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11 Gated in most unfavorable topographic and geotechnical con- ' ditions and it should be eliminated if the number of mine entries is reduced. Entries 2, 3, and 4 are located in a more favorable topography. assuming that the portal cuts remain at approximately the same locations as indicated. Future changes in the bench elevation and the cut locations could of course ' change these conclusions. t Entries 1, 3, and 5 were selected for slope stability analy- ses; the method of analyses is decribed in the Appendix A. Plate ' No. 7 shows a back analysis (a back analysis is the stability analysis which assumes the natural slope without any excavation; ' it either assumes the safety factor equal to one or it calcu- lates the safety factor for known strength properties) of the ' slope at mine entry 5 prior to any excavation. The back analysis shows that if we assume the soil strength parameters as they were obtained by the soil testing and "saturated" conditions with ' ground water coinciding with the topographical surface, the minimum factor of safety is on the order of 1.0 (0.985 exactly). ' This confirms the earlier discussed condition of marginally stable slopes under saturated conditions. It also means that no ' unsupported excavations should be performed on such a steep slope. ' Results of further analyses of the same portal are shown on Plate 8. A first analysis was run assuming that a cut was ex- ' cavated (saturated conditions, Case 5-2). As it could be ex- nected,the minimum factor of safety is slightly lower than in t the back analysis (0.932); it is evident again that the exca- j vation is not feasible. Two further cases (5-3, 5-4) assume the ' ground water lowered to 10 and 20 feet below the surface. Mini- mum factors of safety increase to F.S. = 1.321 and 1.535. For ' fully drained conditions, the factor of safety increases to 1.758. We feel that for the permanent solution, safety factors ' higher than 1.5 should be obtained. ' ~ oeo«rvo caawuw, e¢