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Liberty Mining, LLC <br />DRMS 110 -d Permit Application <br />October 2013 <br />stockpile will not have sufficient size to be of concern. The existing slopes surrounding the <br />mining operations pad have demonstrated stability in previous mining operations at the site. <br />Shear Strength <br />Shear strength is calculated using the Mohr - Coulomb failure criterion (Fredlund et al., 1996). <br />The shear strength of granular soil is frequently characterized by the angle of internal friction (cp) <br />and cohesion (C), as follows: <br />T = c' +(on- uw) tan cp' [1 ] where: <br />T = shear strength <br />c' = cohesion intercept (due to adhesion, cementation, stress history, interlocking of particles, <br />etc.) <br />(p'= effective angle of internal friction <br />Qn= total normal stress on the plane of failure <br />(o-n- uw) = effective normal stress on the plane of failure <br />uw = pore -water pressure. <br />While shear strength (T) was not calculated specifically for the waste rock pile, there is sufficient <br />data from similar waste rock piles that. demonstrate the shear strength of the pile will yield <br />values sufficient for a stable slope. <br />The angle of internal friction angle is a function of the following parameters (Hawley, 2001; Holtz <br />and Kovacs, 2003): <br />1. Particle shape and roughness of grain surface: The v.1aste rock is blasted and thus consists <br />primarily of rough edged materials increasing the friction angle. <br />2. Grain quality: Waste rock is primarily sandstone, a semi weak rock with lower friction <br />coefficient. <br />3. Grain size: Waste rock has been blasted so it ranges in size from small boulders to medium <br />pebbles. The friction angle increases or decreases with increase in grain size. <br />4. Grain size distribution: friction angle typically decreases with decreasing coefficient of <br />uniformity, Cu <br />5. State of compaction or packing: the friction angle typically increases vilith increasing <br />density or decreasing void ratio <br />6. Specific gravity (specific to site geology): The specific gravity for sandstone and shale <br />(mudstone) range from 137.28 - 174.72 (in lbsffP) based on tabular data from EduMine- <br />Professional Development and Training for Mining and the Geosciences. <br />(http -//www edumine. com/xtoolkit/tables/sgtables. htm) <br />7. Applied stress level: (friction angle decreases with increasing confining stress, resulting in <br />a curved strength envelope passing through the origin instead of the classical straight line) <br />Liberty Mining, LLC Moab, Utah SMA Ref 5821897 Pace 15 <br />