覆岩导水裂缝与岩层拉伸变形量的关系研究

为了研究覆岩导水裂缝带内裂隙岩层导水性与覆岩岩层层向拉伸变形的关系,定义了岩层中间层的概念;在假定可以用两段圆弧拟合岩层下沉盆地内外边缘曲线的条件下,导出了岩层层向拉伸率ε的计算公式;统计了近年来的井下导高观测成果。研究得出:当岩层中间层层向拉伸率超过岩石拉伸变形极限时,岩层会产生法向拉伸裂隙;当岩层层向拉伸率大于其临界拉伸率时,该岩层就会成为导水裂缝岩层。岩层层向拉伸率ε主要受岩层层位高度h,煤层采厚m,岩层下沉系数q,边界角δ0和充分采动角ψ等因素的影响。回归分析得出:覆岩岩层越坚硬,则裂采比就越大,导水裂缝带顶部岩层层向临界拉伸率ε0值就越小。

The Relationship Between Permeable Fractured Zone and Rock Stratum Tensile Deformation

To research the relationship between crack stratum’s hydraulic conductivity within perme-able fractured zone and tensile deformation of rock stratum,the concept of interlayer stratum was de-fined first in this paper,then the formula of strata tensile rate ε was deduced,by assuming that two sect of arcs can be used to fit inside and outside brim curve of subsidence trough,and the statistical results of field observation of permeable fractured zone height were obtained at last.The results show that when the tensile rate ε of the interlayer stratum surpasses its deformation limit,the normal tensile crack will be generated,and when ε is larger than the limit rate,the crack stratum will become the hydraulic con-ductivity stratum.In addition,the layer tensile rate ε depends on layer’s height(h),mining thickness(m),stratum’s subsidence ratio(q),boundary angle(δ0) and full mining angle(ψ),and so on.According to the regression analysis of some coal mine’s permeable fractured zone heights,the harder the upper strata is,the larger the ratio of fractured zone height to mining thickness(H-T ratio)is,and the smaller the layer tensile rate of top stratum within water flowing fractured zone is.