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TYC Lunchtime Seminar: Using coarse-grained molecular dynamics to understand clay behaviour

Sara Bandera, Civil and Environmental Engineering, Imperial College London

Monday 30 November 2020
Time: 12pm
Venue: Online
Contact: Ms Hafiza Bibi

Abstract:

Clay minerals are ubiquitous in soil deposits everywhere. Predicting clay behaviour is non-trivial; its response to applied loads is non-linear, rate- and time-dependent, and measurably influenced by the clay chemistry, mineralogy and particle morphology, the stress history of the deposit, the pore water chemistry and temperature. Relatively few studies have documented coarse-grained simulations of clay, which are the only way to quantitatively link particle-scale mechanisms to the complex features of behaviour that are routinely encountered in engineering practice. This lack of research can be attributed to the difficulties in accurately identifying the clay elementary units and the inter-particle forces, which depend on both the particle surface chemistry and the pore fluid composition. This project aims then at improving the understanding of the response of clay to applied loads and deformations by explicitly simulating the interactions between three-dimensional clay particles using the Molecular Dynamics (MD) technique. This contribution considers kaolinite, a non-active clay, under different pH conditions. Kaolinite particles are modelled as flat ellipsoids; inter-particle interactions are described by an analytical expression called the Gay-Berne (GB) potential, which is a modified form of the Lennard-Jones (LJ) potential for aspherical particles. Given its general acceptance in soil mechanics, the DLVO (Derjaguin, Landau, Vervey, Overbeek) theory is used to calibrate the GB potential parameters. Simulations on kaolinite assemblies are performed using the open source molecular dynamics software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator).

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