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<br />' interbedded sandstone and shale materials were assumed to have <br />conservative shear strength values based on past experience in <br />similar environments. The typical shear strength characteristics <br />of the shale materials only were utilized assuming that thinly bedded <br />sandstone units would tend to fail along pre-existing discontinuities. <br />' [Jith minimum elevation of the shear strength characteristics of the <br />shale, this material was assumed to have ~ = 31°, C = 5600 psf <br />' (total stress triaxial data). <br />From past experience, massive sandstone units for the purpose <br />' of analyzing circular failure modes tend to have very high shear <br />strength characteristics. This material was assumed to have ~ = 45°, <br />C = 5000 psf (total stress values). For purposes of analyzing plane <br />failures, either along bedding planes or joint surfaces within the <br />sandstone, a typical sandstone to sandstone contact friction angle <br />' of 29o with no cohesion intercept would be utilized. However, due <br />to the dip of the sandstone layer into the slope and its limited <br />thickness, tae do not feel that the_potential for plane failures <br />within the sandstone layer will have any significant effect on the <br />stability of the refuse area. <br />1 The assumed position of the water table under the most severe <br />conditions is extremely important in a stability analysis. We have <br />been given to understand that the refuse material will typically <br />' be placed in a relatively dry state, and that the refuse disposal <br />site will be graded in such a way so as not to impound water. How- <br />' ever, under the best of drainage conditions, some infiltration of <br />' water into the subsurface will occur. Therefore, it has been <br />assumed that under the worst conditions a perched water table will <br />7 <br />