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<br />-5- <br />• . <br />N <br />_~ <br />FILL SLOPE STABILITY ANALYSIS <br />.ry Fill will be required to construct most of the haul road. Mined <br />J Land Reclamation Board regulation 2CCR 407-2, Paragraph 4.03.1 (3)(ix) <br />~` requires that embankment slopes be no steeper than 1 vertical to 2 <br />• horizontal unless a minimum factor of safety of 1.25 can be achieved. <br />Much of the ground surface in the area of the proposed haul road slopes <br />naturally at about 2:1 (horizontal to vertical). To provide a <br />~ reasonable daylight point, fill slopes of. 1.5 horizontal to 1 vertical <br />fi were incorporated into the design. As part of the design process, <br />~. <br />stability analyses were performed to evaluate fill slope stability. <br />Two modes of failure were considered in our analyses. The modes <br />include a wedge type failure and a circular failure using residual <br />strength parameters reported by Chen and Associates. Factors of safety <br />for both modes were computed considering a surcharge load of 1,500 psf <br />I <br />at the head of the slope induced by truck traffic. The results of our <br />analyses (Figs. 3 and 4) indicate a factor of safety of 2.0 for a wedge <br />type of failure without surcharge and 1.5 when surcharge loads were <br />~._ <br />added. A factor of safety of 1.8 was computed for a circular type of <br />;~ failure, without surcharge load. The factor of safety was reduced to <br />1.6 when truck traffic was considered. <br />Our slope stability analyses considered "dry slope" conditions. The <br />materials used as fill will consist of relatively impermeable compacted <br />claystone. In our opinion, development of a free water surface within <br />~ the fill is unlikely during the 5 year life as long as adequate surface <br /> <br />