Evaluation of the effectiveness of secondary support of haulage drifts based on a comparative analysis of the deformation characteristics of protective structures

Abstract

The object of this study is the processes of managing the state of lateral rocks in the coal rock array with preparatory workings. The influence of deformation characteristics of the protective structures of the preparatory workings on the stability of lateral rocks in the coal rock array has been established. The stable state of the above-the-drift pillars of coal is provided within the deformation resource, which corresponds to the critical level of the specific potential energy of the deformation. The limits of the deformation resource are the range of change in the relative deformation of coal pillars 0.1≤λ≤0.25. When the critical level of the specific potential energy of deformation is passed, at λ˃0.25, there is a relative change in the volume of pillars δλ˃0,1, as a result of which their durability decreases and the state changes. Under such conditions, the residual strength of coal pillars is not enough to limit the movement of lateral rocks, which provokes their collapse. For protective structures made of crushed rock, within the established deformation resource of 0.4≤λ≤0.7, with an increase in static load and cross-sectional area, the specific potential energy of deformation decreases, simultaneously with the relative change in the volume of the embedded material. This is due to the compaction of the crushed rock and an increase in its strength. Regularities of change in the specific potential energy of deformation of protective structures have been established, which, under conditions of uniaxial compression, make it possible to assess, within the deformation resource, their stability. To ensure the stability of lateral rocks in the coal rock array and to preserve the operational condition of the preparatory workings, it is advisable to use protective structures made of crushed rock. This method will limit the movement of the roof and sole in the produced space and avoid collapses.