Hydration, Temperature, and Loading Paths Effect on Mechanical and Stress Relaxation Behavior of Montmorillonite Clay: A MD Study

The mechanical behavior of clay under varying conditions is pivotal for evaluating the stability of deep geological formations, yet its underlying nanoscale mechanisms remain elusive. This study employs molecular dynamics (MD) simulations to investigate the elastic properties, dynamic behavior, and mechanical responses of hydrated montmorillonite across a range of hydration levels (0 ~ 40%), temperature (300 ~ 370 K), and loading paths (compression, tension, shear). Our findings include that: (1) The elastic stiffness and mechanical strength of hydrated montmorillonite decreased significantly with rising water content. (2) The mechanical behavior of montmorillonite was highly sensitive to loading paths and its crystal structure, where tensile and shear strengths along the vertical/interlayer direction were relatively lower than those along the horizontal direction. (3) Temperature effects on the mechanical properties illustrated strong anisotropy, with the response normal to the layers affected more severely than the response along the layers. (4) Stress relaxation was governed by the reorganization of interlayer water, characterized by a transition from non-bonded to bonded energy dominance. Furthermore, elevated hydration and temperature accelerate these kinetics by enhancing atomic mobility. These insights into the coupled thermo-hydro-mechanical behavior of montmorillonite have significant implications for the long-term integrity of geological barrier systems.