Abstract：The permeability of fractured rock is an important parameter in many underground projects, but the permeability characteristics are normally not well known and differ significantly from the effective permeability of rocks with high fracture densities that have been widely studied in previous research. This paper presents a numerical method to model the flows in three-dimensional fractured porous media based on the equivalent discrete fracture network model. This method uses two-dimensional triangular elements to simulate the flows in the fractures and the permeable matrix in the rock which predicts the fluid exchange between the fractures and the matrix. The results are used to derive an analytical expression for the conductivity coefficient of the equivalent element. Then, the Monte-Carlo method is used to analyze the permeability of fractured rock with various fracture densities and scales. The results show that the presence of a fracture network in the study area greatly influences the effective permeability and that the effective permeability of fractured rock has a unique scale effect for low fracture densities. After classifying the effective permeabilities with and without fracture networks in the domain, the average effective permeabilities for the two types show regular variations depending on the scale of the domain. This rule can be used to establish a relationship between the effective permeability of various size rock masses.
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2021, Vol. 61 
