Integrated Geotechnical Risk Assessment of Roof–Pillar–Floor Interaction in Underground Coal Mines under Indian Geological Conditions

Abstract

Surface subsidence associated with pillar extraction represents a coupled geotechnical and societal hazard because the severity of ground movement depends not only on mining induced deformation but also on the vulnerability and exposure of surface assets. This study developed an integrated framework for assessing, classifying and spatially managing subsidence risk in Indian coalfields. The framework combined numerical subsidence predictions, field observations, deformation indicators and Geographic Information System (GIS)-based land-use analysis. Probability of surface damage was evaluated using subsidence magnitude, horizontal strain, curvature and geological uncertainty, while consequence assessment considered building vulnerability, infrastructure sensitivity, population density and land use. These components were integrated through a risk-classification matrix comprising very-low, low, medium, high and critical categories. Spatial risk maps were then developed by overlaying numerical subsidence contours with settlements and infrastructure. Jharia and Raniganj emerged as particularly important high-risk environments because mining-related deformation coincided with populated surface areas; Jharia was additionally affected by fire-related weakening and legacy workings. The framework demonstrated that areas experiencing similar deformation could have substantially different risk levels depending on surface vulnerability. Practical risk reduction measures included controlled depillaring, protective pillars, backfilling or stowing, continuous monitoring, structural reinforcement, buffer zones and relocation where avoidance was not feasible. The study concludes that subsidence management should progress from prediction of ground movement alone toward spatially explicit risk management integrating probability, consequence, monitoring and mine-planning decisions.