Laserfiche WebLink
Slope Evaluation and Remediation <br />West Elk Mine <br />Somerset, Colorado <br />landslide. "Stable material" refers to the soils and rock beyond the smaller, relatively <br />rapidly moving landslide, even if that material is part of the larger, more slowly moving <br />landslide complex. <br />GROUND recommends that the recent landslide materials be excavated in their entirety <br />and the material replaced as properly moisture conditioned, benched, and compacted fill <br />to form a stair -cased buttress for the hillside and the overlying mine road. The buttress <br />fill should be benched into the soils beneath the landslide and provided with back drains. <br />A keyway should be constructed at the bottom of the lowest bench. The roadway then <br />can be maintained or re- constructed as desired. <br />More detailed recommendations regarding these measures are provided below. <br />In addition, GROUND recommends that the margin of the coal stockpile permanently be <br />kept back at least 20 feet back (south) from the break in slope at the intersection of the <br />hillside and the overlying mine road to maintain slope stability. <br />Buttress Fill Parameters The buttress should replace the entire mass of landslide <br />material and extend into the relatively stable material beyond and beneath it. The <br />approximate anticipated limits of the buttress fill are shown in section on Figure 4. The <br />actual limits of the buttress will be determined in the field as the materials comprising the <br />landslide are excavated. <br />The temporary back cut of the remedial excavation should be constructed with benches <br />10 feet in width as shown on Figure 4. The back cut benches should be sloped at a <br />gradient of at least 2 percent back into the slope. The lowest bench should be keyed <br />into the underlying materials as show on Figure 4. The slopes between back cut <br />benches should be cut no more steeply than 1'/2 : 1 (horizontal : vertical). <br />The buttress fill should be constructed of properly compacted fill soils as recommended <br />below. The soils comprising the buttress fill should exhibit an angle of internal friction of <br />at least 30 degrees. <br />The finished slope of the buttress fill should be constructed at an angle no steeper than <br />2:1 (horizontal : vertical) but generally graded to match the original grade. <br />Job No. 11 -6014 GROUND Engineering Consultants, Inc. Page 8 <br />