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Martin Marietta Materials <br />Spec -Agg 2013 Annual Report <br />1) Representative discontinuity orientations (dip and dip direction) from data collected during the <br />October 2012 and March 2013 (Table 1). <br />2) Mine Slope Orientations (dip and dip direction) as presented in Table 2 and shown in Figure 2. <br />A total of thirteen (13) slope orientations were considered. <br />3) Estimated Rock Mass Discontinuity Interface Friction Angle. A typical interface friction angle of <br />33 degrees was considered in all cases for the kinematic analysis, as discussed in Section 6.3. <br />The kinematic analysis stereonet plots are presented in Figures 8 through 15. Representative discontinuity <br />orientations are shown as green lines. The slope orientation for the considered wall is shown as a blue line. <br />The friction circle is shown as a black line. Each kinematic analysis plot is evaluated based on where <br />discontinuities plot in relation to the "critical zone ", which is shown as a light red shaded area on the <br />stereonet plots. <br />6.4.1 Potential Failure Modes <br />6.4.1.1 Planar Failure <br />Planar failure is indicated as a potential failure mode if the dip vector of a discontinuity falls between the dip <br />direction of the slope face and the friction cone representing the assumed discontinuity interface friction <br />angle. The following four conditions, defined by Hoek & Bray (1977), must be met in order for planar failure <br />to occur: <br />1) The plane on which sliding occurs must strike parallel or nearly parallel to the slope face. Typically, <br />discontinuity planes with a dip direction within 30 degrees of the slope dip direction are 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 mass to <br />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 defined <br />by the area of overlap between the friction circle and the great circle representing the plane of the 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). <br />According to the analysis method developed by Markland (1972), a wedge failure can occur when the <br />following criteria are satisfied: <br />1) The plunge of the lines of intersection is less than the dip of the slope face. <br />April 22, 2013 Page 12 Lachel & Associates, Inc. <br />Project 12361005.00 ©2013 All Rights Reserved <br />