Molecular dynamics modeling of a partially saturated clay‐water system at finite temperature

Abstract

Summary The mechanical and hydraulic properties of unsaturated clay under nonisothermal conditions have practical implications in geotechnical engineering applications such as geothermal energy harvest, landfill cover design, and nuclear waste disposal facilities. The water menisci among clay particles impact the mechanical and hydraulic properties of unsaturated clay. Molecular dynamics (MD) modeling has been proven to be an effective method in investigating clay structures and their hydromechanical behavior at the atomic scale. In this study, we examine the impact of temperature increase on the capillary force and capillary pressure of the partially saturated clay‐water system through high‐performance computing. The water meniscus formed between two parallel clay particles is studied via a full‐scale MD modeling at different elevated temperatures. The numerical results have shown that the temperature increase impacts the capillary force, capillary pressure, and contact angle at the atomic scale. The capillary force on the clay particle obtained from MD simulations is also compared with the results from the macroscopic theory. The full‐scale MD simulation of the partially saturated clay‐water system can not only provide a fundamental understanding of the impact of temperature on the interface physics of such system at the atomic scale, but also has practical implication in formulating physics‐based multiscale models for unsaturated soils by providing interface physical properties of such materials directly through high‐performance computing.

Molecular dynamics data for modelling the microstructural behaviour of compacted sodium bentonites

“…When the time-averaged evolution of the values, [dt], is computed, a steady-state value is reached (Fig. 6), which was described, for instance, by Song and Wang (2019). This steady time-averaged value is the value of d represented in Figs.…”

“…Molecular dynamics models (MDM) can be used as an inspection tool. Works like those of Teppen et al (1997), Cygan et al (2009) and Song and Wang (2019) showed that such models are helpful for improving the qualitative description of the microstructural behaviour of clays. However, the MDM results must be interpreted or quantitatively 5 applied with caution, since the data are obtained in systems of limited size and complexity, and their use for continuum modelling is not immediate.…”

Nonequilibrium molecular dynamics (NEMD) modeling of nanoscale hydrodynamics of clay‐water system at elevated temperature

“…Multiscale modeling is a useful tool to study the hydrodynamics of clay at different temperatures. However, one major challenge in multiscale modeling of materials including clay 12,13 is the faithful understanding of physical models at different space and time scales. Thus, to develop a physics‐based multiscale model for fluid flow in clay (a natural nanomaterial) under non‐isothermal conditions, we need to understand the nanoscale hydrodynamics of clay at different temperatures.…”

Preconditioners for multiphase poromechanics with strong capillarity

“…Capillarity arises from surface tension between co‐existing fluid phases in the pore space. It plays a critical role in unsaturated soil mechanics, 19–26 and significantly influences oil recovery predictions 27,28 . The solid deformation is intricately coupled with fluid pressures via nonlinear constitutive laws 29–33 relating the capillary pressure to degree of saturation.…”