Modeling of chemo-hydromechanical behavior of unsaturated porous media: a nonlocal approach based on integral equations

Unsaturated clay is a heterogeneous porous medium consisting of three phases, namely solid soil skeleton, pore water, and pore air. It has been well recognized that the variation of the chemical property of pore fluid in clay can affect the hydromechanical behavior of this material remarkably. In this study, we formulate a non-local chemo-hydromechanical model for unsaturated clay via the constitutive correspondence principle in the state-based peridynamicsa reformulation of classical continuum mechanics using integral equations instead of partial differential equations. We numerically implement this non-local constitutive model through the implicit return mapping algorithm at the material particle level and then integrate the material subroutine into a computational peridynamics code. We conduct a series of numerical simulations of unsaturated clay samples under different chemical loading rates. The numerical results demonstrate that the proposed non-local model can capture the dramatic impact of organic chemicals on the mechanical behavior of unsaturated clay. The numerical results also show that the proposed non-local numerical model can simulate localized deformation in chemically active unsaturated clay because of the intrinsic length scale embedded in the integral equations.