Sand Deposits Research Articles

On the development of Sand Deposits in the Southern Part of the Curonian Spit

As part of paleogeographic studies on the Curonian Spit (geological section GS 024), a coastal section was studied from the sea in the area of the village Lesnoy in the place where relic lagoon oozes come out. The granulometric, chemical and mineral compositions of slope sands were studied for the first time. The heterogeneity of the conditions for the formation of sand strata was confirmed. A high probability of a secondary change in the composition of sediments as a result of weathering processes was revealed. The results of the study indicate a gradual advance of sand deposits on the coastal part of the lagoon, which began about 10 thousand years ago. Differentiation of the sand stratum into the lower and upper parts relative to the interlayer-marker of coarse-grained sand identified in the section may reflect different stages of generation of the sand stratum: from the supposed shallow swell formed during sea level rise to beach and eolian sands.

Which is the dominant source for the aeolian sand in the Badain Jaran Sand Sea, Northwest China: Fluvial or gobi sediments?

Fluvial and gobi sediments play significant roles in the formation of modern sand seas and their evolution. However, little is known about their respective source contributions, especially in quantitative terms. In the present study, we selected the Badain Jaran Sand Sea in Northwest China to quantitatively identify the sediment sources. To achieve this goal, we collected Heihe River sand and gobi sediments (Ejin gobi and the Beida–Yabrai gobis) as the potential sand sources. We performed provenance identification based on robust geochemical indicators, and found that both of these potential sources provided sand materials to the sand sea. Our quantitative analysis based on novel fingerprinting methods, namely consensus ranking (CR) and consistent tracer selection (CTS), suggested that the gobi sediments supplied more sand than the fluvial sand, accounting for 76.85 % and 23.15 % of the total (goodness of fit is 95.8 ± 3.89), respectively. Therein, the Ejin gobi was the dominant source for most regions of the sand sea (63.17 ± 21.43 %), but the Heihe River mainly fed sand source to the southern part of the sand sea (23.15 ± 18.66 %) and the Beida–Yabrai gobis provided the most sand to regions near the fan (13.68 ± 11.49 %). The source supply areas largely control above contribution difference. Our results demonstrate the critical role of gobi sediments for sand accumulation of the Badain Jaran Sand Sea.

Under-deposit microbial corrosion of X65 pipeline steel in the simulated shale gas production environment

The synergistic effect of sand deposit and sulfate-reducing bacteria on the X65 pipeline steel was investigated in the simulated shale gas production environment, by means of weight loss tests, EIS, SEM and EDS. The results indicated that the coexistence of sand deposit and sulfate reducing bacteria (SRB) resulted in 63% reduction in uniform corrosion, but 183% increase in localized corrosion rate. The EIS results revealed that the formation of biofilm altered the protectiveness of the surface mixed layer and showed a trend related to the bacterial growth curve. The mixed layer was also clarified from the cross-section morphology and EDS analysis. This mixed layer may hinder the diffusion of substances to the deposit/steel interface, thus creating a microenvironment at the deposit/steel interface that promotes localized corrosion.

Wind sand tunnel experiment on the windblown sand transport and sedimentation over a two dimensional sinusoidal hill

Wind sand tunnel experiment on the windblown sand transport and sedimentation over a two dimensional sinusoidal hill

Infiltration behaviour and microstructure of filter cake from sand-modified bentonite slurry

This study uses a setup involving a scanning electron microscopy (SEM) to examine the infiltration behaviour and mechanism of the formation of filter cake from sand-modified bentonite slurry. We began by determining whether a filter cake can be formed by using water–bentonite slurry in samples of the fine, medium, and coarse sand (Series 1). Water–bentonite–sand slurries with different mass ratios of bentonite and fine sand (B:S) were subsequently tested using the medium and coarse sand (Series 2). The results show that for Series 1, a thin filter cake (<0.1 mm after drying) with extremely low permeability (∼10−8 m/s) was formed only when the fine sand was used. The filter cake consisted of layers of dense bentonite platelets arranged perpendicular to the infiltration direction. Similar results were obtained for Series 2 between the medium and coarse sand. Within the range of 1:1.5 ≤ B:S ≤ 1:0.5, the low permeable filter cake was formed on the deposited layer of fine sand and bentonite platelet. Contrary to expectations, adding more sand (B:S = 1:2) did not complete the formation of filter cake, and instead led to continuous deposition of fine sand and bentonite platelet, which may cause inadequate effective face support during slurry shield tunneling.

DiatomNet v1.0: A novel approach for automatic diatom testing for drowning diagnosis in forensically biomedical application

Background and ObjectiveDiatom testing is supportive for drowning diagnosis in forensic medicine. However, it is very time-consuming and labor-intensive for technicians to identify microscopically a handful of diatoms in sample smears, especially under complex observable backgrounds. Recently, we successfully developed a software, named DiatomNet v1.0 intended to automatically identify diatom frustules in a whole slide under a clear background. Here, we introduced this new software and performed a validation study to elucidate how DiatomNet v1.0 improved its performance with the influence of visible impurities. MethodsDiatomNet v1.0 has an intuitive, user-friendly and easy-to-learn graphical user interface (GUI) built in the Drupal and its core architecture for slide analysis including a convolutional neural network (CNN) is written in Python language. The build-in CNN model was evaluated for diatom identification under very complex observable backgrounds with mixtures of common impurities, including carbon pigments and sand sediments. Compared to the original model, the enhanced model following optimization with limited new datasets was evaluated systematically by independent testing and random control trials (RCTs). ResultsIn independent testing, the original DiatomNet v1.0 was moderately affected, especially when higher densities of impurities existed, and achieved a low recall of 0.817 and F1 score of 0.858 but good precision of 0.905. Following transfer learning with limited new datasets, the enhanced version had better results, with recall and F1 score values of 0.968. A comparative study on real slides showed that the upgraded DiatomNet v1.0 obtained F1 scores of 0.86 and 0.84 for carbon pigment and sand sediment, respectively, slightly worse than manual identification (carbon pigment: 0.91; sand sediment: 0.86), but much less time was needed. ConclusionsThe study verified that forensic diatom testing with aid of DiatomNet v1.0 is much more efficient than traditionally manual identification even under complex observable backgrounds. In terms of forensic diatom testing, we proposed a suggested standard on build-in model optimization and evaluation to strengthen the software's generalization in potentially complex conditions.

Evaluation of Engineering Site and Subsurface Structures Using Seismic Refraction Tomography: A Case Study of Abydos Site, Sohag Governorate, Egypt

Because of the strategic importance of the Abydos archaeological site in Egypt as a source of wealth for Egyptian tourism, this study was concerned with carrying out geophysical measurements to detect subsurface succession and measure variations in the geotechnical engineering features of the soils/rocks in order to protect this significant area. The findings will assist geologists and seismologists in collaborating with archaeologists for future site development, revitalization, and investment. The primary objectives of this work were to determine the subsurface lithology, evaluate the engineering geotechnical properties of soils/rocks, identify the layer thicknesses, and identify the site class by calculating Vs30. To achieve these goals, seventeen (17) seismic refraction tomography (SRT) P- and S-wave measurements were executed in front of the Osirion location. SeisImager Software was used for the processing and interpretation of the outcomes. The results were the travel time–distance curves, which were used for building the 2D seismic models that exhibited the velocity and the depth of the layered models. These models were validated by our previous works using electric resistivity tomography and borehole data. The results indicated that this site consisted of three geoseismic subsurface layers. The first layer was the surface that was made up of wadi deposits, which were a mixture of gravel, sand, and silt and were characterized by incompetent to slightly competent materials. The second layer corresponded to the sand and muddy sand deposits of competent rock that was of fair to moderate quality. The third layer (clay deposits) had a higher velocity and was more compact and may be employed as a bedrock layer. The elastic moduli, Vs30, petrophysical, and geotechnical properties of the three geoseismic layers were appraised as essential parameters. Integration of petrophysical and geotechnical parameters and elastic moduli revealed that the third layer was composed of competent clays, which were characterized by low values of porosity, void ratio, Poisson ratio, and stress ratio. It also had a high rigidity, Young’s and bulk moduli, concentration and material indexes, N-value, ultimate bearing capacities, and high density values, and vice versa for the first layer. The standard NEHRP site class was B (rocks). These parameters are ordinarily used as key indications and serve as significant inputs for any future work.

Experimental investigation on the effective thermal conductivities of different hydrate-bearing sediments

The natural gas hydrate has been regarded as an important future green energy. Significant progress on the hydrate exploitation has been made, but some challenges are still remaining. In order to enhance the hydrate exploitation efficiency, a significant understanding of the effective thermal conductivity (ETC) of the hydrate-bearing sediment has become essential, since it directly controls the heat and mass transfer behaviors, and thereby determines the stability of hydrate reservoir and production rate. In this study, the effective thermal conductivities of various hydrate-bearing sediments were in-situ measured and studied. The impacts of temperature, particle size and type of sediment were investigated. The effective thermal conductivities of the quartz sand sediments before and after hydrate formation were in-situ measured. The results show the weak negative correlation of effective thermal conductivity of the quartz sand sediment on the temperature before and after the hydrate formation. The effective thermal conductivity of the hydrate-bearing sediment decreases with the increase of particle size of the sediment. The dominant effect of the type of porous medium on the characteristics of the effective thermal conductivity of hydrate-bearing sediment was highlighted. The results indicate that both the effective thermal conductivities of hydrate-bearing quartz sand sediment and hydrate-bearing silicon carbide sediment are weakly negatively correlated with temperature, but the effective thermal conductivity of hydrate-bearing clay sediment is weakly positively dependent on the temperature. In addition, the values of the effective thermal conductivities of various hydrate-bearing sediments are in the order of hydrate-bearing silicon carbide sediment > hydrate-bearing quartz sand sediment > hydrate-bearing clay sediment. These findings could suggest that the intrinsic thermal conductivity of porous medium could control the characteristics of effective thermal conductivity of hydrate-bearing sediment.

Evaluating the Sand-Trapping Efficiency of Sand Fences Using a Combination of Wind-Blown Sand Measurements and UAV Photogrammetry at Tottori Sand Dunes, Japan

Fences are commonly used in coastal regions to control wind-blown sand. Sand-trapping fences and sand-stabilizing fences have been installed at the Tottori Sand Dunes, Tottori Prefecture, Japan, to prevent damage by wind-blown sand; however, the effectiveness of these fences has not previously been quantitatively evaluated. This study analyzed the effects of sand fences on sand trapping using field observations of blown-sand flux and unmanned aerial vehicle (UAV) photogrammetry. The estimated total blown-sand flux in the near-ground surface observed inside and outside the sand fences indicated that wind-blown sand was effectively trapped by the sand fences at wind speeds lower than 17 m s−1, reducing sand flux by more than 80%. The UAV photogrammetry results demonstrated that large amounts of sand were transported from the dune to the fenced area during March and April, and sand initially accumulated on the lee side of the sand-trapping fences, forming a new foredune. Sand accumulated on the existing foredune during April and May, and the vertical accretion around the foredune was two to four times the sand deposition within the sand-stabilizing fences. This indicated the effectiveness of sand-trapping fences for controlling wind-blown sand; however, their efficiency was reduced as they were gradually buried, with sand being trapped by the sand-stabilizing fences.

Field Evidence for the Initiation of Isolated Aeolian Sand Patches

AbstractSand patches are one of the precursors to early stage protodunes and occur widely in both desert and coastal aeolian environments. Here we show field evidence of a mechanism to explain the initiation of sand patches on non‐erodible surfaces, such as desert gravels and moist beaches. Changes in sand transport dynamics, directly associated with the height of the saltation layer and variable transport law, observed at the boundary between non‐erodible and erodible surfaces lead to sand deposition on the erodible surface. This explains how sand patches can form on surfaces with limited sand availability where linear stability of dune theory does not apply. This new mechanism is supported by field observations that evidence both the change in transport rate over different surfaces and in situ patch formation that leads to modification of transport dynamics at the surface boundary.

Satellite-Derived Bathymetry with Sediment Classification Using ICESat-2 and Multispectral Imagery: Case Studies in the South China Sea and Australia

Achieving coastal and shallow-water bathymetry is essential for understanding the marine environment and for coastal management. Bathymetric data in shallow sea areas can currently be obtained using SDB (satellite-derived bathymetry) with multispectral satellites based on depth inversion models. In situ bathymetric data are crucial for validating empirical models but are currently limited in remote and unapproachable areas. In this paper, instead of using the measured water depth data, ICESat-2 (Ice, Cloud, and Land Elevation Satellite-2) ATL03 bathymetric points at different acquisition dates and multispectral imagery from Sentinel-2/GeoEye-1 were used to train and evaluate water depth inversion empirical models in two study regions: Shanhu Island in the South China Sea, and Heron Island in the Great Barrier Reef (GBR) in Australia. However, different sediment types also influenced the SDB results. Therefore, three types of sediments (sand, reef, and coral/algae) were analyzed for Heron Island, and four types of sediments (sand, reef, rubble and coral/algae) were analyzed for Shanhu Island. The results show that accuracy generally improved when sediment classification information was considered in both study areas. For Heron Island, the sand sediments showed the best performance in both models compared to the other sediments, with mean R2 and RMSE values of 0.90 and 1.52 m, respectively, representing a 5.6% improvement of the latter metric. For Shanhu Island, the rubble sediments showed the best accuracy in both models, and the average R2 and RMSE values were 0.97 and 0.65 m, respectively, indicating an RMSE improvement of 15.5%. Finally, bathymetric maps were generated in two regions based on the sediment classification results.

Effect of deposit chemistry on microbial community structure and activity: Implications for under-deposit microbial corrosion.

The deposition of solid particles carried by production fluids from oil and gas companies in horizontal surfaces of different assets has shown to cause severe localised corrosion. Sand, one of the most common deposits in the energy sector pipelines, is frequently mixed with crude, oil, asphaltenes, corrosion inhibitors, and other organic compounds. For this reason, they might favour the metabolic activity of native microbial communities. This study aimed to determine the impact of sand-deposit chemical composition on the microbial community structure and functional attributes of a multispecies consortium recovered from an oilfield and the resulting risk of under-deposit microbial corrosion of carbon steel. Sand deposits recovered from an oil pipeline were used in their raw form and compared against the same deposits exposed to heat treatment to remove organic compounds. A four-week immersion test in a bioreactor filled with synthetic produced water and a two-centimeter layer of sand was set up to assess corrosion and microbial community changes. The raw untreated deposit from the field containing hydrocarbons and treatment chemicals resulted in a more diverse microbial community than its treated counterpart. Moreover, biofilms developed in the raw sand deposit exhibited higher metabolic rates, with functional profile analysis indicating a predominance of genes associated with xenobiotics degradation. Uniform and localized corrosion were more severe in the raw sand deposit compared to the treated sand. The complex chemical composition of the untreated sand might have represented an additional source of energy and nutrients to the microbial consortium, favoring the development of different microbial genera and species. The higher corrosion rate obtained under the untreated sand suggests that MIC occurred due to syntrophic relationships between sulphate reducers or thiosulphate reducers and fermenters identified in the consortium.

GIS and remote sensing – desertification and progression of silting-up in the high plains of Oran in Western Algeria

The expansion of silting in the Algerian High Plains of south Oran (northwestern Algeria) is the ultimate manifestation of desertification. The presence, accumulation or deposition of sands in areas that previously did not contain any is the most visible sign of this silting up phenomenon that has begun to appear in recent decades. The present study focuses on the evolution and progression of silting up in the region under study. It is worth noting that assessing the narrowing of the vast endorheic depressions in this area is a very complicated task due to the vastness of the place. In order to deal with this problem in an efficient manner, it was deemed necessary to use remote sensing as it offers possibilities of global vision of the area to be studied and allows a precise description in time and space of this region. In order to efficiently identify and apprehend the phenomenon mentioned above, it was decided to adopt an analysis methodology that is based on the processing and interpretation of multi-date satellite images, combined with exogenous data. It should be noted that the topographic maps of Mecheria and Ain Sefra are given at a scale of 1/200,000 and are supplemented by some field data, along with some wind data. The analysis of data brought from different sources has made it possible to locate, characterize and map the evolution and the spatio-temporal dynamics of the recent extension of sandy accumulations, old Quaternary dune belts, and shrinking of vast endorheic depressions (Chott El Gharbi and Sebkhat Nâama). It is widely acknowledged that areas that are most affected by the progression of silting are the Plain of Naama, that is surrounded by the first Saharan Atlas ranges and by the orographic corridor formed by the double SW/NE alignment of Djebel (Mount) Morhad, Djebel Suigua, Djebel Aissa and Djebel Mekter located south of Ain Sefra. It is important to note that all this information, which is extracted from satellite images and exogenous data, will be integrated into a GIS.

Architectural Model of a Dryland Gravel Braided River, based on 3D UAV Oblique Photogrammetric Data: A Case Study of West Dalongkou River in Eastern Xinjiang, China

AbstractThree‐dimensional unmanned aerial vehicle (UAV) oblique photogrammetric data were used to infer mountainous gravel braided river lithofacies, lithofacies associations and architectural elements. Hierarchical architecture and lithofacies associations with detailed lithofacies characterizations were comprehensively described to document the architectural model, architectural element scale and gravel particle scale. (1) Nine lithofacies (i.e., Gmm, Gcm, Gcc, Gci, Gcl, Ss, Sm, Fsm and Fl) were identified and classified as gravel, sand and fine matrix deposits. These are typical depositional features of a mountainous dryland gravel‐braided river. (2) Three architectural elements were identified, including channel (CH), gravel bar (GB) and overbank (OB). CH can be further divided into flow channel and abandoned channel, while GB consists of Central Gravel bar (CGB) and Margin Gravel bar (MGB). (3) The gravel bar is the key architectural element of the gravel braided river, with its geological attributes. The dimensions of GBs and their particles are various, but exhibit good relationships with each other. The grain size of GB decreases downstream, but the dimensions of GB do not. The bank erosion affects the GB dimensions, whereas channel incision and water flow velocity influence the grain size of GB. The conclusions can be applied to the dryland gravel braided river studies in tectonically active areas.

Impact of Transient Infiltration on the Ultimate Bearing Capacity of Obliquely and Eccentrically Loaded Strip Footings on Partially Saturated Soils

Soils above the groundwater table and near the ground surface are often partially saturated, and the changes in the degree of saturation and matric suction caused by infiltration may have substantial effects on the stability of geotechnical systems. This work evaluates the significant effect of transient flow on the ultimate bearing capacity of strip footings founded on unsaturated soils under the simultaneous actions of vertical and horizontal loads and moment using the lower-bound theorems of the finite-element limit analysis and the incorporation of second-order cone programming. The unified effective stress theory is incorporated into the soil yield function to model the partially saturated state, and the closed-form solution for one-dimensional transient flow is adopted so as to evaluate the tempo-spatial variations of suction stress. For both sand and clay underlying soils, it is found that the increase of infiltration time leads to a notable decrease of the size of the normalized failure envelopes for either obliquely or eccentrically loaded shallow foundations. The impact of transient flow on the ultimate bearing capacity of surface footings is also observed to be greater for clay soils as compared with sand deposits due to the significant contribution of higher induced suction stress.

Seismic response of a shield tunnel crossing saturated sand deposits with different relative densities

This study investigated the seismic response of a shield tunnel passing saturated sand deposits with different relative densities. The Dafalias and Manzari model was adopted to capture the cyclic behaviour of liquefiable soil subjected to earthquake excitation. A refined lining model was proposed to simulate the mechanical behaviour of segment joints. A fully fluid-solid coupled analysis was then performed to investigate the seismic response of shield tunnels crossing through adjacent sand deposits with different relative densities. The displacement of segment joints and internal force of lining concrete were found to be prominent near the interface. The structure deformation mode consists of the opening, dislocation, and distortion of ring joints. The complicated tunnel deformation mechanism was then clarified. Comprehensive parametric studies were performed to establish some quantitative relationships between the joint displacement and internal force of segmental linings and the normalized parameters. Apart from soil-deposit interface inclination and cover to diameter ratio, the earthquake magnitude and difference in relative densities had a remarkable impact on the seismic response of the tunnel structure near the interface.

Environmental Vulnerability of the Buriticupu River Water Basin, Maranhão - Brazil: The Relief as a Key Element

Studying a watershed in the Amazon region requires understanding that this region has national and global relevance. The fact that the study area is located in the so-called arc of deforestation raises the need to understand its context, its vulnerabilities, and its physical, environmental, and anthropic components. This research assesses the environmental vulnerability of the Buriticupu River Watershed in Maranhão State, Brazil. The aim is to foster improvements that may contribute to environmental planning and, specifically, to water resource management. For this purpose, the authors used the Geographic Information System environment to work with Map Algebra, interrelating primary and secondary data on geology, relief, pedology, and land use and land cover to generate synthesis cartography. The results pointed to areas with predominantly medium vulnerability. However, the analyses highlight alluvial plains, which became the most fragile areas from an environmental point of view. This is mainly because these areas comprise water-saturated soils (gleysols), unconsolidated deposits of sand and silt (alluvial deposits), and extensive humid vegetation, characteristics of igapó and floodplain forests. This research generated a document that applies is applicable to the study area. It also provided, in a systemic and integrated way, a product that will help in planning, which is very important for the creation of a watershed committee, something necessary and still embryonic in Maranhão State, Brazil.

New genus and two new species of stygobiotic snails from Stara Planina Mts, Bulgaria

Two new species, one of them belonging to a new genus are described from two caves in North Bulgaria. Polatenia sinuiapertura n. gen. and n. sp. was found in sand deposits at the entrance of Izvora Cave, Polaten District of Teteven Town, and Kolevia toplensis n. sp. found at the water catchment near Toplya Cave at vicinity of village of Golyama Zhelyazna.

Effect of sand and crosswind on the performance of solar chimney power plant

AbstractA solar chimney power plant (SCPP) is suitable to be deployed in desert areas, but there are few studies on the impact of desert wind and sand. In this paper, numerical simulations for the Spanish prototype SCPP were conducted to investigate desert environmental parameters, including sand movement, crosswind, and sand deposition, on the output performance of SCPP. The results indicate that the main erosion area of the turbine blade in the SCPP is the leading edge of the blade pressure surface. The erosion area of the suction surface is much less than that of the pressure surface, mainly concentrated on the leading edge. The output power of SCPP is reduced by 73.3% because of the crosswind and it decreases by 16.9% after the windbreak wall is installed. The sand and dust deposition would affect the transmissivity of the solar radiation through the collector cover. In a dusty environment for 1 month, the system output power decreased by 12.9%, and the collector efficiency decreased from 34% to 23% due to the sand deposition. These results show that the sand has a considerable negative effect on the performance of SCPP in ways of sand erosion and deposition. Sand removal is necessary for SCPP.

Mechanisms of microplastics trapping in river sediments: Insights from the Arno river (Tuscany, Italy)

Rivers efficiently convey microplastics to the sea, but during this transfer microplastic can be temporary stored in sediments, where they undergo further fragmentation due to biological and physical processes. Aiming at shedding light on mechanisms governing microplastic sedimentation in rivers, we analyse deposits accumulated in alternate bars of the Arno River (central Italy). Specifically, we considered microplastics associated with floating plant debris, and those trapped in clastic suspended and bedload deposits. The overall concentration of microplastic ranges between 0.44 and 5.68 items per gram, and is comparable with that of some highly-polluted rivers in the world. Fibers are prevalent among the recovered items, and composition is dominated by nylon. Our measurements reveal that microplastics can be easily trapped by floating plant debris, and stored on bar top zones and river banks. Microplastics are also trapped in gravel and sand deposits. Sand incorporates microplastics both when it is transported at the river bottom under tractional conditions and during the waning flood stage, when settling processes contribute to bed aggradation. Gravels do not entraps microplastics when they move on the river bed, but they are extremely efficient in trapping microplastics during recessional flood stages, when water infiltrates between larger clasts, where it drops suspended microplastics. Further studies based on application of principles of fluvial sedimentology will provide crucial insights to understand mechanisms controlling transport and storage of MPs in river sediments.