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7. Applied stress level (friction angle decreases with increasing confining stress, <br />resulting in a curved strength envelope passing through the origin instead of the <br />classical straight line) <br />JD -9: This is calculated based on ton/f2. Compared with other uranium mines, JD -9 <br />produces a normal amount of waste rock (50 -300 tons per day); thus it can be <br />assumed that applied stress level will be normal to low. <br />8. Definition of failure conditions (drained or undrained) and degree of saturation. <br />The waste rock coming out of the JD -9 contains moisture but due to the dry <br />conditions of the area the rock does not remain moist. In addition, there are no <br />known seeps or springs underlying the waste rock pile that could compromise the <br />stability below. <br />Based on the known characteristics of the waste rock pile, most of these parameters <br />indicate that the internal angle of friction will be normal. <br />Triaxial strength testing of large size (up to 200 mm) of rock fill particles, similar to <br />those found in mine rock piles, have internal friction angles in the range of 40° to 50 °, the <br />lower end of the range corresponding to fine- grained material, and the upper end of the <br />range corresponding to coarse - grained material (Leps, 1970). For the JD -9 mine an <br />internal friction angle of 40° is assumed in order to calculate the worst case senario. <br />Angle of Repose <br />For final reclamation, the recommended angle of repose for waste dumps 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 />Waste rock pile will be graded at 2(H):1(V), or 26.56° putting the waste pile within the <br />recommended range of (i) unweathered rock — 1(V):1.75(11). <br />Foundation Stability <br />The foundation of the waste rock pile is on a sloping area. The underlying soils have <br />high clay content and there are no known aquifers or seeps 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 />GS -3 <br />