Mesoscale Analysis of Coupled Deformation-Hydration Behaviors of Unsaturated Clay Accounting for Atomistic-scale Interactions

GY Zhou and ZH Shi and JG Qian, COMPUTERS AND GEOTECHNICS, 187, 107489 (2025).

DOI: 10.1016/j.compgeo.2025.107489

The hydro-mechanical behaviors of fine-grained soils are largely dependent on mesoscale (0.1-10 mu m) mechanisms, particularly the relative humidity (RH)-driven evolution of mesoscale clay fabric, which is the key intermediate scale links the atomistic physical processes and macroscale mechanical behaviors. However, the intricacies of these processes in response to the varying RH conditions have remained unclear. Here, we proposed an RH-dependent mesoscale simulation framework by introducing a hydration-dependent multi-energy-well (HDME) potential function. The newly proposed potential function is constructed based on atomistic-scale intermolecular interactions of sodium-based montmorillonite (Na-MMT) under aqueous conditions, to capture the periodic "energy well", and the decaying oscillatory behaviors observed under variable hydration states. The framework then used the HDME potential and coarse-grained molecular dynamics (CGMD) to investigate the deformation behaviors and mesoscale aggregation evolutions of Na-MMT clay particles under loading-hydration combined actions. Results from mesoscale simulations successfully reproduce widely observed hydro- mechanical behavior of fine-grained soils, including RH-dependent compressibility, compression curve crossover within the transformation region (100-300 atm in this study), stress-state-governed transitions between hydration swelling (low confining stress) and collapse (high confining stress), and a notable plastic behavior throughout the loading-unloading and desiccation-rehydration cycle. Mesoscale fabric analyses indicate the above deformation behaviors can be attributed to hydration-induced disaggregation and stress-induced particle alignment and anisotropic fabric.

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