A time-lapse study using self-potential and electrical resistivity tomography methods for mapping of old mine working across railway-tracks in a part of Raniganj coalfield, India

摘要

The first coal mining in India was started in the seventeenth century with an unplanned way in Raniganj coalfield, the coal capital of India. The coalfield was possessed by several small private companies which were nationalized in 1973. A part plan of Chanch/Victoria Area, Victoria West Colliery, BCCL, Raniganj Coalfield, India, indicates an underground coal mine gallery/goaf in the Begunia Coal-seam that connects to a Light Casting Factory. It was established as "Barakar Iron Works" in the year 1881 by the government at that time. It is understood that the approaching gallery was used for coal supply to the "Light Casting Factory" by the mining of "Begunia Coal-Seam". Mostly, these are uncharted and very poorly documented with scarce mine plans. So, the present study attempts to explore the location, depth, extension, and condition of the old working gallery through time-lapse monitoring using a combined study comprising of Self-Potential (SP) and Electrical Resistivity Tomography (ERT) techniques. Four SP profiles data along a line and thirteen ERT profiles data in four different lines were collected across the expected site with different station/electrode spacing covering different profile length in four seasons, viz., Summer (May 2016), Monsoon (August 2016), Post-Monsoon (October 2016) and Summer (April 2017). SP data were analysed using simulated annealing (SA) optimization technique for the evaluation of model parameters. The ERT data were acquired using Wenner, Dipole-Dipole and Schlumberger arrays and inversion of the combined data set was performed using the 2.5D ZZRESINV inversion software. Prominent negative SP signature with equivalent low resistivity anomaly have been delineated that possibly indicate the presence of the old mine working/mine gallery. However, the overall results of time-lapse study inferred that the ground is stable. All results are corroborated with available lithology and field photographs.