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• zones of weakness, however, because orientations are nearly horizontal, they would not be <br />considered a condition of potential failure by themselves during mining activities. <br />From observations of the Laramie Formation at the Keenesburg Mine (Sec 25, T3N, <br />R64W) and core obtained during exploration activities in Sec. ]7, T3N, Rb3W, the clay- <br />shales exhibit a condition of stress release within the formation. Slackened sides or <br />"micro-faults" have very random orientations and are generally continuous for only a few <br />feet. Joint patterns have also been observed in areas of stress due to minor warping and <br />buckling of the Laramie formation clays. These joint patterns have been traced in the A- <br />Pit I~ighwall at the Keenesburg Mine and can be up to 35 feet in length. Displacements <br />along these near vertical failure planes are typically 0 ft. - .5 R., but have been observed to <br />be 5 ft. - 15 R. in areas of more intense faulting. <br />As a result of weathering, three zones occur within the clay-clay shale sequence of the <br />Laramie Formation. The first one, which underlies the unconsolidated eolian sands, <br />consist primarily of a disintegrated, oxidized and weathered material generally 0 ft. - 10 R. <br />in thickness, usually silty and sandy in nature. <br />The next underlying zone, which is approximately 2 - 20 feet in thickness, exhibits <br />I moderate disintegration and contains numerous joints and slackened sides. This zone <br />generally has undergone moderate weathering and has become weaker, and is especially <br />i unstable in the presence of water. <br />• The third and lower most zone has more widely spaced joints and slackened sides. Surface <br />moisture content and thus the degree of weathering is variable and not as extensive in this <br />zone. This material exhibits an overall higher strength than the overlying weathered clay <br />materials. <br />No preferred orientations of slackened sides, joint planes or fault plane surfaces have been <br />determined in the area, however, regional geological structure may suggest strike <br />orientations of larger features faults, etc.) in anorthwest-southeast direction. <br />Drill hole logs for the Keenesburg Mine area can be found in Appendix G. Physical and <br />chemical properties of the stratum within the overburden and interburden and chemical <br />analysis of the coal seam are found in Appendix H. <br /> <br />46 5/96 <br />