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The focus of the study was to evaluate the rock strata transformation above an underground mine panel during pre-and-post mining based on an electrical resistivity tomography (ERT) geophysical technique. The data were acquired using two electrode arrays (i.e., pole-dipole and Wenner-Schlumberger [WS]) with electrode spacing of 6 m up to 570 m in length. The resistivity data were digitally processed through RES2DINV software. The formation of fractured rock in the overburden caused by underground mining operations was clearly distinguished by resistivity anomalies observed using the pole-dipole array. Variation in the hydrogeological condition in the strata was also assessed during the pre-and-post mining conditions. The impact of compression and tension generated in the strata as a result of extraction of coal and subsidence in the overburden rock was observed through prominent resistivity variations observed in an inversion modelling of the WS true resistivity profile. The influence of surface topography in the near surface top weathered rock was also distinctly outlined by the resistivity measurements. ERT is a strong tool capable of providing valuable information regarding strata deformation caused by mining.

Water management is a strategic factor in old coal mine working areas due to disturbance in the aquifer caused by subsidence resulting in drying of wells and streams. Cavity formation due to underground mining leads to roof fall, heaving of clay floors and collapse of coal pillars in soft clay floors. Logging of water in old mine workings is a common phenomenon especially during rainy season. Mine water is extensively used in various mining activities, and hence, a study has been conducted in part of Jamadoba 6 and 7 Pits, Jharia coalfield, India, to assess the hydrological condition during and post-monsoon. Initially, a conceptual model has been prepared to identify the possible sources of water including its path entering into old mine workings. Electrical resistivity tomography (ERT) i.e. Wenner-Schlumberger configuration with quality factor 5 has been adopted as it is effectual and reliable in detecting subsurface cavities at shallow depth and the possible path of transmission of subsurface water into the mine void with season variation. The study helped in identification of abandoned incline, porous and permeable strata conditions. The correlation of the resistivity variations is observed to be in close approximation with working plans and available borehole lithology. This technique proved to be suitable for adopting such studies.

Old mine workings, mainly hidden galleries, goafs, shafts etc may pose a great threat to the local environment and also for future mine development. The present study mainly deals with delineation and mapping of old mine workings over Tikmani-Gareriya section, a part of east Basuria colliery, Jharia coal field, India using state-of-the-art 64 electrodes and 61 channel FlashRES-Universal electrical resistivity tomography (ERT). ERT data have been acquired along a line at 5m electrode spacing covering total profile length of 315m using Wenner, Schlumberger, Gradient and Dipole-Dipole arrays over a known old mine working. Further joint inversion of all combined arrays has also been carried out using 2.5D resistivity inversion program to combine the relative advantage of all arrays for producing superior results. The acquired data have been analysed using four different thresholds for all arrays with quality factors 15, 10, 5, and 1; each with 60mA current. 2D inverse resistivity models generated using Joint inversion of all combined arrays with quality factor 5 provides best result for delineation of coal pillars, galleries and goafs followed by Gradient, Schlumberger, Dipole-Dipole and Wenner arrays with same quality factor. Coal pillars have been identified with relatively high resistivity anomaly whereas galleries and goaf have been delineated with relatively low resistivity anomaly. The estimated range of resistivity variation of coal pillars have been well corroborated with published results. The results prove the efficacy of the ERT technique for detection of old mine workings.

Analysis of non-uniqueness model in resistivity imaging data is vital in inaugurating the consistency of models. Nevertheless, such analysis is moderately unusual in resistivity imaging data set. Electrical resistivity tomography (ERT) technique is being constantly used in many scientific areas including engineering, environmental and archaeological survey. Primarily, the inversion algorithm techniques are employed on synthetic model data set with and without some random Gaussian noise, and its validity is tested by filed data set. The study was conducted in the premises of Central Institute of Mining and Fuel Research (CIMFR), Dhanbad by laying an ERT profile of 480 m length with 5 m electrode spacing using Syscal Pro (Iris instrument) resistivity meter. Two standard arrays were used in this study namely Wenner-Schlumberger and dipole-dipole array. The data set was mixed to a single array to achieve better resolution and enhanced clarification. On processing data by Prosys-II software, it was exported in Res2Dinv software for inversion. In this context, data was inverted by different algorithm techniques i.e. least square (L2-norm) and robust inversion (L1-norm). Exemplary results related to the heterogeneity of the resistivity structure within the high and low resistivity anomaly were obtained by robust inversion method. The obtained results are in broad agreement with the simulation model.

Land subsidence is a serious problem in Indian coalfields due to old underground mine workings. Unfortunately, most of these are uncharted as no mine plans are available. The hidden galleries, goafs, shafts etc. may pose great threat for future mine development as well as to the local environment. The mine workings should be charted to undertake an effective preventive action. In the present study, 2D electrical resistivity tomography (ERT) technique has been used to detect underground mine workings, mainly air or water filled galleries. Initially, the whole exercise has been executed through a synthetic model study. Gaussian random noise of 5mV/A has been added with synthetic data to demonstrate field condition which provides realistic results. ERT survey was conducted over a part of Jogidih coal mine of Jharia coal field in India for a first time. Four electrode configurations, Wenner, Schlumberger, dipole-dipole and gradient were considered for this study. The results indicate the presence of sub-surface water and air filled cavity due to high resistivity contrast with surroundings.

The present study deals with groundwater prospecting in hardrock terrain. Initially, the Wenner–Schlumberger array and the dipole–dipole array data have been acquired using Syscal Junior Switch-48. Furthermore, data acquired using both arrays have been merged using Prosys-II data handling software for the inversion of the cumulative data for possible mapping of water-bearing fracture rock masses with different structural distribution in a complex geological environment. The data have been analysed using RES2DINV software, based on the smoothness constrained least-square technique. Two numbers of 2D electrical resistivity tomography profiles (AA $$'$$ and BB $$'$$ ) have been selected over an official colony of the Turamdih uranium mine for groundwater prospecting, which is located at about 24 km west of Jaduguda, Jharkhand, India. High-resistivity features associated with a dyke-like structure have been delineated in both the profiles. Three low-resistivity features have been delineated as water saturated alluvium/aquifers in profile AA $$'$$ . A low-resistivity feature associated with the water-saturated fracture zone has been identified in profile BB $$'$$ , which is well correlated with the surficial location of an ephemeral channel at the bottom of the hill across the slope. It is observed that geoelectric sections generated by the inversion of cumulative data of both arrays provide superior results compared with the Wenner–Schlumberger and dipole–dipole arrays, separately.

This paper deals with severe issue of groundwater crisis over a part of hard rock terrain in the premises of Central Institute of Mining and Fuel Research (CIMFR), Dhanbad, Jharkhand, India. The goal of this study is delineation and mapping of fractured rock mass for groundwater exploration. Generally, fractured rock formation is the only source of groundwater in hard rock terrain. Electrical resistivity tomography (ERT) survey was conducted along three profiles over different parts of CIMFR premises using Wenner–Schlumberger and dipole–dipole arrays. Combined inversion of both arrays has been carried out during data analysis for better delineation of fracture rock masses in the complex geological environment. Two water-saturated fracture zones have been identified for the availability of groundwater, which has been confirmed by direct borehole drilling. This proves the effectiveness of ERT survey by combined inversion of both arrays for delineation of fracture zones.

Unauthorised coal mining activities may result in development of hidden hollows, rat holes, galleries, goafs, shafts etc., which pose great threats of land subsidence, fire, water flooding leading to severe environmental hazards, health problems and safety issues to the local people. Present study deals with delineation and mapping of unauthorised coal mine voids/galleries over an abandoned old mine around Khudia open cast mine, Nirsa, Raniganj coalfield, India. Electrical resistivity tomography (ERT) study comprising Wenner, Schlumberger, Dipole-Dipole, and Gradient arrays has been carried out along three parallel profiles over the affected area. Further joint inversion of all combined arrays has also been carried out using 2.5D resistivity inversion program, to combine the relative advantages of all the arrays, for producing superior results. 2D ERT sections have been generated for the filtered data sets with a constant quality factors and two different current thresholds. The best results have been obtained, from joint inversion of all combine arrays for the filtered data with higher current threshold. The observed resistivity anomalies are well correlated with the depth of coal seam occurrences as observed in the borehole litholog of nearby area. Finally, a geoelectric model of four unauthorised coal mine galleries has been established with their extension and orientation over the study area. The results demonstrate the suitability of the ERT technique through joint inversion of all combined arrays for characterization of illegal coal mine workings.

The present study deals with the coal fire mapping of East Basuria Colliery, Jharia coalfield, India, using the magnetic method. It is based on the fact that rise in temperature would result significant changes in magnetic susceptibility and thermo-remanent magnetization (TRM) of the overlying rocks. Magnetism increases slowly with the rise of temperature until the Curie temperature. Generally, rock/ overburden loses magnetization and becomes paramagnetic due to heating to Curie temperature, which results with significant reduction in magnetic susceptibility. However, magnetism increases significantly after cooling below the Curie temperature. Several data processing methods such as diurnal correction, reduction to pole (RTP), first and second vertical derivatives have been used for analysis of magnetic data and their interpretation. It is observed that the total magnetic field intensity anomaly of the area varies approximately from 44850 to 47460 nT and the residual magnetic anomaly varies approximately from −1323 to 1253 nT. The range of the magnetic anomaly after RTP is approximately 1050–1450 nT. About 20 low magnetic anomaly zones have been identified associated with active coal fire regions and 11 high magnetic anomaly zones have been identified associated with non-coal fire regions using vertical derivative techniques.

The present study deals with the characterization of subsurface coal fires of East Basuria colliery in Jharia coal field, India using tilt derivative and downward continuation of magnetic data. Magnetic data processing methods such as diurnal correction, noise removal, reduction to pole, tilt derivative and downward continuation have been used to process the data and for the interpretation of results on the basis of magnetic properties of overlying materials which change with the temperature variation above or below the Curie temperature. Most of the magnetic anomalies are associated with coal fire and non-coal fire regions which are correlated with tilt-derivative anomaly and corresponding downward-continued anomaly at different depths. The subsequent surface and subsurface characteristics are explained with good agreement. Approximate source depth of principal anomaly inferred from tilt derivatives method are corroborated with multi-seam occurrences, mine working levels and surface manifestation which are also correlated well with 3D model of downward continued anomaly distribution.

Coal fires pose a serious threat to the environment and it is important to detect them at an early stage for their control and hazard mitigation. The present study addresses an innovative approach for depth estimation of coal fires using self-potential (SP) method and its inversion through particle swarm optimization (PSO) technique. The suitability of PSO inversion technique for self-potential data has been established using synthetic models of spherical and cylindrical objects, and inclined sheet with large horizontal extent as causative sources. Present study reveals that the geometry of subsurface coal combustion is possibly similar to inclined sheet with relatively large horizontal extension. The depth of coal fires has been estimated using PSO inversion of SP anomaly data over the East Basuria colliery, Jharia coal field, Jharkhand, India with good accuracy. The results of the analysis are compared with borehole lithologic log data which proves efficacy of the PSO inversion technique.

The present study deals with delineation and mapping of subsurface voids which are very common around the Patherdih colliery of Jharia coal field, India. These are caused by coal fire and old unplanned/illegal mining activity. Initially, a conceptual model of void formation associated with coal fire has been proposed. The burning of coal leads to the void formation due to volume reduction because of transformation of coal to ashes. It is supposed to have significant resistivity contrasts between bedrock i.e. mainly sandstone/clay stone/shale etc. and void space, which are filled with ashes generated from burned coal seam. Field situations have been simulated through forward modeling and the data generated by gradient and dipole–dipole arrays have been corrupted by 5 % noise. The simulations have been carried out for two voids with varied resistivity. The inversions of the data for both the arrays bring up the dimension of the void within reasonable accuracy unlike its resistivity. In fact, the considered resistive void seems to be a conducting void. In the present study, data have been collected by a state-of-the-art FlashRES-Universal electrical resistivity tomography (ERT) instrument, which have 61-channel and 64 electrode data acquisition capacity. ERT sections have been generated over two profiles using Wenner, Schlumberger, gradient, dipole–dipole and joint inversion of all combine arrays. Different resistive anomalous features with resistivity of about 300–200 Ωm have been delineated in both profiles. These are associated with voids at the depths of about 23–25 and 45–54 m generated by burning of coal seams XIVA and XIV, respectively. The obtained results are in broad agreement with the available litholog and surface manifestation of coal fire. The results prove the efficacy of the ERT technique for detection of voids associated with coal fire.