An open-source numerical laboratory to assess the poromechanical behavior of fractured rocks

The impact of fractures on the behavior of rock masses is frequently assessed with numerical methods for hydromechanical modeling and upscaling. Given the popularity of these methods, they can benefit from an open-source environment for their development. This paper introduces DuMu^x FracLab, a new module of the open-source software DuMu^x that extends the original code, already robust for solving flow and transport in porous media, to support poromechanical analyses in elastoplastic fractured media using the Box method with zero-thickness interface elements for discretization of the porous fractured domain. Novel features include the solution of elastoplastic problems with the Box method and functions that facilitate homogenization and the upscaling of properties with different boundary conditions. Notably, the imposition of periodic boundary conditions is made using a recent methodology based on the mortar method that we adapted for triple-node interfaces. We present the mathematical formulation, the design and main features behind DuMu^x FracLab as well as validation tests. Finally, two numerical examples demonstrate possible applications. The first one deals with the upscaling of stochastic fractured media and the second one reproduces the permeability history of a fractured chalk sample submitted to depletion and extension.