A priori and a posteriori error bounds for the fully mixed FEM formulation of poroelasticity with stress-dependent permeability
Arbaz Khan, Bishnu P. Lamichhane, Ricardo Ruiz-Baier, Segundo Villa-Fuentes
TL;DR
This work develops a fully mixed finite element framework for nonlinear poroelasticity with stress-dependent permeability, leveraging a $Hellinger\text{--}Reissner$-type formulation to achieve robustness in near-incompressible regimes and mass conservation via $PEERS_k$ and $RT_k$ spaces. A Banach fixed-point approach decouples the nonlinear permeability from the linear saddle-point structures, yielding existence and uniqueness under small-data assumptions, and enabling both a priori and computable a posteriori error analysis. The authors derive Céa-type estimates and optimal convergence rates, and design a residual-based a posteriori estimator that is reliable and efficient, driving adaptive mesh refinement in 2D and 3D. Numerical results validate the theory, showing optimal rates, conservation properties, and parameter-robust performance, including adaptive refinements near singularities and material interfaces. The framework is well-suited for soft-tissue and geomechanics applications where permeability depends on deformation, with potential extensions to transient, multiphysics, and thermo-poroelastic settings.
Abstract
We develop a family of mixed finite element methods for a model of nonlinear poroelasticity where, thanks to a rewriting of the constitutive equations, the permeability depends on the total poroelastic stress and on the fluid pressure and therefore we can use the Hellinger--Reissner principle with weakly imposed stress symmetry for Biot's equations. The problem is adequately structured into a coupled system consisting of one saddle-point formulation, one linearised perturbed saddle-point formulation, and two off-diagonal perturbations. This system's unique solvability requires assumptions on regularity and Lipschitz continuity of the inverse permeability, and the analysis follows fixed-point arguments and the Babuška--Brezzi theory. The discrete problem is shown uniquely solvable by applying similar fixed-point and saddle-point techniques as for the continuous case. The method is based on the classical PEERS$_k$ elements, it is exactly momentum and mass conservative, and it is robust with respect to the nearly incompressible as well as vanishing storativity limits. We derive a priori error estimates, we also propose fully computable residual-based a posteriori error indicators, and show that they are reliable and efficient with respect to the natural norms, and robust in the limit of near incompressibility. These a posteriori error estimates are used to drive adaptive mesh refinement. The theoretical analysis is supported and illustrated by several numerical examples in 2D and 3D.
