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• <br />E <br />• <br />In addition, BRL has completed point-load tests on selected intervals. These data are in <br />general agreement with the UCS values. <br />3.3.1 C Sandstone properties <br />Because of the thickness of the C Sandstone and its persistence over the entire mine, we <br />summarize site-specific strength data from this horizon. Based on two site-specific tests <br />at BRL-00-IP-67, the C Sandstone has a UCI of 8,700 psi (ranging from 7,600 to 9,900 <br />psi) and a Young's modulus of 1,700,000 psi. These properties are in general agreement <br />with other local data near Terror Creek (MTI2004) and regional data at neighboring <br />properties. Using an engineering classification of intact rock (Deere and Miller, 1966) <br />(table 2), the C Sandstone is classified as having medium strength and a medium modulus <br />ratio. The modulus ratio is obtained by dividing Young's modulus by uniaxial <br />compressive strength. <br />Table 2-Deere's engineering classification for intact rock. <br />Class Description Uniaxial compressive strength, psi <br />A Very high strength >32,000 <br />B High strength 16,000-32,000 <br />C Medium strength 8,000-16,000 <br />D Low strength 4,000-8,000 <br />E Very low strength <4,000 <br />On the basis of modulus ratio <br />Class Description Modulus ratio <br />H High modulus ratio >500 <br />M Medium modulus ratio 200-500 <br />L Low modulus ratio <200 <br />3.3.2 Near-seam intact strength and structure <br />Figure 4 presents detailed geotechnical logs for DD-D9X43-37 and includes lithology, <br />structure, and material properties near both the Upper B and Lower B seams. The <br />structural log indicates the location of geologic discontinuities, including both natural and <br />drilling-induced fractures. Much additional data regarding the condition of <br />discontinuities (including roughness, aperture, and spacing) were collected, but were <br />Maleki Technologies, Inc. Page 9