Mapping of decades-old underground coal mine workings using electrical resistivity tomography

In this paper, we discuss the necessity of mapping of characterisation of unapproachable underground mine workings by electrical resistivity tomography (ERT). Initially, numerical forward modelling is conducted for considering the possibilities of water fill and air fill void in old workings using Wenner–Schlumberger (WS), dipole–dipole (DD) and inversion of joint of both arrays (WS+DD). Considerable accuracy of cavities dimension, depth and extensions could be recovered from data inversion of joint of both arrays (WS+DD). In field, 2D ERT survey was conducted along three parallel profiles using said configurations over Jharia coalfield, India. Inversion of joint of both arrays was introduced during data analysis for propensities of better demarcation of underground mine workings characterisations under complex geological formations. Furthers, pseudo-3D model was also done by merging 2D ERT parallel profile data for improved visualisation of 3D resistivity distributions of surveyed area. High resistivity contrast in 2D ERT model and 3D volumetric iso-resistivity model provided comfortable guidance in the investigation of possible continuity of barrier between caved panels of XVIA seam. Moderately low resistivity indicated anticipation of XVII seam working filled with water and also validated through the existing mine plan. Thus, interpretation of 3D data eventually helped in convincing outcomes.