Laserfiche WebLink
c~ <br />~1 ~1=.1~ <br />SMITFI WILLIAMS CONSULTANTS, INC. <br />Project: OSA Stability Analysis Job No. 1125C <br />Calculation Title: Squaw Gulch and East Cresson Stability Calculations <br />Pre ared B :Justin Hall Date: 3/13/08 <br />Checked B :John Lu o Date: 3/13/08 <br />pseudo-static analyses conservatively model seismic events as constant acceleration and direction, <br />i.e., an infinitely long pulse. Therefore, it is customary for geotechnical engineers to take only a <br />fraction of the predicted peak maximum acceleration when modeling seismic events using <br />pseudo-static analyses. Two-thirds the peak ground acceleration generated from the maximum <br />credible earthquake (Hynes and Franklin, 1984), was used in the analysis. For the overburden <br />storage areas within Squaw Gulch and East Cresson, the minimum required factor of safety and <br />horizontal coefficient of ground acceleration were 1.0 and 0.08g, respectively, for closure <br />pseudo-static conditions. <br />The material properties used in the analyses were based on previous laboratory testing, field <br />investigations, experience with similar materials, and based on previous amendments. Descriptions <br />of the materials and the basis for the shear strength are summarized below: <br />^ Foundation: The shear strength of the foundation is described by a linear Mohr- <br />Coulomb failure envelope as an effective stress friction angle of 29 degrees with <br />zero cohesion. The average bulk unit weight of the foundation material is 120 <br />pounds per cubic foot (lb/ft3); <br />^ Overburden Material: The shear strength of the overburden material is described <br />by a linear Mohr-Coulomb failure envelope as an effective stress friction angle of <br />39 degrees with zero cohesion based on testing performed on Cresson Ore and <br />reported in a Golder letter dated October 19, 1995 to CC&V entitled "Stability <br />Results of Phase I Pad Haul Road Near Truck Loadout Bin". The average bulk unit <br />weight of the overburden material is 1151b/ft3; <br />Piezometric Surface <br />All of the stability analyses were performed without a piezometric surface. <br />CALCULATIONS: <br />The stability analyses considered: <br />• Arcuate failure surfaces through the foundation and overburden material. <br />• Wedge failure surfaces through the foundation. <br />For circular failure surfaces, Slide employs a searching routine which iterates along a spatial grid to <br />determine the minimum FOS for the given conditions. <br />