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t° <br />• Main CressonSlopeEvaluation AdrianBrown <br />3. GEOMECHANlCAL PROPERTIES <br />3.7 Density <br />A total of 35 rock core samples from three core holes drilled into the East Wall of the South Mine were <br />tested for density (Call and Nicholas, 1994). Density of the rocks averaged 143 lb/ft3, or about 14 cubic <br />feet per short ton, with little variation. <br />3.2 Material Strength <br />The intact strength of the materials which comprise the Main Cresson Mine walls was evaluated by <br />laboratory testing. Tests were performed on samples which were recovered from three geotechnical <br />coreholes drilled into the East Wall of the South Mine in 1994 (Call and Nicholas, 1994). The results of <br />the testing are summarized below. <br />3.2.1 Point load testina <br />Point load tests were performed on 21 rock samples, with the results presented in Table 1. <br />The unconfined compressive strength results presented in Table 1 were computed from the load test data <br />• using the following relationships (Hoek and Bray, 1980): <br />IS = P/DZ <br />UCS = (14 + 0.175 D[mm]) * I$ <br />where: P =point load (force) <br />Is =point load index (pressure) <br />D =core diameter <br />UCS =unconfined compressive strength <br />• <br />1385D.980612 g <br />