Computational Large-Deformation-Plasticity Periporomechanics for Localization and Instability in Deformable Porous Media

In this article, we formulate a computational large-deformation-plasticity (LDP) periporomechanics (PPM) paradigm through a multiplicative decomposition of the deformation gradient following the notion of an intermediate stress-free configuration. PPM is a nonlocal meshless formulation of poromechanics for deformable porous media through integral equations in which a porous material is represented by mixed material points with nonlocal poromechanical interactions. Advanced constitutive models can be readily integrated within the PPM framework. In this paper, we implement a linearly elastoplastic model with Drucker-Prager yield and post-peak strain softening (loss of cohesion). This is accomplished using the multiplicative decomposition of the nonlocal deformation gradient and the return mapping algorithm for LDP. The paper presents a series of numerical examples that illustrate the capabilities of PPM to simulate the development of shear bands, large plastic deformations, and progressive slope failure mechanisms. We also demonstrate that the PPM results are robust and stable to the material point density (grid spacing). We illustrate the complex retrogressive failure observed in sensitive St. Monique clay that was triggered by toe erosion. The PPM analysis captures the distribution of horst and graben structures that were observed in the failed clay mass.