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Grand Island Resources,LLC Page 3 <br /> Idaho Tunnel Portal—Slope Stability Analysis <br /> 1.2 Geology <br /> The Idaho tunnel has been rehabilitated sufficiently to allow the geology to be examined up to and beyond <br /> the county road. GIR has explored the first 200 ft of the Idaho Tunnel in order to investigate the <br /> corresponding ground conditions. Starting at the portal the first 60 ft of tunnel consist of regolith and <br /> colluvial soils. Next is a 28 ft section of fractured and weathered blocky gneiss which extends beyond the <br /> county road. <br /> Grouted threadbar drilled into the slope to further anchor the cellular concrete into the hillside <br /> encountered refusal of the jack-leg drill 15 to 20 ft into the hillside. This is interpreted as indicating the <br /> transition into relatively intact rock comprising the blocky gneiss unit. <br /> The Caribou Road (County Road 126) above the Idaho tunnel is located entirely in mixed soil and rock <br /> colluvium and regolith materials. Fresh gneiss of the Idaho Springs formation is present a short distance <br /> above the road and to the south of the tunnel portal. <br /> Figure 1 presents a schematic cross section of the tunnel and slope which depicts these conditions. <br /> 2.0 STABILITY ANALYSIS <br /> 2.1 Approach <br /> The stability analyses were conducted using the RocScience SLIDE2 software,a 2D slope stability program <br /> for evaluating the safety factor or probability of failure,of circular and non-circular failure surfaces in soil <br /> or rock slopes. Slide2 analyzes the stability of slip surfaces using vertical slice or non-vertical slice limit <br /> equilibrium methods like Bishop, Janbu, Spencer, and Sarma, among others. Search methods can be <br /> applied to locate the critical slip surface for a given slope. The Bishop method of slices for circular failures <br /> surfaces while the Janbu method of slices for satisfying both moment and force equilibrium was adopted <br /> for non-circular surfaces. <br /> SLIDE2 supports a comprehensive list of soil material models including Mohr-Coulomb, undrained, <br /> impenetrable, bilinear, strength as a function of depth, anisotropic strength, generalized shear-normal <br /> function, SHANSEP), and more. Typical rock material models supported by SLIDE2 include generalized <br /> Hoek-Brown (Hoek, et. al, 2018), Barton and Choubey (1977), and Miller (1988) can be handled by <br /> SLOPE/W using the generalized shear-normal function with or without an anisotropic modifier function. <br /> Analyses for the portal slope were performed using Mohr-Coulomb strength criteria for the soil materials, <br /> Hoek Brown (2018)for the regolith and block gneiss and a shear-normal strength function based on Leps <br /> (1970)for the waste rock. <br /> 2.2 Model Input <br /> 3.3.1. Slope Geometry <br /> An idealized representative two-dimensional cross-section was considered for analysis. This section <br /> consisted of the profile along the axis of the tunnel included on Figure 1, consisting of a 28-ft high <br /> excavation at an angle of 75-degrees then natural ground sloping at approximately 40 ft to the edge of <br /> Applied Geologic LLC 5/3/2021 <br />