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It was not possible to obtain test data on the roof shale from <br />,~ Test Boring No. 3, due to its very limited thickness and the poor <br />quality of the core obtained in that zone. We did, however, obtain <br />data from similar shale materials from Test Boring No. 4 located <br />below the burned zone. <br />In the entry and portal area, the influence of the burned zone <br />is very significant. The coal seam itself is absent with only a thin <br />deposit of ash remaining and an open void present. The shear strength <br />of the rock above the burned area appears to have been reduced sub- <br />stantially. The unconfined compressive strength of the sandstone <br />layers was observed to drop something on the order of 503. Similarly, <br />the unconfined compressive strength in the shale layers was observed <br />to drop something on. the order of 47~. Based on an assumed typical <br />value for modulus of rupture in the shale materials on the order of <br />600 psi, the modulus of rupture in the burned zone could have dropped <br />to as little as 78$ of the original value. <br />Due to conditions in this area, we would not recommend the use <br />of roof bolting for permanent support. Instead, we would recommend <br />some form of structural lining. A chart has been provided in the <br />Appendix of this report (Appendix C) which shows an estimate of anti- <br />cipated design pressures to which such a lining might be subjected, <br />as a function of overburden depth, to be utilized in liner design. <br />This chart attempts to account for ground arch effects in areas of <br />deeper cover. <br />With regard to the mine roof outside of the burned area, Test <br />Boring No. 3 would indicate reasonably competent strata for which <br />rock bolting for roof reinforcement should be suitable. Percent <br />3 <br />