Analysis of Maingates Stability in Step Coal Seams During Protection by Coal Pillars

Abstract

The purpose of the work. Studying the stability of haulage drifts of steep coal seams with the method of protecting coal by pillars. An integrated approach was used as research methods, including: a full-scale experiment, analytical studies, interpretation of the results obtained. To assess the durability of mine workings, full-scale experiments were carried out to study the manifestations of rock pressure in the haulage drifts with the method of protecting coal by pillars, when the magnitude of the change in the cross-sectional area and the convergence of side rocks on the contour of the development workings along the length of the excavation section was established. It is fixed that at the maximum relative deformation of coal pillars (ε ≈ 0,7), the loss of the cross-sectional area of the haulage drifts at a distance of l ≥ 60 m behind the working face is more than 50 %, which does not correspond to the operational state of the workings. When studying the deformation properties of protective structures, it was found that after their deformation by 10–20 %, an increase in the convergence of side rocks in the haulage drifts begins, a distortion of the shape and loss of the bearing capacity of coal pillars. The distortion of the shape of the security structures contributes to the intensification of the displacements of the roof on the contour and is accompanied by a deterioration in the durability of the haulage drifts in the excavation areas of the coal mine. It has been proved that on a steep drop, with the method of protecting the haulage drifts with coal pillars, the change in the cross-sectional area of the excavation occurs along a linear relationship with an increase in the length of the excavation section due to the distortion of the shape and loss of the bearing capacity of the security structures. To improve the safety of miners in the excavation areas of coal mines developed steeply falling coal seams, it is recommended to abandon the method of protecting the haulage drifts with coal pillars. To avoid emergencies associated with the collapse of the roof, it seems advisable to use purposeless methods of protection – flexible structures or backfilling of the goaf.