煤炭是我国的重要能源，缓倾斜煤层分布广泛，开采过程中采空区卸压瓦斯涌入工作面，易造成上隅角瓦斯浓度超限。采空区瓦斯抽采是解决上隅角瓦斯超限的主要途径，但是针对缓倾斜煤层的采空区卸压瓦斯抽采技术仍需要进一步研究。论文以典型缓斜煤层工作面为例，通过理论研究、物理相似模拟、数值模拟及现场工业性试验手段研究了采动覆岩卸压范围及裂隙分布规律，依据现场瓦斯涌出量确定了缓斜煤层卸压瓦斯防治方法，建立了采空区流场数值计算模型，研究了卸压瓦斯运移规律，确定了定向钻孔抽采布置参数。

通过物理相似模拟实验研究了采空区上覆岩层移动及垮落规律、采动裂隙演化及分布规律。结果表明，工作面平均周期来压12.9 m，冒落带12 m，裂隙带68.5 m，底板支承应力变化呈“升高—降低—恢复”三个过程，覆岩离层率及裂隙密度呈驼峰形分布，回风巷裂隙区宽度及断裂角均大于进风巷裂隙区。

通过FLAC^3D数值模拟软件研究了上覆岩层塑性区域、采动卸压范围及覆岩位移特征。研究表明，采场上方塑性区域呈梯台形态，下端头覆岩破坏程度更大，上覆岩层倾向方向卸压范围呈非对称抛物线形，工作面下端头位移量大于上端头。

分析并确定了缓斜煤层卸压瓦斯防治方法，通过Fluent数值模拟软件得到了采空区卸压瓦斯运移规律，卸压瓦斯向采空区深部及高处运移，瓦斯浓度随着与工作面距离增加而增大，进风巷侧采空区瓦斯浓度小于回风巷侧；上隅角瓦斯浓度随抽采钻孔距工作面顶板距离增加表现为先减小后增大，当钻孔距煤层顶板25 m时，卸压瓦斯防控效果最好，且瓦斯浓度随着钻孔孔径增大而减小。

现场布置6个高位定向钻孔后，通过监测抽采钻孔参数、上隅角及回风巷瓦斯浓度、工作面风量等数据以验证抽采效果。结果表明，高位定向钻孔有效防止了上隅角瓦斯积聚，抽采期内上隅角瓦斯浓度最大0.71%，日平均0.47%，回风巷最大瓦斯浓度0.69%，日平均0.46%。该研究可为同类型缓倾斜煤层综采工作面卸压瓦斯防治提供一定借鉴，对卸压瓦斯精准抽采具有一定指导意义。

Coal is an important energy source in China. The gently inclined coal seams are widely distributed. During the mining process, the pressure relief gas in the goaf flows into the working face, which is easy to cause the gas concentration in the upper corner to exceed the limit. Gob gas drainage is the main way to solve the gas overrun in the upper corner, but the gob pressure relief gas drainage technology for gently sloping coal seams still needs further research. Taking the typical gently inclined coal seam working face as an example, the paper studies the pressure relief range and fracture distribution law of the overlying rock in the stope by means of theoretical research, physical similarity simulation, numerical simulation and field industrial test. The control method of decompression gas in inclined coal seam was established, the numerical calculation model of the flow field in the goaf was established, the migration law of decompression gas was studied, and the parameters of directional drilling and drainage were determined.

The movement and caving law of strata, the evolution law of mining fracture and the distribution law of mining fracture were studied by physical similarity simulation experiment. The results show that the average periodic weighting of the working face is 12.9 m, the height of the caving zone is 12 m, and the height of the fracture zone is 68.5 m. The change of the supporting stress of the floor presents three processes of ‘rise-decrease-recovery’. The separation rate of the eroded strata and the fracture density show a hump-shaped distribution. The width and fracture angle of the return air fracture zone are greater than those of the inlet air fracture zone.

The plastic zone, mining pressure relief range and displacement characteristics of overlying strata were studied by FLAC^3D numerical simulation software. The results show that the plastic zone above the mining field is terrace shape, and the rock fragmentation degree at the lower end is greater. The pressure relief range in the upward trend direction of the strata is asymmetric parabolic shape. The displacement of the lower end is greater than that of the upper end.

The prevention and control method of pressure relief gas in gently inclined coal seam was analyzed and determined, and the migration law of pressure relief gas in goaf was obtained by Fluent numerical simulation software. The pressure relief gas migrated to the deep and high parts of the goaf, and the gas concentration increased with the increase of the distance from the working face, and the gas concentration in the goaf on one side of the inlet roadway was less than that on the other side of the return airway. The gas concentration in the upper corner decreases first and then increases with the increase of the distance between the extraction borehole and the roof of the working face. When the borehole is 25 m from the roof of the coal seam, the prevention and control effect of pressure relief gas is best, and the gas concentration decreases with the increase of the borehole diameter.

After six high-level directional boreholes were arranged on the site, the drainage effect was verified by monitoring the parameters of drainage boreholes, gas concentration in upper corner and return airway, and air flow rate of working face. The results show that the high level directional drilling effectively prevents the gas accumulation in the upper corner. During the extraction period, the maximum gas concentration in the upper corner was 0.71%, with a daily average of 0.47%, and the maximum gas concentration in the return wind tunnel was 0.69%, with a daily average of 0.46%. This study can provide some reference for the prevention and control of pressure relief gas in fully mechanized coal face of the same type of gently inclined coal seam, and has certain guiding significance for precise extraction of pressure relief gas.

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