Numerical simulation of fracture in rock mass affected by the mining and the optimization of high-located auger field parameters

Starting from the urgent need to reduce coal mining face gas concentration and the gob-mining area gas emission,the present paper intends to introduce the numerical simulation of the entire vibrating process of the overlying strata with the advance of stope face in No.6 Hebi coalmine by using Rock Failure Process Analysis software (RFPA~(2D)).The simulation helps us to gain some valuable information about the movement of the overlying strata and the entire process from distortion to damage as well as its damage regularity.Moreover, we have also worked out the height of the fractured zone in overburden strata by the empirical formula.What is more,the results we have gained on the rock-mass damage regularity,we have divided the cracked rocks in the old gob-mining area into three ones,that is, the natural accumulation area,the structure-supporting area and steady compaction area.Statistically speaking,the rock-falling height range of coal face overlying strata tends to stand between 0 to 12.3 m while the fracture zone height range of coal face overlying strata-between 12.3 m to 44 m by comprehensive judgment,according to which,the optimal drainage layer of highly-located auger field should be between 15 m to 34 m from the coal seam roof,vertical interval from drilling end hole position to coal seam roof should stand between 36 m to 38 m,with the horizontal distance from drilling end hole position to return air course standing between 21 m to 44 m.Optimizing the highly-located auger field drainage parameters,it would be easy to make the gas drainage effective in the range of 16 m to 35 m from the drilling end hole position to the coal seam roof.In such a condition, it would be easy to make the average gas drainage scale up to 6.79 m /min.If so,it would be more facile to solve the gas emission problem of the gob so as to ensure the mining safety.The research results we have gained above,when put into trial application of the projects with proper benefits,help us to accumulate more experience in the mine mind-out areas' gas management.