17:15 〜 18:45
[SCG44-P15] Rheology and Structure of 2D Model Smectite Clay using Coarse-Grained Molecular Dynamics
キーワード：粘土、断層、構造、シミュレーション
The rheology and stability of fault zone is governed by the mechanical behavior of fault gouge. Smectites are commonly found in shallow fault gouges and are well known for their low frictional strength. Although smectite clay is well studied in experiments, the microscopic shear behavior and structure development of clay platelets are still not well understood.
In this study, we study a model clay system using coarse-grained molecular dynamics (CGMD). Clay platelets are simplified as rigid ellipsoids particles interacting via the Gay-Berne potential. The 2D simulation allows for a relatively larger system size and more analysis on the structure change on the shear plane.The system is sheared at constant strain rates for 20 strains after compaction and equilibrium. The structure change is probed from volume fraction, nematic order, particle orientation and parallel radial distribution function. Velocity strengthening behavior is observed over a range of normal stresses from 1.6 to 48.09 MPa and strain rates from 1.68e6 to 1.68e8 /s. The shear stress-strain rate relationship follows the Herschel-Bulkley model. The residual shear stress at zero strain rate limit increase with strain rate. The volume fraction decrease with strain rate and increase with normal stress. During shear, the transient decrease in the volume fraction is associated with decrease in the nematic order parameter and increase in the average particle orientation. The shear stress increase with decreasing volume fraction. This may suggest the shear stress increase in smectite clay is associated with particle misalignment and cluster rotation.
In this study, we study a model clay system using coarse-grained molecular dynamics (CGMD). Clay platelets are simplified as rigid ellipsoids particles interacting via the Gay-Berne potential. The 2D simulation allows for a relatively larger system size and more analysis on the structure change on the shear plane.The system is sheared at constant strain rates for 20 strains after compaction and equilibrium. The structure change is probed from volume fraction, nematic order, particle orientation and parallel radial distribution function. Velocity strengthening behavior is observed over a range of normal stresses from 1.6 to 48.09 MPa and strain rates from 1.68e6 to 1.68e8 /s. The shear stress-strain rate relationship follows the Herschel-Bulkley model. The residual shear stress at zero strain rate limit increase with strain rate. The volume fraction decrease with strain rate and increase with normal stress. During shear, the transient decrease in the volume fraction is associated with decrease in the nematic order parameter and increase in the average particle orientation. The shear stress increase with decreasing volume fraction. This may suggest the shear stress increase in smectite clay is associated with particle misalignment and cluster rotation.