In order to study the coupling evolution law of stress-seepage field in high stress zone under the top-coal caving method,a permeability model under three-dimensional stress was established for coal.The model consists of two parts:the transverse isotropic model based on the matchstick model,and an elastic system composed of coal matrix and fractures.The permeability model is combined with the spatial distribution law of stope stress field to construct the spatial distribution model of the mining-induced coal permeability change ratio(MPCR).Laboratory test results under different conditions of confining,axial and gas pressure are compared with permeability models.The results show that:the permeability decreases exponentially ss the load and gas pressure increase.The permeability model can quantitatively describe the change of coal permeability under loading and unloading conditions,and the correlation coefficient and fit goodness obtained by comparing the results with multiple sets of experimental data are greater than 0.9.The MPCR spatial distribution decreases exponentially with the increase of distance from the working face,and can be divided into four stages:The stress stabilization phase of virgin rock,the MPCR decreases with increasing stress,the MPCR increases with decreasing stress,the constant MPCR with the damage of the coal.According to the comparison between permeability model and field data,the permeability of coal seams increases in stages of the MPCR increases with decreasing stress and the constant MPCR with the damage of the coal,covering the range of coal seam of 55.62 m(Lr=55.62 m).The model can better describe the spatial distribution of MPCR,and the correlation coefficient and goodness-of-fit coefficient with the field data are greater than 0.96.
transverse isotropypermeability modelpermeability enhancement modelpermeability enhancement range
维普
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