Laserfiche WebLink
Angle of Repose <br />Recommended angles of repose for waste areas are: <br />(i) unweathered rock — 1(V):1.75(H) <br />(ii) weathered rock, overburden, up to 15 m high — 1(V):2.5(H) <br />(iii) weathered rock, overburden, greater than 15 m high — 1(V):3(H) <br />(Geotechnical Slope Stability, January, 1995.) <br />The waste rock pile will be graded at 2(H):1(V), or 26.57° (case ii) putting the waste pile <br />within the recommended range. <br />Foundation Stability <br />The foundation of the waste rock pile is a flat, well compacted surface. The underlying <br />soils have a high clay content and there are no known aquifers under the pile. Therefore, <br />there is no water that could enter the pile from below and compromise the stability of the <br />underlying soils or the waste rock pile itself. <br />Factor of Safety (FS) <br />For infinite slopes consisting of cohesionless soils that are either above the water table or <br />that are fully submerged, the factor of safety for slope stability is determined as follows: <br />FS = Tan• /Tan• <br />where, <br />• = the angle of internal friction for the soil <br />• = the slope angle relative to the horizontal <br />(WSDOT Geotechnical Design Manual M) <br />There could be a small amount of cohesion which would add to the strength but this will <br />be ignored in order to calculate the worst case scenario. <br />FS = tan (40 °) /tan (26.57 °) = 1.678 <br />> 1.4 is the recommended parameter for safety factor of permanent slopes, so the waste <br />rock pile is considered stable. <br />