Hydro-mechanical fault reactivation modeling based on elasto-plasticity with embedded weakness planes

Abstract

In this paper, an elasto-plastic constitutive model is employed to capture the shear failure that may occur in a rock mass presenting mechanical discontinuities, such as faults, fractures, bedding planes or other planar weak structures. The failure may occur in two modes: a sliding failure on the weak plane or an intrinsic failure of the rock mass. The rock matrix is expected to behave elastically or fail in a brittle manner, being represented by a non-associated Mohr-Coulomb behavior, while the sliding failure is represented by the evaluation of the Coulomb criterion on an explicitly defined plane. Failure may furthermore affect the hydraulic properties of the rock mass: the shearing of the weakness plane may create a transmissive fluid pathway. Verification of the mechanical submodel is conducted by comparison with an analytical solution, while the coupled hydro-mechanical behavior is validated with field data and will be applied within a model and code validation initiative. The work presented here aims at documenting the progress in code development, while accurate match of the field data with the numerical results is current work in progress.

Keywords

• Fault reactivation
• Plane of weakness
• Finite element
• Argillaceous material
• Clay
• Permeability