A semi-implicit material point method for coupled thermo-hydro-mechanical simulation of saturated porous media in large deformation

The coupled thermo-hydro-mechanical (THM) response of liquid-infiltrated porous media underpins the safe operation and maintenance of key engineering infrastructure. Challenges remain in modeling and understanding the complicated multiphysics processes of porous media subjected to THM loads and undergoing large deformation. In this study, we develop a stabilized material point method (MPM) for modeling the THM responses of large deformation problems in biphasic solid-fluid mixtures. A novel and efficient staggered solution scheme is proposed to solve the governing equations of the coupled system formulated in terms of four primary variables: solid displacement (u), liquid velocity (v), pore pressure (p), and temperature (T). The scheme solves the energy balance equation first and employs the resulting temperature to further advance the calculation of the momentum and mass balance equations using a semi-implicit fractional step method to facilitate equal-order interpolations. Both the incompressible and weakly compressible fluid are considered in the presented fractional step formulations. We also develop the axisymmetric form of the coupled MPM to increase the applicability and efficiency of the method in THM problems. The validity, stability, and robustness of the proposed method are demonstrated through three benchmark problems, including the heating of a saturated half-space, the non isothermal consolidation of a soil column, and a three-dimensional axisymmetric problem pertaining to the thermoelastic response around a point heat source. The predictive capability of the proposed method for large deformation problems is further showcased by the simulation of the progressive failure process of a thermal-sensitive slope.