Laserfiche WebLink
8)All reclaimed slopes within the mining areas will be restored to a minimum slope of 4H:1 V,which <br /> should have no problems with slope stability at such a mild angle.The slope south of the infiltration <br /> pond will be restored at approximately 3H:1 V. For the reclaimed slopes of 2H:1 V,which will not <br /> be used,the following demonstration is presented: <br /> These mined slopes will be in alluvial gravel materials which were identified in all past test excavations <br /> over many decades in the immediate area of 3 miles from the site,which includes the Alma Placer <br /> site.The bank material has fines(< 100 mesh)of approximately 10%and the material is extremely <br /> well cemented,giving it a strength far beyond what would occur in a loose stockpile. The material <br /> has significant strength from cohesion and internal angle of friction. <br /> Partly rounded gravel of this type in place has an angle of repose of approximately 40 degrees(from <br /> Huang-Stability Analysis of Earth Slopes).For non-cohesive soils,this is also the internal angle of <br /> friction ofthe material.The overall slope of 1.5H:1.OV is an angle of 26.6 degrees,therefore,the factor <br /> of safety for non-cohesive soils is defined as the ratio of the tangent of the angle of repose of the material <br /> to the actual tangent of the angle to be employed on the slope. In this case,this is <br /> Factor of safety= Tan 40.0 = .839 = 1.258 <br /> Tan 33.7 .6666 <br /> For a temporary slope,this is a very good safety factor and poses no potential for instability,when <br /> it is known that the above calculation assumes no strength from cohesion and it is evident that the <br /> cohesion of this material is very strong.The requirement for permanent stability is normally a safety <br /> factor of 1.3. In actuality,the safety factor of these mined slopes is more likely to be over 1.6 due <br /> to the cohesion present. This fact is combined with the restrictions on these slopes i.e.,they cannot <br /> be present for more than 2 years,that MSHA requirements must also be followed,and that benching, <br /> Gloria Z Mine 2013 Amendment 81 <br />