Development and verification of three-dimensional equivalent discrete fracture network modelling based on the finite element method

Abstract

The discrete fracture network (DFN) method is essential for estimating the mechanical properties of naturally fractured rock masses. A three-dimensional (3D) equivalent DFN model was proposed and thoroughly validated for fractured rock masses. In the equivalent DFN modelling, the Monte Carlo method and 3D rock failure process analysis (RFPA3D) software were used. Additionally, the fracture and its spatial distribution were described explicitly, and the strength and deformability of complex fractured rock masses were investigated. A case study was conducted at the dam site area of Lianghekou Hydropower Station's the left bank slope. The ShapeMetriX3D system was used to acquire the geometric parameters and probability distribution of fractures via digital photogrammetry. Additionally, a series of numerical models were created by combining the proposed equivalent DFN method with the fracture geometry information from the case study. Based on the concept of scale effect and anisotropy, the representative element volume (REV) and mechanical parameters of fractured rock masses were determined. The mechanical parameters of slope rock masses obtained by the proposed DFN modelling and generalized Hoek Brown strength criterion were compared. Furthermore, the applicability and reliability of the proposed model were validated using site data and numerical verifications. The proposed 3D equivalent DFN modelling can analyze the scale effect and anisotropy of mechanical properties of fractured rock masses effectively. Finally, the influence of water head on the hydraulic characteristics of fractured rock masses was analyzed based on the proposed model. Results showed that fractures were the main pathway of water.