Laserfiche WebLink
11/94 <br /> Rule 6. 5, Page 2 <br /> degrees for residual strength conditions where movement is <br /> currently active to a high of 30 degrees where there has been no <br /> strain. Intermediate strength values are often encountered where <br /> there has been some strain history but not enough to establish a <br /> fully developed shear surface. This condition is sometimes <br /> termed fully softened and friction angles on the order of 20 to <br /> 25 degrees are common. <br /> Reconnaissance of the site did not show signs of any previous <br /> slides. Therefore, a conservative approach of assuming a <br /> bentonitic clay shale alpncjwith a fully softened condition was <br /> used. A friction angle of 20 degrees was derived from bentonitic <br /> shalesfound in other areas is discussed above. Achieving a <br /> minimum factor of safety of 1. 5 will assure the slope will remain <br /> stable. The site is on a somewhat isolated ridge with relatively <br /> steep slopes down away from the proposed pit. No indications of <br /> subsurface water were observed. Therefore, the stability <br /> analysis did not include elevated pore pressures or hydrostatic <br /> conditions. <br /> The topsoil will have little or no effect on the stability of the <br /> gravel slope. It was included in the analysis to reflect post <br /> mining conditions. The stability of the slope during mining <br /> operations will not be compromised with the deletion of topsoil. <br /> There will be no blasting incorporated with the mining <br /> activities. <br /> As mentioned above, the critical slip circle was identified using <br /> the computer program UTEXAS2 and the factor of safety was 1 .785, <br /> which exceeds the minimum target value of 1. 5. The material <br /> strength values used in the analysis along with the geometry of <br /> the critical shear surface and the resulting safety factor are <br /> shown on the attached drawing. <br /> X-2 <br />