Study on in-situ stress evolution law of ultra-thick coal seam in advance mining

The law of stress evolution in advance mining is the basis of roof control in super thick coal seam，but the research results of stress evolution in field mining process are lack at present.Based on the No.8309 working face of Tongxin Mine in Tongmei Group，the insitu measurement of the evolution rule of mining stress in extra thick coal seam is carried out.The field test results show that: with the advance of the working face，the disturbance intensity of coal and rock in front increases，the bearing pressure gradually rises from the original rock stress to the peak strength，and then decreases to the residual strength with the destruction of coal and rock； the lateral horizontal stress shows a steady-state decreasing trend in stages.According to the law of support pressure，the coal and rock in front of the mining face have the characteristics of disturbance zoning: the area 200 m in front of the working face of the experimental point is undisturbed； the area 100～200 m in front of the working face is weak disturbance； the area 50～100 m in front of the working face is strong disturbance； the area 50 m in front of the working face is violent disturbance.Combined with the disturbance intensity of different areas in front of the working face，targeted zoning support measures are proposed advise.The research results can provide guidance for the laboratory test of disturbance stress path and also for the safe-efficient mining of extra thick coal seam.