An approach for support design in depillaring panels of coal mines

Abstract

Among different methods of underground mining technology adopted for coal extraction, bord and pillar mining is the most popular and predominant method of underground mining in India. This method is characterised with small capital investment and faster rate of return on capital. Varying geomining conditions demand scientific approach for design of supports in depillaring panels. In view, this there is a decisive lack of judgement on support design, given the geomining conditions. Support design methods in vogue for depillaring districts do not takes into account, among other parameters, the inclination of the coal seam and direction of in situ stress. Thus, there exists a need for research work aimed at investigating the effective role, inter-alia, of direction of in situ horizontal stress and inclination of coal seams to ensure a better condition of roof and efficient design of effective support system. The authors through this paper intend to address similar problems being faced by the industry. Detailed numerical models for one depillaring panel in Thesgora Mine and in two depillaring panels of Kakatiya Khani (KTK)-KTK-1 and KTK-5 Incline mines respectively of Bhupalpalli area under study have been developed. The models are then calibrated using the empirical relations of pillar strength. Stage-wise extraction in the models is carried out to simulate the change in stress and displacement as the mining activity progresses. Based on the geo-mining data and the numerical models, the rock load heights at four strategic locations namely split gallery, slice, junction and goaf edge have been evaluated in all the depillaring panels under study. Generalised equations for rock load height at different strategic locations in a depillaring panel have been developed. The said empirical relations for rock load height have been derived using parametric study of the numerical models developed for depillaring panels of the selected mines. The equations so developed have a correlation coefficient of maximum 87.8 % and a minimum of 80.5%.