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<br />' Friction Angle Estimation <br />' In early LF&A annual quarry evaluation reports (L&A, 1997-2002), a total <br />representative angle of friction (? + ?) 40° was used for the wedge stability <br />analysis, where "?" was the basic friction angle and 'T was the surface <br />roughness angle (Hoek and Bray, 1977). The roughness angle is the angle <br />between the basic plane of the joint and the planes representing the surface of <br />ripples or undulations of the joint surface. This value was based on our research <br />' of the subject, including published data from various sources, and was a "best <br />guess" given that no actual laboratory testing had been performed previously on <br />' rock from the quarry. However, as a result of the 2003 geotechnical <br />investigation, 20 rock samples were selected for direct shear testing in order to <br />' better define the strength of the rock (L&A, 2003). The test results produced <br />only a basic friction angle, ?, and indicated that the basic friction angle of the <br />' discontinuities ranged from 13.7° to 49.3° with a mean value of 28°. These <br />results do not include the two direct shear tests run on samples with clay <br />' material along the foliation plane, which produced an average friction angle of <br />only 5°. <br />For this current study, a basic friction angle of 28° plus a roughness angle of 5° <br />(total of 33°) has been used for all of the wedge stability analyses. This <br />approach of using ? + i to represent the friction angle of the rock differs from the <br />Mohr-Coulomb strength criterion utilized in the 2003 geotechnical investigation <br />and slope stability analysis, but is utilized due to the geometric input constraints <br />of the stereonet and the wedge stability analysis used in this study. The Mohr- <br />Coulomb approach includes both a friction angle and a cohesion value to define <br />the shear strength of the discontinuities, where the cohesion value is used to <br />account for "the interlocking of asperities on the matching surfaces of the joint, <br />' and the increase in shear strength given by this interlocking..." (Hoek, 2000). <br /> <br />u <br />