Integrating physiographical and geophysical analyses for the remediation of a water-filled abandoned coal mining site in Chasnala Colliery, Jharkhand, India

This study explores the comprehensive approach of utilizing physiographical and geophysical electrical resistivity tomography (ERT) investigation to evaluate and address the challenges associated with abandoned, unplanned water-filled galleries in Chasnala Colliery, located in Jharkhand, India. The integrated methodologies facilitate a thorough examination of subsurface conditions, encompassing factors such as geological stability, hydrological fluctuations, and environmental considerations. Utilizing physiographical analysis is of utmost importance in identifying locations with potential risks and developing appropriate site-specific reclamation procedures in the study area. The ERT analysis has successfully confirmed the findings of the physiographical study, revealing the presence of five distinct underground galleries, namely, GL1, GL2, GL3, GL4, and GL5, that are likely submerged in water. These galleries establish connections between the underground spaces and the groundwater, as indicated by their low resistivity values of ~50 Ωm or less. The resistivity measurements exhibit variations that can be attributed to fluctuations in the underground water content. The Wenner, Schlumberger, and dipole–dipole arrays have adeptly discerned the existence of water-filled underground galleries with commendable accuracy. However, the joint array configuration stands out as the pre-eminent choice among these standards due to its unparalleled technical robustness. The findings concurred with the notable correlation between water-filled galleries’ spatial arrangement and shallow groundwater level. The integration of physiographical and ERT data improves the precision of subsurface characterization, facilitating informed decision-making for efficient water management and site rehabilitation in the context of opencast mining.