Article
Engineering, Geological
Yuxuan Wen, Yida Zhang
Summary: This study uses the discrete element method to conduct a series of tests and finds a tight correlation between the void ratio and the fabric tensor of granular soils. By plotting the void ratio data against the first two invariants of the fabric tensor, a unique surface is obtained. The robustness of this relation is confirmed through testing samples with different initial void ratios under complex loading paths.
Article
Engineering, Geological
Xiaoqiang Gu, Xiaomin Liang, Jing Hu
Summary: Fabric anisotropy is a sought-after micro index to correlate macro mechanical responses of granular materials. In this work, discrete element method (DEM) is utilized to simulate multi-directional bender element tests in granular soils to obtain the evolution of wave velocities during drained conventional triaxial (CT) and true triaxial (TT) tests, and the contact normal based fabric is simultaneously monitored for bridging the fabric anisotropy and wave velocity anisotropy. The results show that stress-normalized wave velocities and microscopic fabric, including contact normal distribution and coordination number, remain nearly constant until a stress ratio threshold is reached. After the threshold value is reached, stress-normalized wave velocities start to decrease, especially in the minor principal stress direction, accompanied by significant adjustment of coordination number and fabric anisotropy. The results also reveal that the normalized wave velocity depends on the contact normal densities in the wave propagation and particle oscillation directions. With the contact normal distribution represented by a density function, a good linear relationship between the microscopic fabric anisotropy and macroscopic wave velocity anisotropy is obtained for both CT and TT tests.
Article
Engineering, Chemical
Bei-Bing Dai, Tian-Qi Li, Lin-Jie Deng, Jun Yang, Wei-Hai Yuan
Summary: In this study, the effect of fabric orientation on the angle of repose was examined through physical experiments and numerical simulations. The results showed that the angle of repose first decreased and then rebounded as the deposition plane's orientation angle varied. The minimum values were observed at specific angles. Numerical analyses revealed the intensification of microstructure reorganization and the decrease in anisotropy magnitude. Based on a conceptual model, the fundamentals underlying the effect of fabric orientation on the angle of repose were clarified.
Article
Engineering, Geological
Yuxuan Wen, Yida Zhang
Summary: This study introduces the concept of critical fabric surface (CFS) and establishes a single CFS spanning across a wide range of coordination numbers. This provides a new perspective to interpret and model the mechanics of granular soils in both pre- and post-liquefied regimes.
Article
Engineering, Geological
Nan Zhang, Ahmadreza Hedayat, Shaoyang Han, Runlin Yang, Hector Gelber Bolatios Sosa, Juan Jose Gonzalez Cardenas, Guido Edgard Salas Alvarez
Summary: The study utilized X-ray computed tomography (μCT) and discrete element modeling (DEM) to investigate the isotropic compression behavior of a granular assembly in relation to particle morphological properties. It was found that particle concavity and interparticle friction had significant influences on the compression behavior of granular assemblies. Microscopic analysis provided insights into the characteristics of granular assembly under isotropic compression.
JOURNAL OF ROCK MECHANICS AND GEOTECHNICAL ENGINEERING
(2021)
Article
Engineering, Civil
Nan Zhang, Shiwei Zhao, T. Matthew s Evan, Yu Du, Yushun Lian
Summary: This article investigates the shear behavior of granular-continuum interfaces by using three-dimensional discrete element modeling. The influence zones vary with normal stresses and soil densities. The micromechanical behaviors and fabric evolution for the interface are studied, and stress and fabric tensors are used to capture the shear strength. Results show that both macro and micro mechanical parameters decrease with increasing confining stress.
EUROPEAN JOURNAL OF ENVIRONMENTAL AND CIVIL ENGINEERING
(2022)
Article
Engineering, Chemical
Jinpeng Qiao, Kejun Dong, Chenlong Duan
Summary: The study utilized the discrete element method to investigate the segregation process of a single large intruder in a vibrated bed of small particles, focusing on the effects of vibration conditions and intruder shape on the intruder's dimensionless ascending velocity. It was found that the ascending velocity changes with the variation of vibration amplitude and frequency, and is influenced by the shape of the intruder.
Article
Engineering, Geological
Q. X. Wu, J. J. Zheng, Z. X. Yang
Summary: This study presents a convenient and efficient DEM sample preparation procedure to generate three-dimensional specimens with different intensities of initial fabric anisotropy. The initial fabric can be altered by changing the bedding plane angle α of the soil deposition relative to the horizontal plane. A range of α values was considered, from -90 to 90 degrees. Undrained rotational shear tests were conducted on these initially anisotropic samples using a novel discrete element approach. The simulation results provide new insights into the strain evolution patterns and fabric evolutions of initially anisotropic samples under undrained rotational shear.
Article
Engineering, Chemical
Yanjie Li, Qi Zhang, Xia Hua, Yu Guo, Jennifer S. Curtis
Summary: This study simulates the triaxial compressions of spherical granular beds reinforced by immersed flexible fibers using the discrete element method (DEM). The results show that the yield stresses of the particle beds increase with higher fiber concentration or aspect ratio, but are not affected by fiber flexibility. The configuration of the immersed fibers significantly impacts the compressive strength of the beds.
Review
Engineering, Chemical
Kamyar Kildashti, Kejun Dong, Aibing Yu
Summary: This paper reviews the current status of contact force models for non-spherical particles, focusing on their relationships with the geometrical, material, and mechanical properties of the particles. The aim of the review is to improve the existing simplified contact force models used in discrete element method (DEM) simulations by selecting better models. The review covers contact force models based on the extension of the classical Hertz theory, the effects of different variables on contact force, and tangential force models for non-spherical particles. Based on the review, a set of improved contact force models for DEM is recommended to accurately predict contact force and area in emerging areas such as nanoparticles and additive manufacturing.
Article
Computer Science, Interdisciplinary Applications
Siqiang Wang, Qi Zhang, Shunying Ji
Summary: A CUDA-GPU parallel algorithm based on super-quadric elements is developed to simulate large-scale non-spherical granular systems, demonstrating its applicability and reliability through various tests.
ADVANCES IN ENGINEERING SOFTWARE
(2021)
Article
Computer Science, Interdisciplinary Applications
An Zhang, Mingjing Jiang, Dong Wang
Summary: To understand the effects of fabric anisotropy on cyclic liquefaction of sands, undrained cyclic triaxial tests on vertical and horizontal specimens were simulated using the discrete element method. The simulation accurately depicted the anisotropic cyclic responses observed in experiments, showing that the vertical specimen is more susceptible to liquefaction than the horizontal specimen under symmetrical cyclic loading conditions. The study investigated various fabric parameters at the particle scale to gain insights into the macro response and applied anisotropic critical state theory to explore the relationship between macro-mechanical behavior and fabric evolution.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Engineering, Civil
Yiming Liu, Chenming Xu, Guofang Xu, Haijun Mao, Zunqun Xiao
Summary: This study investigated the joint influence of particle crushing and intermediate principal stress coefficient on the macro and micro performances of granular assembles using 3D discrete element method. The results showed that particle breakage significantly affects the behaviors of granular soils and does not influence the unique relationship between the intermediate principal stress coefficient and the deviatoric fabric of strong contacts.
KSCE JOURNAL OF CIVIL ENGINEERING
(2021)
Article
Engineering, Geological
Jiangtao Wei
Summary: Numerical tests in DEM simulations were conducted to explore the evolution of particle-void fabric in granular packings during cyclic liquefaction. As the mean effective stress decreases during the process, the particle-void descriptor also decreases, showing a positive correlation between them.
SOIL DYNAMICS AND EARTHQUAKE ENGINEERING
(2022)
Article
Engineering, Chemical
Ali Abbas Zaidi
Summary: This article studies the resistance or granular drag force experienced by an intruder during penetration into granular material, and explains the underlying physics. Numerical simulations using the discrete element method (DEM) show that particles undergo a jamming transition below the intruder, and the region of jammed particles increases with the depth of intrusion, which leads to an increase in the granular drag force.
Article
Engineering, Civil
Nan Zhang, Shiwei Zhao, T. Matthew s Evan, Yu Du, Yushun Lian
Summary: This article investigates the shear behavior of granular-continuum interfaces by using three-dimensional discrete element modeling. The influence zones vary with normal stresses and soil densities. The micromechanical behaviors and fabric evolution for the interface are studied, and stress and fabric tensors are used to capture the shear strength. Results show that both macro and micro mechanical parameters decrease with increasing confining stress.
EUROPEAN JOURNAL OF ENVIRONMENTAL AND CIVIL ENGINEERING
(2022)
Article
Engineering, Multidisciplinary
Shiwei Zhao, Jidong Zhao, Yuanming Lai
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2020)
Article
Computer Science, Interdisciplinary Applications
Shiwei Zhao, Jidong Zhao
Summary: SudoDEM is a novel open-source discrete element code for efficient modeling of non-spherical particles in 2D and 3D, featuring a rich library of particle shapes and efficient contact detection algorithms. The code has been validated and demonstrated its robustness, efficiency and versatility in providing realistic solutions to granular mechanics problems.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Article
Engineering, Multidisciplinary
Shiwei Zhao, Jidong Zhao, Weijian Liang
Summary: The article introduces a novel parallel computing framework for large-scale and multiscale simulations of granular media, utilizing RVE parallelism and GPU-specific techniques. Benchmark tests show that GoDEM can achieve a speedup of approximately 350 compared to a single-CPU-core code.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING
(2021)
Article
Engineering, Chemical
Changhui Zhang, Shiwei Zhao, Jidong Zhao, Xiaowen Zhou
Summary: This paper proposes a 3D Voronoi analysis framework for realistic grain packing based on XCT and DEM, along with an efficient parallel processing tool PySVT. It reveals significant differences in particle characteristics between 2D and 3D, with emphasis on Voronoi cell morphology and local porosity analysis for void phase.
Article
Engineering, Geological
Hao Chen, Shiwei Zhao, Jidong Zhao, Xiaowen Zhou
Summary: The study focuses on the influence of particle shape on the at-rest coefficient of lateral pressure, K0, establishing a relationship between K0 and particle structure through micromechanics-based theories and numerical simulations. Results show that K0 is related to particle shape, with contact force distribution playing the most prominent role in determining K0.
Article
Engineering, Chemical
Zhengshou Lai, Shiwei Zhao, Jidong Zhao, Linchong Huang
Summary: This study revisits the contact resolution of non-spherical particles in DEM through GJK and shape erosion method, highlighting the significant impact of shape erosion on weak contacts within the packing and potential overestimation of contact overlap. However, the negligible effect of shape erosion on the overall coordination number, packing fabric, and stress-strain behaviors is observed. It is recommended to carefully set the erosion ratio to be compatible with the overlaps of strong contacts in practical applications.
Article
Engineering, Geological
Jiayan Nie, Shiwei Zhao, Yifei Cui, Yu Wang
Summary: This study systematically investigates the coupled effects of particle overall regularity (OR) and sliding friction on the shear behavior of dense sands. The findings reveal that different aspects of particle shape can have mutual effects on the overall behavior of sands. Moreover, the study analyzes the microscopic origins of multi-scale shape-dependent shear strength, which is crucial for improving the understanding of the influence of particle shape on the shear behavior of sands.
JOURNAL OF ROCK MECHANICS AND GEOTECHNICAL ENGINEERING
(2022)
Article
Engineering, Multidisciplinary
Weijian Liang, Huanran Wu, Shiwei Zhao, Wei Zhou, Jidong Zhao
Summary: This study introduces a scalable three-dimensional multiscale framework for continuum-discrete modeling of granular materials, combining a continuum-based material point method (MPM) and a discrete element method (DEM). A parallel scheme based on MPI model is developed to address computational cost, achieving significant speedup in large-scale simulations. The framework is validated and applied to simulate the intrusion of a solid object, showcasing its numerical performance and predictive capability.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING
(2022)
Article
Mathematics, Interdisciplinary Applications
Zhengshou Lai, Shiwei Zhao, Jidong Zhao, Linchong Huang
Summary: This paper presents a signed distance field approach for DEM modeling of granular media with arbitrarily shaped particles. The approach uses a generic SDF-based interface to rigorously model particle shapes and their contact operations. It defines the signed distance inside and outside particles and represents the particle surface using the zeroth isosurface of the SDF. The paper also develops specialized grain shape models and a numerical scheme for particle surface discretization and reconstruction. Demonstrative examples validate the proposed approach and computational aspects are discussed.
COMPUTATIONAL MECHANICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Shiwei Zhao, Jidong Zhao, Weijian Liang, Fujun Niu
Summary: The text discusses the intricate coupling between heat generation and transfer with mechanical responses in granular materials, introducing a novel hierarchical multiscale modeling framework TM-DEMPM. This framework utilizes Material Point Method coupled with Discrete Element Method to provide physics-based simulations of thermo-mechanical granular responses, with a proposed hybrid OpenMP and GPU-based parallelization for faster numerical solutions.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Engineering, Multidisciplinary
Shiwei Zhao, Zhengshou Lai, Jidong Zhao
Summary: This article presents a novel approach to accelerate particle-based simulations by leveraging ray tracing cores in addition to CUDA cores on RTX GPUs. A new, general-purpose RT-based neighbor search algorithm is proposed and benchmarked with a prevailing cell-based one. The study demonstrates that the RT-based simulations are 10%-60% faster than the cell-based ones.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING
(2023)
Article
Engineering, Multidisciplinary
Hao Chen, Shiwei Zhao, Jidong Zhao, Xiaowen Zhou
Summary: This study proposes a generalized contact scheme based on a hybrid scheme of material point method (MPM) and discrete element method (DEM) to model multi-body and multi-material interactions. The scheme contains two novel features of particle-particle and particle-structure contact schemes guided by a DEM contact model. It demonstrates that the generalized contact scheme can flexibly capture the mechanical responses of multi-body and multi-material systems in MPM.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Engineering, Multidisciplinary
Shiwei Zhao, Jidong Zhao
Summary: This paper presents a novel approach, called Ray Tracing Discrete Element Method (RTDEM), for efficiently simulating particles with arbitrary shapes. The method uses a triangular mesh and template meshes, along with ray tracing-based algorithms and discrete potential field functions, to accurately and efficiently detect and resolve contacts between the particles.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Review
Physics, Applied
Jidong Zhao, Shiwei Zhao, Stefan Luding
Summary: This Technical Review provides an overview of computational modeling of granular matter, focusing on the role of particle shape and future challenges.
NATURE REVIEWS PHYSICS
(2023)