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PN: 55743PE <br /> October 11, 1029 <br /> Page 2 <br /> deposit will have a temporary inclination approximating the short-term angle of repose of the <br /> material (nominally 1.5:1,h:v, and flatter)with a final reclaimed slope gradient of 2:1,h:v. <br /> Meaningful computer modeling of the existing slope and the proposed shot-rock deposit is <br /> difficult because the stability of the underlying bedrock is primarily related to the joint and <br /> fissure patterns/orientations rather than the strength of the material. The free-draining <br /> "frictional"material is composed primarily of fractured angular rocks and is not typically <br /> modeled using techniques more suited to soil analyses. <br /> Strength characteristics of open graded aggregates were recently evaluated by the United States <br /> Department of Transportation, and presented in "Strength Characterization of Open-Graded <br /> Aggregates for Structural Backfills,"2015, FHWA—HRT-15-034. This publication included the <br /> evaluation of large-sized open graded rock. Based on our experience and our review of the <br /> FHWA report,the angle of internal friction of the cohesionless angular shot-rock is likely to <br /> exceed 40 degrees. <br /> Based on the proposed working face of 1:5, h:v, we obtained a theoretical factor of safety of the <br /> working surface of 1.30, as shown below <br /> .,r,.,.,_.. <br /> F <br /> a• <br /> g. <br /> A <br /> 13 <br /> a r r ■ I w No .w is it r 5 <br /> We performed a rudimentary analysis of the proposed post-reclamation waste pile slope of 2:1, <br /> h:v as shown on the project plans provided to us. <br /> TRAUTNERr4044i1M:11n <br />