Hydraulic-mechanical (HM) processes including fracture propagation in geomaterials are important factors for many geo-environmental issues. A coupled HM simulation tool, TOUGH-RBSN, has been developed to investigate permeability change of porous medium due to mechanical initial compaction and postfailure deformation. TOUGH2 is a widely used simulator of subsurface multiphase flow, and RBSN is a type of mechanical lattice model based on the Rigid-Body-Spring Network concept. In this paper, an implementation of the HM coupled module is first described for stress induced porosity changes which affect the conditions of rock permeability. Thereafter, the basic capabilities of the modeling approach are demonstrated through the transient pulse tests during triaxial compression loading. In most respects, the simulation results meet expectations: permeability decreases due to compaction before the onset of microcracking, and increases during progressive failure process. The visualization of interior damage development is facilitated by a 3D Voronoi-based discretization technique.
Hydraulic-mechanical (HM) processes including fracture propagation in geomaterials are important factors for many geo-environmental issues related to nuclear waste disposal, geologic carbon sequestration, and hydraulic fracturing. For example, crack opening or fault reactivation induced by stress perturbation of rock may significantly change local hydraulic conditions (e.g. permeability), which potentially reduces confinement capability of a radioactive waste repository. Proper modeling of such coupled processes is critical for any performance assessment of geological engineering practices.
Various numerical models have been developed to study coupled HM processes of geomaterials (Yuan & Harrison 2006, Tan et al. 2014). Bruno (1994) used a discrete element model to simulate various biaxial loading conditions and associated permeability changes. Lu et al. (2013) studied the fracture-fluid interaction effects using the finite element model, in which damage and flow coupling is based on the macroscopic elastic modulus tensor. Since geomaterials and fracture processes are three-dimensional, it is important to consider HM processes in spatial domain. However, numerical models related to the coupled HM processes is mostly conducted within a 2D framework. Proper 3D modeling capabilities are needed to study the mechanism of HM processes through comparison with laboratory testings.