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Actual formation of the wedges or plane failures depends upon orientation and <br /> spatial location of the features. Structural mapping should continue on all benches with <br /> both the geologic and engineering staff interpreting the structure to identify the potential <br /> failure surfaces. If large wedges or planes of failure are detected in the wall, rock bolting <br /> schemes can be devised to stabilize the structure. <br /> 4.4.2 Small-Scale Structure <br /> Mapping of potential small wedges formed by the joint sets identified in the <br /> mapping data is shown graphically in Figure 4.6 and 4.7. Seven potential intersections <br /> occur which daylight in the north wall. The intersection I12_13 has formed numerous small <br /> wedge failures in Bench 2 of the north wall and has produced the very rough appearance <br /> shown in Figure 3.2. I12-13 also daylights in the east wall. <br /> The joint sets produce small-scale instabilities that primarily result in operations <br /> safety problems. The wedges generally loosen on the wall forming local safety hazards, <br /> or are removed by the mucking/scaling operation. Removal of the wedges tends to <br /> reduce the bench width. Aggressive scaling of the bench faces is necessary to assure that <br /> the loose structures which daylight are removed. <br /> 4.5 BENCH WIDTH AND FACE ANGLE <br /> Bench widths are reduced below design in the Sunnyside Pit because the blocky <br /> nature of the rock results in the removal of material at the face. This could be improved <br /> by steepening the bench face angle to vertical from 70' and by increasing the bench <br /> width to 18 feet. Changing the face angle should not affect bench stability; however, the <br /> bench width should be increased to keep the composite slope angle from increasing to <br /> much. An 18 ft bench with vertical face should produce a composite angle at Sunnyside <br /> of 62°. <br /> 19 <br />