Effect of Fracture Geometry Parameters on the Permeability of a Random Three-Dimensional Fracture Network

Abstract

In numerous subterranean projects, the impact of groundwater on the safety of the engineering undertaking is of paramount significance. Fractures, functioning as the primary channels for seepage within subterranean rock masses, necessitate the complex and challenging task of accurately characterizing seepage patterns and quantitatively investigating the effect of fissure parameters on fluid dynamics within the rock masses. This article presents a stochastic fissure model incorporated within a finite element framework, which captures the probabilistic distribution of fissures found in nature. It provides a comprehensive analysis of the distribution of pore water pressure and Darcy velocity fields. It unveils the permeation patterns of fissured rock masses and establishes a series of fissure models, quantitatively investigating the correlations between matrix permeability, water pressure, fissure density, fissure length, the length power law, fissure angle, the dispersion coefficient, fissure aperture, and the aperture power law, as well as their influence on the equivalent permeability of the rock mass. The findings reveal that in a discrete fissured rock mass, the greater the matrix permeability, the higher the equivalent permeability, and vice versa. Under water pressures of less than 10 MPa, gravity significantly impacts equivalent permeability, and permeability linearly increases with a rise in fissure density. Longer fractures result in higher permeability, and fractures parallel to the direction of water pressure contribute most significantly to the speed of seepage. Moreover, permeability markedly increases with an increase in aperture. This study provides a comprehensive analysis of the impact of matrix permeability and fissure parameters on equivalent permeability and calculates the permeability of each model. We also propose a set of predictive formulas based on fissure geometric parameters to anticipate the permeability of rock masses.