Deep and large opencast coal mines of 400m to 450m depth are considered important to increase the coal production of India. Planning and managing such large open pits depends upon a thorough understanding of geological and geotechnical aspects of the rock strata comprising the overburden column. The experiences of Singareni Collieries Company Limited (SCCL) located in Telangana, India document borehole geophysical logging as an effective means to generate a continuous description of geological and geotechnical strata features from the surface to total drilled depth. Conventional geophysical logs are used to identify the basic lithologies and construct geological maps of overburden strata. The uniaxial compressive strength (UCS) of sandstones is empirically estimated by correlating P wave velocities (Vp) obtained from sonic logs with the laboratory determined UCS value. Acoustic images help determine the location and trend of fractures and minimum horizontal stress directions. Together, these data provide the basis for characterisation of the rock mass and form the foundation for the effective design of stable pit walls in deep sedimentary strata. This paper presents usage of different geophysical logs at the proposed deep pit at Opencast-II Expansion Project of Ramagundam, SCCL.

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