Analysis of structural instability movement of hard overburden and its influence mechanism on rockburst

A case study was performed at the 13200 working face of Gengcun Coal Mine to investigate the structural instability movement of hard overburden.A structural instability model of the hard rock stratum was constructed to,analyze the structural characteristics,structural formation conditions,structural instability scale and structural instability release energy of hard rock stratum.Calculation formulas were proposed to determine the control effect of hard rock stratum instability on rockbursts.The results show that there is free space under the low and medium hard rock strata of 13200 working face,which has the conditions for the formation of structure.There is no free spaceunder the high-level hard rock stratum and there are no conditions for the formation of structure.According to the borehole columnar shape of 13200 working face and its physical and mechanical parameters,the number and location of key layers of overlying strata were determined,and the instability scale and instability energy release of hard rock structure of the working face were calculated.The calculation results show that during the mining period of 13200 working face,the release energy of initial instability and periodic instability of low and medium hard rock strata exceeds the critical energy of rockburst,which is the main influencing factor of rockburst in working face.The super thick conglomerate in the upper part of the high-level hard rock stratum will not collapse and thus does not directly control the occurrence of rockburst,which is the secondary influencing factor of rockburst in the working face.The key is to reduce the occurrence of rockburst by reducing the instability scale of low and medium hard rock structure and the energy released.The research results can provide an reference for the control of rockburst in other mines with similar hard rock conditions.