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, 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
Thermodynamics
Shuo Shi, Kaijun Jiang, Sheng Chen, Zijian Zhou, Xiaoze Du
Summary: This study investigates the shear-induced anisotropy of the effective thermal conductivity (ETC) in granular packings during quasistatic shear deformation. The discrete element method is utilized to track the position, force, and contact condition of each particle in the packing. The ETC of the packing at different shear strains is evaluated using the particle-resolved finite element method. The findings demonstrate that the anisotropy ratio of the ETC can reach 40% when the shear strain increases to 0.11, primarily due to the variation in the contact network formed during consecutive shear steps. Contacts with large contact radius and strong thermal conductance are shown to align preferentially with the direction of deformation, influencing the anisotropy of thermal conductivity. Grouping contacts into sub-networks based on contact strength reveals that the thermal conductivity anisotropy of a packing is predominantly caused by strong contacts.
APPLIED THERMAL ENGINEERING
(2023)
Article
Computer Science, Interdisciplinary Applications
Jiangtao Wei, Junnan Ren, Haiying Fu
Summary: This paper investigates the effect of weakening of inter-particle friction on granular soil responses. The study shows that the influence of friction weakening is limited under low confining stress but becomes significant with increasing confining stress. From a micromechanical perspective, samples with friction weakening model have lower particle friction, resulting in higher contact sliding ratio and lower tangential contact force, which leads to lower peak strength at the macroscale.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Materials Science, Multidisciplinary
Ze-Xiang Wu, Lei Yang, Zhe Wang, Ying-Chun Zhuang, Dong-Mei Tu
Summary: This paper investigates the influence of periodic temperature change on the properties of dry granular materials through experiments and simulations. It is found that thermal cycling leads to changes in volumetric strain and shear dilatancy level of particles, as well as affecting the contact force and force chain between particles.
MATERIALS RESEARCH EXPRESS
(2021)
Article
Engineering, Geological
Daniel H. Johnson, Farshid Vahedifard, John F. Peters
Summary: This study models the macroscopic frictional behavior of granular soils under monotonic and cyclic loadings, based on micromechanical determination of dissipated energy at particle contacts. By utilizing the discrete element method, the study examines the stored, dissipated, and damping energies associated with shear loading and relates them to friction using the Taylor-critical state power balance relationship. The research also investigates the contributions of different modes of energy dissipation to total frictional resistance.
Article
Mechanics
Payam Poorsolhjouy, Marcial Gonzalez
Summary: This study presents constitutive laws of structural members using granular micromechanics approach, deriving macroscopic behavior by investigating average behavior of grain-pair interactions. Closed-form solutions for constitutive relationship of uniform and functionally graded materials are derived, demonstrating versatility and computational efficiency of the proposed approach. Analyzing structural members made of particle-binder composites reveals interesting one-way and two-way coupling behavior between internal forces and moments that cannot be achieved through closed-form solutions.
COMPOSITE STRUCTURES
(2021)
Article
Mining & Mineral Processing
V. P. Kosykh, O. A. Mikenina
Summary: The experimental and theoretical studies reveal that plane deformation of granular medium leads to the formation of clusters of approximately 10-15 times the diameter of the particles. The study of biaxial compression identifies four basic modes of deformation, corresponding to different shapes of clusters, which exhibit complex alternation behavior. The deformation process also exhibits memory characteristics with a Hurst exponent of 0.84. The limit loads in different modes may differ by 2 or 3 times. When dealing with the deformation of granular media, the discrete element method should be used to calculate the mechanical conditions of domains smaller than 80-100 particle diameters.
JOURNAL OF MINING SCIENCE
(2022)
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
Computer Science, Interdisciplinary Applications
Xuejian Li, Kang Duan, Qiangyong Zhang, Jiarun Li, Rihua Jiang, Luchao Wang
Summary: The permeability of hydrocarbon reservoirs composed of porous rock is anisotropic under asymmetrical stress configuration. The permeability sensitivity of porous sandstone to stresses is investigated by experiments and simulations. An analytical model is proposed to calculate the components of tensorial permeability affected by stresses and evaluate the evolution of permeability anisotropy. The prediction of permeability sensitivity behaviors and anisotropy to stresses are consistent with experimental and simulated results.
COMPUTERS AND GEOTECHNICS
(2023)
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, 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, Chemical
Shuai Zhang, Wei Ge, Guangjing Chen, Zhiling Liu, Tongtong Liu, Lixiong Wen, Chunjiang Liu
Summary: This study observed rare events of granular flow being arrested by the formation of unstable arches and then restarted by their spontaneous collapsing, known as clogging-collapsing events. The research demonstrated that the coordinated evolution of the entire force chain system and the incomplete dissipation of kinetic energy are the main factors responsible for the collapsing.
Article
Engineering, Civil
Chuang Zhou, Jian-Gu Qian, Zhen -Yu Yin, Hao Xiong
Summary: This study investigates the effect of cyclic loading on suffusion in gap-graded soils using computational fluid dynamics and discrete element method. The results show that higher cyclic frequency and strain magnitude lead to more severe loss of fines.
TRANSPORTATION GEOTECHNICS
(2023)
Article
Geosciences, Multidisciplinary
Lucille Carbillet, Fabian B. Wadsworth, Michael J. Heap, Patrick Baud
Summary: The strength of porous rocks varies depending on the porosity and grain size. Synthetic samples showed that different models are needed to accurately predict strength for high-porosity granular samples and low-porosity non-granular samples. A regime plot was proposed to determine the suitable micromechanical model for strength prediction based on porosity and grain size.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Engineering, Geological
Ehsan Yazdani, Amy Nguyen, T. Matthew Evans
Summary: This study investigated the influence of different types of fine materials on the shear-induced instability of sand-fines mixtures from various aspects. Undrained triaxial tests were conducted to evaluate the collapsibility potential of the mixtures. The results showed that the equivalent intergranular void ratio can reduce the influence of fines and provide a strong correlation bearing several aspects of the mechanical behavior of coarse-grained-fines mixtures.
INTERNATIONAL JOURNAL OF GEOMECHANICS
(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, Geological
Ali Dadashisrej, Amalesh Jana, Armin W. Stuedlein, T. Matthew Evans
Summary: The effect of strain history on the monotonic and cyclic response of silt deposits was investigated. It was found that in many cases, the cyclic resistance increased due to beneficial effects such as increased density, pseudo-overconsolidation, and increased lateral stresses. However, inconsistent evolution of cyclic resistance was observed in some specimens when using different shear strain cyclic failure criteria. Staged, strain-controlled tests revealed that large shear strains caused a reduction in cyclic resistance, while small cyclic shear strains led to progressive increases in shear wave velocity.
SOIL DYNAMICS AND EARTHQUAKE ENGINEERING
(2022)
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, Geological
Armin W. Stuedlein, Ali Dadashiserej, Amalesh Jana, T. Matthew Evans
Summary: This study investigates the liquefaction susceptibility and cyclic response of different types of intact silts through laboratory testing. The results indicate that the plasticity index, fines content, and overconsolidation ratio have significant influences on the behavior of silts. Hysteretic metrics provide an objective means to differentiate between different behaviors of silts. Modifications to existing liquefaction susceptibility criteria improve the accuracy of assessing the behavior characteristics of silts.
JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
(2023)
Article
Computer Science, Interdisciplinary Applications
C. S. Sandeep, A. Hernandez, K. Stangeland, T. M. Evans
Summary: The micro-and macroscale mechanical behaviors of granular materials are affected by the morphological features of the grains. Imaging techniques, such as X-ray computed tomography, have limitations in terms of cost and applicability, while 2D digital photographs may be influenced by image resolution and particle orientation. This study evaluates the impact of image quality on shape characterization and establishes relationships between 2D and 3D shape descriptors using computational particle geometries and real beach sand grains scanned by X-ray mu-CT. The results show that image resolution affects both geometric and morphological features, and low-quality 2D images affect shape characterization.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Jeffrey Knowles, Yifei Ma, T. Matthew Evans
Summary: This study presents a new polyhedral reinforced interior shell model (PRISM) based on the discrete element method (DEM) for simulating collisions between polyhedral particles. The proposed model has advantages in terms of computational efficiency and the ability to incorporate inhomogeneous properties at particle-scale. Validation through simulations suggests improved efficiency and efficacy in modeling polyhedral particles with realistic geometric and physical properties.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Engineering, Geological
Amalesh Jana, Ali Dadashiserej, Benchen Zhang, Armin W. Stuedlein, T. Matthew Evans, Kenneth H. Stokoe II, Brady R. Cox
Summary: This study compares the dynamic responses of a low-plasticity silt deposit to multidirectional loading from a vibroseis shaker and controlled blasting. The results show that the vibroseis shaking induced linear-elastic to nonlinear-inelastic responses, while the blast-induced shear waves induced nonlinear-elastic and nonlinear-inelastic responses. Multidirectional loading, excess pore pressure, migration, and impedance are identified as predominant factors affecting the dynamic responses of the silt deposit.
JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
(2023)
Article
Engineering, Multidisciplinary
C. S. Sandeep, T. Matthew Evans
Summary: Woodpecker's head structure provides inspiration for studying soil penetration. The study found that wedge offsets have minimal effect on drag forces, but lift forces can be manipulated by adjusting the top and bottom offsets.
BIOINSPIRATION & BIOMIMETICS
(2023)
Article
Engineering, Geological
Guoliang Ma, Xiang He, Yang Xiao, Jian Chu, Hanlong Liu, Armin W. Stuedlein, T. Matthew Evans
Summary: The precipitation process and flow field of CaCO3 in a heterogeneous chip are studied, revealing that solutions can diffuse into dead-end pores via pore throats and precipitate CaCO3 across the chip. However, the distribution of crystals varies.
CANADIAN GEOTECHNICAL JOURNAL
(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)
Article
Engineering, Geological
Yang Xiao, Qingyun Fang, Armin W. Stuedlein, T. Matthew Evans
Summary: A series of drained triaxial tests were conducted on sandy soils with different mean particle sizes to investigate the effect of particle size and shape on soil strength and dilatancy. The results showed that the maximum and critical-state friction angles of rounded glass bead sands increased slightly with increasing particle size, while the critical-state friction angle of angular crushed glass sands decreased. The maximum dilation angle of both angular crushed glass and rounded glass bead sands increased with larger particle size. The comparison of different sands demonstrated that the strength and friction angle of granular soils are directly influenced by particle angularity and interparticle locking.
INTERNATIONAL JOURNAL OF GEOMECHANICS
(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)
Article
Geosciences, Multidisciplinary
Hailey Bond, Meagan Wengrove, Jack Puleo, Maro Pontiki, T. Matthew Evans, Rusty A. Feagin
Summary: This study used a laboratory experiment to simulate the erosive process of beach scarp formation and observed the changes in pressure gradients and sand erosion during scarp development. A conceptual model for scarp formation is proposed based on the observations in this study.
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
(2023)
Article
Engineering, Geological
Ali Dadashiserej, Amalesh Jana, Armin W. Stuedlein, T. Matthew Evans
Summary: The effect of vertical effective consolidation stress on the cyclic resistance of nonplastic to plastic soils was investigated. It was found that increasing consolidation stress leads to a reduction in cyclic resistance due to the detrimental effects on soil fabric, overconsolidation ratio, and dilative tendencies. Reconstituted clay specimens were used to confirm the sensitivity of cyclic resistance to consolidation stress, with the detrimental effect of suppressed dilative tendencies dominating over the beneficial effect of reduced void ratio. The compressibility of the soil was also found to play a role in cyclic resistance.
JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
(2023)