Evaluation of the permeability anisotropy of three-dimensional fractured rock masses based on a pair of orthogonal measuring windows

The seepage capacity of fractured rock masses is a critical parameter in various engineering and geoscience projects. Due to the complex geometric distribution of fracture network, the permeability of rock masses typically exhibits an anisotropic behavior, necessitating detailed and comprehensive investigation of fracture characteristics to accurately determine permeability anisotropy in three-dimensional (3D) space. In this study, we developed an improved method for determining permeability anisotropy that significantly reduces the need for extensive input of geometric information. We employ the anisotropic ellipsoid, which is a mathematical representation of permeability tensor, to evaluate permeability anisotropy. Through in-depth mathematical derivation, we present a procedure for constructing the anisotropic ellipsoid using geometric trace information from a pair of orthogonal planes, which aligns well with the practical application scenario of underground tunnel excavation. Numerical experiments were conducted to validate our developed method. The mean prediction error rates were 5.2%, 16.8%, and 13.6% across three sets of experiments, experiments, demonstrating the validity of our approach.