Laserfiche WebLink
The minimum interface/internal shear strength within the liner system will control the <br />factors of safety against slope failure. <br />Based on traditional geotechnical practice, a factor of safety of 1.5 was considered <br />acceptable for stability of permanent landfill slopes. For slope stability of liner on <br />sideslopes, a factor of safety of 1.25 was considered acceptable, because of temporary <br />conditions. <br />Module 1 is located to the south of existing LF -1, therefore, Module 1 will not have <br />waste slope along the northern perimeter. The waste slopes along the western, southern, <br />and eastern perimeters of Module 1 will eventually be covered by waste during waste <br />filling in the surrounding modules in the future. Although these slopes will be temporary, <br />they will remain open for a relatively long time. To be conservative, these slopes are <br />considered as permanent slopes, for slope stability analyses purposes. <br />ME T, f -M r• • <br />The slope stability analyses were performed using the 2-dimensional limit equilibrium <br />computer program PCSTABL (Version 6), which was developed originally at Purdue <br />University (1988). It uses the method of slices to compute factors of safety using either <br />the simplified Bishop method for circular failure surfaces, the simplified Janbu method <br />for failure surfaces of general shape, or the Spencer method for failure surfaces of any <br />shape. A sliding block analysis using the Janbu method with active and passive wedges <br />generated according to the Rankine theory was used to locate the most critical failure <br />surface. The Janbu method for sliding block failure surfaces yields slightly conservative <br />factors of safety compared to those from the Spencer method. Therefore, the factors of <br />safety obtained from the Janbu method for some of the critical failure surfaces were <br />recomputed using the Spencer method. <br />3.4 Stability of Liner System <br />3.4.1 Slope Stability of Liner on Sideslopes <br />The liner on interior sideslopes of Module 1 will have maximum slopes of 3H:1 V. The <br />sideslope liner system will have the following critical shear planes, from top to bottom: <br />1. Operations soil layer-geocomposite drain interface <br />2. Geocomposite drain -textured HDPE geomembrane interface <br />i,\ ®\\.SACRFPI\COMMON\sacDP\2002\PR.M18\83\8356082bz.doc EMCOWOWT, Inc. <br />Rev. 0, 07/31/02 <br />3-2 <br />