A Stabilized Explicit Material Point Method for Hydro-Mechanical Coupling in Porous Media Zhang Cheng*, Shiwei Zhao†, Hao Chen† and Jidong Zhao† ABSTRACT Hydro-mechanical behavior in porous media is critical to engineering applications and natural hazard prediction. Although the Material Point Method (MPM) is well-suited for large-deformation soil-water coupling, it remains prone to stress oscillations. This study introduces a stabilized explicit two-phase MPM framework designed to suppress stress oscillations in both fluid and solid phases. For the water phase, a dual volume averaging method with cubic B-spline basis functions smooths the deformation gradient and pressure fields to alleviate pressure oscillations. For the soil phase, a hybrid strain smoothing technique combines cell-based smoothing for deviatoric strain and node-based smoothing for volumetric strain to improve stress stability. Stress oscillations are quantitatively evaluated using the Laplacian of the stress field, computed via a Wendland smoothing kernel. The framework is validated across several benchmark problems, including dam break, column collapse, consolidation, and dynamic soil-water coupling, demonstrating a significant reduction in stress oscillations while preserving computational accuracy. The proposed approach provides a robust and reliable numerical tool for simulating large-deformation hydro-mechanical coupling in porous media. ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (Project No. 52439001) and the Research Grants Council of Hong Kong (GRF Projects No. 16214525, No. 16206322 and No. 16211221, CRF Project No. C7082-22G, and TRS Project No. T22-606/23-R and No. T22-603/24N). Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agencies. [1] Bandara, Samila, and Kenichi Soga. "Coupling of soil deformation and pore fluid flow using material point method." Computers and geotechnics 63 (2015): 199-214. [2] Cheng, Zhang, et al. "Stabilized explicit material point method for fluid flow and fluid-structure interaction simulations using dual high-order B-spline volume averaging." Computer Methods in Applied Mechanics and Engineering 448 (2026): 118428.