Coupled Fracture Modelling with RFPA

Abstract

In order to investigate the hydraulic fracture development of the rock and simulate the cracks driven by fluid flow in rocks, a statistical meso-damage mechanical method is developed, based on the statistical and continuum flow-stress-damage model and the finite element method. The constitutive law of this model considers strength and stiffness degradation, stress-dependent permeability for the pre-peak stage, and deformation dependent permeability for the post-peak stage. The damage evolution and accumulation of mesoscopic representative volume element is used to reflect the macroscopic failure characteristics of rock. Three coupled hydro-mechanical processes are considered: (1) mechanical deformation of the solid medium induced by the fluid pressure acting on the fracture surfaces and the rock skeleton, (2) fluid flow within the fracture, and (3) propagation of the fracture. The global flow, stress and strain fields are solved by the finite element method. An element represents a representative volume element, the initiation and propagation of meso-macroscopic trans-scale cracks and their interaction are manifested by removing the failed elements. The above ideas are formulated in the framework of the coupled fracture modelling, which is encoded and implemented into a self-developed software Rock Failure Process Analysis code (RFPA).