Molecular Dynamics Simulation of Charged Clay Colloidal Assemblages

Interactions between charged clay colloidal particles play important roles in a range of geophysical phenomena including soil mechanics, sediment transport, debris flow, fault slip, and subsidence. Large-scale representation of these phenomena remains challenging because of a lack of appropriate consitutive relations for the mechanical properties of hydrated clay colloidal assemblages as a function of solid density, aqueous chemistry, and deformation history. We present recent efforts to predict these consistitutive relations using all-atom and coarse-grained molecular dynamics (MD) simulations of hydrated clay colloidal assemblages. Simulations span a range of scales from nanometers to micrometers and from individual charged clay particles (with explicit counterion clouds) to assemblages of thousands of clay particles. Our results provide insight into the sensitivity of clay mechanics to salinity and counterion type (Na vs. Ca).