Particle-scale triaxial compression simulations of clay using coarse-grained molecular dynamics
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Accepted version
Author(s)
Nakamichi, Yohei
O'Sullivan, Catherine
Tangney, Paul
Angioletti-Uberti, Stefano
Type
Journal Article
Abstract
Recent advances in particle-scale simulations have enabled detailed investigation of clay behavior
beyond what can be obtained from conventional laboratory tests. However, most previous particle-scale
studies of clay have focused on 1D or isotropic compression, and comparatively few studies have
examined shear response. This paper presents coarse-grained molecular dynamics (CGMD) simulations
of triaxial compression on normally consolidated kaolinite. Two virtual samples were generated under
different pore fluid pH conditions to produce contrasting initial microfabrics: a flocculated sample at
pH=4 and a dispersed sample at pH=8. Triaxial compression simulations were conducted under constant confining pressures of 300, 400, and 500 kPa. The results show that the CGMD simulations qualitatively reproduce key features of clay behavior observed in laboratory tests, including stress-dependent stiffness and shear strength, and convergence toward critical state response at large axial strains. The pH=4 sample exhibited strain-hardening and contractive behavior, while the pH=8 sample exhibited peak strength and dilative behavior, often associated with overconsolidated clay behavior despite being normally consolidated. These contrasting responses were explained micromechanically in terms of different initial microfabrics and their subsequent evolution during shear. Parametric studies further
showed that increasing the coefficient of interparticle friction (𝜇) increased the macroscopic critical
1 ′ ), and that, for the kaolinite and modeling framework considered here, values state friction angle (𝜙𝑐𝑟
on the order of 𝜇 ≈ 1.0 were required to approach experimentally reported friction angles. Furthermore,
′ obtained from the triaxial simulations and the lateral
a linear relationship was observed between sin 𝜙𝑐𝑟
earth pressure coefficient at rest (𝐾0) obtained from one-dimensional compression, consistent with
previously reported experimental trends. These findings demonstrate the value of particle-scale
simulations for linking pH-dependent interparticle interactions, microfabric evolution, and macroscopic
clay behavior.
beyond what can be obtained from conventional laboratory tests. However, most previous particle-scale
studies of clay have focused on 1D or isotropic compression, and comparatively few studies have
examined shear response. This paper presents coarse-grained molecular dynamics (CGMD) simulations
of triaxial compression on normally consolidated kaolinite. Two virtual samples were generated under
different pore fluid pH conditions to produce contrasting initial microfabrics: a flocculated sample at
pH=4 and a dispersed sample at pH=8. Triaxial compression simulations were conducted under constant confining pressures of 300, 400, and 500 kPa. The results show that the CGMD simulations qualitatively reproduce key features of clay behavior observed in laboratory tests, including stress-dependent stiffness and shear strength, and convergence toward critical state response at large axial strains. The pH=4 sample exhibited strain-hardening and contractive behavior, while the pH=8 sample exhibited peak strength and dilative behavior, often associated with overconsolidated clay behavior despite being normally consolidated. These contrasting responses were explained micromechanically in terms of different initial microfabrics and their subsequent evolution during shear. Parametric studies further
showed that increasing the coefficient of interparticle friction (𝜇) increased the macroscopic critical
1 ′ ), and that, for the kaolinite and modeling framework considered here, values state friction angle (𝜙𝑐𝑟
on the order of 𝜇 ≈ 1.0 were required to approach experimentally reported friction angles. Furthermore,
′ obtained from the triaxial simulations and the lateral
a linear relationship was observed between sin 𝜙𝑐𝑟
earth pressure coefficient at rest (𝐾0) obtained from one-dimensional compression, consistent with
previously reported experimental trends. These findings demonstrate the value of particle-scale
simulations for linking pH-dependent interparticle interactions, microfabric evolution, and macroscopic
clay behavior.
Date Acceptance
2026-09-16
Citation
Journal
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Journal
Copyright Statement
Copyright © 2026 Yohei Nakamichi, Catherine O'Sullivan, Paul Tangney, Stefano Angioletti-Uberti. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
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Accepted