Coarse Sand Research Articles

Numerical Approximation Tool Prediction on Potential Broad Application of Subsurface Vertical Flow Constructed Wetland (SSVF CW) Using Chromium and Arsenic Removal Efficiency Study on Pilot Scale

\noindent {\bf Abstract:} This study investigates the potential broad application of Subsurface Vertical Flow Constructed Wetlands (SSVF CWs) for heavy metal remediation, focusing on Chromium (Cr) and Arsenic (As) removal efficiency. A pilot-scale experimental setup was employed, utilizing a SSVF CW filled with 12 mm gravel and 2 mm coarse sand, planted with Phragmites Australis. The research, conducted over 366 days, aimed to develop a numerical approximation tool to predict the performance and applicability of SSVF CWs in various environmental conditions. The experimental system operated at a hydraulic loading rate of $98-111 \mathrm{~mm} / \mathrm{d}$ and a hydraulic retention time of 6 days. Results showed average removal efficiencies of $44.87 \pm 9.52 \%$ for Cr and $43.16 \pm 9.43 \%$ for As. A mass balance analysis revealed that substrate accumulation was the primary mechanism for heavy metal removal, accounting for $29 \%$ of Cr and $26 \%$ of As removal. Plant uptake contributed to $3.5-9.9 \%$ of Cr and $0.3-$ $8.8 \%$ of As removal. Based on these findings, a numerical model was developed to simulate SSVF CW performance under varying environmental and operational parameters. The model incorporated factors such as influent concentrations, hydraulic loading rates, substrate composition, and plant species. Validation against experimental data showed good agreement, with an $\mathrm{R}^{2}$ value of 0.89 . The numerical tool was then used to predict SSVF CW performance across a range of scenarios, indicating potential broad applications in industrial wastewater treatment, mine drainage remediation, and contaminated groundwater cleanup. This study provides valuable insights into the scalability and versatility of SSVF CWs for heavy metal removal, offering a sustainable and cost-effective solution for water treatment challenges.\\

Quantifying aquifer heterogeneity using superparamagnetic DNA particles

Identifying and determining hydraulic parameters of physically heterogeneous aquifers is pivotal for flow field analysis, contaminant migration and risk assessment. In this research, we applied a novel uniquely sequenced DNA tagged superparamagnetic silica microparticles (SiDNAmag) to quantify hydraulic parameters and associated uncertainties of a heterogeneous sand tank. In the sand tank with lens shaped heterogeneity, we conducted three sets of multi – point injection experiments in unconsolidated (1) homogeneous (zone 0), (2) heterogeneous with a no-conductivity-zone (zone 1), and (3) heterogeneous with a high-conductive-zone (zone 2). From the breakthrough curves (BTC), we estimated the parameters distributions of hydraulic conductivity (k), effective porosity (ne), longitudinal dispersivity (αL), transverse vertical (αTV), and transverse horizontal dispersivities (αTH) applying Monte Carlo simulation approach for BTC fitting. The estimated parameters and associated uncertainties for each of the heterogeneous sections were further statistically compared (distribution non-specific Mann Whitney U test) these parameter distributions with parameter distributions estimated from the conservative salt tracer. While the time of arrival and time to peak concentration of SiDNAmag and salt in effluent were comparable, peak concentration of SiDNAmag was 1–3 log reduced as compared to the salt tracer due to first order kinetic attachment. Nonetheless, the parameters and associated uncertainty distributions (5 %–95 %) of K, ne, αL, αTV, and αTH, determined from SiDNAmag BTCs were statistically equivalent to the salt tracer in all three experiment systems. Through our experimental and modelling approach, our work demonstrated that in a coarse to very coarse grain sand medium, with lens shaped heterogeneity, the uniquely sequenced SiDNAmag were a promising tool to identify heterogeneity and determine hydraulic parameters and associated uncertainty distributions.

Experimental Study of a Silica Sand Sensible Heat Storage System Enhanced by Fins

This study aims to assess the thermal performance of silica sand as a heat storage medium within a shell-and-tube sensible heat storage thermal energy system that operates using water as the heat transfer fluid. Two types of silica sand were analyzed, fine sand and coarse sand, to determine which was the best for heat transfer and storage. It was found that the fine sand, which had smaller particles compared to the coarse sand, enhanced the heat transfer in the system. The fine sand required 11.86 h to charge using the benchmark case and 17.58 h to discharge, whereas the coarse sand required 13.36 h to charge and 16.55 h to discharge. Methods of enhancement are also explored by comparing the system performance with the inclusion of four different configurations of copper fins to investigate against a benchmark case without fins in the system with fine sand. When equipped with four radial fins, the system demonstrated a significant enhancement, reducing charging and discharging times by 59.02% and 69.17%, respectively, compared to the baseline. Moreover, the system exhibited an even greater improvement with eight radial fins, cutting charging and discharging times by 63.74% and 78.5%, respectively, surpassing the improvements achieved with four radial fins. The ten annular fins decreased the charging time by 42.58% and the discharge by 62.4%, whereas the twenty annular fins decreased the charging by 56.24% and the discharging by 68.26% when compared to the baseline.

Influence of Pre-sowing Seed Treatments and Growing Media on Performance of Consecutive Sowing for Constant Production of Fenugreek Microgreens (Trigonella foenum-graecum L.) under Shade Net

The present investigation was conducted at the College of Horticulture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth Dapoli, Dist. Ratnagiri, State-Maharashtra, India in 2023-24. The experiment was laid out in a split-plot design with factorial arrangement having eight treatment combinations and three replications. Factor A comprised two pre-sowing seed treatments: W1: Water soaking of seed and W2: without soaking, while, Factor B included four growing media: M1: Soil + FYM (3:1), M2: Coarse Sand, M3: Cocopeat and M4: Soil + Cocopeat (1:1). The data recorded during investigation revealed that the pre-sowing seed treatments and media influenced the growth and yield parameters of fenugreek microgreens. Among two pre-sowing seed treatments, W1 (Water soaking) had superior effect on all growth and yield parameters compared to W2 (Without soaking). Among various growing media M4-Soil + Cocopeat (1:1) found superior in some growth parameters like, days for germination (avg. 3.39), yield (avg. 678.20 g/m2) and maximum number of cycles (avg.13.46). The treatment combination W1M4-[ Water soaking of seed + Soil + Cocopeat (1:1)] performed better in terms of days to germination (avg. 2.88), days required for harvest (8.33), yield (avg. 1505.57 g/m2), number of cycles (avg. 15) in 6 months.

Impact of substrate particle size on the digging behavior of the juveniles of the smooth fan lobster Ibacus novemdentatus Gibbes, 1850 (Decapoda: Pleocymeta: Scyllaridae)

Abstract Aquaculture techniques for fan lobsters are still in an early stage of development due to the limited knowledge on their early-benthic stages. As the lobsters are diggers and thus the substrate influences their survival and growth, the physical characteristics of such substrates are a crucial environmental factor in an aquaculture setting. The appropriate size ranges of the substrate particles are nevertheless unknown. We studied the digging behavior of the juvenile of the smooth fan lobster, Ibacus novemdentatusGibbes, 1850, and examined its ability to dig into sand of different particle sizes to determine the optimal substrate conditions. Digging was completed by 100% of the juveniles in fine sand, 85.7% in medium-size sand, 25.7% in medium-coarse sand, and none in coarse sand. Juvenile digging involves three stages: searching for a location to dig, inserting the tail fan, and submerging into the sediment. The median length of time from the beginning of the experiment to the commencement of tail insertion in juveniles that completed digging did not differ significantly (P = 0.97) with the particle size. Juveniles placed on the substrate with medium-size and medium-coarse sand took significantly longer (P < 0.01) from the start of tail insertion to the complete submersion than those on fine sand. Considering the success rates of digging and the time required to complete digging, fine sand was the most appropriate substrate among the tested particle-size ranges. The juveniles that failed to complete the digging repeated a digging position and attempted to insert their tail fan into the sand without submerging. These juveniles took a significantly longer time (P < 0.05) to attempt to insert their tail fan than the juveniles that successfully completed digging, suggesting that juveniles placed on inappropriate substrates may spend more energy on digging and become more stressed.

Study on the Influence of Walnut Shell Coarse Particles on the Slurry Permeation and the Air Tightness of Filter Cake

Slurry shields rely on the formation of a compact filter cake to maintain excavation face stability and ensure construction safety. In strata with high permeability, significant slurry loss occurs, making filter cake formation and air tightness maintenance challenging. In this study, light organic walnut shell was selected as an additive coarse particle material for slurry. Slurries incorporating two types of coarse particles, sand and walnut shell, were prepared, and tests on slurry permeation and air tightness of the filter cake were conducted in three different strata. The results indicate that the addition of coarse particles effectively improves filter cake formation and air tightness in high-permeability strata. It is essential to use graded particles in highly permeable strata, with controlled maximum and minimum particle sizes. As the content of coarse particles increases, the air tightness of the filter cake initially increases and then decreases. Notably, the air tightness of filter cakes containing walnut shell is superior to those containing sand. Replacing sand with walnut shell as a slurry plugging material enhances filter cake quality in high-permeability strata. For highly permeable strata with a permeability coefficient greater than 1.0 × 10−3 m/s, an addition of 30 g/L to 40 g/L is recommended.

The Jyndevad Experiment: Revealing long-term interactions between liming and phosphorus fertilization in a coarse sand soil

The Jyndevad field experiment, initiated in 1942 on a coarse sand soil in South of Denmark, explores the effect of four liming levels (0, 4, 8 and 12 Mg lime ha−1). These were in 1944 combined with two levels of mineral phosphorus (P) fertilizer (0 and 15.6 kg P ha−1 year−1), with or without a high initial dose of 156 kg mineral P ha−1. This study assesses interactions between liming and P fertilization on soil pH, Olsen-P contents and barley yields covering the last three decades. Annual P application improved barley yield regardless of liming, but the optimal liming level differed from year to year. This emphasizes the need for long-term field experiments to detect the complex interactions between liming and P availability on crop performance. The initial high P dose in 1944 and annual P fertilization increased Olsen-P contents in soil. The unlimed soil with pH(CaCl2) values below 4 had the highest Olsen-P content. The Jyndevad Experiment now harbors wide gradients in soil P (Olsen-P contents: 9–82 mg P kg−1 soil) and pH (3.6–6.9), providing a unique research platform for future studies on interactions between liming and P fertilization on coarse sand soils. We present a selection of studies that have used the Jyndevad Experiment to illustrate the research potential of the experiment.

Exploring Soil–Water Characteristic Curves in Transitional Oil Sands Tailings

Soil–water characteristics curves (SWCC) have proved useful in estimating parameters used in modeling unsaturated geotechnical properties of soils including permeability and strength. Either saturation, gravimetric, and instantaneous and initial volumetric water content designation can be used to develop SWCCs. Studies have shown that any of the designations will give good estimates for soils that do not undergo volume change with suction change whereas, for soils that undergo substantial volume change, only saturation and instantaneous volumetric water content designation obtained by incorporating shrinkage curves can give correct estimates. Transition oil sands tailings have fines content that cannot be categorized as sandy or fine materials, and research on volume change with suction change in these materials is limited. In this study, HyProps, Tempe cells, and a chilled-mirror water potential meter were used to measure suction and corresponding water contents for samples that were prepared by mixing coarse sand and Fluid Tailing by ratios that mimic transition zone tailings. Shrinkage tests were also performed to observe the extent of volume change with suction increase. Air Entry Values (AEV) estimated from SWCCs based on gravimetric water content were found to be lower than those estimated from saturation-based SWCCs due to substantial volume changes in these materials with suction increase. The use of saturation water content designation is recommended in estimating AEV for transitional oil sands tailings. This is useful information in predicting the long term unsaturated geotechnical behavior of these materials for environmental management and safety purposes.

Utilizing Iron Oxidizing Bacteria (IOB) in the Bio-remediation of Subsurface Drinking Water from Haridwar, Uttarakhand, India

Background and Aim: Iron-oxidizing bacteria (IOB) are harmless, chemotrophic organisms that use oxygen to dissolve iron in wastewater contaminated with heavy metals. They thrive in water with iron concentrations as low as 0.1 mg/L, offering a cost-effective, eco-friendly solution for water treatment. In Uttarakhand, widespread iron contamination continues to limit access to safe drinking water despite efforts to address the issue. This study aimed to explore the use of bioremediation and microbial consortia to reduce and eliminate iron contamination in drinking water sources. Methods: The study employed a biosorption process, where the iron-oxidizing bacteria and microbial consortia were immobilized on a solid carrier (coarser sand) to facilitate contact with the contaminated water. The bacteria and consortia adsorbed iron ions from the water onto the surface of the carrier material through various mechanisms, including ion exchange, chelation, and surface complexation. The biosorption experiments were conducted in a batch mode, where the contaminated water was mixed with the carrier material containing the microbial consortium. The mixture was agitated under controlled conditions to promote iron removal. Results: The study assessed the iron removal efficiency of various carriers (gravel, sand, coarse sand, bentonite, and lignite) and iron-oxidizing bacteria (IOB-1 to IOB-6) from 100 water samples collected in Uttarakhand. The key findings are: Carrier Performance: Coarse sand consistently demonstrated the highest iron removal efficiency among all carriers, with an average removal rate of 84.67% ± 0.02%. Microbial Isolate Performance: Among the IOB strains, IOB-1 exhibited the best iron removal efficiency, achieving an average of 46.67% ± 0.08%. Microbial Consortium: The microbial consortium formed using IOB-1 in combination with coarse sand achieved the highest overall iron removal efficiency of 89.33% ± 0.05. These results underscore the effectiveness of bioremediation techniques, particularly using microbial consortia, for addressing iron contamination in water resources. Discussion: The present study demonstrates the efficacy of bioremediation techniques, specifically utilizing iron-oxidizing bacteria and microbial consortia, in addressing iron contamination in water resources. The results indicate that the selected carriers, particularly coarse sand, and the microbial isolate IOB-1 exhibited significant potential for iron removal. Conclusion: The combination of iron-oxidizing bacteria and suitable carriers offers a promising approach for water treatment in regions affected by iron pollution. The microbial consortia entrapped in coarse sand demonstrated superior performance compared to individual strains, suggesting the synergistic effects of microbial interactions.

Experimental Study on Proportion Optimization of Rock-like Materials Based on Genetic Algorithm Inversion.

It is very important to clarify the optimization method of the rock-like material ratio for accurately characterizing mechanical properties similar to the original rock. In order to explore the optimal ratio of rock-like materials in gneissic granite, the water-paste ratio, iron powder content and coarse sand content were selected as the influencing factors of the ratio. An orthogonal test design and sensitivity analysis of variance were used to obtain the significant influencing factors of the ratio factors on seven macroscopic mechanical parameters, including compressive strength σc, tensile strength σt, shear strength τf, elastic modulus E, Poisson's ratio ν, internal friction angle φ and cohesion c. A multivariate linear regression equation was constructed to obtain the quantitative relationship between the significant ratio factors and the macroscopic mechanical parameters. Finally, a rock-like material ratio optimization program based on genetic algorithm inversion was written. The results show that the water-paste ratio had extremely significant effects on σc, σt, τf, E, ν and c. The iron powder content had a highly significant effect on σc, σt, τf and c, and it had a significant effect on ν and φ. Coarse sand content had a significant effect on σc, E and c. The multiple linear regression model has good reliability after testing, which can provide theoretical support for predicting the macroscopic mechanical parameters of rock-like materials to a certain extent. After testing, the ratio optimization program works well. When the water-paste ratio is 0.5325, the iron powder content is 3.975% and the coarse sand content is 15.967%, it is the optimal ratio of rock-like materials.

Mechanistic insights into pore water conversion to gas hydrates in clay minerals

The conversion of pore water to gas hydrates is an important prerequisite for natural gas hydrates (NGHs) accumulation and hydrate-based CO2 sequestration. However, the mechanism of water-to-hydrate conversion in clays, which are prevalent in hydrate reservoirs or marine sediments serving as potential hosts for CO2 hydrates, still remains poorly understood, impeding further advancements in exploiting NGHs and developing CO2 sequestration strategies. In this paper, the characteristics of pore water conversion to hydrates in montmorillonite and kaolin were comprehensively examined through quantitative measurements and NMR analysis, and compared with those in silt and coarse sand. It revealed that the water-to-hydrate conversion was more restricted in clays than in sands. Especially in montmorillonite, since almost all pore water was detected as bound water, the final water conversion was extremely low and sensitive to the subcooling degree. Additionally, as the initial water content increased from 15 wt% to 35 wt%, the final water conversion in kaolin, silt, and coarse sand decreased exponentially due to intensified kinetic limitation, whereas that in montmorillonite initially rose and then fell, attaining the maximum at a threshold of 20 wt%. It is found that the competition between thermodynamic and kinetic limitations controls water-to-hydrate conversion in clays. Specifically, in kaolin, silt and coarse sand, the main controlling factor of water-to-hydrate conversion is the kinetic limitation, as their unconverted equilibrium water is negligible. However, in montmorillonite, the thermodynamic limitation dominates at low water contents, transitioning to kinetic limitation at high water contents. This study provides direct evidence and mechanistic insights into how clays affect water-to-hydrate conversion in porous media, which has significant implications for the geological accumulation of NGHs and the site selection for hydrate-based CO2 sequestration.

Vortex Trapping of Suspended Sand Grains Over Ripples

AbstractCoastal hydrodynamics and morphodynamics integrate the effects of small‐scale fluid‐sediment interactions; yet, these small‐scale processes are not well understood. To investigate sediment trapping by turbulent coherent structures or vortices, the transport of coarse sand over ripples was analyzed in a small‐oscillatory flow tunnel with phase‐separated Particle Image and Tracking Velocimetry. Results from one of the first direct measurements of vortex‐trapped sand grains under oscillatory flows are presented. The vortices mobilized sand grains along the ripple slopes just prior to flow reversal and transported the suspended sediment grains. During several flow cycles, some sand grains were temporarily trapped in the vortex, prescribing semi‐circular trajectories off‐center from the vortex core in quadrants of the vortex that were closest to the ripple slope, as illustrated by Nielsen (1992, https://doi.org/10.1142/1269). Comparisons of the horizontal sediment grain velocity with the horizontal fluid velocity yielded a linear relationship with a slope of 0.87. The vertical grain velocities also varied linearly with the vertical fluid velocity with a slope of approximately 1 and an offset of −0.08 m . The offset is close to the still water settling velocity for coarse sand grains, as hypothesized during vortex trapping. Additionally, estimates of the off‐center distance, between the centers of the semi‐circular sediment paths and vortex cores, compared well with the ratio of the settling velocity to the radian frequency of the vortex yielding a linear regression slope of 0.99. Improved understanding of vortex trapping effects on sediment dynamics may decrease uncertainty in model predictions of large‐scale coastal hydrodynamics and sediment transport.

Anatomy of Niger and Benue river sediments from clay to granule: grain-size dependence and provenance budgets, Nigeria

ABSTRACT This study explores in detail the complexity of textural–compositional relationships in fluvial sediments. To this aim, fifteen size fractions (from clay to granule) of three sediment samples characterized by virtually identical size distribution from the Niger and Benue rivers in central Nigeria were separately analyzed by multiple methods (optical microscopy, manual and semi-automated Raman spectroscopy, X-ray diffraction, elemental geochemistry, Nd isotopes). The independent mineralogical and geochemical datasets thus obtained allowed us to investigate processes of sediment generation for five diverse size modes (clay, fine cohesive silt, very coarse frictional silt, very fine sand, coarse sand) derived in different proportions from different sources (wind-blown dust, soils and paleosols, fine-grained and coarse-grained siliciclastic units, igneous and metamorphic bedrocks). Controls on the size distribution of detrital minerals (settling equivalence, size inheritance, weathering, mechanical durability, and chemical durability through multiple sedimentary cycles) were examined, specifically focusing on tectosilicates and on the long-standing petrological problem of feldspar–grain-size relations. Various factors determine the composition of different size modes: kaolinite-dominated clay derives from both deeply weathered soils or paleosols and distant Saharan sources; cohesive silt is largely recycled from mudrocks and soils formed in sedimentary basins. The proportion of detritus derived first-cycle from basement rocks increases from very coarse silt to very fine sand, whereas the coarse-sand mode is quartz-dominated with scarce plagioclase and amphibole and local occurrence of garnet, staurolite, monazite, or xenotime reflecting a combined influence of size inheritance from igneous (pegmatite) and metamorphic sources, mechanical and chemical durability, and recycling from coarse-grained siliciclastic units. Sediment budgets based on mineralogical, geochemical, and geochronological signatures consistently indicate dominance of Benue sediment supply, although the contribution from the Niger mainstem to the Niger Delta is inferred to have been notably greater in the wetter past, before clastic fluxes dropped in response to the aridification of the Sahel.

Exploring soil erodibility: integrating field surveys, laboratory analysis, and geospatial techniques in sloping agricultural terrains

The escalating trend of land degradation poses a significant challenge, especially in sloping agricultural terrains, driven by the increasing global demand for food and the limited availability of flat arable land. In response to these challenges, farmers are compelled to shift their focus towards cultivating sloping terrains. This research aimed to employ a comprehensive methodology that integrates on-site field surveys, meticulous laboratory soil analyses, and geospatial data for mapping soil erodibility. The parameters under scrutiny encompass various crucial aspects, including soil texture (ranging from coarse sand to very fine sand, silt, and clay), soil structure, organic matter content, and permeability. The meticulous examination of these factors serves as the foundation for calculating soil erodibility, utilizing the well-established Wischmeir and Smith formula developed in 1978. The research findings present a nuanced understanding of soil erodibility in the study location, revealing a spectrum spanning low to very high erodibility. Specific units, such as Unit 1, Unit 2, Unit 3, Unit 7, Unit 9, Unit 10, Unit 13, and Unit 16, exhibit very low to low erodibility. In contrast, Unit 4, Unit 6, Unit 14, and Unit 15 showcase moderate erodibility, while units like Unit 5, Unit 8, Unit 11, Unit 12, Unit 17, and Unit 18 are characterized by moderately high to very high erodibility. These insightful results shed light on the diverse erodibility levels within the studied locations and provide valuable guidance for formulating sustainable land management practices.

Characteristics of the Aeolian Sediments Transported Above a Gobi Surface

AbstractGobi’s (gravel deserts) are one of the largest dust sources in northern China. Previous studies indicated that sand transport processes above the surface differed between Gobi and sand surfaces. However, the sand transport rate and related dust emission processes above Gobi (gravel) surfaces are still poorly understood. In this field study, we quantified this transport to provide important support for parameterizing Aeolian sediment transport models and clarifying the relationship between dust emission and transport. Threshold wind velocity can reach 0.38 ± 0.04 (mean ± SD) m s−1 above Gobi surfaces. Compared to the most commonly used sand‐transport models, we found that the Lettau and Lettau sediment transport model can be used to calculate horizontal sediment transport above a Gobi surface. The relationship between the vertical sediment transport (Fs) and shear velocity could be expressed using a power function. Although the horizontal sand transport and vertical flux (Q and Fs, respectively) above Gobi surfaces can be expressed similarly to previous results (i.e., using similar equation forms), the equation coefficients were much larger for the Gobi surface than for a shifting sand surface; that is, sediment transport was higher above the Gobi surface. This difference resulted from the larger sand transport rate and saltation height above the Gobi surface, and the larger transport and higher saltation height were related to the larger sand transport height and higher content of coarse sand transported above the Gobi surface.

Study of Structural Defects Evolution in Fine-Grained Concrete Using Computed Tomography Methods

Introduction. When studying composite materials for construction purposes, it is needed to consider the mechanisms of formation of the structure and properties of modern concretes in the process of strength development. In studies of modern composite materials based on cement binder, there is no information about the development of structural defects and destruction of the material at the initial stages of strength development. This information can be obtained using X-ray computed tomography, a promising method of nondestructive testing of the state of the material. Therefore, the objective of this work was to study the formation and propagation of cracks in samples of fine-grained concrete with different fractional composition of sand due to natural processes of cement shrinkage, as well as the mechanics of destruction of samples of modified fine-grained concrete when applying a compressive load at the early stages of strength development. Materials and Methods. The study used fine-grained concrete mixtures of three compositions with different sand gradation. The tomography samples were made by placing fresh mixtures in polymer cylindrical containers. Tomography of the samples immediately after manufacture, as well as after 8 and 51 days, was performed in a YXLON Cheetah microfocus X-ray machine. The composition with two-fraction sand was modified by mechanical activation of the components, 20×20×20 mm cube samples were made. Further, compression tests were performed at the Instron installation after 3 and 7.5 hours, and then — tomography of the destroyed samples.Results. It was established that the destruction of contact zones depended on the ratio of the size of the fractions. In the presence of a bulk of coarse sand grains in concrete, the destruction of contact zones was more pronounced and had a main mode. When using fine or polyfraction sand, contact zones were destroyed locally and had a visually smaller area. The images of the destroyed modified sample, tested 3 hours after manufacturing, showed clear cracks and indents on the edges, which indicated the elastic-plastic nature of the destruction. In 7.5 hours, the edges of the sample upon destruction were covered with a network of small cracks; inside the sample there were also numerous cracks and microcracks, which indicated brittle fracture. Based on the obtained images of the deformed structure of modified concrete, the mechanism of transition from elastic-plastic destruction of the material to brittle one was clearly visible.Discussion and Conclusion. The studied dependences of the influence of the size of fine aggregate on the mechanisms of formation and propagation of structural defects contribute to the theory of the processes of destruction of fine-grained concretes. The results obtained prove the prospects of using X-ray computed tomography as a method of nondestructive testing of the internal structure of fine-grained concrete, including at the early stages of strength development.

Method for Augmenting Side-Scan Sonar Seafloor Sediment Image Dataset Based on BCEL1-CBAM-INGAN.

In this paper, a method for augmenting samples of side-scan sonar seafloor sediment images based on CBAM-BCEL1-INGAN is proposed, aiming to address the difficulties in acquiring and labeling datasets, as well as the insufficient diversity and quantity of data samples. Firstly, a Convolutional Block Attention Module (CBAM) is integrated into the residual blocks of the INGAN generator to enhance the learning of specific attributes and improve the quality of the generated images. Secondly, a BCEL1 loss function (combining binary cross-entropy and L1 loss functions) is introduced into the discriminator, enabling it to focus on both global image consistency and finer distinctions for better generation results. Finally, augmented samples are input into an AlexNet classifier to verify their authenticity. Experimental results demonstrate the excellent performance of the method in generating images of coarse sand, gravel, and bedrock, as evidenced by significant improvements in the Frechet Inception Distance (FID) and Inception Score (IS). The introduction of the CBAM and BCEL1 loss function notably enhances the quality and details of the generated images. Moreover, classification experiments using the AlexNet classifier show an increase in the recognition rate from 90.5% using only INGAN-generated images of bedrock to 97.3% using images augmented using our method, marking a 6.8% improvement. Additionally, the classification accuracy of bedrock-type matrices is improved by 5.2% when images enhanced using the method presented in this paper are added to the training set, which is 2.7% higher than that of the simple method amplification. This validates the effectiveness of our method in the task of generating seafloor sediment images, partially alleviating the scarcity of side-scan sonar seafloor sediment image data.

Outburst flood events since the Last Glacial Maximum in the Hutiao Gorge of Jinsha River: Geomorphological evidence from eddy gravel bars

Breaching of natural dams in the Hutiao Gorge of the Jinsha River across the Yulong-Haba Mountains is one of the major geomorphological events in the largest river of Asia. Catastrophic flood events have an important influence on the geomorphological evolution of the First Bend of the Yangtze River since the Last Glacial Maximum (LGM). However, detailed geomorphological evidence, ages, and depositional phases of outburst flooding remain unclear. In this paper, large-scale gravel bars overlying the river terraces and dammed lakes are analyzed within the Daju Basin. The macroscopic geomorphological characteristics of megaflood landforms with large thickness and uniform gravel bars are similar to those of Missoula and Altai megafloods. Morphological analysis shows that eddy gravel bars (EGBs) with rhythmic structure are characterized by a dome-shaped protrusion in the cross section and a gravel mound in the longitudinal section. Each bar with oblique, parallel and massive bedding was analyzed from the horizontal and vertical directions. Three dome-shaped bars clearly show at least three palaeoflood phases. Quartz grain surface macrotextures are mainly V-shaped pits and conchoidal fractures, which exhibits a high-energy environment during the flood. The stratigraphic sequence model of EGBs is dominated by coarse sand and fine gravel rhythmic bedding in high-energy eddy environments and suspended sand deposits in low-energy backwater environments. Such phenomenon reveals megaflood fluctuates, which is also confirmed by geochemical difference. The episode of natural dam break floods triggered by tectonic activity and glacier fluctuation was dated to 20–17 ka during the LGM. Sedimentary pattern of EGBs offers fresh insights into understanding the megaflood geomorphological characteristics of the upper Yangtze River and better identification similar high-energy palaeoflood landforms in the southeast Tibetan Plateau.

Breaching of sand dikes: assessment of 1D and 2D numerical models against laboratory experiments

Dike failures often induce highly damaging floods. Improved understanding of the inherent mechanisms is important to predict and prevent dike failures. This research focuses on sand dike failure by overtopping. During the experiments, the evolution of nine sections was monitored using laser-sheet while the water level in the upstream reservoir was captured using ultrasonic gauges. The impact of the grain size was studied by comparing a fine and a coarser sand. Even though the failure mechanisms look similar in both cases, some differences could be observed in the evolution of the geometry of the dike. Finally, the failure was simulated with 1D and 2D models. The 1D model shows good results for the initial stage of the dike evolution and in predicting the evolution of the width of the breach. The 2D model predicts the morphological evolution of the dike more accurately but slightly overestimates the widening of the breach.

Grain size distribution and heavy minerals in the sediments of Sungai Dungun, Terengganu

Twenty-one samples of sediments were collected from the center of the river channel and 13 sediment samples collected from the riverbank were analysed for their textural parameters (mean, standard deviation, skewness, and kurtosis) to determine the mineral size. The results indicate that sediments from both the center of the channel and the riverbank were dominated by very coarse sand and very fine gravel. Heavy minerals in the sediment were separated using bromoform for density separation, as well as magnetic separation. Ilmenite, magnetite and cassiterite were abundant in the middle of the channel whereas rutile and zircon were found to be dominant at the riverbank.