2024-03-29_REVISION - M1982121 (2)

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KIL D UFF4L RMR Aggregates,Inc. U N U E R a R G U N E. Rock Failure Analyses and Stabilization Report ENGINEER IN G,INC-I'dw Mid Continent Limestone Quarry a steeper slope angle to consider the rolling and steepening beds towards the bottom of the slope as identified by CGS at 38 degrees and in the Secondarily in SlopeW the slope was reduced to 30 degrees to mimic the release plane at the top of the failure. Ultimately the back analysis parameters were taken from the more conservative 30- degree release plane. Plane water pressure was modeled at 30%filled.The empirical strength parameters, corroborated by the back analysis are summarized in Table 2 below. Table 2.Leadville Limestone and Interbed Strength Parameters Material Parameter Cohesion(psf) Friction Unit Weight Angle (deg) (pcf) Empirical 5,000 35 150 Leadville Limestone Backanalysis 10,000 35 15P Empirical 40 25 150 I nterbed Material Backanalysis 550 25 130 Modeling for long-term steady state analysis (Section 6.0) and mechanical stabilization (Section 9.0) use the empirical parameters as those are the more conservative values that have been corroborated by the back analysis. East Fare Stability Slope stability results of the East Face based on modeling of the above conditions indicate a factor of safety of 1.2 for the south facing highwa11. This factor of safety is along a failure plane angle of 30 degrees which correlates to bedding dip of the soft interbed material. A tension crack was inserted as a release plane for the planar slide that correlates to the secondary joint set(mean set plane 45'; 055) mapped in the field an the East face.This joint set is perceived as the release plane for the West face 2023 ground event that can be seen in Photo 2 (Appendix A). Critically, water pressure was deterministically modeled as 30%filled with peak pressure at the tension crack base. Sensitivity analysis shows the factor of safety is particularly sensitive to water level assumptions. For any rock mass there is the possibility of large-scale, random joints with a low strength such as from weathering, historic sliding,or clay infiIIing. If such a joint or several joints exist and if these joints have a disadvantageous orientation and location,then there could be a large-scale slope instability. However, field observations by KUE did not reveal any such joints beyond those previously identified. Page 7 535160'STREET,SUITE 620 1 DENVER,CO 80202 1 (303)732-3692 1 WWW.KILDUFFUNDERGROUND.COM