Laserfiche WebLink
The Mohr-Coulomb strength criteria for the kinematic analyses was conservatively estimated <br /> at 3.2 psi and cp angle of 35 degrees. <br /> Per discussions with Al, the north highwall will be completely mined out during the life of <br /> the mine, and the South Quarry will merge with the Central Quarry at this time, with no <br /> highwall separating the two cells, so a North highwall was not modeled. <br /> No other highwall orientations were modeled as GEI assumes the highwalls will interest each <br /> other at approximately 90' angles with no intermediate slopes/highwalls. <br /> 4.1.1 Planar Failure <br /> Mine highwalls can fail when a plane of weakness daylights into the mine highwall steeper <br /> than the angle of friction. For the South Quarry, the plane of weakness is considered either <br /> primary (or secondary)joint sets or the gneissic foliation. <br /> The primary joint sets present within the South Quarry are the likely plane of weakness when <br /> evaluating the east and north slopes while the secondary joints are less probable, simply <br /> because the frequency and extents of these joint sets are limited. <br /> The highwall orientations described above and primary dip direction of gneissic foliation <br /> preclude planar failure here, as the foliation was mapped with an average strike and dip <br /> between 5 and 360 degrees, and 5 and 80 degrees, respectively, in this area. With this <br /> orientation,the dip is favorable, i.e. into or roughly parallel to the west highwall trend. <br /> When evaluating the west slope, primary joint sets in addition to gneissic foliation are <br /> equally considered. The foliation was mapped with an average strike and dip between 5 and <br /> 360 degrees, and 5 and 80 degrees, respectively, in this area. With this orientation, the dip is <br /> adverse, i.e. out of the east highwall trend. <br /> For planar analysis, RocPlane and steronet versions were developed using the Mohr- <br /> Coulomb strength model (Appendix D). RocPlane was used to analyze for an individual <br /> bench scenario and and stereonets were used for a global view of the entire highwall. Results <br /> from the Rocplane analysis indicate that possible planar failures will be limited in volume <br /> and likely not disrupt mine operations and the results from the stereonet analysis indicate that <br /> the likelihood of global large scale planar failure is small because majority of poles lie <br /> outside critical area of failure. <br /> 4.1.2 Wedge Failure <br /> Wedge failure can occur when discontinuities within the mine highwall (primary, secondary <br /> joint set, gneissic foliation, etc) intersect at an orientation that creates an unstable "wedge" of <br /> rock that can fall into the mine pit. Using highwall orientation (trend) and mapped <br /> discontinuity characteristics (from 2013 to 2016 annual reports), Swedge can compute all <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> South Quarry Highwall Design Technical Revision 14 August 2017 <br />