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Grand island Resources.LLC Page 14 <br /> Idaho Tunnel Portal—Slope StabaUty Analysis <br /> The "Weak Hard Rock" unit represents highly fractured rock with some weathering and is quite variable. <br /> In some areas the material is quite weathered and grades into fully decomposed rock,while in other areas <br /> it more closely resembles fractured hard rock with little weathering present. Assumed rock mass <br /> parameters for Weak Hard Rock: <br /> Intact Rock UCS=1000-2000 ksf(7,000—14,000 psi) <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 /> 3.3.4. 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 /> 3.3.5. 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. Its is anticipated that additional spillings and possibly <br /> forepolling will be required when tunnel rehabilitation resumes. These measures as well as the timely <br /> installation of steel sets or shotcrete and mesh as ground support for the tunnel will be employed to <br /> prevent additional collapse beneath the road. <br /> 3.3.6. Groundwater Conditions <br /> The slope was initially modeled as drained, without groundwater to calibrate the model to conditions <br /> which existed as the excavation was completed. <br /> Subsequently, a parametric study was conducted to evaluate the sensitivity to water levels to reflect <br /> conditions which may exist during spring thaw. This was conducted by progressively raising a perched <br /> water table within the Alluvial Rock unit in 5 ft increments to evaluate the effect this had on the Factor of <br /> Safety. <br /> 3.3.7. Collapse Void <br /> The open collapse void was neglected in the base case analyses since it is not present everywhere within <br /> the slope. However, its inclusion is useful for back analysis to provide constraint on the shear strength of <br /> the material comprising the slope. <br /> The 200 psi cellular concrete void fill is much stronger than the soil and rock colluvium material it replaces. <br /> Additional runs were made to assess the amount of beneficial effect this mass of stronger material has on <br /> stability of the slope in the sections where it will be present. <br /> Appsed GeoLogic LLC 5/7/2020 <br />