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joint fractures extended more than 50 feet. In addition, as can be seen in Figure 5, all the joint <br /> sets are steeply dipping. Only three fractures observed had dips of less than 60 degrees. <br /> Within the limits of the available geotechnical information, a series of stability analyses were <br /> carried out for estimating likelihood of slope instabilities and associated failure modes. The <br /> analyses are based on large scale circular, wedge, plane, and toppling failure modes. <br /> Circular failure mode occurs in weak rock mass conditions. This failure is assumed to take place <br /> over an initially unknown curved failure surface. A circular failure is extremely unlikely to <br /> occur in the granite rock mass observed at the Rose Red Quarry due to its very high compressive <br /> strength and calculated RMR values. This claim is supported by local outcrops within the area <br /> exhibiting near vertical faces without substantial slope failures evident in surrounding area. <br /> Wedge failure mode involves two intersecting discontinuity planes that together create a wedge- <br /> shaped block with a tendency to slide out of the slope face. For a slide to occur, the planes' <br /> intersection line needs to be angled greater than the friction angle of the slide surfaces. <br /> According to the discontinuity orientations depicted in Figure 3, primary and secondary joint <br /> systems intersect to form two possible steeply dipping wedge block orientations. These have <br /> azimuths of 50' and 110°. The plunge of the intersections are 70' and 57' respectively. Both <br /> intersecting joint sets could potentially cause issues in the west wall of the pit if the wall were <br /> mined steep enough. The west pit wall would need to be steeper than 57' before possible wedge <br /> failure could occur. However, mined slopes should be maintained to <50' to ensure no wedge <br /> failure will occur. It is more likely to have small wedge failures in bench faces than for the entire <br /> pit walls in the rock mass within the quarry. <br /> Rock block sliding over planar surfaces becomes increasingly difficult if the dip direction angle <br /> between the plane and sliding block increases beyond 20°. Due to the steeply dipping <br /> orientations of the joint sets, the probability of a block of rock sliding on a pit slope face is <br /> unlikely. The pit slope face would need to be steeper/greater than the fracture dips for this to <br /> plane failures to occur. <br /> Toppling failures occur in the presence of steeply dipping, consistently parallel rock columns <br /> located behind slope face. Topping failure may be a possibility for the joint configuration shown <br /> in Figure 3 if pit slope faces are high. The current 1 H:1 V slope planned for the Rose Red Quarry <br /> Rose Red Quarry Geotechnical Report 9 X 1,,-,,.„,��,a-,���,,,. ,.,, <br />