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CHAPTER II <br />^ <br />I <br />A. GENERAL <br />INTRODUCTION <br />This report gives the results of an investigation of slope parameters in <br />the Red Wing Mine area of Colowyo Coal Company (Figure II-1). The inve~- <br />tigation program was initiated following an oral request from Mr. C. G. <br />Stevens to W. A. Wahler and Associates for a slope design program proposal. <br />An engineering plan for such a program was submitted by W. A. Wahler and <br />Associates on November 27, 1974. The overall concept of this proposal <br />was accepted by Colowyo Coal Company (Purchase Order No. 708, January 6, <br />1974), with the condition that the designed slopes meet any existing <br />requirements of Federal and local governmental agencies. <br />The Colowyo Company will determine the most economic mine depth to which <br />Lhe coal can be mined by the open pit method, based in part on the slope <br />angles determined in this report for the two pit depths. <br />L <br /> <br />L <br />~. <br />L <br />L <br />L <br />B. SLOPE DESIGN CONSIDERATIONS <br />The design of structures in rock, such as an open pit, requires informa- <br />tion concerning the engineering properties of that rock. Unlike steel, <br />wood, or concrete, the overall properties of rock are unique in each <br />environment, and are strongly influenced by local factors, such as cones <br />of weakness. These factors, or defects, are generally planar and often <br />consist of joints, faults, bedding planes, and the like. Because of the <br />lowered strength caused by these defects, they are almost invariably <br />involved in failure situations. Ground water exerts both uplift and cleft <br />pressures and can have a detrimental effect on the stability of the mine <br />wall slopes. <br />WAWRHLEfl Project 0807 II-1 <br />& RSSOCIAI6 . <br /> <br /> <br />• <br />