Investigation of permeability properties and anisotropy characteristics for fractured rock masses

This paper introduces a method for determining the permeability matrix of fractured rock masses using a fracture geometry tensor. By utilizing the eigenvalues of the permeability matrix, the calculated anisotropy index (K_AI) provides insight into the permeability characteristics of fractured rock masses. This index ranges from 0 to 1.414, with higher values signifying a more pronounced degree of anisotropy. Through a detailed analysis of fracture distribution, the study systematically examines the degree of anisotropy across various fracture patterns. It reveals the impact of fracture spacing and aperture on permeability anisotropy, while expertly characterizing the spatial variability of the permeability matrix elements. Furthermore, the relationship between confining pressure and fracture aperture is explored, shedding light on the effects of confining stress on seepage behavior. The findings elucidate how confining pressure alters both the aperture ratio and the anisotropy index of fractures. The mechanisms by which variations in direction and spacing affect permeability parameters under different confining pressures are investigated. By integrating these insights with results from comprehensive field measurements of ground stress, a relationship between stress and depth is constructed, revealing how changes in depth influence permeability characteristics. This research not only advances the understanding of fractured rock masses but also paves the way for more effective management and utilization of subsurface resources.