Sand Research Articles

A new three-dimensional strength criterion considering the transverse isotropy based on the α-Spatial Mobilized Plane

Natural geotechnical materials are affected by sedimentation and exhibit significant anisotropy. To study the transverse isotropy characteristics of soil, the influence of intermediate principal stress and loading direction must be considered. Currently, research on transverse isotropy primarily focuses on the modified stress space, which is cumbersome to apply in multi-yield surface constitutive models. To describe the three-dimensional mechanical properties of geomaterials in real stress space, the α-Spatial Mobilized Plane strength criterion is introduced. Then, combined with the structure tensor, the transverse isotropic three-dimensional strength criterion can account for the effect of the loading angle. Finally, the three-dimensional strengths of Fukakusa clay, unsaturated SP-SC soils, uncemented Monterey sands, Yamaguchi marble, San Francisco Bay mud, Toyoura sand, and Santa Monica Beach sand are predicted on the π-plane. The results show that the αmn-SMP criterion, in the context of transverse isotropy, can describe the three-dimensional mechanical properties reasonably, and it can provide an accurate strength criterion for geotechnical engineering practice.

Research on freeze resistance and life prediction of Desert sand–Crushed stone fine aggregate concrete

Despite the global abundance of Desert sand (DS), its application in engineering remains limited. This application can help alleviate challenges related to high unit costs and the scarcity of natural fine aggregate supplies. Freeze resistance experiments were conducted on C30 concrete incorporating varying proportions of DS, including 0 %, 25 %, 50 %, 75 %, and 100 %. DS was mixed with Tuff crushed stone fine aggregate (Manufactured sand, referred to as MS). The freeze durability of the composite fine aggregate concrete was comprehensively evaluated from three perspectives: surface morphology, a macroscopic analysis including mass loss and relative dynamic elastic modulus (RDEM), and microscopic examinations encompassing pore structure observation and scanning electron microscope (SEM) imaging. Utilizing the damage degree index of the dynamic elastic modulus and the Weibull distribution model, the life prediction process was conducted to elucidate the time-varying behavior of DS-MS concrete. According to the test findings, the concrete specimen DS25-MS75 demonstrates the highest freeze resistance. The mass loss rate shows a pattern of initial decrease followed by an increase with higher desert sand admixture, whereas the RDEM initially increases and then decreases. Optimal desert sand admixture levels can prevent and delay concrete degradation, thereby enhancing its freeze resistance. Excessive desert sand content leads to increased water demand during the curing process, resulting in elevated porosity and facilitating the formation of voids. Under the action of freezing and thawing cycles in water, DS25 %-MS75 % concrete has the longest expected service life with an actual life of 101 years, while DS100 %-MS0 % concrete has the shortest service life with an actual life of only 54.5 years.

A Voice of Liberty and Protest: Exploring Binodini’s Identity Crisis, Power and Self-discovery in Tagore’s Chokher Bali (A Grain of Sand)

The cultural icon and trail blazer of Bengali Renaissance Rabindranath Tagore has experimented successfully upon some great female protagonists in his fiction who have managed to curve a niche for themselves in world literature. A master artist, he has also depicted with his dexterously professional brushstrokes a host of highly progressive and brave female identities with a strong voice of protest against all prejudices of the contemporary backward and prejudiced Hindu communities as well as against all conservative forces of fate and society. Tagore has portrayed extremely meticulously some female voices, attributing them to the strength of motherhood, the beauty of the beloved, and the strong power of womanhood, allowing them to develop their own individual status and identity in a stereotypical, male dominated, and patriarchal Bengali society. This paper undertakes to explore Binodini, a finely crafted character in the Novel ‘Chokher Bali’ by Tagore, who battles over her identity breaks a fresh ground for her own, and emerges as an uncompromisingly assertive woman with a voice and brand of her own. It explores that she is not terrified by the severity of the male gaze or trodden down by the repression of the male centric society in her journey through liberty and blossoms an individual very sure of herself by breaking the image of the traditional Indian womanhood.

Microplastic abundance, characteristics, and heavy metal contamination in coastal environments of Western Sri Lanka

This study was conducted to assess the abundance of microplastics and associated metal contamination at selected beaches in the Western Province of Sri Lanka. Beach sand samples were collected from four beaches: Modera, Negombo, Mount Lavinia, and Panadura. Microplastics were extracted from dried sand samples using a saturated NaCl solution, followed by sieving. Particles were identified using Fourier Transform InfraRed Spectrophotometer, and associated heavy metals; Cr, Pb, Cu, Zn, and Ni were subjected to acid digestion for 24 h before analysis using Microwave Plasma Atomic Emission Spectrometry. More than half of the extracted plastics (56.31%) were identified as microplastics. The average microplastic abundance in beach sand samples ranged from 42.0 to 91.3 items/kg. The sand collected at Mount Lavinia exhibited the lowest sbundance, whereas those from Panadura beach revealed the highest. Hydrodynamic factors like ocean currents, wave patterns, associated with Southwest monsoon period, and human activities may have caused the variability in microplastic abundances and metal contamination. The majority of the microplastics (52.29%) were polyethylene, followed by polypropylene (35.18%), resembling the records of the most common plastic waste types in the country. Most of the microplastics were found to be fragments (87.95%), while white being the prominent color (53.49%). The toxic trace element concentration ranged from 5.0 × 10−3 to 1.8 × 102 μg/g in beaches. This study establishes a baseline for the west coastline prior to the X-press Pearl Ship Disaster in 2021. Future studies are encouraged to assess the beach microplastic pollution across the- Sri Lankan coastline.

Deep Learning-Based Reconstruction of 3D Morphology of Geomaterial Particles from Single-View 2D Images.

The morphology of particles formed in different environments contains critical information. Thus, the rapid and effective reconstruction of their three-dimensional (3D) morphology is crucial. This study reconstructs the 3D morphology from two-dimensional (2D) images of particles using artificial intelligence (AI). More than 100,000 particles were sampled from three sources: naturally formed particles (desert sand), manufactured particles (lunar soil simulant), and numerically generated digital particles. A deep learning approach based on a voxel representation of the morphology and multi-dimensional convolutional neural networks was proposed to rapidly upscale and reconstruct particle morphology. The trained model was tested using the three particle types and evaluated using different multi-scale morphological descriptors. The results demonstrated that the statistical properties of the morphological descriptors were consistent for the real 3D particles and those derived from the 2D images and the model. This finding confirms the model's validity and generalizability in upscaling and reconstructing diverse particle samples. This study provides a method for generating 3D numerical representations of geological particles, facilitating in-depth analysis of properties, such as mechanical behavior and transport characteristics, from 2D images.

Relationships between fecal indicator abundance in water and sand and the presence of pathogenic genes in sand of recreational beaches.

For decades, the risk of exposure to infectious diseases in recreational beaches has been evaluated through the quantification of fecal indicator bacteria in water samples using culture methods. The analyses of sand samples have recently been developed as a complement to the monitoring of recreational waters in beach quality assessments. The growing use of molecular techniques for environmental monitoring allows for the rapid detection of pathogenic genes, thus providing more accurate information regarding the health risk of exposure to contaminated sand. The aim of this work was to determine the relationship between the fecal indicators abundance in water and sand and the presence of Shiga toxin-producer Escherichia coli (STEC) in sand by analyzing samples from touristic beaches using culture-dependent (fecal coliforms assay) and culture-independent (real-time PCR of stx1, stx2, and eae genes) techniques. We found a high concentration of coliform bacteria in water and sand in several beaches in eastern Uruguay, with different levels of sanitation networks and levels of urbanization. The presence of STEC virulence genes (mainly stx1) was confirmed in 8 out of 20 sand samples. The recreational use of sandy beaches may imply a risk to the health of its users, especially near streams and creek outflows, thus highlighting the need of monitoring sand bacteriological quality and pathogens using molecular tools.

Aeolian sand cover on a granite peninsula (Hammeren, Bornholm, Baltic Sea) formed in three episodes during the past 11,600 years

Aeolian sand covers a significant part of the granite peninsula Hammeren on northernmost Bornholm in the Baltic Sea. The coastline of Hammeren is rocky and apart from one relative wide and sandy pocket beach at the east coast only few, small and gravelly pocket beaches exist. The aeolian deposits form three sand covers that stretch inland from the east and northwestern facing coasts of Hammeren. The largest sand cover forms a rising sand plain that cover the granitic landscape up to 700 m inland and reaches up to 60 m above sea level. Historical sources mention aeolian sand movement around CE 1775 in the middle of the Little Ice Age, but until this study no absolute age control has been available to confirm these observations. Luminescence dating of selected sample sites indicates that aeolian sand movement took place in three episodes. The first episode was in the last part of the Younger Dryas at about 11,500 BP, the second episode was in the Danish Late Bronze Age at about 2700 BP, and the youngest episode was indeed during the Little Ice Age around 200 BP (CE 1750). These episodes with aeolian activity all fall during relatively cold climatic intervals and add support to previous studies indicating a link between cold climates an increased storminess in Northwest Europe including the southern Baltic Sea region.

Stability of kangaroo rat burrows in the Sonoran Desert: Evidence of biocementation

Kangaroo rats (Dipodomys deserti) construct complex burrow systems in loose desert sand that survive temperature and relative humidity fluctuations and storms. Animals that burrow in desert sand typically burrow in compacted sand, near plant roots, or when the soil is unsaturated. However, these processes are insufficient to explain tunnel stability of kangaroo rats. Our goal is to understand how kangaroo rat burrows remain stable in loose desert sand, intending to translate this knowledge to geotechnical engineering. A kangaroo rat habitat in the dunes of The Sonoran Desert, AZ, was selected for the study. Dynamic cone penetrometer tests performed at active, abandoned, and no-burrow sites demonstrated that the animals prefer loose sand for burrow construction. Soil samples collected from the burrows' ceilings, subsurface, and surface were characterized. Brazilian tensile strength test results showed that burrow soil has approximately 3 times greater tensile strength than the rest at dry state, which indicates increased interparticle attractive stress in burrow ceilings due to biocementation. Laboratory experiments, scanning electron microscopy, and confocal microscopy images showed that fungal and microbial biofilms provided 17 kPa increase in interparticle attractive stress at less than 1% biomass concentration, indicating potential to be used in soil improvement applications.

Influence of edge scour on lateral responses of monopiles with precast microbial reinforcement

Microbiologically Induced Calcite Precipitation (MICP) technology offers a promising method for stiffness reinforcement of offshore wind turbines (OWTs). However, edge scour around microbial reinforcement raises concerns about potential stiffness degradation. This study examines the effects of edge scour on the lateral responses of rigid piles reinforced with precast microbial reinforcement using a low-pH one-phase grouting method. Results from static tests, validated by numerical simulations, demonstrated that MICP technology bonded loose sand grains with the pile, forming a bio-reinforced pile with a larger diameter in the shallow soil layer, which significantly enhanced the original pile's bearing capacity and stiffness. However, edge scour reduced the embedment depth of the bio-reinforced pile, leading to a decrease in its bearing capacity and stiffness. Geometrically, protection width was found to have a relatively greater influence on stiffness and capacity compared to protection thickness. Additionally, symmetric cyclic loading tests were conducted to evaluate the effects of edge scour on backbone curves, secant stiffness, and damping ratio. Although MICP-based reinforcement notably enhanced both the secant stiffness and damping ratio of the piles, its effectiveness was completely lost once the scour depth reached the reinforcement thickness of the bio-reinforced soil block.

Radioactivity levels and radiological risk assessment in west Antalya beach sands

Radioactivity levels and radiological risk assessment in west Antalya beach sands

Effects of load and high temperature on uniaxial compressive properties of desert sand concrete

In order to explore the influence of load and high temperature on the uniaxial compressive properties of desert sand concrete (DSC), the axial compressive strength test of desert sand concrete after different loads and temperatures was carried out, and the stress-strain curve was measured. The influence of load level, temperature grade and cooling method on the mass loss rate, ultrasonic velocity and uniaxial compressive performance of desert sand concrete after high temperature was analyzed. The results show that as the temperature increases, the mass loss rate of desert sand concrete gradually increases, the axial compressive strength gradually decreases, the peak strain increases significantly, the stress-strain curve tends to be flat, and the elastic modulus decreases continuously. The "pseudoplastic platform" near the axial compressive strength of the stress-strain curve of desert sand concrete after high temperature is more obvious. Based on the two-stage constitutive model of concrete, the constitutive model of desert sand concrete considering the influence of temperature and load level is established. The research results can provide technical support for the performance evaluation of desert sand concrete after high temperature.

Effects of sand grain roughness height on the performance of wind turbine blade section under extreme weather conditions

Wind turbine blades are prone to icing and their performance is affected significantly by the roughness caused by icing and erosion. Numerical models are constructed to simulate the effects of sand grain roughness on the mass of accreted ice and aerodynamic performance. The sand grain roughness height is considered by applying the NASA and Shin et al. models, and the cloud characteristics studied are the liquid water content (LWC), median volume diameter (MVD) and air temperature covering freezing drizzle and in-cloud icing conditions resulting in glaze ice and rime ice, respectively. The numerical model applied the multi-shot approach, and the effects of the number of shots on the ice accretion and aerodynamic performance was examined to determine the optimum number of shots which can be used in the simulation in order to minimize the computational time without affecting the accuracy. The relationship between the sand grain roughness height and aerodynamic performance is studied, revealing that the shallowest roughness heights cause less performance degradation. The mass of ice increases with increasing LWC from 0.05g/m3 to 0.3g/m3 and MVD from 20 µm to 100 µm, which results in a reduction in the lift-to-drag ratio (CL/CD).

A comparative study of the elevated radioactivity in beach placer deposits of Bangladesh.

Beach sediments are mineral deposits formed through weathering and erosion of either igneous or metamorphic rocks. Among the rock constituent minerals are some natural radionuclides that contribute to ionizing radiation exposure on Earth. Kolatoli and Kuakata are the two major beaches with heavy mineral deposits and important tourist sites in Bangladesh. Natural radioactivity in Kolatoli and Kuakata beach sand deposits along the southern coast of Bangladesh was assessed and compared to identify the sources, causes, and possible environmental impact. Result shows most of the radionuclides have higher activity concentrations than the background level, and the activity varies with the sample locations. The dominant radionuclides were found to be the radionuclides of thorium series i.e. Th-232 and Ra-228 followed by uranium series and K-40. The radioactivity in Kolatoli beach sands was observed to be much higher than Kuakata beach due to the presence of a higher content of heavy minerals i.e. illmenite, rutile, zircon, garnet and monazite. Furthermore, monazite and zircon are the two radioactive minerals that are considered to be the main contributors to the radioactivity in Kolatoli beach sand. These minerals are dominated by the activity of thorium series radionuclides i.e. Th-232 and Ra-228 surpass the activity of all other radionuclides such as U-238, U-234, Th-230, Ra-226, Po-210, and K-40. However, major contribution of radioactivity in Kuakata beach sand comes from uranium series radionuclides such as U-238, U-234, Ra-226, and Po-210. Beach morphology, sedimentological, and geochemical evolution of those minerals might be important areas of further study for the radioactivity monitoring activity in those areas.

In a grain of sand: An overlooked over-summering habitat of macroalgae.

In a grain of sand: An overlooked over-summering habitat of macroalgae.

Biosurfactant production by Bacillus cereus GX7 utilizing organic waste and its application in the remediation of hydrocarbon-contaminated environments.

The use of biosurfactants represents a promising technology for remediating hydrocarbon pollution in the environment. This study evaluated a highly effective biosurfactant strain-Bacillus cereus GX7's ability to produce biosurfactants from industrial and agriculture organic wastes. Bacillus cereus GX7 showed poor utilization capacity for oil soluble organic waste but effectively utilized of water- soluble organic wastes such as starch hydrolysate and wheat bran juice as carbon sources to enhance biosurfactant production. This led to significant improvements in surface tension and emulsification index. Corn steep liquor was also effective as a nitrogen source for Bacillus cereus GX7 in biosurfactant production. The biosurfactants produced by strain Bacillus cereus GX7 demonstrated a remediation effect on oily beach sand, but are slightly inferior to chemical surfactants. Inoculation with Bacillus cereus GX7 (70.36%) or its fermentation solution (94.38%) effectively enhanced the degradation efficiency of diesel oil in polluted seawater, surpassing that of indigenous degrading bacteria treatments (57.62%). Moreover, inoculation with Bacillus cereus GX7's fermentation solution notably improved the community structure by increasing the abundance of functional bacteria such as Pseudomonas and Stenotrophomonas in seawater. These findings suggest that the Bacillus cereus GX7 as a promising candidate for bioremediation of petroleum hydrocarbons.

Biosurfactant-mediated transport of tetracycline antibiotics in saturated porous media: Combined effects of the chemical properties of contaminants and solution chemistry conditions

The mobility of tetracycline antibiotics (TCs) in saturated aquifers is possibly affected by the presence of biosurfactants, which are widespread in the aquatic/soil environments. This study investigated the mobility characteristics of various tetracyclines—specifically tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC)—within quartz sand columns in the presence of rhamnolipid, a common biosurfactant. Exogenous rhamnolipid significantly inhibited the transport of the three TCs over the pH range of 5.0–9.0 (e.g., the mass of retained TC, OTC, and CTC increased from 32.6 %, 26.9 %, and 39.2 % (in the absence rhamnolipid) to 39.4 %, 38.9 %, and 51.7 % (in the presence of rhamnolipid), respectively). This observation could be attributed to the bridging effects of this biosurfactant. Specifically, the hydrophilic head of rhamnolipid molecules is likely associated with the surfaces of sand grains through surface complexation and/or hydrogen bonding interactions. Accordingly, the hydrophobic moieties of the deposited rhamnolipid molecules (i.e., the aliphatic chains) interact with the hydrophobic groups of TCs molecules via hydrophobic interactions. Interestingly, the extent of the inhibitory effect on CTC mobility was greater than that on OTC and TC, which was related to the different hydrophobic characteristics of the three antibiotics. Furthermore, the inhibitory effect of rhamnolipid on the transport of TCs diminished as the pH of the background solution increased. This observation was attributed to the weakened bridging effects, resulting from the reduced deposition of the biosurfactant on the sand surfaces. Additionally, the cation-bridging mechanism involved in the retention of TCs in the addition of rhamnolipid when the background electrolyte was Ca2+ (i.e., Ca2+ ions served as bridging agents between the deposited rhamnolipid molecules and TCs). The insightful findings enhance our understanding of the critical roles of biosurfactants in influencing the environmental dynamics and ultimate fate of conventional antibiotic pollutants within groundwater systems.

Assessment of potentially toxic element contamination in wetland sediments of Boracay Island, Philippines

Boracay Island, Philippines, famous for its white sand beaches, has wetlands increasingly threatened by human activities. This study evaluated the ecological state of Boracay Island's wetlands and assessed the consequences of anthropogenic activities on sediment quality. Results showed that sediments from Wetland Nos. 3 and 4 have higher concentrations of potentially toxic elements (PTEs) than Wetland No. 1. Comparative analysis with other Southeast Asian wetlands revealed that Boracay's sediments contain the highest average values of As, Cd, Cu, Ni, Zn. Enrichment factor values suggest that the moderate enrichment of Cd, Cr, Cu, Mo, Pb, and Zn in the wetland sediments can be attributed to anthropogenic activities on the island. Elevated concentrations of Cr, Cu, and Zn above interim sediment quality guidelines indicate occasional adverse biological effects on aquatic biota. These findings provide a crucial baseline for future pollution monitoring and highlight the need for ongoing conservation efforts in Boracay's wetlands.

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.

Survival strategies of Bar-tailed Godwit in tropical sand beaches: Straight-line and zigzag foraging techniques

The near-threatened Bar-tailed Godwit (Limosa lapponica) makes the longest non-stop endurance flights among shorebirds. They are regular winter visitors to the Kadalundi-Vallikkunnu Community Reserve and adjoining sand beaches along the west coast of India. The research investigates their foraging strategies within sand beaches, observed over six years (2016-2022). Extensive field observations across major sand beaches documented two distinct modes of continuous stitching behaviour; a straight-line mode and a zigzag mode. Despite predation pressure and human disturbances, Bar-tailed Godwits achieved high prey capture rates, likely due to the abundance of benthic invertebrates. The study also revealed the prevalence of this behaviour and its association with rate of prey consumption, particularly focusing on the availability of Cosmonotus crabs, the dominant prey species. The zigzag pattern, was associated with higher prey capture rates, suggesting an adaptive response to prey distribution. Our findings suggest that, this unique foraging strategy allows Bar-tailed Godwits to optimize prey capture while conserving time and energy, especially in resource-scarce environments. Furthermore, the implications of these behaviours are discussed in the context of prey availability, nutrient content, and the energetic demands of long-distance migration, shedding light on to the adaptive mechanisms employed by shorebirds in challenging habitats.

The variation of particle concentration with height of wind-blown coral sand

Wind-blown coral sand movement is common in the marine coral sand island environment but received much less research attention compared to desert and coastal sands. We used the particle image velocimetry technique with wind tunnel experiments to determine the decay trends of the particle number density, nominal particle area density, and actual particle area density with height for wind-blown coral sands from the South China Sea. Then, a new morphology factor FM that consists of volume V, density ρs, drag coefficient CD, and projected area A of coral sands, was defined to evaluate the influences of particle characteristics on wind-blown sand movement and the results were compared with those of quartz sands from an inland desert. We found that the average FM of coral sands is more comparable to that of coarse quartz sands than smaller size groups. Coral sands tend to move nearer the surface during aeolian processes compared to smaller quartz ones due to their larger FM. The decay rate of particle number density of coral sands with height is similar to that of coarse (0.8–1 mm) quartz sands, but significantly larger than that of smaller quartz ones. The decay rate of the actual particle area density of coral sands with height is larger than that of their nominal particle area density, so that significant deviations may exist if a fixed particle size and spherical shape are assumed to study wind-blown particle movement. The present work contributes to understand the effect of particle characteristics on the wind-blown sand movement from a physical mechanism perspective for both desert quartz sands and marine coral sands.