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For pseudo -static analysis, a horizontal force coefficient of 0.15 is commonly used. If <br />the results of pseudo -static analysis indicates a factor of safety less than 1.5, CCR Title <br />27 requires that further analysis to demonstrate that the proposed design would be <br />acceptable during the Maximum Credible Earthquake (MCE). For the Forward Landfill <br />project, this seismic displacement analysis was completed using a procedure described <br />by Bray and Rathje (1998). The procedure is based on the method described by <br />Newmark (1965) for determining displacement of a rigid block resting on a sliding <br />plane subjected to earthquake -type motions. The Newmark procedure is based on the <br />premise that the sliding block will undergo displacement only during the periods when <br />the maximum ground acceleration, (kmax), exceeds the yield acceleration (ky) for the <br />sliding block, or no displacements occur when ky is greater than kmax (i.e. ky/kmax>1)- <br />Bray and Rathje refined the procedure for solid -waste fills to incorporate the dynamic <br />response characteristics of the sliding block, and intensity and duration of ground <br />motions at the site during the design earthquake. <br />3.2 Critical Geometries and Interfaces <br />The gross stability of the landfill and liner system was assessed using the maximum <br />slope height and slope gradient for the proposed landfill development (Figures 1_and <br />2). Because the actual interface strengths of landfill liner materials will vary with the <br />manufacturers of particular products used, a pa ram etric,analys s,was-.done to.deveJop.a <br />range of acceptable strength parameters (i.e. combination of cohesion and angle of <br />friction) that will provide a minimum static factor of .safety of 1.5. As shown in the <br />attached stability cross-sections, the following range of parameters were used in the <br />analysis: <br />Material <br />Angle of Internal <br />Unit.Weiaght <br />Cohesion <br />Friction <br />(Ib./cu. Ft.) <br />(Ib./sq. Ft.) <br />de rees <br />Native soils 1 <br />0 to 33 <br />120 to 125 <br />0 to 2300 <br />Refuse 2 <br />3,0 <br />8Q <br />200 <br />Textured HDPE/ Non -Woven <br />4 to 11 <br />NA <br />0 to 950 <br />Geotextile Interface 3 <br />Internal Strength Hydrated <br />5 <br />NA <br />400 <br />GCL 4 <br />Non -Hydrated GCL (Textured <br />14 <br />NA <br />0 <br />HDPE GCL) (3 <br />(1) - CH2MHill (1992) <br />(2) - Singh and Murphy (1990) <br />(3) - Range of Values Considered Obtainable <br />(4) - Cetco Manufacturer Certification <br />As determined in CH2MHill's geotechnical evaluation of the existing Forward Landfill <br />0 (1992), the native soils in the area consist of interbedded layers of sand, silt, and lean <br />L:Allied\2000.193\Reports\finaljtd:Appendix E GLA:08/16/01 <br />