Ground movements over longwall workings in the Kamptee coalfield, India

Subsidence investigations were conducted over three superimposed longwall panels in the Kamptee coalfield of Central India. The extracted contiguous seams were lying below a water bearing unconfined aquifer. Filling of voids with sand hydraulically was practised to avoid a sudden inrush of water into the under-ground workings through ground-movement induced cracks. The non-effective width of extraction varied between 0.55 and 0.61 times the thickness of intact rockmass in the overburden. The maximum subsidence, slope, compressive and tensile strains were 9% of extraction thickness, 6.1, 6.6 and 5.3 mm m−1, respectively. The angle of draw was influenced by the presence of a fault and composition of superincumbent strata. The ground movements lowered water table by 6.5 m in the unconfined aquifer due to the mining.