Grain Size Distribution Research Articles

The impact of wide-graded debris flow on sediment-trap dams in the Tibetan Plateau: an experimental study

In the Tibetan Plateau, pronounced topographical relief (steep mountains and deep valleys) coupled with intense weathering processes generates highly fragmented slope surfaces, creating debris-flow source materials with exceptionally heterogeneous grain-size distributions. These conditions frequently produce debris flows that exhibit extraordinary impact forces which cause severe damage to sediment-trap dams. Through 27 sets of flume experiments that systematically varied the particle-size distribution ( d max ), bulk density ( γ ) and flume slope ( θ ), this study investigates the impact mechanisms of wide-graded debris flows on sediment-trap dams. The results demonstrate that debris-flow interactions with sediment-trap dams occur through three distinct phases: (1) impact run-up, (2) rotational backflow and (3) depositional back-silting. Lower bulk-density flows exhibited greater run-up heights and more pronounced phase differentiation. Measured impact forces ( F ) showed an inverse relationship with bulk density ( γ ↑→ F ↓), while displaying positive correlations with both slope gradient ( θ ↑→ F ↑) and maximum particle size ( d max ↑→ F ↑). This occurs because higher- γ flows experience increased internal shear resistance, resulting in a reduction in velocity. Steeper slopes enhance kinematic energy, while larger particles generate more concentrated momentum transfer during impact. Sensitivity analysis revealed that d max exerts dominant control over impact dynamics compared to γ and θ . These findings provide critical insights for sediment-trap dam design in high-altitude debris-flow mitigation systems.

TEXTURAL ANALYSIS AND HYDRAULIC CHARACTERISTICS OF AJALI SANDSTONES OF OBOLLO-AFOR AND ENVIRONS IN ANAMBRA BASIN, SOUTHEASTERN, NIGERIA

The movement and storage of groundwater are determined by the porosity and hydraulic conductivity of the medium, which defines its permeability. Hydraulic conductivity depends on both the properties of the porous material and the fluid, and it has long been linked to the grain-size distribution of granular media. This study highlights the textural characteristics and hydraulic conductivity of Ajali Sandstone in Obollo-Afor area (southeastern Nigeria). The investigation approach involved field sampling and collection of 12 sandstone samples from different outcrop locations followed by laboratory studies such as grain size analysis. Grain size analysis and textural studies show that the sandstones mean range from 0.96-1.87 (av. 1.52). Other parameters such as coefficient of uniformity (Cu) range from 2.133 to 4.263 (av. 0.399), while sorting values of 0.83-1.10 (av. 0.96) imply moderately sorted sediments. The sandstones are mostly platykurtic and coarse skewed indicating sand of fluvial origin ranging from channel floor, point bar to braided rivers. Analysis shows that the sediments were deposited in beach/shallow agitated and fluvial agitated environments. The Ajali Sandstone porosity values range from 36.53%-42.6% (av. 39.9) and the hydraulic conductivity values of 2.579-68.101m/day (av. 43.741m/day). These values of porosity and hydraulic conductivity are indications of high specific yield for the sandstone of the study area.

Thermal damage in crystalline rocks: the role of heterogeneity

Accurately evaluating the impact of microstructural heterogeneity on thermal damage and failure mechanisms in crystalline rocks is crucial for geothermal energy development and the establishment of nuclear waste repositories. However, in thermal damage analyses of crystalline rocks using the discrete element method, most studies fail to account for the reduction in mineral mechanical and thermal properties caused by temperature increases. This study uses a Grain-Based model to simulate the microscopic mineral structure of crystalline rocks, focusing on analyzing the effect of heterogeneity. Thermal damage resulting from the uneven expansion of minerals is simulated by assigning specific thermal properties to each mineral. The temperature-induced degradation of mechanical and thermal properties is incorporated by introducing a temperature-dependent relationship for these characteristics in crystalline rocks. Along with moment tensor inversion theory, the microseismic behavior of crystalline rocks is explored to enhance understanding of rock failure mechanisms. The results indicate the following: (1) Thermal stress depends on the mineral’s size, shape and arrangement. The sharp corners and edges of irregularly shaped minerals are more likely to become stress concentration points under the influence of temperature. (2) Peak strength gradually decreases with increasing heterogeneity and larger grain sizes. A negative correlation between quartz content and peak strength becomes more evident when the temperature exceeds 450 °C. (3) The combined effects of high temperature and heterogeneity lead to a more significant increase in the b value. Smaller grains increase the complexity of crack paths, leading to more frequent branching at grain boundaries and resulting in higher b values. (4) The uneven distribution of grain sizes is the primary factor influencing the mechanical properties of crystalline rocks, while grain size is a secondary factor. At the same temperature, samples with more uniform grain distributions and smaller grain sizes exhibit higher thermal stability.

Multifractal Characteristics of Grain Size Distributions in Braided Delta-Front: A Case of Paleogene Enping Formation in Huilu Low Uplift, Pearl River Mouth Basin, South China Sea

Multifractal analysis has been used in the exploration of soil grain size distributions (GSDs) in environmental and agricultural research. However, multifractal studies regarding the GSDs of sediments in braided delta-front are currently scarce. Open-source software designed for the realization of this technique has not yet been programmed. In this paper, the multifractal parameters of 61 GSDs from braided delta-front in the Paleogene Enping Formation in Huilu Low Uplift, Pearl River Mouth basin, are calculated and compared with traditional parameters. Multifractal generalized dimension spectrum curves are sigmoidal and decrease monotonically. Multifractal singularity spectrum curves are asymmetric, convex, and right-hook unimodal. The entropy dimension and singularity spectrum width ranges of silt-mudstones and gravelly sandstones are wider than those of fine and medium-coarse sandstones. The symmetry degree scopes from different lithologies are concentrated in distinguishing intervals. With the increase of grain sizes, the symmetry degree decreases overall. Both the symmetry degree and mean of GSDs are effective to distinguish the different lithologies from various depositional environments. A flexible and easy-to-use MATLAB (2021b)® GUI (graphic user interface) package, MfGSD (Multifractal of GSD, V1.0), is provided to perform multifractal analysis on sediment GSDs. After raw GSDs imported into MfGSD, multifractal parameters are batch calculated and graphed in the interface. Then, all multifractal parameters can be exported to an Excel file, including entropy dimension, singularity spectrum, correlation dimension, symmetry degree of multifractal spectrum, etc. MfGSD is effective, and the multifractal parameters outputted from MfGSD are helpful to distinguish depositional environments of GSDs. MfGSD is open-source software that can be used to explore GSDs from various kinds of depositional environments, including water or wind deposits.

Spatio-temporal variations on alluvial fan channel width in response to grain size on the channel bed under constant upstream boundary conditions

It has been widely accepted that channel geometry on alluvial fans is predominantly controlled by upstream boundary conditions and remains stable if those conditions do not change. This study challenges that notion by examining how channel width on alluvial fans varies in space and time under constant upstream conditions. Experiments using a sediment mixture (sand and crushed walnut) with constant sediment and water discharge rates reveal distinct patterns in channel width. In lower water discharge runs, total channel width decreases over time, while in higher discharge runs, it increases. Theoretical principles suggest that channel width is inversely proportional to grain size. Sand results in a wider channel width compared to walnut sediment, making its proportion along the channel a key factor in controlling the average channel width. The disproportional advancement of sand reaches relative to the fan margin, which varies across different discharge runs, drives changes in slope and channel width over time. This study highlights that surface grain-size distribution can change as the fan grows, even when external conditions remain constant, leading to variations in channel geometry. Sedimentary records often attribute signal changes to upstream boundary variations. However, our findings highlight the critical role of intrinsic fan width dynamics, underscoring the need to consider this factor in fan evolution studies.

Precipitation-assisted heterostructure in a FeMnCoCrCuC high entropy alloy enables superior mechanical property

High-entropy alloys in which the face-centered cubic structure is dominant cannot meet practical engineering application requirements due to their insufficient strength. Traditional strengthening methods can improve strength of materials, but they inevitably lead to decreased ductility. In this work, mechanical properties of a face-centered cubic-structured FeMnCoCrCu high-entropy alloy were improved by doping a substantial amount of carbon and employing a processing route that combines cold rolling and annealing. A dual-heterostructure characterized by both bimodal grain-size distribution and non-uniform distribution of nanoscale precipitates was constructed. The average grain sizes were 21.6 and 5.9 μm for the coarse and fine grains, accounting for 56.6% and 43.4% of the material, respectively. On the other hand, the finer M23C6 precipitates in the grain interior had an average size of 73.1 nm, constituting 3.4% of the coarse-grained region and 10.7% of the fine-grained region. The larger M23C6 precipitates at grain boundaries had an average size of 182.4 nm, with an overall volume fraction of 1.5%. This heterogeneous microstructure endowed the alloy with superior strength and work-hardening capacity compared to the carbon-free alloy. The yield and tensile strengths reached 500 MPa and 979 MPa, respectively, while maintaining a uniform elongation of 42%. This study not only identifies the origin of strengthening and micromechanism of plastic deformation in the carbon-alloyed dual-heterostructured alloy but also elucidates the formation of the specified microstructure. The findings provide theoretical guidance for developing advanced alloys with both high strength and good ductility.

Rheology of debris flows: Insights from experiments with coarse‐grained matrix

AbstractDebris flow is characterized by a heterogeneous mixture of water and sediment with varying rheology. The granular effects on rheology are usually attributed to the bulk concentration of solids without considering the variability of granular configuration, as signified in the grain size distribution (GSD). In this work, the GSD effects on debris flow rheological properties were explored using the parameters μ and Dc derived from a unified GSD function, P(D) ~ D‐μ exp(‐D/Dc), that are widely applicable for debris flow materials. Compared with other experiments using artificial fine‐grained slurry (with grain size <2 mm) at a given solid volume concentration (Cv), the realistic coarse‐grained matrix (up to 10 mm) of fresh debris flows was used for the experimentation, under shear rate up to 40 (s−1) as in natural conditions. The results show that the flow can be categorized as Herschel‐Bulkley (HB) fluid, with an average consistency index of 0.45, signifying the shear thinning effect. The yield stress and effective viscosity exhibit a power‐law with μ and an exponential relationship with Dc, revealing the interlock between fine and coarse grains. Then, a modified HB model was proposed using the GSD parameters to specify the granular effects and explain the velocity fluctuation of debris flow surges. This work represents the first attempt to express rheological properties as a function of the unified GSD parameters and is potentially instrumental in formulating debris flow dynamics incorporating granular effects.

Investigating the influence of the radiative torque disruption on the size evolution of dust in the heliosphere

ABSTRACT In this paper, we conduct a detailed study on the effect of radiative torque disruption (RATD) mechanism on the fragmentation of micrometre-sized dust grains into nanoparticles within the heliosphere. We start by estimating the disruption time-scales for dust grains under various centrifugal stresses. Our numerical calculations demonstrate that RATD is a highly effective mechanism for breaking down micrometre-sized grains, producing nanoparticles more efficiently than other fragmentation processes. RATD also prevents micrometre-sized grains from being expelled by radiation pressure. Our findings indicate that the location of the present water snow line depends not only on temperature but also on the size of dust grains. For smaller grains, the snow line can shift outward beyond the position defined by thermal sublimation. Furthermore, we model the size distribution of dust grains modified by the RATD mechanism using a simplified model, showing that rotational disruption significantly decreases the number density of micrometre-sized grains while substantially increasing the number density of submicrometre-sized grains. However, the fraction of dust grains aligned at high-J attractors by radiative torques less than 80 per cent can considerably weaken the effect of RATD on the grain size distribution. Finally, we suggest several experiments that could potentially test the RATD mechanism and discuss the uncertainties of our model in more realistic applications to heliospheric dust.

РАЗРАБОТКА СЛОЖНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ НА ОСНОВЕ MgO, ПОЛУЧАЕМЫХ КОЛЛОИДНЫМ МЕТОДОМ

Technological approaches to the formation of pure and composite materials with the composition MgO : SiO2 : CaO : BaO, obtained using colloidal methods, are considered. Structural transformations occurring in the synthesized xerogel blanks during their heat treatment in air at temperatures ranging from 400 to 600°C were studied using scanning electron microscopy. At 400 °C, the size distribution of primary grains ranges from 37 to 56 nm, at 500 °C – from 33 to 74 nm, and at 600 °C – from 40 to 64 nm. X-ray phase analysis showed that the formed nanocomposite has a crystalline structure with a uniform distribution of impurities. EDX studies confirmed the calculated initial composition of the obtained material. Disks with diameters of 13, 20, and 40 mm were formed from the obtained composite for experiments on water purification from petroleum product contamination

PolyPal: A parallel microscale virtual specimen generator

PolyPal: A parallel microscale virtual specimen generator

Various wind activity proxies unmixed from grain-size distributions of surface eolian sands at the desert scale in the Tengger Desert, Northwest China

Various wind activity proxies unmixed from grain-size distributions of surface eolian sands at the desert scale in the Tengger Desert, Northwest China

Small-strain thermo-mechanical performance of lunar mare and highlands regolith simulants under Earth's atmospheric pressure and in vacuum

Small-strain thermo-mechanical performance of lunar mare and highlands regolith simulants under Earth's atmospheric pressure and in vacuum

An iterative program to back-analyze grain-size distribution from a predetermined soil–water characteristic curve

An iterative program to back-analyze grain-size distribution from a predetermined soil–water characteristic curve

Sediment Characteristics in the Sungai Belacan Beach Sambas Regency

Research on the sediment characteristics at Sungai Belacan Beach, Sambas Regency, is crucial for understanding the coastal environment and its dynamics. The composition of sediments, grain size distribution, and transport processes play significant roles in shaping coastal ecosystems. The objective of this study is to examine the distribution of sediment grain sizes and their relationship with oceanographic parameters, such as tides, currents, and waves. A quantitative method was employed, with sediment samples collected using a sediment grab at eight station locations. The analysis of sediment characteristics was conducted through granulometric approaches and statistical analysis of grain sizes. The results indicate that the sediment fraction is dominated by sand, with an average grain size ranging from 0.86 to 1.56 mm, classified as medium to coarse sand. The sorting values range from 1.19 to 1.51, indicating poorly sorted sediments. The skewness values range from 2.36 to 3.26, categorized as very fine skewed. The kurtosis values range from 0.66 to 0.87, classified as platykurtic to very platykurtic. The average current velocity is 0.0413 m/s, with a mixed diurnal tidal pattern, and significant wave heights ranging from 0.11 to 0.42 meters, with a monthly average of 0.23 meters. The analysis shows that only Mean Size and Skewness have a significant relationship with wave height.

Investigation of the main drivers influencing sediment property change and coastal erosion in Central Vietnam

Coastal zones worldwide are densely populated and, as a result, among the areas most affected by urbanization. However, coastlines are very dynamic and always changing due to a variety of human and natural factors. One of today’s most concerning coastal risks is erosion, which can seriously harm buildings and infrastructure along the coast. The Cua Dai estuary in Vietnam, which serves as an outlet of the Thu Bon River, has been experiencing coastal erosion in recent decades. Following human activity in the upstream region, the erosion got severe, such as dam development and sand mining activity. As a result, a comprehensive evaluation of hydro-morphodynamics, sediment transport, and coastal interventions is necessary. We conduct campaigns to understand better the grain-size distribution along the cross-shore profile and the variation of median grain-size diameter (d50), which will help define a representative d50 to characterize the beaches. In addition, images from satellite observations depict coastal erosion patterns. The findings can improve our understanding of the budget from the mountain to the sea. They can be used to recommend specific measures for mitigating or intervening in hotspot areas.

Experimental Investigation of the Influence of Grain Size Distribution and Sediment Disposition on Local Scour Around Bridge Pier

Scour around bridge piers due to flooding is the leading cause of bridge failure. Numerous numerical and experimental studies have investigated local scour under various sediment properties, pier geometries, and hydraulic conditions. In this paper, we present the results of an experimental study on the influence of sediment grain-size distribution and disposition on local scour around a circular bridge pier. The study aims to qualitatively evaluate how various factors, particularly grain size distribution and sediment disposition, affect local scour in open-channel flow. Four factors were tested: flow rate, channel slope, grain size distribution, and sediment disposition. Results show that both sediment properties and their arrangement significantly impact the maximum scour depth. While channel slope also affects local scour, its influence is less pronounced than that of flow rate. The most significant changes in scour volume are attributed to sediment disposition in the channel. These findings highlight the critical role of sediment composition and arrangement in bridge pier scour mitigation and provide valuable insights for riverbed protection and hydraulic structure design.

Creep Failure Behavior in the Weak Areas of 12Cr1MoV Main Steam Pipe Elbow Utilized in Thermal Power Plants.

The main steam pipe elbow is a critical metallic component in thermal power plants. Due to prolonged exposure to high temperatures and pressures, it experiences microstructural degradation and creep damage, thereby affecting its service life. Currently, there is debate regarding the location of the weakest region within the elbow, with uncertainty over whether it lies in the inner arc or neutral plane area. This study investigates the microstructure and creep properties of both the inner arc and neutral surface regions of an elbow that has been in operation for 183,088 h, aiming to identify the actual weak region and explore the underlying creep damage mechanisms. The results indicate that under identical temperature and stress conditions, samples from the neutral plane region exhibit significantly higher creep rates and shorter creep rupture times compared to those from the inner arc region. This suggests that the creep life in the vicinity of the inner surface in the neutral plane is markedly lower than that in the inner arc region. Microstructural analysis before and after creep fracture reveals that key factors influencing the creep performance of 12Cr1MoV elbows include carbide size, precipitation amount and distribution, grain size and morphology, as well as the stability and uniformity of grain orientation. Specifically, the growth of intragranular precipitates, the accumulation and non-uniform distribution of grain boundary carbides, and the non-uniform distribution of grain sizes all contribute to the rapid formation of creep cracks and premature material failure. This study concludes that the weakest region in the elbow is located at the inner surfaces of the neutral plane. Future inspections and life assessments of thermal power plant elbows should therefore focus on this area to enhance the accuracy of life evaluations and ensure the safety of thermal power plants.

Unraveling the risk of dredging on river bars for mineral sand mining: an engineering geological approach

Sand mining using dredging technology from channel bars is a common technique worldwide. To minimize adverse effects of dredging, geo-engineering nature of the soil should be evaluated before mining. Therefore, the present study deals with the potential risks associated with dredging for mineral sand extraction by analyzing the engineering geological properties of the soil from the Brahmaputra River bar and the surrounding areas, Bangladesh. A detailed engineering geological analysis was conducted using field and laboratory testing methods, including Standard Penetration Tests (SPT), mineralogy, grain size distribution (GSD), California Bearing Ratio (CBR), and direct shear tests. The findings divulge that the soil in the study area is light gray, unconsolidated, moderately sorted, poorly graded, and classified as fine-to-medium silty sand. SPT-based liquefaction potential assessments suggest that the soils are highly susceptible to liquefaction, particularly during dredging or seismic events. The study also identifies the risk of localized slumping and soil instability, which exacerbated by micaceous and quartz-rich sands. The CBR results further classify the subgrade as weak to medium-strong, indicating risks of slumping, erosion, and instability. The non-cohesive granular soil in the area may liquefy or be susceptible to erosion, wave attack, bank slope failures, and seepage development during and after dredging as indicated from GSD and direct shear test results. Thus, proper safety precautions, including soil stabilization techniques, controlled dredging, and slope reinforcement, should be taken before dredging on such river bar to minimize risk. This research offers practical guidance for dredging companies to minimize risks and improve soil stability, contributing to safer and more sustainable river bar dredging operations worldwide.

Integrated Lithium-Rich yLi2MnO3∙(1-y)LiNi1/3Co1/3Mn1/3O2 Layered Cathode Nanomaterials for Lithium-Ion Batteries.

Integrated Li- and Mn-rich layered cathodes yLi2MnO3∙(1-y)LiMO2 (M = Mn, Co, and Ni) have shown their ability to deliver specific capacities close to 300 mAh g-1, but their significant drawbacks are capacity fading and voltage decay during cycling. In this study, new stoichiometric high-voltage Li-rich oxides with y = 0.0, 0.3, and 0.5 are synthesized in identical conditions using a sol-gel method. These compositions were analyzed to determine their optimal configuration and to understand their extraordinary behavior. Their nanostructural properties were investigated using XRD and Raman spectroscopy, while the morphology and grain-size distribution of the samples were characterized by BET, SEM and HRTEM analyses. The electrochemical performances of the integrated Li- and Mn-rich compounds were evaluated through galvanostatic cycling and electrochemical impedance spectroscopy. The best cathode material 0.5Li2MnO3∙0.5LiNi1/3Co1/3Mn1/3O2 had a capacity retention of 83.6% after 100 cycles in the potential range 2.0-4.8 V vs. Li+/Li.

Rapid Grain Segmentation of Heat-treated and Annealed LPBF Haynes 282 Using an Unsupervised Learning-Based Computer Vision Approach

Grain size distribution is a critical factor in determining materials’ physical and mechanical properties, including thermal conductivity, hardness, and creep behavior. Understanding the distribution of grain sizes is essential for advancing the comprehension of material properties and improving materials development and design. Traditional methods for determining grain size, such as electron backscatter diffraction (EBSD), are resource-intensive, underscoring the need for more efficient approaches to grain segmentation in standard micrographs, such as those obtained via SEM and optical imaging. This paper presents a streamlined, unsupervised computer vision pipeline that employs superpixel segmentation and region adjacency merging techniques to segment and measure grain geometry from micrographs efficiently. The pipeline is validated using two methods: hand-labeled SEM images of laser powder bed fusion (LPBF) fabricated Haynes 282 Ni-alloy and open-source EBSD data of IN100 from Dream3D. Both validation approaches achieved IoU and Dice scores greater than 0.9, while processing an image with a resolution of 1000 × 1000 pixels in under 40 s, demonstrating a fast and sufficiently accurate pipeline.