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K1L D UFF RMR Aggregates, Inc. <br /> U N ❑ E R G R O U N ❑ Rock Failure Analyses and Stabilization Report <br /> E NGIN E E R I N G,INC. Mid Continent Limestone Ouarry <br /> RMRA will develop and discuss the process under their full mining plan. RMRA will perform this work <br /> from a safe position outside of the release plane. This approach stabilizes the slope for long term <br /> stability within the massive limestone. As stated above, there is a possibility of local wedges of the <br /> upper limestone unit remaining where the bedding slope has locally dipped differently or a unknown <br /> joint in the top of the massive limestone has created a wedge. In these circumstances, if the wedge <br /> cannot be scaled or blasted safely, mechanical stabilization would be warranted for life safety. <br /> 8.1. ACTIVE MECHANICAL STABILIZATION <br /> Mechanical stabilization shall be utilized on the Mid Continent Limestone Quarry if the upper <br /> limestone layer is encountered within a highwall or bench. Mechanical stabilization will be utilized to <br /> pin the upper limestone layer to the lower massive limestone with the use of tiebacks to increase the <br /> resisting force of the upper limestone layer. <br /> A preliminary design of the anchorage system was performed. For this analysis, a general limit <br /> equilibrium method slope stability analyses for the East and West face were performed using the <br /> software program RocPlane from RocScience (v.4.011). A factor of safety is calculated by modeling <br /> the 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 method. <br /> Potential upper limestone slope heights ranging from 5 feet to 15 feet were modeled to determine <br /> the resisting force required to reach a factor of safety of 1.5. <br /> Several mechanical stabilization methods were considered, ultimately a 7-strand anchorage was <br /> selected for both logistical purposes and the stand lengths can be changed to accommodate longer <br /> lengths for this difficult to reach location. In some modeled instances, the upper limestone could <br /> exceed greater than 10 ft thickness which would require a long total length of 45 feet. Given the load <br /> and lengths necessary, a traditional bar would be exceptionally long requiring coupled bars and likely <br /> a crane, becoming logistically cumbersome. A concrete bollard with tie backs was also considered and <br /> has been effectively used locally. However, the concrete bollard would require either pumping <br /> concrete from the base of gravity feed from above. Neither are logistically realistic for the as-needed <br /> local stabilization approach. The 6-inch hole could only be reduced in diameter if the number of <br /> strands was reduced, requiring much longer bond lengths per strand, much longer strands and <br /> therefore a much longer drill hole. The longer drill hole would require a much larger drill rig. <br /> Due to the 6-inch hole diameter and depths required, a berm is needed to resist the upper layer from <br /> failing and to be used as a work bench to install the required anchors. Table 5 below provides details <br /> of the necessary anchorage, hole diameter and lengths. <br /> Page 14 <br /> 535 16th STREET,SUITE 620 1 DENVER,CO 80202 1 (303)732-3692 1 WWW.KILDUFFUNDERGROUND.COM <br />