THE INFLUENCE OF DEFORMATION PROPERTIES OF SECONDARY SUPPORT STRUCTURES OF MINE GATEROADS ON THEIR RESISTANCE ACCORDING TO THE LENGTH OF THE EXTRACTION PANEL

Abstract

Purpose. To increase the effectiveness of measures to reduce injuries and create safe working conditions for miners in a deep coal mine with steeply inclined coal seams, assess the impact of deformation properties stiffness of secondary support structures of mine gateroads on their stability in the coal-rock strata according to the length of the extraction panel. Methods. To achieve this purpose, the results of in-mine instrumental observations of the stability of haulage roadways under different supporting methods were analyzed, considering the deformation properties of secondary support structures and features of geomechanical processes in the surrounding coal-rock strata during unloading. Results. The conditions for maintaining the mine gateroads within the extraction panel during the methods of supporting practised at the mine were estimated by the magnitude of the convergence of the roof and floor strata on the contour of the haulage roadway and its derivatives. It is determined that in the zone of influence of coal extraction, in the process of deformation of coal pillars or vertical timber sets up to 16-22%, there is a loss of their stability, an increase in the load on the secondary support structure, the intensification of the increase in roof displacements over 0.08 m with a convergence rate of 4.5-5.6 mm/day. In the process of deformation of 4-point chock by 65%, the rate of convergence at the initial stage (30% deformation) increases to 5.1 mm/day, with an average increase in roof displacements to 0.05 m, and then gradually decreases over time, which favourably affects the stability of roof and floor strata and roadways. Reduction of the haulage roadway cross-section when it is supported by coal pillars or vertical timber sets on 45-50% is the result of the destruction of secondary support structures when the rate of convergence of the roof and floor strata along the extraction area is not limited. When supporting the haulage roadway with a 4-point chock reduction of the roadway cross-section by 30% is due to the compression of the secondary support structures, which helps to limit the growth of roof displacements and reduce the rate of convergence of the roof and floor strata behind the working face. Novelty. The estimation of the haulage roadways stability on the steeply inclined coal seams according to the length of the extraction panel is based on the use of regularities of deformation properties of secondary supporting structures of mine gateroads and geomechanical processes in the coal-rock strata when the change in the rate of convergence of the roof and floor strata on the contour of roadways is considered in the zone of influence of coal extraction works. Practical significance. To prevent the collapse of the roof and floor strata in the extraction area of the deep coal mines with steeply inclined coal seams, it is necessary to use yielding secondary support structures of mine gateroads.