Granular Material Research Articles

Behavioural responses to horizontal vibrations of quasi-2D ideal granular beds: an experimental approach

In this experimental study, granular bed response to horizontal vibrations of various frequencies and amplitudes are examined with high-speed imaging. Ideal granular beds consisting of spherical glass beads are horizontally vibrated in a quasi-two-dimensional arrangement, firstly with homogeneous granular media and then with a ternary mixture to explore how bed response deviates with changes to material composition. Phenomena of note are the tendency for the homogeneous material to subdivide into discrete areas of crystalline lattice structures, bounded by non-crystalline lines of bead contacts, labelled in this paper as ‘shear lines’. Shear line failure arises as neighbouring crystalline areas slide relative to one another along their shared non-crystalline border, combining to form one larger crystalline area. Under vibration conditions where particle agitation and relative movement is high, sloshing occurs in the upper bed and triangular granular-gas regions form in the top corners. The ternary mixture also exhibits sloshing at low frequency and large amplitude, but the inhomogeneity of its composition prevents formation of ordered crystalline regions and shear lines, instead promoting low percolation and a jamming effect underneath the sloshing region. Surprisingly strong convective responses are induced in the inhomogeneous bed with more energetic vibrations. From the analysis of shear lines in the homogeneous beds, and of convection in the inhomogeneous beds, comparisons between homogeneous and inhomogeneous bed behaviour are drawn. Results are used to discuss how behavioural response of non-cohesive granular material to horizontal vibrations is ultimately tied to, and changes with, the geometric complexity of the internal packing structure. The concept of ‘geometric compatibility’ between constituent particle species in an inhomogeneous granular medium is proposed as an explanation for the low percolation and strong convective response to vibration.Graphical abstract

Investigation of the load sustaining micro mechanisms of cemented sand using the mesoscale FEM approach

While the mechanics of cemented granular material have already been approached by means of constitutive modeling, the capacity of introducing the precise internal structure of multiphase media in numerical simulations offers an alternative perspective of investigation. In specific, means of X-ray computed tomography are able to quantify the internal irregular geometry of the composite material in the form of three-dimensional images. Image analysis can be applied in order to distinguish the topology of each material phase and advanced meshing techniques are able to form a twin meshed domain. The current paper deals with the quantitative description of the morphology of small cemented sand samples, the application of developed image analysis algorithms to treat imaging artefacts (mainly due to beam hardening), the equivalent mesh generation via the image adapted meshing technique and the numerical testing using the Finite Element Method. Four samples are imaged, meshed and numerically tested in uniaxial compression; the mesoscale finite element simulations are able to display the intergranular stress transmission chains. A statistical analysis of the load carried by the granular skeleton provides evidence of the influence of the cementation degree and the compaction of the aggregates on the uniformity of the stress distribution.

Modelling the Influence of Erosive Fluidization on the Morphology of Fluid Flow and Escape Structures

Focused fluid flow through sub-seafloor pipes and chimneys, and their seafloor manifestations as pockmarks, are ubiquitous. However, the dynamics of flow localization and evolution of fluid escape structures remain poorly understood. Models based on geomechanical mechanisms like hydro-fracturing and porosity wave propagation offer some useful insights into fluid flow and escape dynamics, but face limitations in capturing features like mobilized granular matter, especially in the upper sediment layers where the link between fracture and pockmark is not always clear. Here, we propose a mathematical model based on the multiphase theory of porous media, where changes in subsurface and seafloor morphology are resolved through seepage-induced erosion, fluidization, transport, and re-deposition of granular material. Through simulation of an idealized scenario of gas escape from overpressured shallow gas reservoir, we demonstrate that our model can capture flow localization and formation of pipes, chimneys, and pockmarks. Our simulations show (1) formation of conical focused-flow conduits with a brecciated core and annular gas channels; (2) pockmarks of W and ring shapes; and (3) pulsed release of gas. Sediment erodibility and flow anisotropy control the morphology of focused fluid flow and escape structures, while permeability shows negligible impact. While the geological setting for this study is theoretical, we show that our results have real-world analogs.

On a mathematical model of the cooling and crystallization of metal drops during centrifugal granulation

A mathematical model has been developed for the crystallization of aluminum alloy granules under cooling conditions in an aqueous and water-steam media. The practical significance of the mathematical model lies in predicting the average value of the dendritic parameter of the obtained granules depending on the granulation method, the characteristics of the granulation process and the size of the obtained granules. The average value of the dendritic parameter makes it possible to predict the fineness of the granule structure and, consequently, the mechanical properties of the granular material. The mathematical model makes it possible to determine the speed of a melt drop in an aqueous media and takes into account the presence of a steam jacket effect, i.e., a vapor layer that appears between a crystallizing drop and an aqueous media, which significantly reduces the intensity of heat removal and the rate of crystallization. The application of the mathematical model was tested on the obtaining of granules of high-alloyed aluminum alloys (alloys D1 and D16 of the Al–Cu–Mg system, alloys V95 and V96Ts of the Al–Zn–Mg–Cu system), made by centrifugal spraying of the melt from a perforated rotating crucible and drip method during cooling in an aqueous media. The cooling rate and the crystallization rate of the granules obtained in real experiments were determined by measuring the dendritic parameter of the material structure. The mathematical model showed a high convergence of the simulation results and of real experiments of aluminum alloy granulation.

RALGAPA1 Deletion in Belgian Shepherd Dogs with Cerebellar Ataxia.

Several genetically distinct forms of cerebellar ataxia exist in Belgian shepherd dogs. We investigated a litter in which two puppies developed cerebellar ataxia. The clinical signs stabilized at around six weeks of age, but remained visible into adulthood. Combined linkage and homozygosity mapping delineated a 5.5 Mb critical interval. The comparison of whole-genome sequence data of one affected dog to 929 control genomes revealed a private homozygous ~4.8 kb deletion in the critical interval, Chr8:14,468,376_14,473,136del4761. The deletion comprises exon 35 of the RALGAPA1 gene, XM_038544497.1:c.6080-2893_6944+1003del. It is predicted to introduce a premature stop codon into the transcript, truncating ~23% of the wild-type open reading frame of the encoded Ral GTPase-activating protein catalytic subunit α 1, XP_038400425.1:(p.Val2027Glnfs*7). Genotypes at the deletion showed the expected co-segregation with the phenotype in the family. Genotyping additional ataxic Belgian shepherd dogs revealed three additional homozygous mutant dogs from a single litter, which had been euthanized at five weeks of age due to their severe clinical phenotype. Histopathology revealed cytoplasmic accumulation of granular material within cerebellar Purkinje cells. Genotyping a cohort of almost 900 Belgian shepherd dogs showed the expected genotype-phenotype association and a carrier frequency of 5% in the population. Human patients with loss-of-function variants in RALGAPA1 develop psychomotor disability and early-onset epilepsy. The available clinical and histopathological data, together with current knowledge about RALGAPA1 variants and their functional impact in other species, suggest the RALGAPA1 deletion is the likely causative defect for the observed phenotype in the affected dogs.

Cohesive zones to model bonding in granular material with the material point method

Modeling the behavior of granular materials was one of the first applications of the Material Point Method due in large part to the method’s ability to treat contact between bodies. Here, we further demonstrate that capability, and extend it to include inter-granular bonding. Bonds between grains in contact are represented using cohesive zones. The specifics of this approach are described and example calculations are carried out in two and three dimensions to demonstrate the capability. We demonstrate the ability to influence both the stiffness and strength of bonded granular materials.

Shaking table study on rubber-sand mixture cored composite block as low-cost isolation bearing for rural houses

Historical and recent earthquakes have caused severe damage to rural houses worldwide, which are often characterized by low story heights, high stiffness, and limited budgets. In this regard, low-cost seismic isolation strategies hold great potential for protecting low- and medium-rise buildings. This paper proposes a novel rubber sand mixture cored composite block (RSMCB) as a low-cost alternative to conventional expensive isolation bearings. The construction of the RSMCB involves filling the hollow of a plain concrete block with a lightweight material made of granulated rubber and natural sand and then covering the surface with a square brick slightly smaller than the hollow's size. To evaluate the effectiveness of the RSMCB, a series of shaking table tests were conducted, covering factors of rubber content, cover plate size, upper block mass, and paving mode. The results indicate that the utilization of the RSMCB layer effectively mitigates large displacement in the superstructure during the cyclic loading, thereby functioning as an energy dissipation and seismic reduction measure. Moreover, the isolation effect of the RSMCB layer increases with the seismic intensity attributed to the nonlinear variation of dynamic parameters of the mixed granular material with shear strain. These findings suggest that the proposed isolation strategy improves the strength and vertical stiffness of the original sand-rubber layer, making it a desirable and sustainable solution for seismic design applications in rural housing.

Assessing the ovarian development of Macrobrachium amazonicum (Heller, 1862) phenotypes by means of an integrative analysis

Macrobrachium amazonicum is a species of economic interest with a wide distribution in the Americas and high morphological and reproductive variability. Three phenotypes can be observed in this species: i) large-size amphidromous, ii) large-size and iii) small-size hololimnetic prawns. In the present work, the morphological, histochemical and ultrastructural aspects of ovarian development in the three phenotypes were comparatively analyzed. In addition, the interaction between the ovary and the hepatopancreas was investigated in these phenotypes through the use of gonadosomatic (GSI) and hepatosomatic (HSI) indices. Despite the morphological differences and different reproductive strategies adopted by the females, the macroscopic, histochemical and ultrastructural patterns of ovarian development showed no differences between the phenotypes. The ovaries were macroscopically classified into five stages of development (I to V). In early stages (I and II), the ovaries are full of oogonia, previtellogenic oocytes and oocytes in primary or endogenous vitellogenesis. At these stages, the rough endoplasmic reticulum (RER) produces a granular electron-dense material and sends it to the Golgi apparatus, where it will be modified, compacted and transformed into immature yolk granules. From stage III, secondary or exogenous vitellogenesis begins (with no interruption of endogenous vitellogenesis), where follicular cells nourish the oocytes and extracellular material is absorbed by endocytic vesicles, which fuse with immature yolk granules (forming mature granules) or with existing mature yolk granules. In stages IV and V, secondary vitellogenesis continues and mature yolk granules progressively occupy the cytoplasm. In M. amazonicum, the patterns of increase in oocyte diameter are quite similar between phenotypes, being greater in the small-size phenotype. This is related to the formation of larger oocytes/eggs and the production of large lipid reserves for their larvae. Changes in GSI and HSI during ovarian development show strong similarity between phenotypes, supporting the results obtained by histology and ultrastructure. Females in stages III and IV mobilize hepatopancreas reserves for ovarian maturation, which justifies the higher HSI values recorded in these stages. On the other hand, females in stage V show higher GSI and lower HSI values, indicating a mobilization of resources for the end of ovarian development as the females are ready to spawn.

Ultrastructural skin alterations of healthy subjects with anti-desmoglein 1 antibodies in endemic areas to pemphigus foliaceus: A case series

BackgroundEndemic pemphigus foliaceus and endemic pemphigus vulgaris are autoimmune dermatologic disorders endemic to the Peruvian Amazon. ObjectiveTo determine the ultrastructural skin alterations of three healthy subjects with anti DSG-1 antibodies in areas endemic to pemphigus foliaceus and pemphigus vulgaris in the Peruvian Amazon. Patients and methodsCase series carried out from data of three clinically healthy subjects positive to anti DSG-1 antibodies, from Peru. This study consists of a sub-analysis of data gathered in a previous study. ResultsUltrastructural results are presented from the skin biopsies of three clinically healthy patients positive to anti-desmoglein 1 (DSG-1) antibodies. High Resolution Optical Microscopy (HROM) showed the absence of acantholysis. Transmission Electron Microscopy (TEM) showed the widening of intercellular space between keratinocytes, the presence of vacuoles in intercellular space with granular material and cytoplasmic vacuolization, loss of desmosome structure, loss of normal distribution among tonofilaments and lateral separation among cells in the stratum basale. ConclusionAccording to our results, healthy subjects that present anti-desmoglein 1 antibodies can develop ultrastructural alterations that are visible through transmission electron microscopy but not through conventional optical microscopy.

Dynamics of granular debris flows against slit dams based on the CFD–DEM method: effect of grain size distribution and ambient environments

AbstractEarth surface flows in nature, like debris flows and rock avalanches, have threatened people’s safety and infrastructure during past decades. Though grain size distribution (GSD) has been acknowledged as a crucial characteristic in granular material behaviour, its coupled effects associated with environments on engineering structures such as the slit dam remain unclear. To bridge the gap, this paper reveals the coupled effect of the GSD and ambient environments (i.e. slope angles and saturation conditions) on avalanche/debris flows’ impact on the slit dam using a Computational Fluid Dynamics/Discrete Element Method (CFD–DEM) model. To describe strain-dependent rheological characteristics of debris fluids, the Herschel–Bulkley–Papanastasiou model is implemented in the finite volume method framework. A power grain size distribution law is considered to quantify GSDs, in which a fractal parameter takes charge of GSD types. After model verification with experimental/theoretical results, the impact force against slit dams, granular dynamics and final deposit patterns under a series of ambient circumstances are presented. Taking advantage of the CFD–DEM method, the impact force and kinetic energy induced by fluid and solid phases are discriminated. The contribution of solid and fluid phases to both impact force and dynamics appears to be dependent on GSDs. Accordingly, compared with saturated avalanche flows (i.e. debris flows), slit dams result in higher retaining efficiency when confronted with dry avalanche flows. Regarding a narrow diameter range used in analyses, the grain diameter ratio is then enlarged up to eight to reveal the potential size effect. As for the coupled role of GSDs and slope angles, in contrast to slope angles, the influence of GSD on avalanche flow interaction with slit dams is much smaller. Additionally, provided a narrow diameter range, the effect of GSDs on impact force can be partially attributed to the change in average grain diameter. After presenting the significance of ambience and GSDs to avalanche/debris flows, a series of parametric studies around the effect of fluid grid size, particle shape and the initial porosity of granular samples are discussed, aiming to advance the understanding of their influence in the interactions between debris flows and the slit dam.

A DEM-based approach for modeling the thermal-mechanical behavior of frozen soil

The mechanical characteristics of frozen soil under various temperatures have theoretical and engineering significance for improving the efficiency of permafrost excavation and ensuring the stability of permafrost area engineering. A novel approach based on Discrete Element Method (DEM) is proposed to simulate the temperature effect of frozen soil. An existing 3D contact model for cemented granular material is extended to include the effects of temperature on bond strength and modulus of ice cementation, which are verified by existing analytical solutions and experimental data, and a simplified method is employed to simulate the influence of ice crystal expansion on the void ratio of frozen soil, whereafter, the modified contact model is calibrated by the results of the temperature-controlled triaxial test. This approach was proven to be effective by comparing the simulation results with the experimental results. The micro mechanical behavior of frozen soil samples was studied. The results showed that different types of bond contact had different effects in the shearing stage. The structural ‘weakening’ and ‘strengthening’ of the frozen soil occur simultaneously during the loading process, and the structural damage is mainly caused by the plastic damage induced by the relative slip between soil and ice particles.

DEM analysis of crushing evolution in cemented granular materials during pile penetration

The present study demonstrates that the 3D discrete-element method provides a practical model approach to visualize the cemented grain crushing evolution under pile penetration. A combined method using a rigorous breakage criterion based on octahedral shear stress (OSS) was implemented in the particle flow code PFC3D. First, the pile penetration is simulated by considering the grains as uncrushable with a screening of highly stressed grains exceeding the threshold defined by the OSS failure condition. Then, the simulation is repeated where crushable agglomerates replace the highly stressed grains. This method is more accurate than the replacement method and more efficient than the agglomerate method. A quarter of the numerical model was considered after validation to achieve an acceptable computational time for parametric studies. Parametric investigations were performed on the effects of particle crushing, boundary conditions, pile tip shape, and pile penetration velocity on the penetration resistance behavior. In agreement with the observations of the physical calibration chamber, the present results indicate that the proposed modeling approach is reliable in reproducing the concentration of crushed granular material particles in the vicinity of the pile tip and shaft. In addition, grain crushing has been found to reduce both penetration and shaft resistance.

Breakage in quasi-static discrete element simulations of ice rubble

Breakage of particles plays a key role in force transmission in granular materials. Discrete element method (DEM) simulations are often used to model granular materials, but modeling particle breakage in them remains a challenge. Models for breakage of non-spherical particles are scarce and often the existing models are computationally heavy to be used in simulations with large numbers of particles. To address this, the present study develops a particle breakage model for quasi-static DEM simulations of non-spherical particles that fail due to shear. The model is novel, since it is based on experimental observations and high resolution modeling. Breakage models based on experimental evidence are rare as it is often virtually impossible to gain detailed data on the mechanisms related to breakage. The developed particle breakage model was integrated into a DEM code and direct shear box experiments on ice rubble, a granular material consisting of ice particles, were then simulated. Accounting for particle breakage in DEM simulations improved their accuracy: simulations were compared to experiments and the results were found to be in better agreement when particle breakage was taken into account. The effect of particle breakage on the shear strength of a granular material was found to be independent of particle size, decreasing fast with increasing particle strength. The combined effect of shear box length and breakage was also studied. The results showed that the strength of a granular material may be determined reasonably well with a shear box that has a box to particle length ratio greater than 60.

Mutation in Methionyl-tRNA Synthetase 1 Causing Pulmonary Alveolar Proteinosis

Background: A chronic history of exertional dyspnea, dry cough, and fatigue, associated with reticulonodular ground-glass opacity indicates an underlying interstitial lung disease (ILD). Pulmonary alveolar proteinosis (PAP) is a rare cause of ILD, in which there is abnormal accumulation of surfactant material in alveoli, thereby impairing gaseous exchange. In children, PAP is usually due to genetic mutations. We report a child with PAP due to mutation in methionyl-transfer RNA synthetase 1 (MARS) gene. Clinical Description: An 8-year-old boy presented with persistent dry cough, and exercise-induced breathlessness for 2 years of age, associated with failure to gain weight. He had multiple exacerbations in the past, requiring common symptomatic treatment, but with minimal improvement. On presentation to us, the child had tachypnea, hypoxia (oxygen saturation [SpO2]: 85%), and Grade 2 clubbing, with bilateral fine crepitation in bilateral lung fields. Management and Outcome: The child was stabilized by providing oxygen via high-flow nasal cannula. Blood investigations were largely normal. His chest X-ray and computerized tomography (CT) of the chest were suggestive of childhood ILD. A lung biopsy revealed periodic acid–Schiff-positive eosinophilic granular material in the alveolar spaces without any fibrosis, suggesting a diagnosis of PAP. Next-generation sequencing revealed a compound heterozygous mutation of the MARS1 gene resulting in PAP. Parental segregation analysis showed each one to be a carrier of one of the genes. Therapeutic whole-lung lavage (WLL) was carried out, following which symptoms improved markedly. SpO2 increased and the child was able to be weaned off oxygen and discharged. Three years, postdischarge, the child is asymptomatic and thriving well. Conclusions: PAP may be a cause of ILD in a child. Although the etiology can be ascertained by high-resolution CT of the chest and bronchoalveolar lavage, further genetic analysis should also be undertaken in children to identify the exact defect. WLL can provide a good outcome in children with PAP due to MARS mutation.

Mixing Power Requirement Determination in Agitated Drum Using Dimensional Analysis

The mixing of granular materials in an agitated drum can be characterized by the dimensionless power equation. The equation was created by dimensional analysis, for which the parameters affecting the mixing power requirement were collected based on the literature. The most important of these are the rotational speed, the drum loading factor, the geometric and physical properties of the mixing drum and the granular materials. The dimensionless power equation is used to estimate with reasonable accuracy the Power number within the given range of applicability , which has been validated by measurements. From the Power number, the mixing power requirement of the mixed granular material can be calculated, which can be used as operational data for selecting the mixing motor.

Review of Proliposomal Gel for Transdermal drug delivery system

Proliposomes are an innovative kind of carrier-mediated drug delivery that offers numerous advantages over traditional liposomes. The conventional liposomes are susceptible to oxidation or hydrolysis, as well as sedimentation, aggregation, or fusion with other substances. While, proliposomes are far more stable than liposomes, making them better suited for the delivery of pharmaceuticals. They are a dry, free-flowing, granular substance that, when it comes in touch with water or a biological fluid inside the body, instantly transforms into a liposomal dispersion. Future systems for delivering medications could be proliposomes. They have achieved a considerable improvement in resolving the stability, bioavailability, and solubility of poorly soluble medicines difficulties associated with liposomes with their non-invasive drug administration into or across the skin. They are a better alternative to the liposomal vesicular system because of their increased physical and chemical stability and potential for scalability for commercial viability. Because they are in dry powder form, they can be manufactured into unit dose forms like tablets, capsules, and beads, among other things. Because of all these advantages, proliposomes have been used for a variety of medical applications.

Design of Cost-Effective and Sustainable Treatments of Old Landslides Adapted to the Moroccan Road Network: A Case Study of Regional Road R410 Crossing the Rifan Structural Domain

The Moroccan road network is susceptible to multiple landslides annually, particularly in the northern regions due to high rainfall and specific geology. These events result in significant economic and social negative consequences, highlighting the need for sustainable and cost-effective solutions for network maintenance. This study outlines the methodology employed in addressing the issues within the RR410 regional road (Rifain region of Morocco), which entailed a thorough examination of the malfunctions, specific surveys, laboratory testing, and problem modeling. By incorporating long-term test-derived shear strength parameters, the model indicated that the road platform was stable, and back analysis using TALREN 4 software allows for model calibration. At kilometric point 23, using earthwork-based solutions (e.g., purging and replacing the base layer, employing granular water-insensitive substitution material) was found to provide a sustainable alternative to the expensive reinforced concrete-based solutions commonly used. Furthermore, these solutions contributed to the use of environmentally friendly and locally sourced materials. Road alignment rectification to anchor the platform in suitable soil was also an effective solution, as demonstrated at kilometric point 48. Additionally, enhancing the drainage and sanitation infrastructure, such as installing draining trenches, spurs, and reinforcing existing water structures, is a crucial aspect of addressing most landslides in the region.

Numerical investigation of drag force on a spherical intruder by granular material

Insertions of large objects or intruders into granular material are common both in nature and in industrial applications. The intruder experiences resistance or granular drag force (analogy from fluid) during penetration into granular material due to the formation of inter-particle force chains. The main aim of this article is to study the drag force on an intruder during penetration in granular material and explain the underlying physics. For this study, numerical simulations are performed using the discrete element method (DEM). It is observed by studying various characteristics of granular material that particles undergo jamming transition below the intruder, and the region of jammed particles increases with the depth of intrusion, which is the main reason for the increase in the granular drag force with the depth of intrusion.

Transmission loss measurement of recycled granular material using wave decomposition by impulse response extraction based on deconvolution

A simplified method for measuring transmission loss with a single fixed microphone inside an impedance tube is proposed. The separation of the incident wave from the reflected wave is achieved by deconvolving the loudspeaker driver voltage signal with the microphone signal to extract the impulse response. Random noise and a sinusoidal sweep signal were used as excitation signals for extraction of the impulse response, and two deconvolution methods were employed: linear deconvolution based on the adaptive LMS algorithm and simple spectral division. To avoid the overlap of incident and reflected pulses, a long impedance tube was used. Using a long impedance tube eliminates the need for an anechoic tube termination and the need to calibrate microphones. It is found that a reflective tube termination provides more accurate results compared to an approximately anechoic termination. The approximately anechoic termination shortens the available time window of the reflected pulse because it reflects some of the low-frequency sound. The standard deviation of the results and the dynamic range of the proposed method were determined experimentally. The applicability of the new method was tested on samples of unconsolidated granular material recycled from construction sites. The measured transmission losses of the different granular fractions were compared with a theoretical model for transmission losses at low frequencies. Samples consisting of smaller granule fractions were found to have surprisingly high transmission loss values. The design of the extended vertical impedance tube in combination with the proposed method is cost effective, speeds up the measurement procedure and provides reliable results.

Cohesion and aggregates in unsaturated wet granular flows down a rough incline

Multi-phase flows, encountered in nature or in industry, exhibit non-trivial rheological properties, which we attempt to better understand thanks to model materials and appropriate rheometers. Unsaturated wet granular flows down a rough inclined plane turn out to be steady and uniform for a wide range of parameters, despite the cohesion and the grain aggregates. The cohesive Mohr–Coulomb yield criterion extended to inertial granular flows, with a cohesion stress dependent on the liquid content and an internal friction coefficient dependent on the inertial number, allows for predictions in good agreement with our experimental measurements, when one introduces a grain aggregate size, which defines the appropriate length and relaxation time scales in the inertial number. We found that the grain aggregate size depends not monotonically on the liquid content and does not scale with the cohesion length induced by the cohesion stress, due to the non-trivial distribution of the liquid within the granular material.