2017-04-14_REPORT - M1974004 - Laserfiche WebLink

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Martin Marietta Materials Spec-Agg 2017 Annual Report locations and orientations for the Southwest and Southeast Walls correspond to the same wall locations and orientations analyzed in previous annual reports (Figure 2). The stereonet plots for Southwest Walls 1 and 2 do not show indications of potential planar or wedge failure modes based on the 2015 discontinuity measurements (Figure 13). However, even a slight variability of the joint sets P-2 and P-4 will have potential to form wedges within the critical zone for these walls. The stereonet plot for the South and Southeast Wall shows one discontinuity intersection that falls within the critical zone, suggesting that wedge failure is kinematically possible for this slope orientation (Figures 14 and 15). The intersecting sets that may result in wedge failure includes joint sets P-3 and P-6. The signatures of P-6 appears to be relatively strong in the Southern Expansion Area (Figure 6) based on the 2013-2015 and current(2016)data. The development and size of wedge failures will be controlled by the variability and limited lateral extent of the discontinuities. As excavation proceeds for the Southern Walls, additional measurements are needed to refine the representative discontinuity orientations of these joint and foliation sets in this area to evaluate their potential contribute to large-scale slope failure modes. Planar failure is not indicated in the stereonet plot for the South and Southeast Wall (Figures 14 and 15). 7.0 CONCLUSIONS AND RECOMMENDATIONS The results of the structural geologic evaluations and kinematic structural discontinuity analyses for the Spec-Agg Quarry do not indicate any immediate concerns with respect to large-scale instabilities in the current final quarry wall faces based on our field observations and current rock mass assumptions. The stability of the slopes is enhanced by the absence of significant hydrostatic pressure, by current mining procedures, and by the current reclamation process being implemented by Martin Marietta at the site. While large-scale failures are not anticipated, the slopes will continue to experience minor raveling as a result of small-scale failures (planar or wedge failure), particularly in near-vertical temporary bench faces prior to reclamation. For the 2017 Annual Report, kinematic analyses are based on discontinuity measurements derived principally from data collected from the historic dataset supplemented with data collected during the July and December 2016 site visits. The 2017 analysis is not intended to supersede results of analyses performed for prior years. Rather, they are meant to compliment previous years' analyses and enable monitoring of possible new trends in the data that could result in previously unconsidered failure modes. In general, the data collected during the July and December 2016 site visits correspond reasonably well with representative discontinuity orientations used in previous reports; we have not noted any major difference that will change our kinematic analyses for the 2017 Annual Report. The kinematic analysis for East Walls 1 and 2; Northeast Walls 1, 2, and 3; Northwest Wall;West Walls 1, 2, and 3; South Wall; and Southeast Wall each indicate the possibility for wedge failures to occur. Additionally, the analysis for Northeast Walls 1 and 3 shows the potential for planar failure exists with the slightest variation of joint sets P-2 or P-3. The walls of the quarry in these areas should continue to be monitored closely as mining continues to assess the potential for the indicated failure modes to contribute to large-scale slope instability of a final mine highwall based on the properties, continuity, regularity, and variation in orientations of the discontinuities involved. February 27,2017 Page 11 Lachel &Associates, Inc. Project 16C64003 00 ©2017 All Rights Reserved