Study On Hydraulic Slit Gas Drainage Technology In JianShe Coal Mine

Coal is the energy with the highest proportion of consumption structure in China,but with the increase of mining depth,the problem of coal and gas outburst in coal mine is becoming more and more prominent.The regional measures to prevent coal and gas outburst accidents mainly include mining protective layer and coal gas pre drainage technology.At present,the hydraulic pressure relief and antireflection technology adopted in China has far better outburst prevention effect than the traditional gas drainage method in practical application,but the situation of outburst coal mines is very different.When using hydraulic technology,the drilling parameters can not be completely copied for reference.This paper uses COMSOL numerical simulation software to establish a two-dimensional model with the size of 40×40m to compare the difference of gas extraction effect between slit drilling and ordinary drilling,and the influence of hole spacing on gas extraction effect of slit drilling.Three test groups are arranged on site to verify the difference of gas drainage effect and explore the most suitable slotted drilling spacing for the target coal mine.The results have practical reference value for the construction scheme optimization of gas pre drainage drilling in Xingwen Jian She coal mine.The main conclusions are as follows:(1)The numerical simulation shows that the gas drainage effect of slotted drilling is better than that of ordinary drilling;With the increase of spacing,the effect of gas pressure relief decreases gradually;After the borehole spacing is adjusted to12 m,the time for pumping to meet the standard(below 0.74mpa)is increased to 80 d,and it is more reasonable to predict the borehole spacing of 8m or 10m;(2)The field verification shows that the direct disturbance radius of slotted drilling is 4.09 times higher than that of ordinary drilling;The disturbed surface area per meter is increased by 4.08 times;The direct disturbance volume is increased by45.9 times;The average gas concentration increased by 2.79 times within 30d;The ultimate extraction capacity is increased by 3.05 times;Moreover,the attenuation coefficient of gas drainage volume of 12 m spacing slotted holes is large,the net amount of gas drainage is also significantly less,and the overall pressure relief effect is not ideal;(3)Arranging boreholes at a spacing of 10 m can reduce the drilling construction quantity in the test area by 73%,save the construction cost and time,and have good economic benefits.It is suitable for the Jian She coal mine.