Study On Tongxin Mine Dual Seam Strata Fracture Evolution And Control Technology Research

There are double system coal seam of the top floor is hard in the Datong mining area. At present, the upper coal resources of Jurassic was exploited completed, the main mining 3-5# coal seam of Lower Carboniferous Permian, the stable broken roof structure of the Jurassic has been activatied again in the process of 3-5# coal seam mining unger the goaf. The pressure of unstable roof was passed down coal pillar, the stress field near the working face of bottom coal seam was changed and partial pressure was increased, which may induced rock burst and other related disasters. Based on the 8207 working face occurrence conditions in Datong mining area, the evolution law of overlying strata settlement,separation and fracture in the process of coal mining was analyzed and the mechanism of "activation" instability in the roof of Jurassic coal seams was revealed by combination of theoretical analysis, similar material simulation and field monitoring, the main conclusions are as follows:(1) Based on Tongxin mine geological exploration data, at the production site selected cores, and the indoor test was done, the main physical and mechanical parameters of Tongxin mine 3-5# coal seam roof strata. On the basis of this, spatial and temporal evolution of roof break of double coal seams was Simulated and the evolution law of overlying strata subsidence, separation and fracture of the double coal seams is analyzed by similar material simulation test.(2) The mechanical model of the broken roof "activation" instability was established, and the mechanism of the roof failure of the Jurassic coal seam group was obtained; the support load at different stages of 3-5# coal seam mining was calculated and influence of residual coal pillar in Jurassic coal seam on support pressure of 3-5# coal seam.(3) The influence range of residual coal pillar stress concentration was obtained by site mine pressure monitoring of the 8207 working face of Tongxin mine in Datong mining area, support resistance formula was verified by the analysis of the end resistance. On the basis of this, it is proposed that the stress concentration of the lower coal seam can be reduced by the technology of mining optimization, hydraulic fracturing and mining filling, so as to ensure the safe exploitation of the 3-5# coal seam in carboniferous.