Modelling the crystalline swelling process of montmorillonite incorporating boundary effects

Abstract

Crystalline swelling behavior of montmorillonite (Mt) profoundly impacts the phenomenological properties of expansive clays. Accurately modeling the evolution of basal spacing is essential for assessing the performance of expansive clay materials in geotechnical applications, particularly in high-level radioactive waste (HLRW) repositories. This study aims to address the primary limitation of existing crystalline swelling models, which fail to account for boundary effects dependent on clay structure. A mass transfer boundary is integrated into the Laird model, and its validity is substantiated through basal spacing measurements of tactoids and bentonites. The mass transfer boundary is described using the soil water retention curve (SWRC) for bound water. Furthermore, net hydration energies are determined using an empirical function, eliminating the need for experimental calibration of effective diabattivity. The modified model is validated against experimental data for three common bentonites: GMZ, MX-80, and Kunipia. It demonstrates enhanced predictive accuracy compared to the previous model and effectively captures the continuous swelling process. Additionally, this approach provides a numerical tool for calculating the evolution of potential energy and dielectric constant within interlayer spaces.