  Soft biological tissues demonstrate strong time-dependent and strain-rate
mechanical behavior, arising from their intrinsic visco-elasticity and
fluid-solid interactions (especially at sufficiently large time scales). The
time-dependent mechanical properties of soft tissues influence their
physiological functions and are linked to several pathological processes.
Poro-elastic modeling represents a promising approach because it allows the
integration of multiscale/multiphysics data to probe biologically relevant
phenomena at a smaller scale and embeds the relevant mechanisms at the larger
scale. The implementation of multi-phasic flow poro-elastic models however is a
complex undertaking, requiring extensive knowledge. The open-source software
FEniCSx Project provides a novel tool for the automated solution of partial
differential equations by the finite element method. This paper aims to provide
the required tools to model the mixed formulation of poro-elasticity, from the
theory to the implementation, within FEniCSx. Several benchmark cases are
studied. A column under confined compression conditions is compared to the
Terzaghi analytical solution, using the L2-norm. An implementation of
poro-hyper-elasticity is proposed. A bi-compartment column is compared to
previously published results (Cast3m implementation). For all cases, accurate
results are obtained in terms of a normalized Root Mean Square Error (RMSE).
Furthermore, the FEniCSx computation is found three times faster than the
legacy FEniCS one. The benefits of parallel computation are also highlighted.
