Assessing the geomechanical state of the main working network state in the case of undermining in the conditions of weak rocks

Abstract

Purpose. Geomechanical substantiation and determination of the parting state parameters for specific mining-geological and mining-technical conditions based on the analysis in order to substantiate the safe operating conditions of the undermined main working network. Methods. An algorithm for studying the state of the undermined main working network includes: analysis of the texture and mechanical properties of parting rocks; mine instrumental observations of the rock pressure manifestations in the main workings; modeling of the parting state using the finite element method (FEM); calculation and analysis of its stress-strain state (SSS) with prediction of the degree of stope operations influence on possible violations of the requirements to safety rules for the main working network operation. Findings. The texture peculiarities and mechanical properties of lithotypes around the network of main workings, the parting and the zone of future stope operations in the lower seam have been analyzed. The current state of the main workings has been studied and, together with the preliminary analysis, the rock pressure manifestations with an emphasis on the probable stope operations influence in the lower seam are predicted. For the final solution of this issue, the parameters have been substantiated and a geomechanical model of a parting behavior has been developed. Having calculated and analyzed the SSS of parting rocks, the conclusion can be drawn about the possibility of safe operation of the main working network. Originality. New knowledge has been gained about the peculiarities of distributing SSS components in the parting, which are distinguished by its large thickness (about 100 m), but by weak strength properties of all lithotypes without exception, which are further reduced by weakening factors of fracturing, stratification and moisture from a large number of coal seams occurring throughout the height of a parting. To study the state of a parting, for the first time, a spatial geomechanical model has been validated and constructed, taking into account all the elements reflecting mining-technical situation. Practical implications. Based on the analysis of parting SSS, the existence of its stable part with a thickness of about 37 m has been proven, which ensures the absence of the stope operations influence in the lower seam on the state of the main working network of the upper horizon, that is, the safe conditions for their operation have been substantiated. The conducted research is the basis for the development of recommendations for ensuring accident-free operation.