Stability of the coal seam roof during the sudden collapse of lateral rocks

Abstract

Purpose. To study the effect of dangerous manifestations of rock pressure (in the form of sudden lateral rock collapse) on the state of the coal seam roof developed in difficult mining and geological conditions by various methods of controlling mining pressure and protecting workings.Methods. Analytical studies were carried out using the basic principles of the theories of elasticity, classical mechanics, and oscillations. The roof rocks were presented in the form of a beam whose free end has different versions of support.Findings. As a result of the conducted studies, it was established that in the case of caving in the stratified rock strata, in order to preserve mine workings in the operational state, roof rocks should rest either on filling mass or yielding supports. This will reduce rigidity of the given system and the magnitude of the acting force during the strike of stratified rocks on the beam, due to the increase in the time interval between the application of this force and the maximum deflection of the roof rocks of the developed seam.Originality. To determine the stress state of the immediate roof rocks of the developed coal seam, it is necessary to take into account rigidity of the system under consideration. The rigidity value is determined not only by the static deflection of the structure (beam), but also by the yielding capacity of the support under consideration. Practical implications.The proposed approach to predicting stability of mine workings will contribute to the creation of safe working conditions during mining operations in complex mining and geological conditions, including sudden collapses of lateral rocks.

Experimental characteristics for deformation properties of backfill mass

“…In real conditions of mining the coal seams with backfilling of the mined-out space, the backfill mass perform the functions of a supporting structure. They provide supporting of side rocks in the mined-out space behind the longwall face and prevent dangerous rock pressure manifestations, such as sudden collapse of the stratified rock stratum [18]. The world experience of mines and pits that use backfilling of the minedout space to protect mine workings and surface objects indicates that a change in the geometry of the backfill mass significantly influences on its compressibility.…”

“…In this research, the values of the rigidity coefficient С (N/m) of backfill mass is determined based on Hooke's law [18], taking into account the crushed rock of different fractions, when:…”