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Understanding of hard particles in morphologies and sizes on microstructures of particle random packings is of significance to evaluate physical and mechanical properties of many discrete media, such as granular materials, colloids, porous ceramics, active cells, and concrete. The majority of previous lines of research mainly dedicated microstructure analysis of convex particles, such as spheres, ellipsoids, spherocylinders, cylinders, and convex-polyhedra, whereas little is known about non-convex particles that are more close to practical discrete objects in nature. In this study, the non-convex morphology of a three-dimensional particle is devised by using a mathematical-controllable parameterized method, which contains two construction modes, namely, the uniformly distributed contraction centers and the randomly distributed contraction centers. Accordingly, three shape parameters are conceived to regulate the particle geometrical morphology from a perfect sphere to arbitrary non-convexities. Random packing models of hard non-convex particles with mono-/poly-dispersity in sizes are then established using the discrete element modeling Diverse microstructural indicators are utilized to characterize configurations of non-convex particle random packings. The compactness of non-convex particles in packings is characterized by the random close packing fraction fd and the corresponding average coordination number Z. In addition, four statistical descriptors, encompassing the radial distribution function g(r), two-point probability function S2(i)(r), lineal-path function L(i)(r), and cumulative pore size distribution function F(δ), are exploited to demonstrate the high-order microstructure information of non-convex particle random packings. The results demonstrate that the particle shape and size distribution have significant effects on Z and fd; the construction mode of the randomly distributed contraction centers can yield higher fd than that of the uniformly distributed contraction centers, in which the upper limit of fd approaches to 0.632 for monodisperse sphere packings. Moreover, non-convex particles of sizes following the famous Fuller distribution of the power-law distribution of the exponent q = 2.5, have the highest fd (≈0.761) with respect to other q. In contrast, the particle shapes have an almost negligible effect on the four statistical descriptors, but they are remarkably sensitive to particle packing fraction fp and size distribution. The results can provide sound guidance for custom-design of granular media by tailoring specific microstructures of particles. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical study of the thermal conductivity of Si–Ge nanograin mixtures using a multiscale computational methodology based on solving the Boltzmann transport equation for phonons with first-principles techniques. A size-dependent correction factor is developed to account for the spatial dependence of the phonon distribution function on nanograin size, with parameters derived from the phonon properties of infinite Si and Ge crystals. This approach makes it possible to accurately calculate the thermal conductivity within a single nanograin, using force constants obtained from first-principles calculations. Thermal energy transport by phonons across grain boundaries is modeled by accounting for phonon transmission by two-phonon processes, weighting specular, and diffuse transmission for each phonon mode as a function of the root-mean-square roughness of the boundary relative to the phonon wavelength. The boundary thermal conductance model, previously validated against experimental data, is implemented using first-principles techniques. This approach excludes specular transmission for phonon modes with specific symmetries while ensuring conservation of the total number of modes in each symmetry class. The study examines the influence of grain size, nanograin mixture composition, temperature, and boundary asperities on the thermal conductivity of nanograin mixtures. [ABSTRACT FROM AUTHOR]

This research established a systematic method to generate various pore-size distributions (PSDs) and studied the effect of PSDs on the shock compaction response of granular materials using two-dimensional mesoscale simulations under identical porosity. Simulations utilized various PSDs for three particle shapes (circle, ellipse, and square). Contacting particle configurations using three PSDs, characterized by spatially uniform distributed pores to heterogeneous distributed pores, and non-contacting particle configurations under a single case of PSD were tested. The PSD of generated particle sets was characterized using coordination number, mean diameter, and bimodality coefficient as statistical metrics. Mesoscale simulations showed that regardless of the conditions of pore distributions, shock compaction of granular materials consistently demonstrates a precursor, shock compaction front, and end. However, the shock compaction velocity of contacting particles was dependent on the PSDs despite the constant initial porosity. The compaction velocity was faster in particle configurations with relatively uniform pore distributions than in heterogeneous pore distributions, which our study demonstrated can be attributed to particle rearrangement during compaction. Circular-shaped particles had high sensitivity in shock compaction response to the various PSDs. Furthermore, a contacting particle configuration tended to propagate the shock compaction wave relatively faster than particles that were in a non-contact configuration. This study established the relative importance of considering PSD as a metric over the coordination number in studies of the shock compaction response of granular materials. Further, insights are provided on the evolving shock substructure to characterize the shock compaction response of granular materials. [ABSTRACT FROM AUTHOR]

Saturated packing is a random packing state of particles widely applied in investigating the physicochemical properties of granular materials. Optimizing particle shape to maximize packing density is a crucial challenge in saturated packing research. The known optimal three-dimensional shape is an ellipsoid with a saturated packing density of 0.437 72(51). In this work, we generate saturated packings of three-dimensional asymmetric shapes, including spherocylinders, cones, and tetrahedra, via the random sequential adsorption algorithm and investigate their packing properties. Results show that the optimal shape of asymmetric spherocylinders gives the maximum density of 0.4338(9), while cones achieve a higher value of 0.4398(10). Interestingly, tetrahedra exhibit two distinct optimal shapes with significantly high densities of 0.4789(19) and 0.4769(18), which surpass all previous results in saturated packing. The study of adsorption kinetics reveals that the two optimal shapes of tetrahedra demonstrate notably higher degrees of freedom and faster growth rates of the particle number. The analysis of packing structures via the density pair-correlation function shows that the two optimal shapes of tetrahedra possess faster transitions from local to global packing densities. [ABSTRACT FROM AUTHOR]

The granular materials of soft particles (SPs) demonstrate unique viscoelasticity distinct from general colloidal and polymer systems. Exploiting dynamic light scattering measurements, together with molecular dynamics simulations, we study the diffusive dynamics of soft particle clusters (SPCs) with spherical and cylindrical brush topologies, respectively, in the melts of SPs. A topologically constrained relaxation theory is proposed by quantitatively correlating the relaxation time to the topologies of the SPCs, through the mean free space (Va) of tethered SPs in the cluster. The tethered SPs in SPCs are crowded by SPs of the melts to form the cage zones, and the cooperative diffusion of the tether SPs in the zones is required for the diffusive motion of SPCs. The cage zone serves as an entropic barrier for the diffusion of SP clusters, while its strength is determined by Va. Three characteristic modes can be confirmed: localized non-diffusive mode around critical Va, diffusive mode with Va deviating far from the critical value, and a sub-diffusive mode as an interlude between two limits. Our studies raise attention to the emergent physical properties of materials based on SPs via a topological design while opening new avenues for the design of soft structural materials. [ABSTRACT FROM AUTHOR]

When a cubic lattice is confined by a surface layer, the effective thermoelastic properties can be tailored by the prestress produced by the surface. The thermal expansion coefficient, temperature derivative of elasticity, and the equation of state (EOS) of the solid depend on the potential of each bond and the lattice structure, which can be predicted by the recently developed singum model. This paper first uses a granular lattice confined by a spherical shell to demonstrate singum modeling of the thermoelastic behavior of the cubic lattices and then extends it to atomic crystal lattices by considering the surface tension and long-range interactions. Given the elasticity and the EOS of a cubic crystal, the interatomic potential can be inversely derived. As the bond length changes with thermal expansion and pressure, the singum model predicts the temperature- and pressure-dependent elasticity. Using the orientational average, isotropic elastic constants can be obtained for polycrystals. The case study of copper (Cu) demonstrates the versatility of the model for different cubic lattices and predicts the experimental results of pressure- and temperature-dependent elasticity. The singum model is general for different lattice types and EOS forms and provides clear physical and mechanical meanings to correlate the interatomic potential, EOS, and elasticity in the closed-form formulation, which is very useful in engineering design and analysis of metal structural members in fire, geothermal, and space applications without the needs of large-scale numerical simulations. [ABSTRACT FROM AUTHOR]

The study of granular avalanches in rotating drums is not only essential to understanding various complex behaviors of interest in granular media from a scientific perspective; it also has valuable applications in regard to industrial processes and geological catastrophes. Despite decades of research studies on avalanches, a proper understanding of their dynamic properties still remains a great challenge to scientists due to a lack of state-of-the-art techniques. In this study, we accurately predict the avalanche dynamic features of three-dimensional granular materials in rotating drums, by using graph neural networks on the basis of their initial static microstructures alone. We find that our method is robust to changes in various model parameters, such as the interaction potential, size polydispersity, and noise in particle coordinates. In addition, with the grain-scale velocities obtained either from our network or from numerical simulations, we find an approximately equal and strong correlation between the global velocity and global velocity fluctuation in our 3D granular avalanche systems, which further demonstrates the predictive power of our trained graph neural networks to uncover the fundamental physics of granular avalanches. We expect our method to provide more insight into the avalanche dynamics of granular materials and other amorphous systems in the future. [ABSTRACT FROM AUTHOR]

Light weight deflectometers (LWDs) are portable and cost-effective devices that play a vital role in checking the quality of highway foundations and base installations for sports facilities such as football pitches and athletics tracks. As LWDs are accepted for use as part of compliance testing, it is essential that the results produced are reliable. This paper summarises the results of two UK-wide correlation trials carried out in 2021 and 2022. Machines and operators from 42 organisations attended the trials, in which the performance of 175 LWDs was assessed against the larger falling weight deflectometer (FWD). This paper provides some background to the use of LWDs and the design of the trial, including the collection and analysis of data. The relationship between the LWD and the FWD, including data variability and the influence of different testing regimes, was examined. The main findings of the trials are summarised and recommendations are made to maintain the precision of LWD devices. [ABSTRACT FROM AUTHOR]

Vibrofluidization in monodisperse granular materials is a hierarchical phenomenon involving different spatial and temporal behaviors, known to produce macroscopic structures with well-defined properties and high reproducibility. However, as witnessed by the paucity of relevant results in the literature, investigating the collective organization of particles across such different length and time scales becomes particularly challenging when multi-component systems are considered, i.e. if the considered vibrated material is not monodisperse. In this work, this problem is addressed through numerical simulation of the governing equations accounting for (dissipative) inelastic and frictional effects in the framework of a DEM (Discrete Element Method) method. Binary and ternary particle distributions are considered and, in order to filter out possible density-driven particle segregation or mixing mechanisms, particles are assumed to be iso-dense. The problem is initially analyzed through the coarse-grained lens of patterning behavior (supported by a Voronoi analysis for many representative cases) and then from a micromechanical level in which statistical data based on particle collisions and related dissipative effects are used to gain additional insights into the observed macroscopic trends. It is found that, starting from the initial traditional monodisperse case, the addition of particles with smaller sizes (while keeping the overall mass and depth of the considered layer almost unchanged) generally leads to a corrugation in the otherwise perfect symmetry of the original patterns, which is similar to that already seen in companion situations related to viscoelastic fluids. Moreover, while in the case of an initially hexagonal pattern, this topology is generally retained, in other situations, the initial perfection is taken over by less regular waveforms. Specific circumstances also exist where the initial square symmetry is lost in favor of a triangular symmetry. In all cases, segregation effects simply manifest as a preferential concentration of particles with larger size in an intermediate layer, which apparently behaves as a cohesive entity during each vibration cycle. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) is widely used to investigate the micromechanical behavior of granular materials. The accuracy of numerical modelling using this method depends greatly on the correct selection of the components of the rheological model. On the other hand, the rheological model is affected by the geometric shape, movement, and constituent particular materials. In this study, the stored and dissipated energy variations in the granular media in linear and non-linear contact models, as well as the change of the damping coefficient at the contact points under cyclic loading, were studied. The numerical model with linear and non-linear contact models was studied in four cases including the application of the normal and shear damping coefficient, and both normal and shear dashpots with the same and different values. The results showed that in the linear contact model, when the damping coefficient was applied only in the normal direction, the energy level was lower than the other three cases. However, in the non-linear model, all four cases had almost the same behavior. In the linear model, the amount of dissipated energy due to viscous damping was more than dissipated energy due to the friction sliding. However, in the non-linear model, dissipated energy due to sliding was more than the dissipated energy due to viscous damping. [ABSTRACT FROM AUTHOR]

Geotextiles have been used as filters in geotechnical and geoenvironmental works for decades. Despite their broad utilization, these filters still find obstacles to the expansion of their application in larger projects and under complex soil and flow conditions. However, environmental issues are increasingly pressing for a greater use of geotextile filters in substitution to natural granular materials. Even though many important studies in the literature have improved the understanding of soil-fluid-geotextile filter interaction, some issues still require thorough investigation aiming at a better understanding of the behaviour of geotextile filters and the development of better design methodologies. This paper discusses how geotextiles filters are expected to behave in the field and some contradictions between idealized and real behaviour. Concerns regarding the use of geotextile filters under severe and critical conditions and how filter malfunction can be avoided or minimised are also addressed as well as approaches available to predict filter behaviour. A broad investigation on geotextile filter behaviour under severe and critical conditions was carried out and shows that these filters have been very successful, particularly bearing in mind the small number of failures in comparison with the huge number of applications of geotextile filters. [ABSTRACT FROM AUTHOR]

Amorphous solids are diverse materials that take on various forms such as structural glasses, granular materials, foams, emulsions, and biological systems. Recent research has made significant progress in understanding non-phonon vibrational modes universally present in amorphous materials, which have been observed as excess vibrational modes over the Debye law, known as boson peak, as well as quasi-localized vibrational modes. These vibrational modes are crucial to explaining material properties of a wide range of amorphous materials, from "hard" solids like structural glasses to "soft" solids like foams and emulsions. However, we still lack a theoretical framework that can comprehensively explain them in a unified manner. Here, we propose a unified theory for viscoelasticity and sound damping which are significantly different between hard and soft amorphous solids but are ultimately determined by non-Debye scaling laws of the non-phonon vibrational modes. Our theory can explain acoustic properties of structural glasses, which have been measured experimentally with light, inelastic X-ray, and neutron scattering techniques, on one hand, and viscoelastic properties of foams and emulsions, which have been measured by various macrorheology and microrheology techniques, on the other. We thus provide a comprehensive explanation for these experimental measurements of two distinct types of amorphous solids. Non-phonon vibrational modes are crucial for understanding the properties of amorphous solids, from hard solids like structural glasses to soft solids like foams and emulsions. The authors propose a unified theory to explain the acoustic properties of structural glasses, which have been measured experimentally with scattering techniques, alongside the viscoelastic properties of foams and emulsions, measured through rheological techniques. [ABSTRACT FROM AUTHOR]

The concept of friction was integrated into the broader field of tribology in the 20th century. Here, we revive the older friction coefficient concept and show that it is the defining parameter for a family of granular materials. We show, for the first time, that kinetic friction coefficients of such systems can be described as a function of the lubricating fluid and the shape of the granules, without any fitting parameters. With this, we define the value and conditions for the minimal friction of this system and show how it can increase depending on the properties of the system. This paper shows that the minimum possible friction for an assembly of granular media is the same universal constant of ¼ that da Vinci identified for kinetic friction between two rigid bodies. [ABSTRACT FROM AUTHOR]

Granular agricultural products can often be packaged quantitatively before sales. The speed and accuracy of material feeding are important indicators to evaluate quantitative feeding in quantitative packaging production lines. However, it is difficult to accurately and efficiently feed the granular agricultural products, due to the irregular appearance, uneven and easy dispersion. In this study, discontinuous totalizing quantitative feeding was proposed, according to the volume and gravity (static weighing). A closed-loop control system was constructed with iterative learning. A dynamic quantitative feeding equipment was also developed for the granular agricultural products. The feeding mechanism of the equipment was composed of several measuring cups with variable volume under accurate control by the shaft. The reinspection mechanism of the equipment was composed of a reinspection weighing scale, removal, and unloading device, in order to inspect the actual quality of the feeding. The working procedure of the equipment was as follows. Firstly, the packaging target quality was evenly divided into several parts. And then each part of the target quality was quantitatively fed with a measuring cup during feeding. Furthermore, a gravity (static weighing) quantitative feeding was used to inspect the actual quality of the previous one before feeding to the next measuring cup in each group. The inspected error was used to adjust the volume of the next measuring cup in the same group. Finally, the actual quality of all measuring cups was totalized to obtain the packaging target quality. Since the packaging target quality was obtained by totalizing the feeding of several measuring cups, the volume of the following measuring cups was continuously corrected to make the totalizing feeding actual quality of measuring cups approach the packaging traget quality in a group of feeding, regardless of whether there was an error in the first few measuring cups. This discontinuous totalizing feeding was integrated to improve the quantitative accuracy of the equipment. Taking 600 g of soybeans, red beans, or mung beans as examples, a series of quantitative feedings were carried out on the equipment. The experimental results showed that the feeding quality error was controlled within 0.2% when the number of measuring cups was 5 and the equipment rotational speed was 2 r/min. The error was effectively reduced during dynamic quantitative feeding. Particularly, the quantitative accuracy was much higher than that in the national standard requirement. The finding can provide a feasible technical solution to the high-accuracy quantitative feeding of granular agricultural products, such as traditional Chinese medicine pill packaging, quantitative sowing and fertilization, and quantitative feeding of granular fertilizers. [ABSTRACT FROM AUTHOR]

An experimental study on the collapse of partially immersed granular columns is investigated, mainly considering the effects of aspect ratio and water depth on the granular dynamic and final deposit. According to the dimensionless time of collapse, two asymptotic regimes of the partially immersed granular column collapse were found, which are a regime similar to the free fall flow regime and a regime similar to the completely immersed inertial flow regime. Due to the incomplete impregnation of the granular materials and the evolution of the free fluid surface, the fluid resistance generated by the fluid covering the granular materials surface was discovered, which led to the difference between the partially immersed case and the completely dry or immersed case. In addition, we analyze the effect of water depth on the dynamics of granular collapse and deposit properties. Finally, a prediction model for the final runout distance of partially immersed granular collapse in relation to the water depth and aspect ratio was established and validated with the experimental data. [ABSTRACT FROM AUTHOR]

The flow of wet granular materials released down an inclined channel is investigated experimentally. The observed flow reveals three typical flow regimes corresponding to varying inclination angles, aligning with the dynamics observed in the dry particle case. The presence of interstitial liquid significantly increases the critical angles required for transitions between these regimes. Each regime exhibits distinctive evolving features in front shapes and surface morphologies, primarily depending on grain-scale cohesion induced by capillary forces between particles, which are directly related to particle size. Consequently, a phase diagram encapsulating diverse characteristics of wet granular flows is constructed in the phase space of two relevant parameters, emphasizing the front shape and surface morphology of wet granular flow while concurrently considering the associated flow regime. The generation mechanisms are also discussed based on the effect of cohesion on the motion of particles. Finally, simplified theoretical models, grounded in the law of conservation of momentum and Savage–Hutter theory, are developed to depict the evolving characteristics of the front in different regimes of inclined wet granular flows. [ABSTRACT FROM AUTHOR]

Granular soil generally exhibits an anisotropic stiffness in engineering but challenging to quantify in situ and laboratory condition, due to a lack of the appropriate factor and quantitative research. In this paper, discrete element method is employed to create two typical types of soil fabric and conduct shear wave measurement in double direction, with the microscopic parameters monitored to investigate the connection with macroscopic stiffness anisotropy. The results show that the reference fabric increases as fabric anisotropy increases first and then decreases with further increase in the XZ stress plane, while always decreases approximately linearly in the XY stress plane. The reference fabric is determined by the contact density in the direction of wave propagation and particle perturbation under microscale examination. The results also reveal a linear relationship between the macroscopic stiffness anisotropy and microscopic fabric anisotropy, which could be used as an effective method to reflect the degree of anisotropy in situ by wave measurement. And the applicability of the expression of small-strain shear modulus is also discussed. [ABSTRACT FROM AUTHOR]

Cohesive material columns have been extensively used in foundation improvement projects to enhance the bearing capacity of composite foundations and mitigate post‐construction settlement. However, the low permeability of cohesive material columns restricts the dissipation of pore water primarily through the top surface of the foundation, potentially resulting in longer drainage paths compared to foundations treated with granular material columns or vertical drains. Moreover, the impact of non‐Darcian flow within soils on consolidation behavior becomes increasingly pronounced as the drainage path increases. Consequently, a novel analytical model for the consolidation of impervious column‐assisted foundations is established, which can incorporate the seepage model accounting for the initial hydraulic gradient. The accuracy and reasonableness of the obtained solution are then validated by conducting a comparative analysis with existing models and through a detailed case study. Furthermore, a parametric analysis is conducted to delve into the influence of several crucial factors on the consolidation performance. The findings demonstrate that non‐Darcian flow has a greater influence on composite foundations compared to natural foundations. Additionally, the threshold value of the well‐diameter ratio decreases with the increase in the initial hydraulic gradient. Finally, the final seepage front remains at a shallower position when the column–soil modulus ratio becomes larger, and the influence of non‐Darcian flow on the consolidation rate becomes more pronounced. [ABSTRACT FROM AUTHOR]

In the present study, the centrifuge modeling approach was utilized to investigate the efficacy of dual-functional hybrid geosynthetics as reinforcement in alleviating the destabilizing effects of rainfall on geosynthetic-reinforced soil walls (GRSWs) with low-permeable backfill. A series of centrifuge experiments were executed employing a tailored in-flight rainfall simulation mechanism, generating mistlike fine droplets at 40g on a rigid-facing GRSW with a height of 10 m and provided with a low-permeable silty sand backfill. To comprehensively assess the performance, pore water pressures were continuously monitored using pore pressure transducers. Digital image analysis (DIA) was employed to evaluate surface settlements, wall face movements, and strains encountered by geosynthetic layers during rainfall. The centrifuge test results indicated that GRSW without any drainage provisions developed substantial pore water pressures and experienced a catastrophic slip failure within a brief period of rainfall exposure. Providing a granular drainage layer behind the facing in isolation was noticed to be futile with a GRSW failure in 16.85 days, coupling the drainage layer with hybrid geosynthetic reinforcements with high transmissivity characteristics showcased exceptional hydraulic and deformation characteristics and demonstrated remarkable resilience even under the influence of an imposed surcharge load. Consequently, rigorous seepage and stability analyses were performed, yielding outcomes in consonance with the observations from the centrifuge experiments. The integration of hybrid GRSW with the drainage layer behind the facing experienced considerably low pore water pressures and high safety factors, even following exposure to a 30-day antecedent rainfall. Practical Applications: This study underscores the pivotal role of hybrid geosynthetics in contemporary geotechnical engineering, providing robust solutions for mitigating rainfall-induced challenges in various geotechnical structures. The combination of nonwoven geotextile and geogrid layers in hybrid geosynthetics significantly augments drainage efficiency, particularly in low-permeable soils, attenuating pore water pressures and enhancing its stability. The bottom-up construction methodology for GRSWs facilitates the seamless incorporation of such permeable hybrid geosynthetics alongside a granular drainage layer behind the facing, improving in-plane and vertical drainage and preventing catastrophic failures. This methodology extends the longevity and reduces maintenance expenditures of retaining structures, presenting a durable and economical solution. The research advocates for the development of climate-resilient infrastructure, which is crucial amidst the increasingly erratic nature of rainfall due to climate change. This innovative approach promotes sustainable construction by utilizing locally available fine-grained soils, eliminating the necessity for costly granular materials. Additionally, the findings from the study can help in policy revisions and updating construction guidelines toward safer and more efficient field practices. [ABSTRACT FROM AUTHOR]

In recent times, immersed methods such as the finite cell method have been increasingly employed in structural mechanics to address complex-shaped problems. However, when dealing with heterogeneous microstructures, the FCM faces several challenges. Weak discontinuities occur at the interfaces between the different materials, resulting in kinks in the displacements and jumps in the strain and stress fields. Furthermore, the morphology of such composites is often described by 3D images, such as ones derived from X-ray computed tomography. These images lead to a non-smooth geometry description and thus, singularities in the stresses arise. In order to overcome these problems, several strategies are presented in this work. To capture the weak discontinuities at the material interfaces, the FCM is combined with local enrichment. Moreover, the L 2 -projection is extended and applied to heterogeneous microstructures, transforming the 3D images into smooth level-set functions. All of the proposed approaches are applied to numerical examples. Finally, an application of cemented granular material is investigated using three versions of the FCM and is verified against the finite element method. The results show that the proposed methods are suitable for simulating heterogeneous materials starting from CT scans. [ABSTRACT FROM AUTHOR]

Particle strength is one of the critical factors that causes the degradation of the mechanical behaviour of crushable soil. Because of the complexity of particle shape, its effect on particle strength has not been completely understood. In this study, single particle crushing tests were performed on carbonate gravel particles with three size fractions (i.e. 5–10 mm, 10–15 mm and 15–20 mm) and three shapes (i.e. blocky, rodlike and flaky), using a PartAn3D Maxi large particle size and shape analyser to obtain the shape characteristics of the particles. The determination of crushing strength for particles with complex shapes was discussed, and it was found that it is appropriate to use the area equivalent circle diameter to obtain the crushing strength. The influence of particle size and shape parameters, including the elongation index, flatness index, intercept sphericity, circularity and convexity, on the crushing strength were identified, and an index termed the form factor considering dimensions in three directions was proposed to describe the effect of particle shape. Based on this form factor, a probabilistic model was established to predict the distribution of crushing strength of carbonate gravel particles with various sizes and shapes. The proposed model could be used in the discrete-element method to consider the influence of shape in addition when evaluating particle breakage. [ABSTRACT FROM AUTHOR]

Assessing the shear strength of coarse granular soils is challenging because testing devices in the laboratory often limit the maximum particle size (dmax). Although engineering standards define representative elementary volumes (REVs) using the aspect ratio α = X/dmax, where X is the characteristic sample size, they often disagree on the minimum α, as the effects of sample scale on shear strength are still not well understood. This paper presents a discrete-element study on the combined effect of specimen size and grading on the critical state shear strength of granular materials. The study covers a wide range of aspect ratios and demonstrates that the macroscopic response is stable for α ≥ 15 – which is significantly higher than the standard requirement of α ≥ 10 for simple shear tests. The granular microstructure is also strongly affected by α and the formation of column-like structures of grains carrying strong contact forces, reaching sample size independent conditions only for α ≥ 20. Such column-like structures are shown to be primarily composed of the largest classes of grains, supporting the fact that grading has no effect on the critical state shear strength and dmax correctly serves to scale a granular sample to the size of the testing device. [ABSTRACT FROM AUTHOR]

This paper presents results obtained from the discrete-element method (DEM) to study the effects of particle shape on the shear behavior and breakage of ballast aggregates. In this study, a series of direct shear tests have been performed on granular assemblies having various shape sphericity and roundness values. A clump-based degradation (breakage) model is incorporated into the DEM simulation to capture the breakage of aggregates during shearing. The results show that the decrease of particle sphericity and roundness results in an improvement in the shear performance of granular assemblies but subsequent exacerbation in particle breakage, which in turn reduces the shear strength and volumetric dilation. The breakage of particles localizes within an inclined band, with the width and inclination angle of the band increasing in assemblies comprising particles of low sphericity and roundness. A micromechanical analysis is conducted to examine the anisotropy of internal structures and particle motions in granular assemblies. It is observed that both the shape of particles and their breakage significantly influence these factors. Through microscopic analysis, a fundamental governing mechanism of particle shape effects on the shear strength and the breakage of granular materials is investigated at the macroscopic scale. [ABSTRACT FROM AUTHOR]

Infilled joints or faults are often subjected to long-term stable shear forces, and nature surface processes of normal unloading can change the frictional balance. Therefore, it is essential to study the sliding behavior of such granular materials under such unloading conditions, since they are usually the filling matter. We conducted two groups of normal unloading direct shear tests considering two variables: unloading rate and the magnitude of constant shear force. Dry sands may slide discontinuously during normal unloading, and the slip velocity does not increase uniformly with unloading time. Due to horizontal particle interlacing and normal relaxation, there will be sliding velocity fluctuations and even temporary intermissions. At the stage of sliding acceleration, the normal force decreases with a higher unloading rate and increases with a larger shear force at the same sliding velocity. The normal forces obtained from the tests are less than those calculated by Coulomb's theory in the conventional constant-rate shear test. Under the same unloading rate, the range of apparent friction coefficient variation is narrower under larger shear forces. This study has revealed the movement patterns of natural granular layers and is of enlightening significance in the prevention of corresponding geohazards. [ABSTRACT FROM AUTHOR]

Background: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is one of the most common inherited cerebral small vessel diseases caused by the NOTCH3 gene mutation. This mutation leads to the accumulation of NOTCH3 extracellular domain protein (NOTCH3ECD) into the cerebral arterioles, causing recurrent stroke, white matter lesions, and cognitive impairment. With the development of gene sequencing technology, cysteine-sparing mutations can also cause CADASIL disease, however, the pathogenicity and pathogenic mechanisms of cysteine-sparing mutations remain controversial. Objective: To analyze the pathogenicity and pathological features of cysteine-sparing mutations in both in vitro and in vivo mouse models. Methods: A cysteine-sparing mutant of NOTCH3ECD R75Q was constructed by lentiviral transfection in vitro , and the NOTCH3 R75Q knock-in mouse model was constructed by CRISPR/Cas-mediated genome engineering in vivo. A cycloheximide pulse-chase experiment was used to analyze the degradation of NOTCH3 extracellular domain proteins, and the deposition characteristics of NOTCH3ECD were quantitatively analyzed by immunohistochemical staining. The characteristics of the smooth muscle cells and granular osmiophilic materials were observed using electron microscopy. Results: We elucidated that the NOTCH3 R75Q mutation is pathogenic. NOTCH3ECD R75Q was found to be resistant to protein degradation and more likely to cause abnormal aggregation of NOTCH3ECD, resulting in reduced cell activity in vitro. The NOTCH3 R75Q mouse model showed pathological characteristics of CADASIL, with age-dependent NOTCH3ECD, granular osmiophilic material, and degenerated smooth muscle cells detected in the brain. Conclusion: To our knowledge, this is the first study to analyze the pathogenicity of NOTCH3 R75Q cysteine-sparing mutations in both in vitro and in vivo models. We demonstrate that NOTCH3ECD induced by NOTCH3 R75Q mutation has toxic effects on cells and reveal the deposition characteristics of NOTCH3ECD in the brain. This provides a feasible model and lays the foundation for further studies on the pathogenesis and therapeutic strategies of NOTCH3 cysteine-sparing mutations. [ABSTRACT FROM AUTHOR]

Self-assembled configurations are versatile for applications in which liquid-mediated phenomena are employed to ensure that static or mild physical interactions between assembling blocks take advantage of local energy minima. For granular materials, however, a particle's momentum in air leads to random collisions and the formation of disordered phases, eventually producing jammed configurations when densely packed. Therefore, unlike fluidic self-assembly, the self-assembly of dry particles typically lacks programmability based on density and ordering symmetry and has thus been limited in applications. Here, we present the self-assembly of particles with momentum, yielding regular arrays with programmable density and symmetry. The key is to embed anti-repellent structures, i.e. traps, that can capture kinetic particles individually and then robustly hold them against collisions with other momentum granules during a dynamic assembly procedure. By using anti-repellent traps, physical interactions between neighbouring particles can be inhibited, resolving many phenomena related to the uncertainty of space-sharing events in granular packing. With our self-assembly strategy, highly dense yet unjammed configurations are demonstrated, which conserve the inherent randomness in the location information of each granule in the trap and are useful for robust multilevel authentication systems as unique applications. Self-assembly in granular materials is challenging due to particle collisions in the air, leading to disordered, jammed configurations, unlike fluidic systems where density and symmetry can be controlled. The authors report embedding anti repellent structures to enable organized self-assembly by capturing and holding kinetic particles, thus allowing for programmable density and symmetry in granular materials. [ABSTRACT FROM AUTHOR]

The localization of deformations plays a crucial role in the failure of granular materials. Concerning classical continuum constitutive models, the localization of deformations is considered to be connected to the loss of ellipticity of the governing rate equilibrium equations, and entails mesh sensitivity in finite element simulations. While previous studies are often limited to strain localization analyses of individual tests, the focus of the present contribution lies on studying the localization properties in general constitutive states. For this purpose, a staggered optimization algorithm for determining the loss of ellipticity, considering both extreme values, minimum and maximum, of the determinant of the acoustic tensor, is proposed. Part of this algorithm representing a novel application of spherical Fibonacci lattices for discretizing the feasible domain of the associated optimization problem. In the presented localization study of the widely recognized modified Cam‐clay model, special attention is paid to determining the influence of the individual model parameters. Specifically, three factors favoring strain localization are found, namely (i) a low value of the ratio of the primary compression index and the recompression index, (ii) a large value of the critical state frictional constant, as well as (iii) a large value of Poisson's ratio. Moreover, a structural finite element study is performed, confirming the results of localization analyses at the constitutive level. [ABSTRACT FROM AUTHOR]

Snow, characterized as a unique granular and low‐density material, exhibits intricate behavior influenced by the proximity to its melting point and its three‐phase composition. This composition entails a structured ice skeleton surrounded by voids filled with air and spread with liquid water. Mechanically, snow experiences dynamic transformations, including bonding/degradation between its grains, significant inelastic deformations, and a distinct rate sensitivity. Given snow's varied structures and mechanical strengths in natural settings, a comprehensive constitutive model is necessary. Our study introduces a pioneering formulation grounded on the modified Cam‐Clay model, extended to finite strains. This formulation is further enriched by an implicit gradient damage modeling, creating a synergistic blend that offers a detailed representation of snow behavior. The versatility of the framework is emphasized through the careful calibration of damage parameters. Such calibration allows the model to adeptly capture the effects of diverse strain rates, particularly at high magnitudes, highlighting its adaptability in replicating snow's unique mechanical responses across various conditions. Upon calibration against established experimental benchmarks, the model demonstrates a suitable alignment with observed behavior, underscoring its potential as a comprehensive tool for understanding and modeling snow behavior with precision and depth. [ABSTRACT FROM AUTHOR]

Polyurethane polymer-reinforced granular material (PPGM) can be used for ground improvement due to its high strength and drainage capacity. However, in engineering practice, clogging may occur that influence the permeability of PPGM. This study makes a laboratory assessment of the permeability of PPGM with and without clogging. It is found that the permeability coefficient of clean PPGM decreases as the content of polyurethane polymer increases, due to the reduction of its porosity and pore constriction size. To account this effect, a modified constriction size formula of PPGM is proposed. With the increase of the extent of clogging, the permeability coefficient of clogged PPGM decreases due to its decrease in the constriction size. A monotonic increase of the permeability coefficient of the mean constriction size of PPGM is found. [ABSTRACT FROM AUTHOR]

Granular materials are widely encountered in food processing, but understanding their behavior and movement mechanisms remains in the early stages of research. In this paper, we present our recent modeling and simulation work on chute granular flow using both the discrete element method (DEM) and continuum method. Based on the simulation data, we apply machine learning techniques such as Random Forest, Linear Regression, and Ridge Regression to evaluate the effectiveness of these models in predicting granular flow patterns. The granular materials in our study consist of soft-sphere particles with a 1 mm diameter, driven by gravity as they flow down a chute inclined relative to the horizontal plane. Our DEM and continuum simulation results show good agreement in modeling the chute flow, and the machine learning approach demonstrates promising potential for predicting flow patterns. The results of this chute flow study can provide a benchmark solution for more complex flow problems involving factors such as particle shape, size, interparticle interactions, and external obstacles. [ABSTRACT FROM AUTHOR]

The aim of this study is to research the flow property of granular materials under nonlinear vibration, which directly affects the stability of the unloading system and the motion state of granules. According to the mechanical constitutive relation, the coupled suspension–tire model with nonlinear ordinary differential equations is established and the kinematic equations of granules are derived. Furthermore, the amplitude–frequency responses of the coupled system and force transmissibility are obtained by the incremental harmonic balance method (IHBM) with high-order approximation, and then the flow characteristics of granular materials are investigated based on the approximate analytic solution under nonlinear vibration. The theoretical analysis and numerical simulation show that the coupled suspension–tire system presents a softening nonlinear feature and the peaks are significantly smaller than that of the linear system, which further affects the motion rules of granular materials. As a result, different sliding states and flow paths are observed under the same operating conditions. This research not only shows the unloading mechanism and vibration transmission characteristics between the continuum structure and granular material but also theoretically explains the control mechanism of the coupled continuum–granular system. The research is instructive in improving the unloading efficiency of granules in practical engineering. [ABSTRACT FROM AUTHOR]

Laboratory leaching tests are tools to assess the mobility of environmental contaminants released from granular materials. Comparative leaching tests were performed using four PFAS-contaminated soils whose concentration patterns of 10 selected perfluoroalkyl and polyfluoroalkyl substances (PFAS) differed due to the two types of contamination sources. This study aimed to evaluate the equivalence of two usual laboratory-scale leaching test procedures, batch and column percolation tests, at liquid-to-solid ratios (L/S) of 2 l/kg, which is the current practice within the German assessment framework, and 10 l/kg (relevant for some EU regulations such as the landfill directive). The differences between the replicates of leaching tests investigating PFAS were smaller for column percolation tests than for batch tests, probably mainly due to the greater sample size and the better representativeness of the sample portion analyzed. It was observed that batch tests overestimate the release of shorter-chain PFAS, whereby the effect was greater with carboxylic than with sulfonic acids. Currently, the limits of detection of analyses given by the DIN standard with regard to PFCA and PFSA in soils are partly not sufficient to detect very low contents, whereas the detection of selected PFCA and PFSA in eluates is more sensitive, in accordance with the available standards. This results in limitations when calculating mass balances. [ABSTRACT FROM AUTHOR]

This paper proposes a method for synthesizing granular ZSM-23 zeolite with a high degree of crystallinity and hierarchical porous structure. This method is based on crystallizing granules composed of powdered ZSM-23 zeolite and a specially prepared amorphous aluminosilicate. It has been shown that these granules have superior mechanical strength compared to granular zeolite-containing materials, which are made from a mixture of ZSM-23 zeolite crystals and Al2O3. It has been demonstrated that when 0.5% of Pt granular ZSM-23 zeolite is used, with a high degree of crystallinity and a hierarchical porous structure, it exhibits higher activity and selectivity in the hydroisomerization of n-hexadecane compared to a bifunctional catalyst, which is a mechanical mixture of ZSM-23 zeolite crystals and Al2O3, with the metal deposited on the granules. [ABSTRACT FROM AUTHOR]

Aggregates used in civil engineering are irregular-shaped granular materials. Angularity is an important shape feature of aggregates (and for various other granular materials). Various alternative approaches are available in the literature on quantitative estimation of angularity, suggesting that there may not be any unique definition of angularity of irregular-shaped granular materials. The present paper reviews a few such measures of angularity proposed by past researchers and identifies some possible inconsistencies in these approaches. In the present work, the possible inconsistencies in such approaches are identified, and subsequently, a new automated angularity estimation approach based on corner point detection and its tangent space analysis is proposed. Some of the identified inconsistencies, such as inconsistencies with the existing corner point detection algorithms, were resolved with this proposed approach. Finally, this approach is applied to a few two-dimensional (2D) profiles of a few aggregates, and the results are presented. [ABSTRACT FROM AUTHOR]

The Traffic Speed Deflectometer (TSD) is a mobile vehicle that measures deflection slopes. Deflection slopes have been utilised in previous studies to backcalculate pavement layers' moduli. However, the nonlinear stress-dependency and cross-anisotropy of unbound granular materials and fine-grained soils were overlooked in those studies. Utilising the Finite Element Method (FEM) based on static analysis in this study to evaluate a three-layered flexible pavement system with specific material properties and layer thicknesses revealed that neglecting the nonlinear stress-dependency of base and subgrade layers underestimated the permanent deformation life of the backcalculated pavement by more than 45%. Neglecting the cross-anisotropy of the base layer with the design anisotropy ratio of 0.5 increased the backcalculated Asphalt Concrete (AC) modulus by more than 21%, increased the estimated permanent deformation life of the pavement by more than 160%, and decreased the backcalculated base modulus by around 28%. Neglecting the cross-anisotropy of the subgrade with the design anisotropy ratio of 0.5 almost increased the estimated permanent deformation life of the pavement by 15%. The results underscore the necessity to consider the nonlinear stress-dependency and cross-anisotropy of unbound granular materials and fine-grained soils in backcalculating pavement layers' moduli from TSD deflection slopes. [ABSTRACT FROM AUTHOR]