Abstract
Three-dimensional simulations of a monotonic quasi-static interface behaviour between initially dense cohesionless sand and a rigid wall of different roughness during tests in a parallelly guided direct shear test under constant normal stress are presented. Numerical modelling was carried out by the discrete element method (DEM) using clumps in the form of convex non-symmetric irregularly shaped grains. The clumps had an aspect ratio of 1.5. A regular grid of triangular grooves (asperities) along the wall with a different height at the same distance was assumed. The numerical results with clumps were directly compared under the same conditions with our earlier DEM simulations using pure spheres with contact moments with respect to the peak and residual interface friction angle, width of the interface shear zone, ratio between grain slips and grain rotations, distribution of contact forces and stresses. The difference between the behaviour of clumps and pure spheres with contact moments proved to be noticeable in the post-peak regime due to a different particle shape. The rolling resistance model with pure spheres was proved to be limited for capturing particle shape effects. Three different boundary conditions along the interface were proposed for micropolar continua, considering grain rotations and grain slips, wall grain moments and wall grain forces, and normalized interface roughness. The numerical results in this paper offer a better understanding of the interface behaviour of granular bodies in DEM and FEM simulations.
Highlights
The safety of engineering systems adjacent to soils in static and dynamic conditions is strongly affected by the strength of soil–structure interfaces
The numerical results in this paper offer a better understanding of the interface behaviour of granular bodies in discrete element method (DEM) and FEM simulations
The paper includes the following novel points: (1) comprehensive 3D analyses of the interface behaviour with the real mean grain diameter of the sand using irregularly shaped grains by taking into account the effect of different interface roughness, (2) a detailed comparison of the interface behaviour between grain clumps of the same shape and pure spheres with contact moments under the same conditions to show the particle shape effect on the shear resistance and shear localization and (3) a proposal of simplified interface boundary conditions of different roughness for micropolar continua by considering grain rotations, slips, moments and forces related to the normalized interface roughness
Summary
The safety of engineering systems adjacent to soils in static and dynamic conditions is strongly affected by the strength of soil–structure interfaces. The paper includes the following novel points: (1) comprehensive 3D analyses of the interface behaviour with the real mean grain diameter of the sand using irregularly shaped grains by taking into account the effect of different interface roughness, (2) a detailed comparison of the interface behaviour between grain clumps of the same shape and pure spheres with contact moments under the same conditions to show the particle shape effect on the shear resistance and shear localization (such a comparison was not performed for sand–structure interface problems yet) and (3) a proposal of simplified interface boundary conditions of different roughness for micropolar continua by considering grain rotations, slips, moments and forces related to the normalized interface roughness. The aspect index (the ratio between the maximum and minimum clump diameter) was 1.50, the convexity index ‘1’
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