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• <br />• <br />6.0 DEVELOPMENT OF DESIGN GEOLOGIC COLOMN <br />6.1 CORRELATION OF LITHOLOGIES <br />Each of the electric and lithologic logs from the five drill <br />holes located within the permit boundary were interpreted and <br />then integrated into one design geologic column to be used <br />throughout the study. The design column represents the major <br />lithologies of the five drill hole logs and their relative <br />positions. This design geologic column, shown in Appendix B, <br />Fiqure B2, consists of 18 formations, four of which are the major <br />coal seams, C - F. Coal seams A and B were not included because <br />of the restrictions on the number of formations allowed by the <br />slope stability model used in this study. <br />6.2 ASSIGNMENT OF FORMATION PROPERTIES <br />All of the rock mechanics testing data was sorted according to <br />relative position in the design geologic column and assigned a <br />formation number. All data for a formation was then analyzed <br />statistically and the standard deviation for the data determined. <br />These are summarized in Appendix A, Tables Al and A2. Formations <br />No. 1, 2 and 14 have no testing data available. <br />The.friction angles and the cohesion intercepts were then <br />determined from the average unconfined compressive strengths <br />using the Empirical Failure Criterion for Jointed Rock Masses <br />developed by Dr. Evert Hoek. For this analysis the rock was <br />• classified as 'Good Quality Rock Mass' and given the empirical <br />11 <br />