A Theory for Stress‐History Dependent Permeability Tensor of Crystalline Rocks With Isotropic Microfabric Under Pseudo‐Elastic State

The permeability tensor for crystalline rocks with isotropic fabric was formulated in terms of their micro‐fabric and stress tensor without introducing any curve fitting parameters. We paid much attention to the methodology for determining all parameters involved in the theory. The present theory yields a non‐linear equation and demonstrates that the permeability of rocks and rock masses is strongly dependent on the stress history. Cyclic loading of the effective confining pressure exerts a tremendous effect on the permeability of a rock mass. Based on experimental data on a joint in dolerite, the present theory suggests that the permeability of a dolerite rock mass decreases by about two‐orders of magnitude just after three loading cycles. A new method was developed to determine the pseudo‐elastic constant for microcracks in rocks, and the pressure‐dependent permeabilities for Inada and Westerly granites were predicted using them, in good accordance with the experimental data as long as a pressure was less than 60 MPa. A coefficient related to connectivity among cracks in a given crack system was newly formulated by introducing the critical crack density, beyond which cracked body behaves like a porous medium. The permeability under differential stress was also formulated and it was found that the general trend predicted by the theory accords well with experimental evidence.