SLOPE STABILITY ANALYSIS OF INTERNAL DUMP SLOPE IN AN OPENCAST COAL MINE

摘要

Sasti opencast mine of western coalfield limited is located in the west of the Wardha valley coalfields. The area falls within Chandrapur district of Mahsrasira. It is presently mining one coal seam (13 to 18m thick) and the entire mine is capped with a thick black cotton soil of (10 to 20m) [Fig2]. Black-cotton soils are inorganic clays of medium to high plasticity and form a major soil group in central India. Black-cotton soils derive their name because of their colour, it is characterized by its extreme hardness when dry and by its high expansive properties during process of wetting leading to sudden decrease of shear strength parameters. Majority of excavated rocks and black-cotton soil are back-filled In the de-coaled area by both Shovel-dumper combination and Dragline. Following geo-engineering parameters are considered in the stability analysis-a) Geo-mining parameters of mine b) Geo-technical parameters c) Hydro-geological parameters d) Seismic effect of the area and the effect of blasting during rock excavation. In this mine, Dump stands above slushy mixture termed here as interface material. After mining of coal, the competent floor of the mine (which is a medium hard sandstone with a cohesion in the range of 3-8 MPa) is covered with a slushy mixture (interface material) of blasted and fragmented rock, black cotton soil and accumulated water from ground water table. This interface material lying on an inclined mine floor (3 to 5 degree) plays an important role in the stability of these internal dumps. In this mine, interface layer varies from 5 to 15m. This paper presents recommended internal dump slope for varying