浅埋近距离煤层内错布置采空区自燃危险区域研究

Study on dangerous area of goaf spontaneous combustion in shallow and close distance coal seams with inner crossing layout

浅埋近距离煤层内错布置开采下部煤层时,地表裂隙易与复合采空区相互贯通,造成地表漏风,使采空区,特别是上部老采空自燃危险区域的分布难以预测。针对此问题,以酸刺沟煤矿6上109工作面至地表空间为研究对象,在漏风测定及束管监测的基础上,建立地表与复合采空区漏风模型,借助FLUENT数值模拟软件,研究地表漏风对复合采空区自燃危险区域的影响。研究表明,地表漏风最终汇入下部采空区回风侧,加大了其自燃危险区域范围;漏风流在向回风侧偏移的过程中,由于煤柱的阻挡,风速逐渐降低,与下部漏入的风流共同作用,使上部老采空区形成了氧浓度中间低四周高的不规则环状自燃危险区域;下部采空区进风侧向上的漏风增加了本煤层采空区的总漏风量,加大了其自燃危险区域宽度,同时增加了上部老采空区局部氧浓度,使其自燃危险性增大。

When mining the lower coal seam in shallow and close distance coal seams with inner crossing layout, the surface cracks are easy to communicate with the composite goaf and cause surface air leakage, which makes the distribution of dan gerous area of spontaneous combustion in goaf, especially the upper goal being difficult to predict. To solve this problem, taking the space from 109 working face in 6 upper seam to the surface in Suancigou Coal Mine as the research object, on the basis of air leakage measurement and beam tube monitoring, the air leakage model of surface and composite goaf was estab- lished, and the numerical simulation software FLUENT was used to study the influence of surface air leakage to dangerous ar- ea of spontaneous combustion in composite goaf. It showed that, the surface air leakage flows into the air return side of lower goaf, which increases the range of dangerous area of spontaneous combustion. For the air leakage flow in the process of migration to air return side, due to the blocking of coal pillar, the air speed reduces gradually, and it interacts with the lower air leakage flow, which makes the formation of dangerous area of spontaneous combustion like irregular ring with low oxygen concentration in the middle and high oxygen concentration around it in the upper goaf. The upward air leakage at the inlet air side of lower goal increases the total air leakage of goaf in this coal seam, enlarges the width of dangerous area of spontaneous combustion, at the same time, it increases the local oxygen concentration of upper goal, and enlarges the risk of spontaneouscombustion.