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Grand Island Resources,LLC Page 5 <br /> Idaho Tunnel Portal—Slope Stability Analysis <br /> GSI=45 (Blocky/Disturbed/Seamy with rough,slightly weathered, iron stained surfaces -or-Very <br /> Blocky with smooth, moderately weathered and altered surfaces) <br /> mi= 25 <br /> D=0 <br /> The cellular concrete void fill is much stronger than the soil and regolith material it replaces. Laboratory <br /> testing results on test cylinders cast during the pours exhibited an average 28-day strength of 109 psi. <br /> This material was modeled with a unit weight of 35 pcf and shear strength of 50 psi. Riprap which was <br /> infilled with cellular concrete was modeled as cellular concrete. <br /> Since the precise source for the waste rock is unknown, the material properties adopted for the waste <br /> rock fill material were conservatively modeled using the lower bound shear strength envelop presented <br /> by Leps (1970)2 for rock fill composed non-compacted, weak or poorly graded particles. The Leps <br /> approach models the variance in material strengths relative to varying confining pressures and the degree <br /> of particle interlocking or crushing that results. Table 1 presents the shear-normal parameters used for <br /> the waste rock fill. <br /> Table 1—Shear Strength of Waste Rock Fill <br /> Normal Stress (psf) Shear Stress(psf) <br /> 144 205 <br /> 288 376 <br /> 720 858 <br /> 1441 1600 <br /> 2880 3035 <br /> 7201 6834 <br /> 14405 12744 <br /> 28807 23747 <br /> 3.3.3. Ground Support Elements <br /> Due to their relatively short length and irregular pattern of placement,the soil anchors were neglected in <br /> the analyses. The shotcrete will have little overall effect on global stability of the slope and was also <br /> neglected in the analyses for conservatism. The primary purpose of the shotcrete is to control shallow <br /> surface sloughing and raveling. <br /> 3.3.4. Idaho Tunnel <br /> Due to the ground support elements that will be employed and its small size relative to the scale of the <br /> slope,the tunnel opening was not included in the stability section. Spillings installed above the top of the <br /> tunnel opening will become integrated with the cellular concrete void fill to help stabilize the opening and <br /> face of the excavation below the County Road. <br /> z Leps,T.M., 1970; "Review of Shearing Strength of Rock Fill"ASCE Journal of the Soil Mechanics and Foundations Division,Vol. <br /> 96,No.SM4,July,pp 1159—1170. <br /> Applied Geologic LLC 5/3/2021 <br />