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2s <br /> <br />RESULTS SIGNIFICANCE <br />ROCK STRENGTH <br />Strength Magnitudes. The rock strength magnitudes are <br />indicative of moderately strong to strong rocks. Relative to <br />individual rock types, the claystones would be classified as lower <br />strength rocks in that they are only about one-half as strong as <br />either the sandstones or siltstones. <br />SZakingJSvelling Potential. The siltstones and claystones <br />both show a potential for water induced disintegration. Under <br />hydraulic mining conditions the humidity may be quite high in <br />the mine and longer term entries may tend to have slaking problems <br />wherever either siltstones or claystones form the immediate roof. <br />Whenever sandstones form the immediate roof no slaking or related <br />phenomenon should occur. The swelling potential is essentially <br />zero except in the siltstones where a very small amount of swell- <br />. ing was detected. All in all, no swelling problems of any kind <br />are expected. <br />COAL STRENGTH <br />Strength Magnitudes. The actual uniaxial compressive strength, <br />triaxial compressive strength and Brazilian tensile strength re- <br />vealed the coal to be fairly weak. However, geologic weaknesses, <br />including cleats and possible drilling damage, may have been re- <br />sponsible for the lower than expected results. The point load <br />tests, however, did give what are believed to be much more accurate <br />results. Based on the point load tests, the coal uniaxial com- <br />pressive strength in the Upper Wheeler Seam is projected to be on <br />the order of 20 MPa. For the Lower Wheeler Seam, the projected <br />uniaxial compressive strength is believed to be on the order of <br />15 MPa. These values are more in line with what should be expected <br />and they should be used for pillar design. <br /> <br />