DEM modelling of mini-triaxial test based on one-to-one mapping of sand particles

Abstract

This paper presents a discrete-element method simulation of mini-triaxial tests on a sand with realistically shaped grains. It compares the results with physical experiments at multiple length scales, including the macroscopic sample length scale and the particle scale. A series of image-processing techniques were utilised to binarise, segment and label the raw data in images obtained from the mini-triaxial test. The images were obtained using an X-ray synchrotron radiation scanner. A spherical harmonic analysis was used to filter the image data and to reconstruct the natural particle morphology. Two parameters, these being the radius ratio of the smallest to largest sphere [Formula: see text] and a characteristic distance [Formula: see text] within the multisphere clump method, were chosen to represent the realistic particle morphology, balancing accuracy against computational cost. A one-to-one discrete-element model, where every particle in the physical experiment has its own numerical twin, was constructed. The discrete-element model was contained by a numerically generated flexible membrane allowing free deformation of the specimen under a prescribed confining stress, as in a physical triaxial test. Finally, attention was given to particle scale properties and their influences on the mechanical response of the discrete-element model. For a given strain rate it was found that shear modulus and friction coefficient affect the initial stiffness, the peak load and the dilation significantly. This study, and the simulation results within it, demonstrate that the proposed modelling approach is capable of reproducing macroscopic (e.g. stiffness, deviatoric stress response and volumetric response) and particle-level (e.g. displacement, rotation and branch vector orientation) behaviours that are very similar to what occurs within physical experiments, validating the effectiveness of the proposed one-to-one mapping technique.

A Prediction Method for the California Bearing Ratio of Soil‐Rock Mixture Based on the Discrete Element Method and CT Scanning

“…In addition, due to its high resolution and nondestructive nature [8,9], the numerical simulation of SRM from the microperspective based on X-ray computed tomography (CT) has gradually become the focus. Wu et al [10] obtained the three-dimensional structure of sand via an X-ray synchrotron radiation scanner and simulated the triaxial test of sand by DEM, which verified the effectiveness of CT technology in the study of SRM. Yan et al [11] used sphere unit and sphere unit combination to simulate soil particles and rock particles, respectively, and studied the influence of spatial distribution of soil-rock particles on SRM macromechanics.…”

Mechanical Properties of Rock–Coal–Rock Composites at Different Inclined Coal Seam Thicknesses

“…Before performing the numerical simulation, it was necessary to verify the micro-parameters so that the numerical parameters are consistent with those obtained in the laboratory [26][27][28][29]. In this study, the parameter calibration method was used to calibrate the coal and rock parameters.…”

EDEM-FLUENT coupled simulation of coal-gas outburst two-phase flow

“…The geometric dimensions of the numerical model are based on the physical simulation test system developed in previous work (Wang and Wu, 2017;Wang K and Wang L, 2019;Wu et al, 2020), and the full-scale model of the physical simulation test system is carried out to have good comparative data. The total length of the model is 9.41 m, and the outburst cavity is a cylinder with a diameter of 0.2 m and a length of 0.3 m. In order to avoid the small structure existing in the modeling to increase the burden on the mesh generation and numerical solution, the pressure sensors in the simulated roadway are not created, as shown in Figures 3 and 4.…”