ASSESSMENT OF ASYMMETRY AND HETEROGENEITY OF CONVEYOR ROADWAY’S INSTABILITY AT ALL STAGES OF THE LIFE CYCLE: CASE STUDY PRJSC POKROVSKE COLLIERY

Purpose. To study the deformation features of preparatory mining roadways at all stages of their life cycle in the case of PrJSC Pokrovske Colliery. Methods. The research methods employed in the study included instrumental measurement, visual observations and photographic documentation, as well as methods of analysis and synthesis. Results. The time-dependent process of surrounding rock fracturing is a consequence of the synergistic effect of the physical and mechanical properties of rocks and geostresses. Even at the stage of conveyor roadways construction, despite the approximate symmetry of geostresses in the surrounding rocks, frequent asymmetric fractures occur. This asymmetric instability can be explained by the mesoscopic heterogeneity of the rock and small-amplitude geological disturbances. The impact of the longwall mining leads to an increase in asymmetric instability. This is caused by the asymmetry of the stress field, in particular by the formation of abutment pressure, which shifts the vector of maximum stresses in the cross-section of the roadway in the direction opposite to the longwall. Field studies of the deformation process in the PJSC Pokrovske Colliery confirm theoretical views on the deformation process. At the same time, the heterogeneity of vertical and horizontal convergence along the mining route was identified. It was established that the deviations of vertical convergence from the average value exceed the permissible statistical error by more than three times. Local destruction of the mining fastening and deformation of rocks that require additional supporting resources were established. Scientific novelty. Based on the review of literature and instrumental observations of the contour deformation in preparatory roadways, a non-uniform nature of deformation in both the cross section and along the length of the roadways was identified. The fluctuation of the deviation of the vertical convergence from the average forecast value to 16% was determined, which is accompanied by failure of the support system. Practical significance. It was determined that the reserve for ensuring the operational stability of conveyor roadways secured by combined support with multi-level rock bolt systems consists in preventive additional local support in sections of the mine identified as potentially dangerous to instability.