Multi-scale modelling of kaolinite triaxial behaviour

Abstract

To understand the relationship between microscopic variables and macroscopic engineering properties of kaolinite particles, a molecular dynamics simulation of triaxial shear tests was developed. The calculations were based on a coarse-grained representation of kaolinite particles, considering the action of Derjaguin–Landau–Vervey–Overbeek forces and the granular interactions. The objective of this study was to provide an understanding of the micro- to macro-linkage of mechanical properties through the development of a versatile numerical framework to accurately duplicate the interactions between clay particles and to study the three-dimensional mechanical behaviour of granular matters. To understand the capabilities of the method, several computer simulations of the periodic true triaxial compression and extension tests of both isotropically and one-dimensionally consolidated specimens were carried out.

Coarse-grained molecular dynamics simulations of clay compression

“…They considered about 1,000 composite particles and used periodic boundary conditions to prevent boundary effects. A similar modelling approach was used to simulate kaolinite in one-dimensional compression (Sjoblom, 2016) and triaxial compression (Aminpour and Sjoblom, 2019). In both cases, composite particles with a diameter-to-thickness ratio ≈ 12 were modelled as rigid hexagons using two types of smaller sub-particles to differentiate the responses of the particle faces and edges.…”

“…Interparticle forces were captured using the DLVO theory with the addition of Stern and Born short-range repulsion forces, modelled by means of orthogonal springs. LAMMPS was used with periodic boundary conditions and a typical cubic sample contained 4,700 (Sjoblom, 2016) or 1,000 (Aminpour and Sjoblom, 2019) particles. The sphere clumps used in prior 12 studies comprised 122 and >160 sub-spheres (Liu, 2015;Sjoblom, 2016, respectively) so that up to ≈ 15,000 sub-sphere interactions must be calculated for a single face-face interaction between two particles.…”

Molecular Dynamics Modeling of Kaolinite Particle Associations

“…Molecular simulation offers one of the most suitable tools for obtaining detailed information about the structure and dynamics of clay minerals at the atomic level. − Molecular modeling could also provide validation of experimental results and lead to further refinement of numerical models and further understanding of clay processes. While previous clay molecular dynamics studies have been successfully carried out across a wide range of scales, almost all of them were limited to perfect infinite clay lamellae .…”

Simulating multifaceted interactions between kaolinite platelets

“…Despite these difficulties, there have been several noteworthy attempts to simulate clays at the particle scale, using either DEM or molecular dynamics (both of these approaches focus on computing the motion of a large number of interacting particles, although they differ slightly in terminology). As will be discussed however, these previous numerical models simulating kaolinite [1][2][3][4][5][6][7][8][9] have used simplified and potentially inaccurate particle interactions. Several of these past attempts have compared well with specific experimental data, however none of them took into account the different interactions between the various surfaces of individual clay platelets.…”