DEM modeling of particle breakage in silica sands under one-dimensional compression
- Authors: Shi, Danda , Zheng, Lin , Xue, Jianfeng , Sun, Jing
- Date: 2016
- Type: Text , Journal article
- Relation: Acta Mechanica Solida Sinica Vol. 29, no. 1 (2016), p. 78-94
- Full Text: false
- Reviewed:
- Description: A Discrete Element Method (DEM) model is developed to study the particle breakage effect on the one-dimensional compression behavior of silica sands. The 'maximum tensile stress' breakage criterion considering multiple contacts is adopted to simulate the crushing of circular particles in the DEM. The model is compared with published experimental results. Comparison between the compression curves obtained from the numerical and experimental results shows that the proposed method is very effective in studying the compression behavior of silica sands considering particle breakage. The evolution of compression curves at different stress levels is extensively studied using contact force distribution, variation of contact number and particle size distribution curve with loading. It is found that particle breakage has great impact on compression behavior of sand, particularly after the yield stress is reached and particle breakage starts. The crushing probability of particles is found to be macroscopically affected by stress level and particle size distribution curve, and microscopically related to the evolutions of contact force and coordination number. Once the soil becomes well-graded and the average coordination number is greater than 4 in two-dimension, the crushing probability of parent particles can reduce by up to 5/6. It is found that the average contact force does not always increase with loading, but increases to a peak value then decreases once the soil becomes more well-graded. It is found through the loading rate sensitivity analysis that the compression behavior of sand samples in the DEM is also affected by the loading rate. Higher yield stresses are obtained at higher loading rates. © 2016 The Chinese Society of Theoretical and Applied Mechanics.
The combined scaled boundary finite-discrete element method : Grain breakage modelling in cohesion-less granular media
- Authors: Luo, Tao , Ooi, Ean Tat , Chan, Andrew , Fu, Shaojun
- Date: 2017
- Type: Text , Journal article
- Relation: Computers and Geotechnics Vol. 88, no. (2017), p. 199-221
- Full Text: false
- Reviewed:
- Description: A computational technique combining the scaled boundary finite element method (SBFEM) and the discrete element method (DEM) is developed. Both methodologies work in tandem to model two mechanisms i.e. grain-to-grain interaction via DEM; and breakage of individual grains via SBFEM. Both play important roles in characterising the response of granular soils. The combination of the two methods results in some advantages in computational flexibility and implementation in modelling grain breakage in granular materials. Parametric studies demonstrate the method's ability to reproduce stress-strain curves in bi-axial tests of granular rock-fills; and qualitatively predicts characteristics of grain breakage observed in laboratory tests. © 2017 Elsevier Ltd
Modeling the particle breakage by using combined DEM and SBFEM
- Authors: Luo, Tao , Ooi, Ean Hin , Chan, Andrew , Fu, Shaojun
- Date: 2017
- Type: Text , Conference proceedings , Conference paper
- Relation: 7th International Conference on Discrete Element Methods, DEM7 2016; Dalian, China; 1st-4th August 2016; published in Springer Proceedings in Physics Vol. 188, p. 281-288
- Full Text: false
- Reviewed:
- Description: A novel computational method is developed in this study through the coupling of the discrete element method (DEM) and the scaled boundary finite element method (SBFEM). The objective of the developed technique is to model the particle breakage phenomenon in granular materials. This method models individual grains as single star-convex arbitrary sided polygons. The DEM is used to resolve the dynamics of each grain whereas the SBFEM is used to determine its corresponding stress state after a DEM analysis. The flexibility of both the SBFEM and DEM enable the grains to be formulated on arbitrary sided polygons so that the morphology of each grain to be replicated using only a single polygon. Grain breakage condition is determined if the stress state in a polygon satisfies a mechanically driven criterion e.g. the Hoek-Brown criterion is used. Once the breakage condition is detected, the resulting grain is split into two separate polygons. The resulting new polygons are directly modelled by the DEM and SBFEM without any change to the formulation. The feasibility of the developed method is demonstrated using a numerical example. © Springer Science+Business Media Singapore 2017.
- Description: Springer Proceedings in Physics
A combined DEM-SBFEM for modelling particle breakage of rock-fill materials
- Authors: Luo, Tao , Ooi, Ean Tat , Chan, Andrew , Fu, Shaojun
- Date: 2017
- Type: Journal article
- Relation: Yantu Lixue/Rock and Soil Mechanics Vol. 38, no. 5 (2017), p. 1463-1471
- Full Text: false
- Reviewed:
- Description: Both experimental and numerical results demonstrate that particle breakage has significant influence on the macro mechanical response of granular soils. In this study, a novel computational method was proposed to simulate particle breakage phenomenon in granular soils. The proposed method based on the discrete element method (DEM) and the scaled boundary finite element method (SBFEM) has advantages of each method. Individual grains of soil are modelled by a single star-convex polygon with an arbitrary number of sides. The DEM is used to determine the motion of particles and the interaction among particles, whereas the SBFEM is applied to obtain stress states of grains at the end of each time step. Since the SBFEM flexibly describes the morphology of each grain with a single polygon consisting of an arbitrary number of sides, it greatly reduces the necessary computational resources for stress analysis. When the stress state has been confirmed, Hoek-Brown criterion is chosen to determine the 'plastic points' within each particle. Once the ratio of 'plastic points' reaches a predefined threshold, the particle breakage is triggered. As a straight breakage line is assumed for simplification, the particle is split into two when breakage occurs. The newly generated polygons are directly modelled by the DEM and SBFEM without any change of the formulation, and thus this method does not need to predefine sub-particles and re-meshing elements. At last, the feasibility of the newly developed method is verified by a biaxial benchmark test. © 2017, Science Press. All right reserved.