This same lining system will also be used as an interface liner on the northern slope. FORWARD LANDFILL WMU F-03 AND F-WEST DESIGN REPORT 3-4