PREDICTION OF SUBSIDENCE DUE TO COAL-MINING IN RANIGANJ COAL FIELD, WEST-BENGAL, INDIA

Raniganj coalfield is in a major coal-producing area and suffers subsidence problems due to underground mining. The occurrence of a thick coal seam at shallow depth is the main reason for the subsidence and as a result collapses have occurred in many coal mines in recent years. We attempt to predict the subsidence occurring in Indian coalfields in general and, in particular, in the Raniganj coalfield using a visco-elastic model. In this model, we have considered the coal seam as a beam resting between visco-elastic media which deform due to transverse shear after mining. The governing equations have been solved for two cases, coal mines with (a) rigid (hard), and (b) flexible (soft) overburdens. The ground subsidence has been computed for two coal mines. The computed subsidence profiles of the Ratibati and Shivadanga coal mines of the Raniganj coalfield are compared and the results show a reasonable match between the predicted and observed subsidence in the case of Ratibati coal mine. In the case of Shivadanga coal mine the predicted subsidence profile is found to be larger than the observed profile. However, the bottom of the observed troughs is found to match the predicted troughs. Detailed analyses have been carried out to investigate the effect of mine parameters on the subsidence.