Substantiating the parameters for selecting a pillar width to protect permanent mine workings at great depths

Application of a method to protect permanent mine workings by large pillars requires thorough analysis of geomechanical processes aimed at providing stability for a mine working during its long-term operation. The purpose of the paper is to study the processes of coal rock mass deformation to substantiate the selection of the protective pillar width. The examples to be considered are represented by mining-geological conditions of a central panel of PJSC Colliery Group "Pokrovske" where four permanent mine workings are planned to be driven. To substantiate the width of protective pillars, geomechanical stability of mine workings have been assessed in terms of the effect of stoping operations of the adjacent longwalls of the block and beyond their effect. It has been shown that insufficient dimensions of a support pillar result in considerable influence of stoping operations on the stability of permanent mine workings. Along with the increasing dimensions of a support pillar, the pressure in the rocks around the permanent inclined mine workings decreases, and the support load decreases as well. In terms of the appropriate dimension of the support pillar, the boundaries of the effect become smaller; the bolting and frame support provides completely the required mine working stability.