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<br /> <br /> <br />-11- <br />• PILLAR DESIGN - UTE WATER CO. AREA <br />. The pillars designed to protect the Ute Water Co's. surface facilities are based <br />an the overall test results and an the nearby 3rd East Section test results. These <br />r pillars ore designed to carry full (maximum) tributary ores loading, which assumes ro <br />load could be transferred by arching to the larger, and safer, adjacent entry barrier <br />and drain pillars. <br />Figure 4 and Table 4 present the results of these analyses over the full range <br />of depths which could potentially effect the surface facilities. The recommended pillar <br />• sizes are designed to exceed the stability of the pillars in Panel "G." The degree of <br />increase in the factor of safety exhibited by Panel "G" pillars is presented in Table <br />5. These increases in factor of safety represent minimum increases. The use of 2nd <br />East physical properties to evaluate the strength of Panel "G" pillars and then the 3rd <br />East physical properties to evaluate the pillars under the Ute Water Co's. surface <br />facilities increased the indicated factor of safety. The percentages are shown on Table <br />5. These later increases are probably somewhat more reaiistie. <br />The result of this analysis is a recrommendation to use 14 by 80-ft pillars for <br />the area that rnuld conceivably effect the Ute Water Co's. surface facilities. This <br />area extends 100 ft outside any structures or water lines that must be protected. This <br />in effect assumes an mgle of draw of 22° and an average depth 'of 250 ft. The high <br />proportion of sandstone visible in outcrops above the mine and the general decrease <br />in the angle of draw with increased proportions of sandstone in thG overburden above <br />' • coal seams (Abel and Lee, 1980) prompts this recommendation. It would be more <br />conservative to employ the NC8 (1975) 35 angle of draw which applies to the British <br />coal measures, containing 2/3 to 3/4 shale. It would be appropriate to determine the <br />• lithologic distribution in the overburden above the Cameo "8" seam. <br />