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were used to evaluate the cause of failure on the West wall and will be used to help develop <br /> conceptual design and mitigation support for the East and West faces. General limit equilibrium <br /> method slope stability analyses for the East and West face were performed using the software <br /> program RocPlane from RocScience (v.4.011). A factor of safety is calculated by modeling the <br /> effects of joint shear strength (in this case, primarily the weak interbed), water pressure within <br /> the joint, joint orientation and slope geometry intersections within a Monte Carlo sampling <br /> method. The models were checked by the limit equilibrium method of slices (Morgenstern- <br /> Price) using the software program Slope/W from Geostudio 2023.1. Using this methodology, <br /> the factor of safety for a given geometry is determined by calculating the ratio of resisting <br /> forces to driving forces on trial failure surfaces. Slip surface scenarios analyzed for this report <br /> were block specified.The slip surface with the lowest factor of safety against sliding is <br /> described as the minimum factor of safety for the defined conditions. The Long Term Steady <br /> State was analyzed to consider the extended term stability of the highwall, and the rock <br /> strength is characterized by effective stress parameters. <br /> To determine the geologic input parameters for the Mid-Continent Limestone Quarry stability <br /> modeling, characteristic values of the Leadville limestone were initially taken from empirical <br /> data in peer-reviewed publications and verified by publicly available typical values for the units <br /> encountered on the slope. Based on tests performed by the United States Bureau of <br /> Reclamation' on the Leadville Limestone in the Paradox Valley, the friction angle of the <br /> limestone is approximately 40 degrees, and the cohesion is approximately 3,050 psi. Caltrans6 <br /> estimates for hard rock masses, like limestone, the friction angle of the rock mass varies from <br /> 35 degrees to 45 degrees and the friction angle of the joint areas can vary from 35 degrees to <br /> 40 degrees. No site-specific strength testing has been completed. Mohr-Coulomb strength <br /> criterion framework was utilized to define bedrock and joint material strengths. Mohr-Coulomb <br /> assumes an inherent cohesion in over-consolidated fine-grained or cemented soils and bedrock. <br /> And finally, a back analysis of the West Face ground event was used to corroborate these <br /> empirical values. The stability analyses parameters were manipulated to achieve a factor of <br /> safety of less than 1.0, in both RocPlane (FOS 0.99) and checked in Slope/W (FOS 0.92), <br /> indicating probable failure (Appendix D). Plane water pressure was modeled at 30%filled. The <br /> initial and properties reevaluated following the back analysis are summarized in the table <br /> below. <br /> 5 Ake, J., Mahrer, K., O'Connell, D., Block, L., 2005, Deep Injection and Closely Monitored Induced <br /> Seismicity at Paradox Valley, Colorado., United States Bureau of Reclamation. <br /> 6 California Department of Transportation., 2013, Rock Strength and Its Measurements. <br /> Page. 6 <br /> 535 16th STREET,SUITE 620 1 DENVER,CO 80202 1 (303)732-3692 1 WWW.KILDUFFUNDERGROUND.COM <br />