Semi-Empirical Model for Predicting Pot-Hole Depth in Underground Coal Mining

Pot-hole subsidence can be induced by extracting underground coal seam at shallow depth and is a matter of great concern. This has been the case in some of the coal mines of South Eastern Coalfields Limited, a subsidiary of Coal India Limited. Many of the old underground coal mines developed by bord and pillar method of mining lying at shallow depth are posing stability concerns to the habitat due to pillar collapse and gallery widening under the creep loading and weathering. This requires a systematic study for developing an in-depth analysis on various parameters which influence pot-hole occurrence and also for formulating suitable predictive models. A study was conducted to analyse the pot-hole subsidence data related to 34 pot-hole cases and develop a semi-empirical model for simulating pot-hole depth. This study was carried out in some of the Indian coal mines during different stages of coal extraction, i.e. development and depillaring. Data analysis indicates that height and width of extraction, thickness of soil and rock layers, weighted density and compressive strength are key contributing parameters for the occurrence of pot-hole subsidence. The predicted results match with the actual pot-hole depth measured in the field, validating the model.