Study On The Stability Of Soaking Coal Pillar Under The Influence Of High-strength Mining In Fully Mechanized Mining Face

Xiaojihan Coal Mine is a mine with complex hydrogeology.2# main mining seam is the main aquifer,and the amount of groundwater gushing out in the mining process of the working face is very large..Groundwater has a great influence on the stability of coal pillars.Under the long-term immersion of water,the mechanical properties of coal pillars are weakened and the strength of coal pillars is reduced,so the stability of coal pillars is also reduced.And Xiaojihan Coal Mine is a modern high-yield mine with large mining height and fully mechanized mining technology as its main technology.The working face advances rapidly,the strata pressure appears intensely,and the strong strata pressure occurs frequently,which has a great influence on the stability of coal pillars.Under this background,this paper studies the influence of advance speed and water content of coal seam on the stability of section coal pillar,and the corresponding research results can provide the necessary theoretical basis for the stability control of section coal pillar under the influence of mine water.(1)The experimental results show that the peak strength and elastic modulus of coal increase first and then decrease with the increase of water content and loading rate,and there are critical water content and critical loading rate.And with the increase of loading rate and water content,the failure of coal mass near the peak strength gradually changes from brittle failure to ductile failure.The larger the loading rate,the larger the water content,the more obvious this phenomenon is.(2)The simulation results show that the horizontal displacement and the vertical stress and the area of plastic zone of coal pillar decreases first and then increases,with the increase of the water content of coal seam and the advancing speed of working face.Therefore,there are critical water content and critical advancing speed,which make the stability of protective coal pillar reach the highest level.(3)the theoretical analysis show that coal seam water content directly affects the ultimate strength of coal pillars.When the water content of coal seam is critical,the ultimate strength of coal pillars is the highest and the stability of coal pillars is the highest.The advancing speed of working face affects the weighting strength of working face.When the advancing speed is at the critical advancing speed,the weighting strength of working face is the smallest and the stability of coal pillars is the highest.By introducing the weakening factor ? of water content on the strength of coal body and the influence factor ? of advancing speed on the stress concentration factor of coal body,the stress concentration factor of coal pillar in the section affected by the two factors is redefined as(7)1(10)?(8)(7)1(10)?(8)K.So,the reasonable reserved width of section coal pillar affected by moisture content and advance speed of working face can be deduced by using the existing width model of coal pillar reserved.The formula can roughly estimate the reasonable setting width of coal pillars under different water content and advancing speed of working face.(4)Put forward two pertinent methods that draining the water content of the coal seam to the critical water content state and changing the advancing speed of the working face to the critical advancing speed,and then tests the feasibility of these two methods on the spot.Through field testing,it is found that when the advancing speed of the working face is at the critical advancing speed,the weighting of the working face is the weakest,the damage of the protective coal pillar is the smallest,and the stability of the coal pillar is the highest;when the water content of the coal seam is at the critical water content,the strength of the protective coal pillar is the highest,the compressive capacity is the strongest,and the outburst of two sides of coal pillar is the smallest.