The paper deals with geotechnical study for the final slope of 140m high final open pit mine slope at SE Block of West Bokaro Collieries, Tata Steel. It is mainly characterized by sandstone and coal. The bulk density and direct shear tests were conducted at Rock Mechanics Laboratory of CIMFR on the samples collected from the field. The geotechnical mapping was done on the exposed benches of the quarry as per the norms of International Society of Rock Mechanics (ISRM 1978). The kinematic analysis was done to determine the critical orientation of structural discontinuities. After identifying kinematically possible failure modes, detailed slope stability analysis was carried out by GALENA software based on limit equilibrium method. The present study reveals that the 140m high final slope could be designed with 47 degree overall slope angle. The sensitivity analysis shows that the influence of water is also alarming. It was recommended that the slope should be kept in drained geomining condition by providing suitable drainage and keeping drainage effectively maintained.
The geotechnical study was conducted for optimum slope design of final highwall at SE Quarry, West Bokaro. The Quarry-SE is situated in Jharkhand state and is owned by M/s. Tata Steel Ltd.
The rock discontinuities were mapped at the exposed benches of the pit as per the norms of International Society of Rock Mechanics (ISRM 1978). Geotechnical mapping was undertaken to determine the critical orientation of structural discontinuities. After identifying kinematically possible failure modes, detailed slope stability analysis is carried out by limit equilibrium method. Sensitivity analysis was done to determine the most effective remedial measure for any critical slope.
The slopes of the quarry are mainly characterized by Overburden sandstone and coal. The sandstone is well jointed. The average annual rainfall is around 1400 mm. The eastern part of the pit has been fully developed. The groundwater condition in drained geomining condition of the final highwall slope was considered to be with 30m water table from the pit bottom. It was considered based on field observations, engineering judgment and previous experiences in this type of geomining condition in adjacent mines. The most likely geo-mining condition for the quarry would be drained condition. The undrained geomining condition was simulated by the presence 75m water table from the pit bottom. This condition was considered to arise when the mine management does not implement the remedial measures related with the drainage in totality.