APPLICATION OF A ROCK BUTTRESS IN THE DESIGN OF SLOPES OF A STRIP COAL-MINE ADJACENT TO A HIGHWAY

Eskihisar open pit mine, located at Yatagan, southwest Turkey, produce s thermal coal for a power generating plant. As mining of strips advan ced southwards, instability appeared to be highly critical due to the movements in the southeast wall slopes adjacent to the state highway r unning parallel to the pit boundary. This situation called for an imme diate response to initiate a detailed geotechnical investigation progr am and to redesign the pit slopes. This paper outlines the most probab le mode and mechanism of instability along the southeast wall, as well as field and laboratory studies, results of back analysis, discussion of the data requirements, and results of slope stability analyses per formed to ensure adequate overall stability. The studies revealed that the most critical failures may occur along two or three planar surfac es, by combination of fault, bedding plane, and localized strata steep ening adjacent to the fault. in multiplanar failure mode controlled by faulted blocks. The stability is sensitive to changes in length of th e lower part of the basal sliding surface, as well as to the configura tion and shear strength of black and highly plastic underclay. The eff ects of a buttress of intact rock and slope flattening on the stabilit y are compared and discussed.