Coupling evolution mechanism of mining-induced overlying strata stress field and crack field under extremely thick igneous rock

In order to solve the problem of dynamic disasters like severe surface subsidence,gas drainage well outburst and supports crushing accident induced by overlying extremely thick igneous rock breaking at No. 10 coal seam in Yangliu coal mine,on the basis of crack property analysis of extremely thick igneous rock,this paper investigates the crack development law and mining stress distribution under extremely thick igneous rock by using physical simulation, numerical simulation and theory analysis method. And then some indexes data with working face advancing like the crack development height of igneous rock before and after its breaking,the peak abutment pressure and the maximum height of stress concentration area are obtained. In this research the coupling evolution mechanism of mining-induced stress field and crack field under extremely thick igneous rock is revealed. It can be summarized as coal mining→stress redistribution→stress concentration→crack development→overburden strata break→stress transfer→crack extension→ “arc” separation layer→igneous rock break→dynamic disaster. Thus the “gob backfilling technology-separation layer grouting technology-protection layer mining technology” technical system of disaster prevention is proposed based on stress concentration and crack development control.