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
Mechanics
Rossella Laudani, Martin Ostoja-Starzewski
Summary: The violation of the entropy inequality in macroscopic granular media undergoing collisional dynamics is found to be a result of the fluctuation theorem of nonequilibrium thermodynamics. Through molecular dynamics simulations, it is determined that the occurrence of negative entropy increments is influenced by the Eulerian velocity gradient and the Young modulus of the disks.
JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME
(2021)
Article
Materials Science, Multidisciplinary
X. Tang, J. Yang
Summary: This study presents a novel grain-scale model to investigate the effect of particle morphology on elastic wave propagation in granular materials. The results show that increasing particle aspect ratio leads to a notable rise in elastic wave velocity, while increased particle blockiness causes a moderate reduction in velocity. Furthermore, particles with higher aspect ratio have a broader range of transmitted frequencies compared to those with greater blockiness.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2021)
Article
Engineering, Geological
Weibin Mo, Rui Wang, Jian-Min Zhang, Yannis F. Dafalias
Summary: This study investigates and quantifies the evolution of fabric tensors under cyclic loading using discrete element method (DEM) tests. Two different continuum evolution rate equations are used for simulations, and the results show that the novel Combined Fabric Evolution (CFE) equation can accurately simulate fabric evolution under different conditions.
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
(2023)
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
Debdeep Sarkar, Meisam Goudarzy, Torsten Wichtmann
Summary: The aim of this study was to provide evidence of the influence of particle size on the dynamic properties in granular materials. The results showed that particle size had a significant influence, particularly for larger mean grain sizes. The influence of particle size diminished for materials with a mean size greater than 2 mm, but still had a relatively small influence on materials with lower mean particle sizes.
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, 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
Mechanics
Eloise Marteau, Jose E. Andrade
Summary: This article investigates the impact of particle shape on force chains in granular materials, showing that force chains are less prevalent in assemblies of arbitrarily-shaped particles compared to circular-shaped samples. Interlocking contact mechanisms are identified as essential for the emergence of stable force chains and explaining the enhanced shear strength observed in arbitrarily-shaped samples.
JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME
(2021)
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
Tao Wang, Antoine Wautier, Sihong Liu, Francois Nicot
Summary: This study investigates the influence of fines content on the non-associated plasticity of binary mixtures using 2D DEM simulations. It finds that fine grains help stabilize the granular assembly, limiting plastic deformations and reducing microstructure reorganizations. Fines content affects the plastic flow direction but not the normal direction of yield surface.
Article
Physics, Fluids & Plasmas
Tomas Trewhela, J. M. N. T. Gray, Christophe Ancey
Summary: The study investigates the segregation of single large intruder particles in granular materials, finding that segregation rate is influenced by size ratio and local strain rate. Larger size ratios result in faster segregation rates, while ratios closer to unity lead to stronger rotation effects.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Engineering, Mechanical
Mehdi Pouragha
Summary: This study provides a correlation analysis for the evolution of contact fabric in granular materials and finds that there is a strong correlation between contact fabric and total strain.
JOURNAL OF ENGINEERING MECHANICS
(2022)
Article
Engineering, Mechanical
Ghassan Shahin, Eric B. Herbold, Stephen A. Hall, Ryan C. Hurley
Summary: The study reveals a hierarchy in the length scales of granular solids, with lengths governing structural variables being the shortest, lengths of stress variables being intermediate, and lengths of energy dissipation being the longest. All structural and mechanical length scales obey a power law based on the theory of Geostatistics, implying that the length scales can be found by analyzing samples significantly smaller than the length scales themselves. The length scales are also found to be sensitive to boundary conditions, implying that they are extrinsic features of granular media.
EXTREME MECHANICS LETTERS
(2022)
Article
Mechanics
Vishnu Kumar Sahu, Soniya Kumawat, Shivani Agrawal, Anurag Tripathi
Summary: This study investigates the density segregation of multi-component granular mixtures in a dense, gravity-driven flow over a rough and bumpy periodic chute surface through theory and simulations. The present approach generalizes existing theoretical and rheological models for binary mixtures to multi-component mixtures, accounting for the inter-coupling of rheology with segregation. The theoretical predictions show excellent agreement with DEM simulations for a variety of compositions and density ratios.
JOURNAL OF FLUID MECHANICS
(2023)
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, 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, 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, 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, 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)
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)
Proceedings Paper
Engineering, Civil
E. Yazdani, B. Montoya, M. Wengrove, T. M. Evans
Summary: Erosion of coastal dunes during storm events is a common problem, and bio-mediated ground improvement can help reduce their impact. In a near-prototype-scale experiment, a model sand dune was constructed and bio-cementation was applied to one section. Pressure and moisture sensors, as well as pore pressure sensors, were used to study surface erosion and internal instability. Lidar technology was used to assess the performance of the dune under surge flow, and triaxial tests were conducted to measure the strength and stiffness of the cemented sand.
GEO-CONGRESS 2022: GEOENVIRONMENTAL ENGINEERING; UNSATURATED SOILS; AND CONTEMPORARY TOPICS IN EROSION, SUSTAINABLITY, AND COAL COMBUSTION RESIDUALS
(2022)
Proceedings Paper
Engineering, Civil
Ariadna Covarrubias Ornelas, Jiayao Wang, Diane Moug, T. Matthew Evans, Anika Walter
Summary: Diatoms, a challenging geomaterial, have a significant impact on engineering behavior. The liquid limit and plastic limit of diatomaceous soils increase as the proportion of diatom particles increases. This research developed a reasonable method to estimate the diatom particle proportion in soil using scanning electron microscopy (SEM) analysis, and found a correlation between physical soil properties and diatom proportion.
GEO-CONGRESS 2022: SITE AND SOIL CHARACTERIZATION, COMPUTATIONAL GEOTECHNICS, RISK, AND LESSONS LEARNED
(2022)
Proceedings Paper
Engineering, Civil
J. Wang, T. Chin, D. Moug, T. M. Evans
Summary: This study investigates the eccentric behaviors observed during liquid limit testing on diatomaceous soil. It finds inconsistencies in the test results using different methods and proposes modifications to the test procedures and equipment.
GEO-CONGRESS 2022: SITE AND SOIL CHARACTERIZATION, COMPUTATIONAL GEOTECHNICS, RISK, AND LESSONS LEARNED
(2022)
