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4. Grain size distribution (friction angle typically decreases with decreasing coefficient <br />of uniformity, Cu) <br />LP -21: Free dumping or plug dumping (dumping in small piles on the surface of the <br />rock pile, grading the material, and compacting in layers or lifts resulting in dense <br />layers with no real particle size segregation) is primarily used at LP -21 resulting in <br />particle distribution which increases slope stability. <br />5. State of compaction or packing (friction angle typically increases with increasing <br />density or decreasing void ratio) <br />LP -21: It can be assumed due to the type of rock and the method of dumping (see # 4 <br />above) that the rock pile is fairly compacted. <br />6. Specific gravity (related to mineralogy) <br />LP -21: 2.20 -2.80 gm/cc is the specific gravity of sandstone based on tabular data <br />from EduMine - Professional Development and Training for Mining and the <br />Geosciences. ( http: / /www.edumine.com/xtoolkit /tables /sgtables.htm) <br />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 />LP -21: This is calculated based on ton /ft Compared with other uranium mines, LP- <br />21 produces a normal to low amount of waste rock (50 -300 tons per day), thus it can <br />be assumed that applied stress level will be normal to low. <br />8. Definition of failure conditions (drained or un- drained) and degree of saturation. <br />LP -21 is a dry mine thus the waste rock typically has little to no moisture and <br />precipitation is the area is low. <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 to high. <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). <br />Angle of Repose <br />Recommended angle of repose for waste areas are: <br />(i) unweathered rock — 1(V) : 1.75(H) <br />GS -2 <br />