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Abstract Permeability in brittle rocks under compressive stress changes with crack growth. A method to calculate permeability evolution is presented，in which both experimental phenomenon and inherent mechanism of permeability evolution are taken into account. The mechanical model is based on the research of ZHU Qizhi et al，two modifications are applied to frictional criterion and potential function；and the modified anisotropic damage model is used to simulate triaxial compression test of Lac du Bonnet granite. According to damage variable and crack normal and tangential deformation obtained in mechanical model，a function of connectivity coefficient is used to describe the ratio of the crack involved in hydraulic flow to total number of crack，more and more cracks are involved in hydraulic flow when microcracks grow；the cubic law is used for seepage flow in a single crack，crack radius and equivalent aperture are defined by micromechanical result；a method is proposed to analyze permeability evolution in brittle rocks under deviatoric stress. The proposed method is employed to simulate in-situ permeability test of Lac du Bonnet granite. Comparison between axial and lateral permeability evolutions under increasing deviatoric stress is carried out；axial permeability evolution under different confining stresses is also predicted. It is shown that the numerical simulation results and experimental data are in good agreement.
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Received: 08 October 2007
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