RESEARCH OF THE DEFORMATION CHARACTERISTICS OF COAL PILLARS PROTECTIVE STRUCTURES OF HAULAGE DRIFTS

Abstract

Purpose. Investigate the deformation characteristics of over-track coal aggregates as a way of protecting the preparatory workings and evaluate their impact on the stability of side rocks in the coal massif to ensure safe working conditions for miners in the mining areas. Method. To achieve the goal, laboratory studies of the deformation characteristics of protective structures in the form of whole coal were performed on models of equivalent materials. The models, with the ratio of sample length to width a/b=(1-2), were subjected to uniaxial compression. Results. It has been proven that the potential energy of coal aggregates is a function of their state, which takes into account the change in volume and shape under the action of an external load. It was experimentally established that under conditions of uniaxial compression in the range of changes in the relative deformation of coal aggregates 0.1≤λ≤0.25 depending on the size of the structures used, with an increase in the cross-sectional area of protective structures, the growth of the load continues without loss of their bearing capacity. Within the limits of the established safe deformation resource, the potential energy of overstretched coal units reaches a critical level, at which the stable state of the deformable structures is realised for a short time. At the transition of the critical level of the safe deformation resource, when λ>0.25, there is a loss of stability of the wholes, intensification of the convergence of the side rocks and their breaking, with subsequent collapse. Overstretched cells, within the limits of a safe deformation resource, are able to concentrate the potential energy of compression. The main element in the mechanism of destruction of over-stretched coal units is the critical density of elastic energy, the amount of which depends on their size. Scientific novelty. It was experimentally established that under the conditions of uniaxial compression of superstriped coal units with the ratio of their length to width a/b=(1-2) until the moment they lose stability, between the magnitude of the relative deformation and the change in the cross-sectional area of the used protective structures in contact with the side rocks in the produced space of the coal massif, there is a logarithmic functional dependence that allows determining their safe deformation resource. Practical significance. Coal targets, as protective structures of limited sizes, also have a limited safe deformation resource, which depends on the size of the structure and restrains the use of this method of protection of rollback stretches in the development of steep formations.