Laserfiche WebLink
• Waste rock will be transported to the top of the pile via conveyor and will be <br />spread with heavy equipment that will access the top of the pile from existing <br />roads leading to the top of the mesa from the northeast. A constructed road that <br />traverses the pile and the north hillside and terminates on the top of the waste <br />pile will provide access for light duty vehicles. The road will initially be <br />constructed as shown up to the point where it attains its highest elevation on the <br />north hillside. Then it will gradually drop back down toward the valley floor as it <br />heads east, upvalley. As the pile volume increases in elevation it will <br />progressively cover this portion of the road until the maximum volume is reached <br />and the road will appear as shown on the plans. This will give continuous access <br />as the pile grows with time. <br />Stability Analysis <br />A limit equilibrium analysis for plane surfaces was used to assess the stability <br />of the design configuration. The analysis is appropriate for simple geometries <br />with plane failure surfaces. Because of the very shallow depth to bedrock a <br />circular failure plane is unlikely and a plane failure surface parallel to the bedrock <br />is expected. Static equilibrium equations were derived for the specific geometry <br />occurring at this site. <br />The limit equilibrium stability analysis is dependent on three soil properties: <br />• effective cohesion, effective friction angle and the unit weight of the material. To <br />determine field estimates of these properties, soil samples and testing were <br />completed by Lambert and Associates, Inc. (Consulting Geotechnical Engineers <br />and Materiat Testing). A hollow stem auger was used to drill through the entire <br />thickness of the existing pile. Samples were extracted at various depths and <br />used to estimate the soil properties. <br />Direct shear tests were performed to determine the effective cohesion and <br />friction angle. The result of these tests covered an exceptionally wide range and <br />thus a triaxial shear test was performed to confirm the appropriate values. The <br />unit weight of the material was determined during compaction tests. Test results <br />are reported in the properties table shown above. <br />Safety factors computed using these parameters were from t.5 to 2. The <br />analyses included pore water effects, which lowers the safety factor resulting in a <br />conservative estimate. The required safety factor must be equal to or greater <br />than 1.5. <br />Construction <br />The waste pile will be constructed in stages, progressively extending up the <br />drainage as needed. Prior to development of a new stage, the topsoil will be <br />removed and stockpiled. All vegetation will be removed prior to stripping of the <br />topsoil. <br />January 1998 <br />