Laserfiche WebLink
To: Chris Nyikos, Project Manager - Mountain Coal Company <br />Subject: Geotechnical Review of Updated PR-2 Conveyor Alignment <br />Date: July 17, 2009 <br />Project: 06/26-1004 <br />place of old Cross Section B) is located on a roughly east-west alignment to evaluate the proximity of the <br />building to the east slope of the LRP near the access road. <br />The geotechnical properties assigned to each layer in the analysis remain unchanged from those <br />recommended in the 1999 report and are assumed to represent the material strength in the drained <br />condition. For conceptual purposes, the Screening and Preparation Plant facility was assumed to impart a <br />uniformly distributed load of 4,000 psf across the proposed footprint. The slope stability analysis was <br />completed using SLOPE/W, included as part of the GeoStudio 2004 suite, developed by Geo-Slope <br />International. The Spencer method to evaluate force and moment equilibrium was used in the analysis. <br />The results of the analysis indicate factors of safety of 1.8 and 2.0 for cross sections A and C, respectively. <br />In both cases, the resultant factor of safety was equal to or greater than 1.5, indicating the LRP is stable <br />under the proposed slope geometry and assumed building loads. <br />The critical slip surface in both cross sections is associated with a relatively shallow slope failure, and the <br />slip surface does not intersect the proposed footprint of the Screening and Preparation Plant facility. To <br />further investigate the potential effects of the building load on the factor safety for both slopes, the <br />uniformly distributed load associated with the facility was gradually increased to 20,000 psf in a parametric <br />study. The building load affects the factor of safety for this cross section when the building load exceeds <br />13,000 to 15,000 psf. However, even at a building load of 20,000 psf, the factor of safety for both cross <br />sections is approximately 1.7. <br />The results of the analysis show that both of the critical cross sections associated with the conceptual <br />geometry of the LRP and proposed Screening and Preparation Plant facility have a factor of safety of at <br />least 1.5, indicating they are stable as proposed. No stabilization will be required in the vicinity of the <br />proposed Screening and Preparation Plant facility, as well as for the LRP. <br />-6-