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K1L D UFF RMR Aggregates, Inc. <br /> J N ❑ E R G R 0 U N ❑ Rock Failure Analyses and Stabilization Report <br /> NGIN E E R I N G,INC. Mid Continent Limestone Ouarry <br /> The initial empirical and final properties reevaluated following the back analysis are summarized in <br /> the table below. <br /> Table 2. Leadville Limestone and Interbed Strength Parameters <br /> Material Parameter Cohesion (psf) Friction Unit Weight <br /> Angle (deg) (pcf) <br /> Empirical 5,000 35 150 <br /> Leadville <br /> Limestone Post- <br /> 10,000 35 150 <br /> Backanalysis <br /> Empirical 40 25 150 <br /> Interbed <br /> Material Post- <br /> Backanalysis 550 25 130 <br /> East Face Stability <br /> Slope stability results of the East Face based on modeling of the above conditions indicate a factor of <br /> safety of 1.2 for the south facing highwall. This factor of safety is along a failure plane angle of 30 <br /> degrees which correlates to bedding dip of the soft interbed material. A tension crack was inserted as <br /> a release plane for the planar slide that correlates to the secondaryjoint set (mean set plane 45°; <br /> 055) mapped in the field on the East face.This joint set is perceived as the release plane for the West <br /> face 2023 ground event that can be seen in Photo 2 (Appendix A). Critically, water pressure was <br /> deterministically modeled as 30% filled with peak pressure at the tension crack base. Sensitivity <br /> analysis shows the factor of safety is particularly sensitive to water level assumptions. <br /> For any rock mass there is the possibility of large-scale, random joints with a low strength such as <br /> from weathering, historic sliding, or clay infilling. If such a joint or several joints exist and if these <br /> joints have a disadvantageous orientation and location, then there could be a large-scale slope <br /> instability. However, field observations by KUE did not reveal any such joints beyond those previously <br /> identified. <br /> 5. ROCKFALL <br /> 5.1. ROCKFALL MODELING <br /> Rockfall modeling was performed on three transects along the East face that are representative of <br /> the varying geologic and topographic conditions (Figure 2a).The three slope geometries were created <br /> from LiDAR data provided by RMRA. Modeling was performed using the computer program Rockfall <br /> v.8.004 by RocScience that simulates the bounce paths of rock blocks down a slope, and calculates <br /> block velocities, end points and kinetic energies at user specified points along the slope.The rockfall <br /> simulation uses coefficient of restitution (both normal and tangential) parameters to model the loss <br /> of kinetic energy between the rockfall block and ground surface at the point of impact. Based on the <br /> Page 7 <br /> 535 16th STREET,SUITE 620 1 DENVER,CO 80202 1 (303)732-3692 1 WWW.KILDUFFUNDERGROUND.COM <br />