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Martin Marietta Materials <br /> Spec-Agg 2017 Annual Report <br /> 1) The plane on which sliding occurs must strike parallel or nearly parallel to the slope face. <br /> Typically, discontinuity planes with a dip direction within 30 degrees of the slope dip direction are <br /> considered. <br /> 2) The failure plane must"daylight" in the slope face (i.e., the dip of the failure plane must be smaller <br /> than the dip of the slope face). <br /> 3) The dip of the failure plane must be greater than the angle of friction of the plane. <br /> 4) Release surfaces,which provide negligible resistance to sliding, must be present in the rock <br /> mass to define the lateral boundaries of the slide. <br /> On the stereonets, criteria for planar sliding are satisfied when the dip vector of a discontinuity plots within <br /> the critical zone, shown as shaded regions in Figures 8 through 15. The limits of the critical zone are <br /> defined by the area of overlap between the friction circle and the great circle representing the plane of the <br /> slope face. <br /> 6.4.1.2 Wedge Failure <br /> Wedge failure is characterized by sliding that occurs along the line of intersection of two discontinuities <br /> (Hoek & Bray, 1977). According to the analysis method developed by Markland (1972), a wedge failure <br /> can occur when the following criteria are satisfied: <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 /> On the stereonets, Markland's criteria for wedge sliding are satisfied when the intersection of two <br /> discontinuities plot within the critical zone. <br /> 6.4.1.3 Toppling Failure <br /> Toppling failures can occur where planes share a similar dip direction to the slope face and where they <br /> dip relatively steeply into the slope face. In our opinion, toppling failure is not likely to be associated with <br /> large-scale instability on the scale of an entire mine highwall. Therefore, toppling was not considered in <br /> our kinematic analysis. However, small-scale toppling failures are likely to occur locally at the site <br /> contributing to localized rockfall. <br /> 6.4.2 East Walls <br /> For the 2017 Annual Report, we analyzed two east wall orientations based on the locations shown in <br /> Figure 2 and Table 2: East Walls 1 and 2 corresponds to the same wall location and orientation analyzed <br /> in the previous 2013-2016 annual reports (Figure 2). <br /> The stereonet plots for East Walls 1 and 2 each show one discontinuity intersection that falls within the <br /> failure envelope, suggesting that wedge failure is kinematically possible for these slope orientations <br /> (Figure 8). The intersecting set that may result in wedge failure includes joint P-5 and joint P-7. <br /> The development and size of these wedge failures will be controlled by the variability and limited lateral <br /> extent of the discontinuities. Based on the current and previous data set,joint P-5 and joint P-7 have <br /> weak signatures represented by relatively few measured orientations representing these features (Figure <br /> 6). As excavation proceeds in the eastern walls, additional measurements are needed to refine the <br /> February 27,2017 Page 8 Lachel &Associates, Inc. <br /> Project 16C64003 00 ©2017 All Rights Reserved <br />