Granular Material Research Articles

Evolution of the strain localization and shear-zone internal structure in the granular material: Insights from ring-shear experiments

Shear zone is widely observed in natural faults and landslides as well as laboratory experiments on granular material. Understanding the shear-zone evolution process in granular materials is crucial in studying the dynamics of the landslides and faults. However, it is still not well understood. To this end, we conducted a series of ring-shear experiments to investigate the evolution of strain localization and shear-zone internal structure in cohesive and non-cohesive granular materials. The quantitative evaluation was conducted by using high-solution X-ray computed tomography (CT). The analyses included visualization of shear-zone internal structure and quantification of particle shapes, orientations, and grain-size distributions at different shear strain levels. We found that with the increase of shear displacement, the large particles inside the shear zone became more and more rounded, but without an orientation, wear and attrition resulted in an abundance of nanoparticles within the shear zones. We also found fine-particle layers (nanoparticle layers) formed on either side of shear zones during shear localization, implying that shear development progressed from a shear zone to an interface. These findings offer some new understanding of the evolution of shear zones in granular materials.

NUMERICAL MODELLING OF TSUNAMIS GENERATED BY GRANULAR LANDSLIDES IN OPENFOAM

Landslide-generated tsunamis are a relevant source of hazard for coastal areas. In this paper, the preliminary modelling results of tsunamis generated by deformable landslides by using computational fluid dynamics (CFD) methods, in OpenFOAM, is presented. The numerical approach presented here consists in modelling the granular material by using a Coulomb viscoplastic rheology. This numerical model is applied to reproduce three literature benchmark cases (2D submerged, 2D and 3D subaerial, respectively). Some preliminary qualitative and quantitative numerical results, compared to the experimental ones, are presented in the paper.

Evaluation of the crushing characteristics of industrial waste aggregates as construction materials

Overexploitation of natural resources like sand and stone aggregates for construction purposes, and on the other hand, the generation of huge quantities of different industrial wastes in recent years pose a threat to the environment. One of the promising solutions to both of these problems could be bulk utilization of industrial waste aggregates in civil and construction industries. In order to check the utilization prospects of any industrial waste aggregate, its crushing characteristics is one of the important parameters that needs to be evaluated. This is due to the fact that the engineering behaviour and integrity of any granular media is highly dependent on the breakage potential or the crushing characteristics of the materials. In the present study, some of the industrial waste aggregates viz., Blast furnace slag (BFS), Quarry waste (Q-Waste), Marble waste (M−Waste), and Overburden sand (OB-Sand) are selected for evaluation of their crushing characteristics. Various parameters such as mineralogy, grain morphology, gradation, mean grain size, the initial state of compaction, and stress levels which play an important role in deciding the crushing strength of a granular material are considered in the present study. A series of one-dimensional compression tests are performed at different stress levels (i.e., 5, 10, 20, 30, 40 MPa) after compacting the industrial waste aggregates to different compaction states. Based upon the experimental results, BFS and OB-sand were found to be the most and least crushable materials, respectively. Mathematical equations are also proposed in this paper for the prediction of relative breakage. These are found to be very suitable for industrial waste aggregates. It is highly believed that the results obtained from the present study can be used as a pre-reference while selecting any of the mentioned materials for construction purposes.

Модель "трубок-слоев" намагничиваемой цепочки шаров: магнитные свойства, оценка гиперусиления поля между шарами

A chain of granules is the magnetic flux conductive channel in the magnetized granular material. Experimental data on magnetic fluxes were obtained for eight conditional cores (different relative radii rc / R = 0.2--0.9) of the magnetized chain of spheres making it possible to establish the magnetic flux data for seven "pipe-layers" of the rp / R = 0.25--0.85 average radius. In the H magnetized field strength range from 10 to 50--55 kA/m, field dependences of this parameter and of the more universal parameter (independent of the radius of the spheres in the chain) of the magnetic flux density, i.e., magnetic induction in each "pipes", are close to the linear ones. Thus, the values of their magnetic permeability μp which are individual for different "pipes", turn out to be essentially constant in this range of H, which also carries important information about how many times the local field intensity h between the spheres exceeds the value of H. At rp / R ≤ 0.4, the h values are exceeding by an order of magnitude or more the H value, and at rp / R > > 0.4 and up to the periphery of the inter-sphere --- by several times. The μp = h / H decreasing dependence on rp / R, which is of interest in solving problems of the materials fine magnetic separation (using the magnetized matrix media), obeys the inverse quadratic function, and the field inhomogeneity level to the inverse cubic function

EFFECTS OF CONSTITUENT MATERIAL PROPERTIES ON EROSION OF FLAT BED AND RECESSION OF BLUFF

Seashores and river bottoms are constantly eroded by the flow processes. Grains of various types, including gravel, sand, silt, and clay, mixed at different ratios, and demonstrating varying characteristics, are the constituent materials of these eroding land features. The present study quantifies the importance of the geomechanical properties of soils, with a large fraction of granular material and a smaller portion of fine grain particles, on the incipient motion of the sediment under steady-state flow. Further, it highlights the implications of the soil properties on the erosion and recession of steep beach and bluff systems.

Microstructure and compression properties of semisolid CrCuFeMnNi high-entropy alloys

CrCuFeMnNi high-entropy alloys were investigated for semisolid processing due to their high compositional flexibility. They exhibited a highly globular semisolid microstructure, with small transformed solid globules. The alloys had a mixture of BCC and two FCC phases, with BCC fractions remaining almost constant while the fractions of both FCC phases changed with Cu content. Although the predicted and experimental equilibrium phase fractions differed, measured compositions were close to equilibrium. During semisolid compression, peak stresses decreased, and the deformation plateau increased with liquid fraction. Furthermore, the alloys behaved like a cohesionless granular material.

Methodological problems of friction force measurement of plant granular materials

The methodology for measuring the frictional force of granular materials of plant origin is complex, since it requires taking into account both variable material factors and the use of available measurement methods in an appropriate way. This article deals with one of the important aspects of the application of a measurement methodology using bottomless containers. The effect of grain pressure on the side walls of the measuring container on the value of grain pressure on the measuring surface was studied. Five different granular materials (wheat, oat, beans, maize, peas) were used as the research material. To analyse the problem, the Janssen model was used as a basis, which describes the normal pressure of the granular material at the bottom of the container depending on certain factors. The tests were carried out for different heights of the material layer and different load values. After analysing the measurement values with calculated values, modifications of the base model were proposed. This modification allowed a high (close to 1) model fit to the measured values. The proposed approach can be useful in carrying out measurements of the friction force of granular materials, since it allows one to estimate the value of the actual pressure of the material on the contact surface. This provides an opportunity to make better use of the horizontal tribometer with a measuring container with support.

Theoretical and Experimental Analyses on the Sound Absorption Coefficient of Rice and Buckwheat Husks Based on Micro-CT Scan Data.

In this study, the sound absorption coefficients of rice and buckwheat husks were estimated. Computed tomography (CT) images were processed to determine the circumference and surface area of voids in the granular material, and the normal incident sound absorption coefficients were derived. In addition, the tortuosity, which expresses the complexity of the sound wave propagation through the structure, was measured for each material. The theoretical sound absorption coefficients were then compared to the measured sound absorption coefficients with and without consideration of the tortuosity. A correction factor was used to bring the surface area of the granular material closer to the actual surface area and observed that the tortuosity obtained theoretical values that matched the trend of the measured values. These results indicate that using CT images to estimate the sound absorption coefficient is a viable approach.

Preparation of functional polyhydroxyalkanoate microspheres and their antibacterial activity and osteogenic effect evaluation

To construct polyhydroxyalkanoate (PHA) microspheres loaded with bone morphogenetic protein 2 (BMP-2) and human β-defensin 3 (HBD3), and evaluate the antibacterial activity of microspheres and the effect of promoting osteogenic differentiation, aiming to provide a new option of material for bone tissue engineering. The soybean lecithin (SL)-BMP-2 and SL-HBD3 were prepared by SL-mediated introduction of growth factors into polyesters technology, and the functional microsphere (f-PMS) containing BMP-2 and HBD3 were prepared by microfluidic technology, while pure microsphere (p-PMS) was prepared by the same method as the control. The morphology of microspheres was observed by scanning electron microscopy and the water absorption was detected; the release curves of BMP-2 and HBD3 in f-PMS were detected by ELISA kit. The antibacterial effect of microspheres in Staphylococcus aureus and Escherichia coli was tested with the LIVE/DEADTM BacLightTM bacterial staining kit; the biocompatibility of microspheres was tested using Transwell and cell counting kit 8 (CCK-8). The effect of microspheres on osteogenic differentiation was determined by collagen type Ⅰ (COL-1) immunofluorescence staining and alkaline phosphatase (ALP) concentration. In this experiment, the f-PMS and p-PMS were successfully constructed. Morphological characteristics showed that p-PMS surface was rough and distributed with micropores of 1-3 μm, while f-PMS surface was smooth and existed white granular material. There was no significant difference in water absorption between the two groups (P>0.05). The release curves of BMP-2 and HBD3 in the f-PMS and p-PMS were basically the same, showing both early sudden release and late slow release. The antibacterial activity of f-PMS was significantly higher than that of p-PMS in the test that against Staphylococcus aureus and Escherichia coli (P<0.05), but there was no significant difference in biocompatibility between the two groups (P>0.05). The results of osteogenic differentiation of human BMSCs showed that the fluorescence intensity of osteogenic specific protein COL-1 of f-PMS was significantly higher than that in p-PMS, and the activity of ALP in f-PMS was also significantly higher than that in p-PMS (P<0.05). The p-PHA have good antibacterial activity and biocompatibility, and can effectively promote the osteogenic differentiation of human BMSCs, which is expected to be applied to bone tissue engineering in the future.

Discrete Element Simulation of the Shear Behavior of Binary Mixtures Composed of Spherical and Cubic Particles

This research paper presents an investigation into the shear behavior of binary mixtures composed of cubic and spherical particles, employing the discrete element method (DEM) through triaxial tests simulations. A range of binary particle samples with varying volume fractions of cubic and spherical particles is generated for analysis. The study primarily focuses on examining the contracting-dilatancy relationship of binary granular material samples by scrutinizing deviatoric stress and volumetric strain curves, while considering the influence of confining pressure, initial porosity, and particle size ratio. Furthermore, the paper sheds light on the evolution of microstructures during the shearing process by presenting coordination numbers and rotational velocity fields for different particle types (overall particles, cubic particles, spherical particles), as well as between cubic-spherical particles. The findings demonstrate the substantial impact of both the volume fraction of cubic particles and the particle size ratio on the shear behavior of binary particles at both macroscopic and microscopic scales. Additionally, a comprehensive investigation reveals the dependence of anisotropy in normal contact forces, tangent contact forces, and contact orientations on the volume fraction of cubic particles.

Grid-layout ultrasonic LoRaWAN-based sensor networks for the measurement of the volume of granular materials

The aim of this paper is to propose a novel methodology for the measurement of volume of masses of granular material: this term encompasses a wide range of materials like grain, sand, coal and so on. The proposed approach is based on the exploitation of grids of ultrasonic ranging sensor nodes, placed above the material mass, exploiting LoRaWAN connectivity for data transmission and measuring the actual level of the material in each single spot. A geometrical approach is applied to the measured data for the computation of the volume. The proposed approach was tested by means of simulations and exploiting a reduced-scale experimental setup: different grid layouts were implemented and tested, with the aim of increasing the measurement accuracy. Since the presented experimental setup can be seen as a worst case scenario, the achieved results can be assumed as an upper bound for the accuracy of the proposed layout.

Comparative Analysis of Helical Piles and Granular Anchor Piles for Foundation Stabilization in Expansive Soil: A 3D Numerical Study

This study investigates the performance of granular anchor piles and helical piles in expansive soils. Expansive soils pose challenges for engineering due to their significant swelling and shrinkage characteristics. Special considerations are required for constructing foundations on expansive soil to mitigate volumetric changes. While helical piles provide uplift resistance in light structures, they may not fully stabilize foundations in expansive soils. In contrast, granular anchor piles offer a simpler alternative for resisting uplift forces. A numerical study was conducted to analyze the pullout loads, compressive loads, and heave behavior of these anchor techniques. The results demonstrate that granular anchor piles outperform helical piles in terms of pullout and compressive performance, with improvements ranging from 17% to 22.5% in pullout capacity and 0.5% to 19% in compressive capacity, depending on specific pile lengths and diameters examined. However, both techniques show similar effectiveness in reducing heave, achieving reductions of over 90% when specific conditions are met. Additionally, the use of high-rise cap piles contributes to significant heave reduction, effectively minimizing heave to nearly negligible levels compared to low-rise cap piles. It is found that the relative density of the granular material has a more pronounced effect on the pullout load compared to the compressive load, and its impact varies depending on the length of the pile. Therefore, it is recommended to avoid high relative density when the pile is entirely within the expansive soil while utilizing higher relative density is beneficial when the pile penetrates and settles in the stable zone.

The influence of water sorption on the microstructure of a hydro-sensitive granular material (couscous) deduced from simultaneous neutron and X-ray tomography

The effects of water on the behaviour of granular materials can be significant. Besides capillary bridges, several other chemo-hydro-mechanical processes can affect the response of hydro-sensitive granular assemblies, when water sorption critically alters the individual particles properties (i.e., swelling, deterioration of mechanical properties). It is very common to find such materials in food and pharmaceutical industries, where water sorption can often lead to important resources waste while processing or storing the product. It is therefore necessary to understand the phenomena that affect the material’s functionality, often related to particle agglomeration and degradation. However, despite the relevance of the problem, our knowledge about these phenomena is still relatively poor. With this study we aim to explore the link between water content increase and particle, contacts and assembly scale phenomena. Simultaneous neutron and X-ray tomography allows us to investigate respectively the water uptake and microstructure evolution of two couscous assemblies exposed to high relative humidity while subjected to constant stress, a configuration chosen to simulate the conditions in an industrial silo-storage. We acquire a data-set of images, from which we follow and quantify the variations of water content distribution and the resulting volumetric response of thousands of particles through bespoke algorithms. Despite the abundance of water provided, we observe spatial gradients in water content distribution and consequently in particle swelling. We find that the relation between these two variables can be described as (quasi-)linear. The contact area growth also seems to follow a similar trend.Graphic abstract

Use of glass waste as granular material in pavement layers

The valorisation of waste glass is part of a sustainable development plan. It presents several challenges, starting with the elimination of the various types of waste sent to landfill and the related costs, the reduction of the inconveniences associated with glass (shards, landfill fires), the development of new economic sectors and raw material saving (aggregate quarries). Several research works have previously been carried out to highlight the interest of using waste glass as a partial replacement for unbound granular aggregate in pavement structure. Nevertheless, industrialists remain reluctant to apply such a technique, which encourages researchers to extend their studies in order to properly control the behaviour of granular materials containing glass grains and consequently give more confidence to companies to enforce this technical solution. The present work consists in studying the influence of the shape of glass grains less than 5 mm (rounded and sub-rounded) on the mechanical behaviour of granular pavement materials. The study consists in making a comparison, from a behaviour point of view, between the two forms of glass grains obtained from two different grinding processes. As a result, the Proctor test clearly shows that there is no significant difference between rounded and sub-rounded shape in terms of compactabiliy. It was noted that the addition of particles of recycled glass makes the mixture more insensitive to water. It has been also found that the limiting percentage of addition of glass particles is situated between 20% and 30% reported to the total mass of the mixture.

Effect of material hydraulic properties on temporal moisture variations and performance of unbound pavements with sprayed seals

Moisture is widely recognised as a primary factor responsible for road failures. In particular, unbound pavements with sprayed seals, a common type of flexible pavement used in Australia and New Zealand are highly susceptible to moisture-related performance losses. The wearing course of these pavements, i.e. the sprayed seals, is moderately permeable, which allows for moisture exchange between the environment and the pavement structure throughout its service life. As a result, the moisture content of pavement layers varies according to the prevailing climate, which could cause noticeable performance reductions.This study extensively investigates the moisture variations in pavement layers of unbound pavements with sprayed seals during the service life due to the variations of ambient climatic conditions. The moisture variations in 18 different typical sprayed sealed pavements were numerically simulated for 10-year climates of Melbourne and Adelaide. Both the degree of saturation (Sr) and suction (s) variations were simulated for a number of practical scenarios. The results indicated that the pavement layers reach an equilibrium condition within less than 6 months under the climates considered. A series of sensitivity analyses were performed to evaluate the effect of hydraulic properties of seal, unbound granular material (UGM), subgrade and effect of water table depth on the moisture variations of pavement layers. The parametric analysis revealed that relatively permeable seals facilitate significant wetting of the UGM layer and substantial drying due to variations in prevailing climatic conditions. Moreover, this study identified primary influencing factors that determine the equilibrium state and the temporal moisture variations of the pavement layers. The effect of water table depth is evaluated for different subgrade conditions. A pavement performance evaluation conducted following the effective stress concept, the factor Sr.s is presented in this study. Overall, the results highlight the importance of considering temporal moisture variations in the design stage to improve pavement performance.

Chemical availability of fallout radionuclides in cryoconite

Atmospheric deposition on glaciers is a major source of legacy fallout radionuclides (FRNs) accumulating in cryoconite, a dark granular material with surface properties that efficiently bind FRN contaminants (specifically 137Cs; 210Pb; 241Am). Cryoconite-bound FRNs in glaciers can be released when they interact with and are transported by glacial meltwater, resulting in the discharge of amassed particulate contaminants into aquatic and terrestrial environments downstream. The environmental consequences of FRN release from the cryosphere are poorly understood, including impacts of cryoconite-sourced FRNs for alpine food chains. Consequently, there is limited understanding of potential health risks to humans and animals associated with the consumption of radiologically-contaminated meltwater. To assess the chemical availability of cryoconite-adsorbed FRNs we used a three-stage sequential chemical extraction method, applied to cryoconite samples from glaciers in Sweden and Iceland, with original FRN activity concentrations up to 3300 Bq kg−1 for 137Cs, 10,950 Bq kg−1 for unsupported 210Pb (210Pbun) and 24.1 Bq kg−1 for 241Am, and orders of magnitude above regional backgrounds. Our results demonstrate that FRNs attached to cryoconite are solubilized to different degrees, resulting in a stage-wise release of 210Pbun involving significant stepwise solubilization, while 137Cs and 241Am tend to be retained more in the particulate phase. This work provides an insight into the vulnerability of pristine glacial environments to the mobilization of FRN-contaminated particles released during glacier melting, and their potential impact on glacial-dependent ecology.

Design of Innovative High-Performance Polymer for Passive Lunar Dust Mitigation

Dust in space environments is now recognized as a major concern for successful manned and robotic exploration and colonization missions. Indeed, a thin layer of dust covers the lunar surface made of loose granular material, consisting of a broad range of shapes, sizes, and types of sediments, which mainly consists of silicate minerals in the form of micrometric, sharp, abrasive, porous, chemically reactive dust particles. The aim of this paper is to present preliminary results related to the design and development of an innovative, lightweight, high-performance polymer with an elevated strength-to-weight ratio able to mitigate particle contamination. In detail, dust mitigation or the minimization of the surface energy and consequently the adhesion forces among the external layers and the granular dust micrometric particles can be achieved through modifications of the surface properties by means of both chemical and physical methodologies. The proposed approach, to realize an innovative material and not a hydrophobic coating, is potentially applicable to a wide range of technological conditions and it relies on reproducible and controllable chemical modifications of the material’s surface properties through the design and synthesis of suitable base materials i.e., aromatic polyimides and copolyimides and incorporation of special low molecular weight additives, i.e., surface migrating agents, loaded directly within the reacting mixture during the intermediate phases of the copolymerization. The materials investigated in this work exhibit mechanical properties able to withstand the extreme space environment conditions and an elevated non-sticking behaviour of its surface layers in contact with granular, micrometric dust particles of lunar regolith i.e., abhesion capacity.

Tegument Ultrastructure and Morphology of the Capsule Surrounding the Tetrathyridia of the Genus Mesocestoides Vaillant, 1863 in the Liver of the Root Vole

The ultrastructure of the tegument of encapsulated tetrathyridia of the genus Mesocestoides Vaillant, 1863 (Cestoda, Cyclophyllidea, Mesocestoididae) from the liver of root voles Microtus oeconomus (Pallas, 1776) and the structure of the three-layered capsule surrounding them were studied for the first time. Several types of extracellular structures were noted on the surface of the tetrathyridia tegument: vesicles, fine granular material, and vacuoles. In addition, the phenomenon of shedding microtriches, which have expanded parts, was found. Host cells in contact with extracellular material show signs of destruction. A characteristic feature of the capsules surrounding the tetrathyridia is the reticular structure of the fibrous layer containing both native and degenerating inflammatory cells.

A duodenal diverticulum in a deerhound

AbstractA 23‐month‐old, spayed, female deerhound experienced an acute onset of anorexia and regurgitation. The initial regurgitant contained leaves and grass, but over the next 24 hours, it changed to dark brown granular material consistent with digested blood. Radiography revealed a dilated segment of bowel caudal to the liver, suggesting mechanical or functional intestinal obstruction. Exploratory laparotomy revealed a roughly spherical, 6‐cm diameter diverticulum in the proximal duodenum, which was removed by resection and anastomosis. The dog made an uneventful recovery. To date, duodenal diverticula have been reported predominantly in young Boxers. This is the first report of a duodenal diverticulum in a deerhound.

ПРОГНОЗУВАННЯ НЕСУЧОЇ СПРОМОЖНОСТІ ПЛИТНОГО ФУНДАМЕНТА ЗА ЧИСЛОВИМ МЕТОДОМ ГРАНИЧНИХ ЕЛЕМЕНТІВ

Construction is one of the leading branches of the national economy in the historical aspect of its development. The first design task is to determine the strength of building structures. Therefore, the study of the stress-strain state and related calculations are the most important in construction. The purpose of studying soil mechanics and foundation construction techniques is the calculation and construction of structures on or in soil. The main task is the construction of structures with a sufficient degree of reliability.The selection of an adequate theoretical model remains the main problem of soil mechanics. Indeed, the deformation of the dispersed granular material of the soil takes place during the mutual sliding of the grains, the rheology of the soil is complex, as evidenced by a large amount of experimental material. Today, the path of development of soil mechanics is related to the study of problems within the framework of the elastic-plastic dilatation model and the improvement of this model based on experiments. A mathematical model of a technical object at the micro level is a system of differential equations in partial derivatives, the exact solution of which can be obtained only in a few partial cases, therefore a discrete model is built using numerical methods that use the Poisson idea that the behavior of a complex model can be represented by the behavior of its individual component elements. The intensive development and widespread use of computers significantly brought fundamental mathematical problems closer to applied ones, and strengthened their mutual influence.The emergence of a new, powerful and general method of research - a numerical experiment, more than ever before closely connected the physical content of the problem, its mathematical formulation, numerical methods of calculation and modern computers. The work uses the numerical method of boundary elements. A promising way to develop foundations and foundation structures is to use the ratios of the theory of plastic flow, and the level of development of soil mechanics significantly affects the economy and reliability of the decisions made.