A semi-theoretical method for determining the anisotropic permeability based on average permeability of rock masses

Determining the anisotropic permeability of rock masses plays an important role in various geoscience and engineering projects. Since hydraulic aperture is difficult to be measured directly, numerical or theoretical methods for calculating directional permeability are usually used for qualitative technical support, rather than quantitative analysis. A semi-theoretical method is proposed in this study to estimate the directional relationship based on average permeability, where the latter can be obtained through a relatively cheap single-borehole water pressure tests. In this method, hydraulic aperture is replaced by aperture ratio, which can be quickly determined through field investigation by experienced geologists. Compared to adopting multiple-borehole water pressure tests to determining the anisotropic permeability, the new developed method can significantly reduce the testing cost. Numerical experiments are conducted and validated our method, the results show that the mean error rates are generally below 20%.