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<br />(Figure 9). The datasets have been broken down based on the location and year <br />that the data were collected. The southern expansion area is separated <br />geographically from the middle level and main pit area of the quarry (labeled <br />' middle level) by the approximately east-west trending fault that is mapped <br />between the areas (Figure 3). Currently the 1997-2002 data continue to be <br />' analyzed as a single data set, but data collected since 2003 have been <br />separated for the analysis based on this potential boundary. <br />To adequately understand the impacts of the new data on wall stability, the <br />planes representing each discontinuity set and the plane representing the <br />orientation of the respective quarry wall slope face were plotted on individual <br />' stereonets. The stereographic analysis of each quarry wall is presented in <br />Figures 10 - 15. <br />6.2 Wedge Stability Analysis <br />' As presented in earlier annual reports, the method of stereographic analysis <br />developed by Markland (1972) was used for this study. Markland's test is <br />' designed to identify the possibility of a wedge failure in which sliding takes place <br />along the line of intersection of two discontinuities (Hoek & Bray, 1977). <br />According to Markland's test, sliding can occur when: <br />' 1) The plunge of the lines of intersection is less than the dip of the slope face. <br />2) The plunge of the lines of intersection exceeds the angle of friction. <br />The trends of the lines of intersection that can daylight onto the slope have been <br />I identified with arrows on the stereonets for each of the wall orientations (Figures <br />10 - 15). Based on the results discussed in Section 4, the limiting resistance to <br />' sliding is drawn as a dashed circle on the stereonets having a radius equivalent <br />to a friction angle of 33°. Markland's two criteria for sliding are satisfied when the <br />intersection of the discontinuities plot on the stereonets within the hatched <br />regions that are bounded by the friction circle and the great circle representing <br />-17-