Abstract: To research the relationship between crack stratum’s hydraulic conductivity within permeable fractured zone and tensile deformation of rock stratum, the concept of interlayer stratum was defined 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 conductivity 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.

Key words: permeable fractured zone, stratum tensile, interlayer stratum, tensile rate, regression analysis