地下煤火燃空区覆岩裂隙分布模型和局部化特征

Distribution model and localization features of rock fissures over combustion space area of underground coal fire

在推导出覆岩层下沉曲面方程和微元面平面伸张量方程的基础上构建了地下煤火燃空区各覆岩离层裂隙率、破断裂隙率和总裂隙率的二维分布模型,经实例分析发现,覆岩裂隙场是由离层裂隙场和破断裂隙场组成的竖向不连续具有各向异性的非均质多孔介质,覆岩四周裂隙率大,内部裂隙率小;随着覆岩埋深减小,裂隙发育程度逐渐降低,离层裂隙率极大值由0.36、0.20、0.14、0.12逐次降低,破断裂隙率极大值由0.32、0.11、0.05、0.02逐次降低;在覆岩中部区域出现裂隙率竖向变化突变点;覆岩周边裂隙率分布形式由破断裂隙主导,内部则由离层裂隙主导。基于钻孔红外热像分析技术提出了一种间接性的覆岩裂隙现场实测方法,经验证选取的5个点的裂隙率计算值与实测值的差异率都小于9%,差异率低,模型具有较高的可靠性。

Based on the derived equations of overlying strata subsidence and infinitesimal surface stretching, two-dimensional and nonhomogeneous distribution model of delamination fracture rate, broken fissures rate and total fracture rate of the overlying strata in the combustion space area of underground coal fire is constructed. And through a case study, it is found that the fracture field of overlying strata is the vertical discontinuous, anisotropy and heterogeneous porous media composed of delamination fracture field and broken fissures field. Some conclusions are drawn as follows:(1) The fissure rate in the surrounding of overlying strata is large; and the internal region is small.(2) With the decrease of depth of overlying strata, fissures growth extent reduces gradually. The maximum value of delamination fissure rate successively reduced from 0.36 to 0.20, 0.14, 0.12; and the maximum value of broken fissure rate successively reduced from 0.32 to 0.11, 0.05, 0.02.(3) There is a mutational point of the vertical variation of fissure rate in the central area of overlying strata.(4) The distribution of fissure rate in the surrounding of overlying strata is led by broken fissures, but the internal region is led by delamination fissures. Finally, an indirect measurement method of overlying strata fissures has been proposed on the basis of the infrared thermal image analysis technology. And the high reliability of the model was confirmed by this method.