倾斜厚煤层卸压瓦斯靶向区辨识及抽采关键技术

Key technologies for extraction and identification of gas target area for pressure relief in inclined thick coal seam

为了研究倾斜厚煤层卸压瓦斯靶向区演化规律的煤层倾角效应,运用物理相似模拟试验及理论分析相结合的研究方法,开展不同煤层倾角条件下采动覆岩卸压瓦斯靶向区裂隙演化规律的研究,得到了靶向区破断裂隙宽度、离层裂隙面积占比以及裂隙分形维数随煤层倾角变化的演化规律,进而建立了靶向区演化煤层倾角效应模型。结果表明:破断裂隙宽度呈现采空区两侧边界区域大于中部,低层位大于高层位的分布特征,同时破断裂隙宽度受铰接梁影响较强,随着煤层倾角的增大(0°<15°<30°),在第1层铰接梁所在层位上部邻近区域破断裂隙宽度相比下部邻近区域大幅度减小,仅有下部邻近区域的52.8%,64.3%以及71.1%;瓦斯运移优势通道带内离层裂隙面积占比呈现底部最大,顶部次之,中部最小的分布规律;上覆岩层裂隙分形维数整体呈现先减小后增大的现象;基于第1层铰接梁与裂隙分形维数极小值点所在层位两侧裂隙演化规律差异明显,将瓦斯运移优势通道带按空间层位上的高低依次划分为低层位靶向区、中层位靶向区和高层位靶向区。最后,基于采动裂隙椭抛带理论,在工作面侧瓦斯运移优势通道带基础上,建立了考虑煤层倾角因素的倾斜厚煤层卸压瓦斯靶向区空间形态数学方程,形成了靶向区卸压瓦斯抽采方法选择依据,为优化倾斜厚煤层工作面卸压瓦斯抽采布置参数提供参考依据。

In order to study the dip angle effect on the evolution law of the target area for pressure relief gas drainage in inclined thick coal seams,the physical similarity simulation test and theoretical analysis were combined to study the fracture evolution in the target area under different coal seam dip angles.The evolution law of broken fracture’s width,the area proportion of bed-separated fracture,and the fractal dimension of fracture with the change of coal seam dip angle in the target area were obtained,and then the coal seam dip angle effect model of the targeted area evolution was established.The results showed that the broken fracture’s width presented the distribution characteristics that the boundary area on both sides of the goaf was greater than that in the middle,and the low horizon was greater than that in the higher horizon.What’s more,the broken fracture’s width was strongly affected by the hinged beam.With the increase of the coal seam dip angle(0°<15°<30°),the broken fracture’s width in the upper region of the first layer of hinged beam is significantly reduced compared with that in the lower region,which is only 52.8%,64.3%,and 71.1%,respectively.The area proportion of bed-separated fracture in the dominant gas migration channel zone was the largest at the bottom,followed by the top,and the smallest in the middle.The fractal dimension of overlying fractures decreased first and then increased as a whole.The fracture evolution laws were obviously different on both sides of the layer where the hinged beam of the first layer and the minimum fractal dimension of the fracture were located.Therefore,the dominant channel belt of gas migration was divided into low-layer target areas,middle-layer target areas,and high-layer target areas according to the level of the spatial horizon.Finally,based on the theory of mining fracture ellipse belts and the dominant gas migration channel zone at the working face side,the mathematical equation of the target area in inclined thick coal seams was established considering the coal seam dip angle,and the basis for selection of pressure relief gas drainage methods in the targeted area was formed.It provided a reference for optimizing the parameters of pressure relief gas drainage in an inclined,thick coal seam working face.