Effects Of Hydraulic Fracturing On Stress Distribution In Mult-seam Mining Condition

In close mult-seam mining, up and down coals mining process will increase the influence ofeach other, the upper coal seam mining will cause the surrounding rock mass of stressredistribution. Thus, before the mining of lower coal seam, the structures of the roof have beendamaged, after the upper coal mining caving, the coal gangue and coal pillar design, will becontribute to forming stress concentration in the section of the bottoms, leading to its stressdistribution and roof structures changing before the mining of lower coal seam, what brings tomany unique characteristics of mine pressure appear. So studying the law of working face rockpressure phenomena of close mult-seam mining is particularly important.In this paper, studied by the theoretical analysis, numerical simulation and field testmethods for the Study on the Effects of Hydraulic Fracturing on Stress Distribution inMult-Seam Mining Condition opens a systematic research, the main work and results are brieflyintroduced as follows:(1) Analyzing the deformation of roadway surrounding rock affected by mining and damageof floor strata, using the slip line field theory to calculate the floor damage depth reduced by thecoal pillar abutment pressure influence.(2) Utilizing the similar material simulation, the paper analyzes the influence of M9-10coalseam working surface strata movement and damaging p rocess after the exploiting of M4-5coalseam of Tun Bao mine.(3) Studing the influence of coal’s strength and the law of mine pressure appearance afterseam water injection, and compareing the compression, tension and shear strength of coal samplein three different moisture content, and giving reason why water injection changes the strength ofcoal from the aspects of mechanical.(4) By using numerical simulation, simulating the coal seam injected water, analyzing theinfluence to the lower coal seam after mining the upper coal seam and appearing changes of mining stope plastic and stress during the mining processes of the lower coal mining.(5) According to the on-site support load measured in the process of mining face, analyzingand summarizing the trend and tendency of mine pressure appearing.