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A - 8 <br />A-6 STABILITY ANALYSES <br />Method of Calculating Slope Stability. <br />The stability of existing and proposed slopes at the <br />Mt. Gunnison mine were analyzed using the Simplified Bishop <br />method. This is a method of slices applicable to circular <br />failure surfaces which satisfies overall moment and vertical <br />force equilibrium, but does not satisfy the moment equilibrium <br />of individual slices or horizontal force equilibrium. It has <br />been shown to produce accurate results over a wide range of <br />conditions. The computer program STABL, developed by the <br />School of Civil Engineering at Purdue University, was used <br />for all analyses. <br />Material Properties. <br />The material properties used for stability analyses have <br />been developed based on laboratory testing and back analysis <br />of existing failures. <br />The results of triaxial testing of relatively undis- <br />turbed samples of colluvium and landslide material are pre- <br />sented in part A-5. These tests indicated the following <br />effective stress parameters to be appropriate for these ma- <br />terials: <br />Friction angle (degrees) 30.5 <br />Cohesion (pounds per square foot) 300 <br />Unit weights of 115 pcf for unsaturated and 120 pcf for <br />saturated materials were assumed. <br />aeo-Hrow ca,swno. ~+c <br />