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A further analysis of the available cluster data was used to assess the hypothesis <br />that distinct "structural blocks" exist within the quarry, a cluster analysis showing <br />the poles based on collection areas has been developed (Figure 9). The <br />datasets have been broken down based on the location and year that the data <br />were collected. The southern expansion area is separated geographically from <br />the middle level and main pit area of the quarry (labeled middle level) by the <br />approximately east-west trending fault that is mapped between the areas (Figure <br />3). Currently the 1997-2002 data continue to be analyzed as a single data set, <br />but data collected since 2003 have been separated for the analysis based on this <br />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 />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 />_17_ <br />