Extraction of coal under a surface water body - a strata control investigation

The extraction of coal seams under built-up structures and especially under water bodies has been a challenge to the miners due to the potential risk of disturbance to the surface. A number of safety and ground control problems are associated with the mining operations under water bodies. These can be dealt with through proper planning for the optimization of coal recovery and systematic strata control investigations. At Godavari khani (GDK) no. 3 incline of the Singareni Collieries Company Limited (SCCL), two panels namely SS-10/1A and SS-10/1B in no. 1 seam, were identified for extraction under the surface water body called Janagaon tank. A feasibility study was carried out by the authors for working these panels, and hydraulic sand stowing method was recommended. Further, strata behaviour monitoring was carried out using remote type geotechnical instruments during the extraction of pillars in one of the panels. The extraction of the pillars in the experimental panel progressed smoothly without any strata control problems. The mine management could extract coal reserves in the panel with more than 60% recovery, which were otherwise unworkable. This paper presents the feasibility of extraction of pillars under the Janagaon tank, and strata behaviour observations made during the actual extraction.