Laserfiche WebLink
4.0 PIT STABILITY EVALUATION <br /> 4.1 TECHNICAL APPROACH <br /> Evaluation of the pit wall stability was performed based upon the following criteria. <br /> • Global Stability -- The pit dimensions and geology were compared to case <br /> history data to estimate the overall stability of the design and establish a <br /> comparative factor of safety. <br /> • Intermediate Stability -- The potential for intersection of the mapped fault <br /> structural features to cause local, intermediate stability problems was eval- <br /> uated. <br /> • Small-Scale Stability -- The potential for joint sets mapped in the walls to <br /> cause small instability in the benches was evaluated. <br /> The case history data for global stability is based upon published information. Potential <br /> for intermediate and small-scale stability problems was evaluated using stereographic <br /> analysis of the kinematics for wedge sliding. The data base is currently to small to <br /> produce a statistical evaluation of probability of failure; however, overall stability and <br /> indications of potential problems is possible at this stage. <br /> 4.2 PIT LAYOUT AND GEOMETRY <br /> The Sunnyside vein strikes generally N450E and dips 75' to the southeast. A small <br /> section of the vein outcropping on the floor of the Sunnyside Basin is being recovered by <br /> the pit. The natural slope of the alluvial material in and around the outcrop was near 32°, <br /> and the walls of the basin slope upward above the pit at angles up to 36°. <br /> The planned walls in the deepest section of the pit are shown by the cross section in <br /> Figure 4.1. Face angles were proposed at a 70' slope with 12 ft benches every 20 to 33 <br /> feet. The north wall of the pit strikes at N100°E, and is the most extensive excavation <br /> 11 <br />