Laserfiche WebLink
• Western Associates Coal <br />May 26, 1982 <br />The residual stre:gth conditions produced minimum factors of <br />safety between 0.77 and 2.2. The thickness of collu~•ium <br />(measured perpendicular to the slope) which will produce a factor <br />of safety of 1.0, 1.25 and 1.50 was estimated to be 13 feet, 10.5 <br />feet, and 8.5 feet, respectively. <br />The peak strength conditions produced minimum factors of safety <br />between 0.92 and 2.6. The thickness of colluvium which will <br />produce a factor of safety of 1.0, 1.25, and 1.50 was esti;ated <br />to be 16.5 feet, 13.0 feet, and 10.5 feet, respectively. Results <br />of the slope stability analysis performed are presented on the <br />attached tables. <br />CONCLUSIONS AND RECOMMENDATIONS <br />The results of the stability analysis presented above indicate <br />that the modeled conditions vary between unstable to very stable <br />(indicated factors of safety between approximately 0.77 and 2.6) <br />depending on the thickness of colluvium in relationship to the <br />excavated section of the access road. <br />• Our experience in the area has been that virtually all cuts in <br />the access road are founded in the bedrock. The slope stability <br />model utilized in this analysis is predicated on that assumption. <br />Based on the results of our analysis, we feel a moderate to very <br />stable condition will exist wherever excavations penetrate a <br />thickness of not more than 13 feet of colluvial soil (measured <br />perpendicular to the slope face). <br />If exceeding the maximum depth of colluvium cannot be avoided, we <br />would recommend that the excavated slope be flattened as close as <br />possible to approximate natural slope conditions or other methods <br />of shoring the slope be utilized. <br />We trust that the information presented in this report is <br />sufficiently detailed tc satisfy your needs and permit proper <br />review and approval by the State and Federal regulatory agencies. <br />If you require additional information or clarification of the <br />results presented, please contact us. <br />Respectfully submitted, <br />ROCKY MOUt7TAIP] GEOTECHNICAL <br />~• ~-~ <br />~ `~~ <br />• Richard J ceenwocdy ~'Rr <br />Project E ineerV <br />RJG/sam ~ '' " <br />1i <br />~;.. , . <br />~,, < ' t <br />enl~ neth M e s <br />Principal in Ch ae <br />