Research on energy release laws and rock burst prevention and control technology in extra-thick coal seam variable face stopes

YANG Xu; QI Xifeng; ZHAO Zhipeng; MENG Fanran; MA Xiangyu

doi:10.13347/j.cnki.mkaq.20240976

Abstract：Aiming at the problems of difficulty in controlling the stability of surrounding rock and high impact risk in the mining of variable face stope,taking I010206 working face of Kuangou Coal Mine in Xinjiang as the engineering background,FLAC3D numer-ical model and periodic fracture mechanical model of working face roof are established,and the stress and energy evolution charac-teristics of surrounding rock in variable face stope are analyzed,and the mechanism of induced impact caused by overburden failure in working face is revealed,and the technology of hydraulic fracturing roof to relieve danger in advance is put forward,and the pres-sure relief effect is compared and tested.The research results show that:during the mining period,with the increase of the width of the working face,the peak value of the advanced abutment pressure and the degree of stress concentration increased significantly,the peak value of the advanced abutment pressure increased from 13.05 MPa to 16.67 MPa,and the peak value of strain energy density increased from 46.77 kJ/m3 to 96.72 kJ/m3,during the mining process of the working face,due to the presenece of hard roof,large areas of unsupported roof are prone to form,the elastic strain energy accumulated with the roof significantly increases.When the hard roof reaches its limit span,it breaks and releases a lot of energy,which is easy to cause the mine pressure to appear;after the working face is widened,the roof load increases,and the overburden load is transferred to the coal body in front of the working face and the coal bodies inclined to the upper and lower sides of the working face.The stress concentration is higher after the abutment pressure of I010408 working face in B4-1 coal seam is superimposed with the abutment pressure of I010206 working face in B2 coal seam after mining,and the lateral abutment pressure of goaf and the high static load and the high dynamic load of roof caving in a large area are more likely to induce rock burst.In view of the site impact risk factors such as high energy concentration of the roof and strong dynamic load disturbance when the hard roof collapses,the advanced weakening measures of hydraulic fracturing roof are put forward.Through the pressure relief effects of hydraulic fracturing and pre-splitting blasting compared and tested by support pressure and micro seismic data,it is found that after using hydraulic fracturing technology,the weighting step of roof in working face is reduced,micro seismic signals show the characteristics of low energy and high frequency,and the impact risk of working face is obviously reduced,which ensures the safe mining of working face.