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~i <br /> <br />and a waste disposal slope from locations near the mine as indicated in <br />Figure 38 are shown in Figure 3C. The least squared fit regression lines <br />to the surface profiles give excellent fits and indicate slope angles of <br />38.3° far the waste disposal slope and 39.7° for the talus slope. <br />The presence or absence of failure scars determines the slope stability <br />analysis technique used. The natural slopes in the immediate area do not <br />show any type of failure scars on them. The applicable method of failure <br />on this pile is a wedge failure (Coates, 1970; Hook and Bray, 1974). <br />Knowing the physical properties of the dump materials, and the geometry, <br />a calculation using the Mohr-Coulomb criteria will assess the stability <br />of a dump. <br />The dump and natural talus materials are coarse and will not build up pore <br />water pressure in the mass of the broken materials. OXY has run more than <br />20 fragmentation experiments in which the broken materials were screened, <br />and produced less than 2 percent by weight of "less than 3/8 inch" materials. <br />In comparison with naturally occurring materials, the blasted rock has less, <br />small and fine material than, for example, a flood plain alluvial gravel <br />(see figure 4). The waste and talus piles will not become blocked since <br />insufficient fine material occurs to seal the spaces between the larger <br />fragments. The alluvial gravel has considerably more fine material yet <br />does not build up pore pressure in similar circumstance, therefore the <br />dump materials will not build up pore water pressure. <br />The angle of internal friction of a fragmented mass is discussed by Metcalf <br />(1966) and concluded to be nearly equal to the angle of repose. The angle <br />. of internal friction in this case would be in the 3~ to 38° range. An <br />independent evaluation is provided by a series of triaxial tests. The <br />-4- <br />