Research On Overlying Rock Fracture Evolution Law And Directional Drilling Gas Drainage Technology In Shaqu No.1 Mine

Because the design of the drainage borehole in the mining fracture zone is based on the movement characteristics of the roof strata in the goaf and the development law of the overlying rock fractures,in practical application,due to the unreasonable design of the parameters such as the borehole layout horizon,the internal dislocation spacing,and the borehole diameter,the problems of low extraction concentration,discontinuous extraction,and short effective extraction time of the borehole often occur,and under the condition of superposition mining of the short distance coal seams,the overlying rock fracture is the main reason The distribution law of fracture evolution will be more unclear.Therefore,in order to deeply and comprehensively understand the movement and fracture law of overlying strata in close distance coal seam group mining,accurately grasp the spatial distribution characteristics of "gas enrichment area" in overlying strata fracture body,and then reasonably design the borehole layout parameters in fracture zone to improve the borehole drainage efficiency.Taking the 4305 rear working face of No.3 + 4 coal seam in Shaqu No.1 mine as the research object,the paper studies the temporal and spatial evolution of overburden mining stress field and displacement field,analyzes the spatial distribution form of overburden mining cracks,accurately divides the favorable areas of gas drainage,and obtains the outburst coal seam group According to the evolution law of overlying rock fracture,the design parameters of directional drilling in overlying rock fracture zone are optimized.The research results show that: the fracture development area is mainly concentrated in the overburden above the cut,above the working face and about 30m-36 m away from the roof of the working face,and there are mutual communication fractures between the fracture development area above the cut,above the working face and the roof overburden fracture development area,and the overall distribution area of the fracture zone roughly presents a fracture trapezoid Based on the critical values of the height,horizontal position and angle parameters of the fracture development zoning in overlying strata,the reasonable layout parameters of the directional long boreholes are given: the layout height of the directional long boreholes in the belt roadway is 28m? 38 m,and the horizontal staggered distance is 14 m ? 30m;the layout height of the directional long boreholes in the track roadway is 28 m ? 42 m,and the horizontal staggered distance is 15 m ? 32 m.Based on the above research results,the design parameters of directional long drilling in overlying strata mining fractured zone are optimized,and the gas concentration in the upper corner of working face and return air flow is monitored in real time.It is found that the maximum values of both are 0.43% and 0.3%,but the maximum values of gas concentration in the two positions are within the safe range,which indicates that the arrangement of directional drilling in roof fractured zone is reasonable and can effectively reduce the gas concentration Finally,an accurate determination method of directional long borehole layout parameters based on quantitative characteristics of mining fracture zoning is proposed.Combined with the selection of drainage pipeline,sealing technology and optimization of drainage parameters,the key technology system of directional long borehole accurate drainage in mining fracture zone of Shaqu No.1 coal mine is finally formed.