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<br /> <br /> Friction Anaie 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 />' n <br />i <br />l <br />h <br />th <br />i <br />f <br />i <br />ti <br />" <br />° <br />b <br />l <br />d "1' <br />th <br />rf <br /> a <br />ys <br />s, w <br />ere <br />as <br />r <br />a <br />~ <br />was <br />e <br />c <br />c <br />on ang <br />e an <br />e su <br />was <br />ace <br />' roughness angle (Hoek and Bray, 1977). The roughness angle is the angle <br />h <br />f <br />l <br />b <br /> etween t <br />e basic plane o <br />the joint and the p <br />anes 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 />' published results do not include the two direct shear tests run on samples with <br /> clay material along the foliation plane, which produced an average friction angle <br />' of only 5°. For this current study, a basic friction angle of 28° plus a roughness <br /> angle of 5° (total of 33°) was 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 /> <br /> <br />-9- <br />