High Sand Content Research Articles

Soils with more clay and dense vegetation were rich in soil carbon along Wadi Al-Sharaea, Makkah, Saudi Arabia

In arid ecosystems, lack of vegetation and nutrients can negatively impact soil carbon (C) content. In the current study, our goals were to assess soil C stocks to a depth of 50 cm in an arid ecosystem (Wadi Al-Sharaea, Saudi Arabia) and determine their relation to different vegetation cover. To address our research objective, a total of 102 quadrate (randomly selected) were established along the desert wadi. Soil samples were collected to a depth of 50 cm with 5 cm interval, then Soil Bulk Density (SBD, g/cm3), Soil Organic C Content (SOC, g C/kg), and stocks (kg C/m2) were estimated. Both soil mechanical and chemical analyses were conducted for a composite soil sample. Study sites were categorized based on their visual vegetation cover (VC) percentage (%) into three major groups: 1) scarce vegetation cover (VC less than 25%); 2) medium vegetation cover (VC is higher than 25% and less than 75%); and lastly 3) dense vegetation cover (VC is higher than 75%). Soils were characterized by higher sand content (48.2%, both fine and coarse compiled) than silt (36.7 ± 1.64%) or clay (10.1 ± 1.28%). There were significant differences among soil Calcium (Ca) and Potassium (K) content (p < 0.05), while those plant communities with medium vegetation cover showed the highest soil content of Ca and K (1.7 ± 0.24 and 0.2 ± 0.03 meq/l, respectively). Plant communities with dense vegetation cover had the lowest SBD (1.96 ± 0.03 g/cm3) and the highest SOC stocks (14.9 ± 2.1 kg C/m2). Moreover, our data analyses indicated that SBD and SOC content had strong and negative correlation, where soils with dense vegetation cover had the most significant correlation (R2 = 0.95). Our results recommend that soil carbon stocks to a depth of 50 cm based on different vegetation cover of arid ecosystems should be implemented on global soil carbon budget to better elucidate factors controlling SOC content at the regional and global scales.

Estimation of hydraulic parameters in a heterogeneous low‐lying farmland near Venice

AbstractEstimating the hydraulic properties of the vadose zone is essential to understand soil‐water dynamics and achieving appropriate water management in agricultural lands. Inverse modelling methods are commonly used to estimate hydraulic properties from field observations. Unlike the extensively applied local search methodologies, data assimilation techniques can fully account for multiple uncertainties and are becoming a widely used tool for estimating hydraulic parameters. However, only few applications on real field tests are available. The main objective of this study was to estimate the van Genuchten‐Mualem (VGM) parameters and the saturated hydraulic conductivity () of a heterogeneous low‐lying farmland at the margin of the Venice Lagoon, Italy, characterized by high peat content, sandy drifts, and a very shallow water table. To this end, two methods were tested, that is, the Ensemble Smoother (ES) and the Levenberg–Marquardt (LM) algorithm associated with hydrological modelling performed with Hydrus‐1D. Volumetric water content (VWC) observations were collected at three monitoring sites from May to September 2011. Results on parameters highlighted that the ES technique effectively reduced the uncertainty of and , but it was less effective on and . The results on VWC showed that the ES efficiency decreased with the increasing non‐linearity of the system (e.g., higher sand content) and when the variability of the experimental data was lower (e.g., deepest soil layers where saturation remained permanently close to 1). Both LM and ES allowed to reproduce the VWC observations in the calibration and validation phases, with the former and the latter performing better in the case of sandy and peat soils, respectively. As concerns the method applicability, the ES was less time‐demanding as it efficiently updated all the parameters at once and was less dependent on the user choices. Finally, the paper points out the importance of previous knowledge of the VGM parameters (e.g., from lab hydraulic analyses) in defining the constraints for the optimization.

Предварительные результаты технико-технологического анализа керамики с поселения Потаповы лужки-III (Томское Приобье)

The article presents the results of a technical and technological analysis of the developed and late Bronze Age ceramics from the Potapovy Luzhki-III settlement in the Tomsk Ob river region. The studies were carried out within the framework of the historical and cultural approach according to A.A. Bobrinsky’s method. The main task was to identify the specific features of cultural traditions in the selection of raw materials and the preparation of the pottery paste, and a comparative analysis of the data obtained. As a result of the study, it was established that iron-rich and non-iron non-sanded and heavily sanded clays were used for the making of ceramics. The Samus ceramics are made mainly from plastic clays differing in their degree of iron content, and the vessels of the late Bronze Age are made from low iron content clays with high content of fine sand. A single recipe was revealed: clay + crushed stone + organic matter. A comparative analysis with previously obtained data showed that the discovered tradition to use low iron content clays and non-iron clays for the ancient ceramics of the Tomsk Ob river region is also characteristic of the Bronze Age ceramics from the Potapovy Luzhki-III settlement. Also characteristic of this area is the addition of crushed stone to the pottery paste. It is noteworthy that there are no signs of mixing of cultural traditions in the preparation of the pottery paste on the site.

Assessment of Soil Physico-Chemical Properties on a Toposequence of an Erosion Site in Ikeduru, Southeastern Nigeria

The study was carried out to assess soil physic-chemical properties of an erosion site in Ikeduru, Imo State Nigeria, which has experienced land degradation over the years. Three profile pits were dug, described and samples collected for the physico-chemical laboratory analysis. Data obtained were analyzed using Genstat Discovery, Edition 4 for a CRD experiment. The outcome shows soils was deep, fine weak, dark brown, brown, red and dark reddish brown in the Munsell colour code. An LSD, a correlation at 5% probability level was used to separate the means significantly. Correlation investigation was carried out to explain relationships among selected physico-chemical properties of the studied soil. The particle size distribution indicated high sand content and low clay content in the three profiles selected with SCL as dominating textural class, except for 1.85 g cm-3 bulk density which was observed to be safe in all the profile pits examined, the silt ─ clay ratio was low (&amp;lt;1), except at the surface soil in the foot-slope (1.09). Soil pH (KCl) was moderately acidic at the summit. The organic matter had significant positive correlations with TN (r = 0.99***), Ca (r = 0.85**), Mg (r = 0.59*), K (r = 0.61*) and ECEC (r = 0.74**). Phosphorus maintained significant positive relationships with all basic cations with correlation coefficients that ranged from 0.51* for K to 0.59* for Ca. Total exchangeable acidity had a significant (P&amp;lt;0.001) negative relationship with %BS (r =-0.98***). It has been seen that the main causes of erosion are unprofessional land use forms.

Sedimentary facies and clay mineralogy of the late Pleistocene Landsort Deep sediments, Baltic Sea — Implications for the Baltic Ice Lake development

ABSTRACT The Landsort Deep is the deepest part of the Baltic Sea and contains an excellent high-resolution late Pleistocene sediment record suitable to study the retreat history of the southern margin of the Fennoscandian Ice Sheet and the development of the ice-marginal Baltic Ice Lake (BIL) from ~13.5 to 10.5 ka BP. The studied cores are from the lithostratigraphic Units V and VI of Hole M0063C that were recovered during the Integrated Ocean Drilling Program (IODP) Expedition 347. The subdivision and interpretation of the studied BIL record are based on the identification of seven distinct sedimentary facies, grain size characteristics, detrital clay minerals, water and carbon content, and physical properties. The ice-rafted debris (IRD) in the lowermost part of Unit VI indicates a proximal glaciolacustrine environment. The onset of the Fennoscandian Ice Sheet deglaciation during the warm Bølling/Allerød interstadial caused a rise of the proglacial lake water level and the transition from ice-proximal (IRD-containing sediments) to ice-distal varved sediments (rhythmically laminated silty clays) detected within the middle part of Unit VI. This depositional unit of constant sedimentation was followed by the first drainage event of the BIL, which led to the deposition of a distinct clay-rich interval representing erosion and redeposition of the emerged lake bottom sediments. The reduced grain size of the overlying sediments is associated to the onset of cooler climate conditions and a possible ice sheet readvance during the Younger Dryas that resulted in a decrease of meltwater release and sediment availability. The higher sand content and kaolinite peak are associated to a rapid ice retreat and the release of abundant sediment laden meltwater plumes at the end of the Younger Dryas. The final drainage of the BIL enabled the erosion of coastal clay sediments, and the termination of the ice lake stage led to enhanced clay sedimentation to the Landsort Deep.

Numerical Simulation of the Proppant Settlement in SC-CO2 Sand-Carrying Fluid in Fracturing Fractures

Supercritical CO2 fracturing has unique advantages for improving unconventional reservoir recovery. Supercritical CO2 can penetrate deep into the reservoir and increase reservoir reform volume, and it is less damaging to reservoir and easy to flow back. However, when the supercritical CO2 flows as the sand-carrying fluid in the fracture, the settlement of the proppant is still worth studying. Based on the study of supercritical CO2 density and viscosity properties, assuming that the reservoir has been pressed out of the vertical crack by injecting prepad fluid, the proppant characteristics in sand-carrying fluid under different conditions were studied by numerical simulation. After the analysis, the proppant accumulation and backflow will occur at the end of the crack. Large sand diameters, high fluid flow rates, high sand concentrations, high reservoir temperatures, and low reservoir pressures can help to shorten deposition time, and the small particle size, high fluid flow rate, low sand concentration, low reservoir temperature, and high reservoir pressure can help increase the uniformity of sand deposition. Shortening the sand deposition time can help to complete the fracturing efficiently, and increasing the deposition uniformity can improve the fracture conductivity. This article has studied the proppant settling and crack formation characteristics. It is hoped that this study can provide theoretical support for field fracturing and provide theoretical assistance to relevant researchers.

Comparative study of pre-Hispanic and colonial adobes in Mexico. Preliminary inferences on the effects of the granulometric distribution and used recycled materials in the state conservation of earth architecture

The characterization of the pre-Hispanic and colonial adobes used in the construction of buildings in Mexico was carried out to know the differences between their processes and manufactures. The eight samples obtained correspond to adobe blocks 0.45 m long x 0.35 m wide and 0.12 m thick, which were part of the interiors of houses, the structure of fences, and hacienda galleys. These samples were investigated using X-ray Diffraction, X-ray Fluorescence, and Scanning Electron Microscopy techniques to determine the morphometry of the material and its chemical and mineralogical composition. Likewise, some analyzes were performed to determine their mechanical properties (simple compressive strength), physical properties (granulometry, solid density, cohesion, plasticity index, porosity, and moisture content), and biological (organic matter content). The results obtained in terms of the granulometric distribution indicate that pre-Hispanic adobe has a higher content of sand than silt-clay and gravel, while the colonial adobes present a low or null content of gravel with a higher content of silt-clays. Regarding the organic matter content, the colonial adobe presents the highest percentages compared to those of the pre-Hispanic adobes. Taking into account the above the pre-Hispanic adobes have better resistance and durability than colonial adobes due to their granulometric distribution, low organic matter content, good cohesion, high plasticity index, and the use of materials found in their natural environment, while the colonial used recycled materials, coming from the economic activity to which the hacienda was dedicated, for example, agriculture, mining, livestock, this has given rise to different manufacturing techniques and construction styles that reflect the state of conservation of buildings throughout the pre-Hispanic and colonial times. The granulometric distribution that pre-Hispanic adobe provides favorable physical and mechanical qualities for any construction technique, so it is recommended to use this formula to manufacture resistant and durable adobe.

Quantify distribution of topsoil erodibility factor for watersheds that feed the Al-Shewicha trough – Iraq using GIS

Abstract Soil functions such as water storage, soil filtration, and reducing reservoir life due to sediment load are directly affected by the process of “soil erosion.” The Universal Soil Loss Equation was adopted to predict the erodibility factor for watersheds feeding the Al-Shewicha trough. The K-average factor’s determined value was 0.156, indicating that the K-factor had substantial variability. The K-factor for erodibility values was linked to the high sand content in the topsoil of the study area because of the high sand content of the topsoil. The topsoil is coarse-textured and then permeable. ArcGIS (geographic information system) was used to obtain the distribution of soil types as well as the erodibility factor distribution.

Deriving parametric and probabilistic Kd values for fluoroquinolones in soils

The evaluation of the sorption affinity of fluoroquinolone antibiotics (FQs) in soils, by means of the derivation of solid-liquid distribution coefficients (Kd), is a valuable information for assessing their environmental mobility. Aiming to develop Kd (FQ) prediction tools in soils, in the first stage of this study we constructed a Kd (FQ) sorption dataset using current literature data. Furthermore, additional sorption and desorption data for norfloxacin were obtained in seven different soils of contrasting properties. Sorption isotherms of norfloxacin were linear under the experimental conditions tested and desorption percentages increased for scenarios in which low sorption was noted. Sorption tests in the same soils were then extended to ciprofloxacin, enrofloxacin and ofloxacin and pooled in the dataset, revealing comparable Kd (FQ) values among the FQ tested after analyzing the overall dataset consisting in 312 entries of Kd (FQ). A partial least square (PLS) regression model was then developed to predict values of Kd (FQ) based on specific relevant soil properties (i.e., pH, cation exchange capacity and organic carbon and texture information), and, for the first time, FQ properties (fraction of cationic FQ species) affecting sorption. Additionally, probabilistic, Kd (FQ) best estimates in soils were derived through cumulative distribution functions (CDFs) for the overall and for partial datasets created by grouping Kd (FQ) values according to key soil properties affecting FQ sorption (i.e., pH, organic carbon content and texture information). This latter approach permitted to derive more representative Kd (FQ) best estimates for the soils to be assessed, and with a lower related variability than that derived from the overall dataset. Best estimates Kd (FQ) values were > 1000 L kg−1 for most acidic to neutral soils, suggesting strong sorption, although lower sorption and thus higher environmental mobility may be expected in scenarios with soils with alkaline pH, low OC and high sand contents. SynopsisThis study aims to derive parametric and probabilistic Kd values for fluoroquinolone antibiotics in soils on the basis of a few relevant soil physicochemical properties.

Measuring sand content using sedimentation, spectroscopy, and laser diffraction

Sand (2,000–50 µm), silt (50–2 µm) and clay (<2 µm) have been determined by sedimentation methods (i.e., hydrometer and pipette), but increasingly laser diffraction and visible and near-infrared (vis-NIR) or mid-infrared (MIR) spectroscopy are being used. It is necessary to understand the comparability and limitations of these methods. We compared these different methods using 121 soil samples from the Central Sand Plains of Wisconsin, for total sand content as well as five sand fractions (very coarse, coarse, medium, fine, and very fine). Spectroscopic methods are not hindered by assumptions of sphericity or constant particle density; yet these model-based methods require calibration by laboratory methods that do rely on these assumptions. Vis-NIR and MIR spectroscopic model predictions of total sand content differed when calibration laboratory data were obtained from the hydrometer and pipette method. The laser method was not able to accurately measure sand fractions and the fractions were poorly to moderately predicted by vis-NIR (R2 = 0.01 to 0.61) but slightly better using MIR (R2 = 0.23 to 0.71). The hydrometer method overestimated the total sand content compared to the pipette; the laser method was only moderately correlated to both pipette and hydrometer. Spectroscopic modeling of total sand content was very good (R2 = 0.91 to 0.94), but results were affected by the laboratory calibration method and models calibrated with reference hydrometer data overestimated total sand content. We conclude that MIR predictions of sand content provide the best results, but models must be calibrated with the pipette method for soils with high sand contents.

Use of Airborne Radar Images and Machine Learning Algorithms to Map Soil Clay, Silt, and Sand Contents in Remote Areas under the Amazon Rainforest

Soil texture has a great influence on the physical–hydric and chemical behavior of soils. In the Amazon regions, due to the presence of dense forest cover and limited access to roads, carrying out surveys and mapping of soils is challenging. When data exist, they are relatively sparse and the distribution is quite uneven. In this context, machine learning algorithms (ML) associated with remote sensor covariates offer a framework to derive digital maps of soil attributes. The objective of this study was to produce maps of surface and subsurface soil clay, silt, and sand contents in a 13.440 km2 area in the Amazon. The specific objectives were to (a) evaluate the gain in prediction accuracy when using the P-band of airborne radar as a covariate; (b) evaluate two sampling approaches (Reference Area—RA and Total Area—TA); and (c) evaluate the transferability and performance of three ML algorithms: regression tree (RT), random forest (RF), and support vector machine (SVM). The study site was divided into three blocks, called Urucu, Araracanga, and Juruá, respectively. The soil dataset consisted of 151 surface and subsurface sand, silt, and clay observations and 21 covariates (20 relief variables and the backscattering coefficient from the P-band). Both the RA and TA sampling approach used 114 observations for training the prediction models (75%) and 37 for validation (25%). The RA approach was better for the development of sand and silt models. Overall, RF derived the most accurate predictions for all variables. The effect of introducing the P-band backscattering coefficient improved the sand prediction accuracy at the surface and subsurface in Araracanga, which had the highest sand content, with relative improvements (RI) of the R2, root mean square error (RMSE), and mean absolute error (MAE) of 46%, 3%, and 4% at the surface, respectively, and 66.7%, 4.4%, and 5.2% at the subsurface, respectively. For silt, the P-band improved the predictions at the surface in Araracanga, which had the lowest silt contents among the blocks. For clay, adding the P-band improved the RF predictions at the subsurface, with RI of the R2, RMSE, and MAE of 29%, 5%, and 5%, respectively. Despite the low observation density, inherently hindered by the low accessibility of the area and high costs of sampling thereof, the results showed the potential of ML algorithms boosted by airborne radar P-band to map soil clay, silt, and sand contents in the Amazon.

Reversibility of glyphosate sorption in pampean loess-derived soil profiles of central Argentina

There is a growing concern about glyphosate's behavior in the environment. Herbicide behavior in soils greatly depends on adsorption-desorption phenomena, which have shown great variability in soils, although the reversibility of this process has been less examined. The adsorption-desorption behavior of glyphosate was measured on representative soil profiles of the northeast region of Argentinean Pampas, a semi-arid crop cultivating region. Two soil profiles samples (P1 and P2, both Entic Haplustoll) were collected and segmented into depth increments of 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Batch adsorption/48 h-desorption isotherms were performed in a controlled setup. Soil samples had a high sand content (77–92%), and a low content of clay (<3%), but markedly differing in the available P content, especially in the upper layers of soil profiles (0–40 cm, P1 range 133–170 ppm; P2 range 7–43 ppm). Adsorption-desorption isotherms showed a similar range of variation, between 150 and 1400 L kg −1for KFads and 450–1400 L kg −1for KFdes, without appreciable evidence of hysteresis (0.95 ± 0.05). Sorption capacity parameters showed a distinct behavior with depth, P1 exhibiting a U-shape with minimum values at intermediate depths (20–60 cm), while P2 decreases sharply between 0 and 40 cm. General linear models considering the specific surface area (SSA) of each sample and the spatial correlation structure for soil profiles showed a main positive association of KFads and KFdes with the soil organic matter, together with a positive association with iron content (KFads), and a negative association of KFdes with available P content. These results indicate high adsorption extents and sorption reversibility of glyphosate to sandy loam soils of the region, which implies the potential for the herbicide to be available for leaching or degradation under a scenario of intensive use.

Accumulative Strain of Sand-Containing Soft Soil Reinforced by Cement and Sodium Silicate under Traffic Loading

The accumulative strain of sand-containing soft soil is crucial to the stability of the construction of embankment engineering such as expressways and high-speed railways. However, little attention has been devoted to the accumulative strain of sand-containing soft soil. In the current study, a series of cyclic triaxial tests were performed to investigate the accumulative strain of sand-containing soft soil reinforced by cement and sodium silicate under traffic loading. In addition, the accumulative strain model was proposed to describe the characteristic of accumulative strain. The results show that for the specimens with a high sand content (25%, 30%, and 35%), the accumulative strain increases obviously with the increase of the sand content. For the specimen with a cement content of 3%, the accumulative strain increases distinctly with the increasing loading time. The accumulative strain is strongly influenced by confining pressure. When the repeated cyclic stress amplitude is greater than 0.17 kN, the increase rate of accumulative strain is greater. The shorter the curing time is, the greater the accumulative strain is. The calculated results of the accumulative strain model show a good agreement with test data. Hence, the accumulative strain model can better describe the characteristic of accumulative strain.

Effect of biodegradable poly-3-hydroxybutyrate amendment on the soil biochemical properties and fertility under varying sand loads

BackgroundPoly-3-hydroxybutyrate (P3HB) is a bacterial intracellular carbon and energy storage polymer, used as a thermoplastic polyester in a wide array of industrial and agricultural applications. However, how the soil microbiome and fertility are altered by exogenously applied P3HB has been relatively unexplored. This study aimed to assess the effects of P3HB addition to nutrient restricted soil: its biological properties and lettuce (Lactuca sativa L. var. capitata L.) biomass production. The experiment was designed to evaluate impacts of spatial arrangement of the relatively organic-rich (soil organic matter, P3HB particles) versus poor fractions of the matrix with confounding factors such as variable microbial biomass, inherent nutrient/energy status, different water relations (due to variable hydrophysical properties of soil augmented by sand at different ratios).ResultsThe results revealed that P3HB in soils induced inconsistent to contradictory changes in the microbial abundance as well as in most enzymatic activities. The differences were conditioned by the sand content both under P3HB presence or absence. On the other hand, dehydrogenase, urease activities, basal and substrate-induced soil respirations were mostly enhanced by P3HB addition, directly with increasing sand content (several respiration types). Nevertheless, P3HB significantly inhibited lettuce biomass production.ConclusionsP3HB introduction to soil boosts the microbial activity owing to the preferential utilization of P3HB as C source, which depletes soil N and strongly inhibits the plant growth. Enhanced microbial activity in P3HB-amended soils with high sand content (60–80%) suggested that in nutrient-impoverished soil P3HB can temporarily replace SOM as a C source for microbial communities due to the shift of their structure to preferentially P3HB-degrading microbiome.Graphical

Measurement and simulation of electrical resistivity of cement-based materials by using embedded four-probe method

The electrical resistivity of cement-based materials is an important index that can be used for designing durable, multifunctional, and smart concrete structures. However, the measurement and prediction of electrical resistivity are far from being well addressed for cement-based materials. In this study, a modified four-probe test using embedded fine copper rods as electrodes was developed to measure the electrical resistivity of cement-based materials. A coupled thermal-electrical analysis was conducted to verify the feasibility of the modified four-probe method. The simulated results show that a linear relation between the electrical resistivity and the apparent electrical resistance. The contact resistance of the interface between the specimen and the electrodes has little effect on the electrical resistivity. The applied voltage ranging from 4 V to 28 V has a minor influence on the measured electrical resistivity. The electrical resistivity of the specimens cured under standard condition is greater than that under sealed condition. The electrical resistivity of cement-based materials cured under both sealed and standard conditions increases with increasing curing age. A higher volume fraction of sand contributes significantly to a higher electrical resistivity of cement-based materials. Moreover, the homogenization results indicate that the differential scheme predictions coincide quite well with the measured electrical resistivity of cement-based materials with a wide range of sand volume fractions (0%∼60%). The Voigt scheme, the self-consistent scheme, and the Mori-Tanaka scheme can predict well the electrical resistivity of cement-based materials with a low volume fraction of sand (<20%), but fail to give a good prediction at a higher sand content.

Influences of sand concentration and flow velocity on hydro-abrasive erosion behaviors of HVOF sprayed Cr3C2–NiCr and WC–Cr3C2–Ni coatings

Improving the hydro-abrasive erosion (HAE) resistance of the existing flow-handling components has been a matter of continuous effort for the hydraulic machineries. In current work, the effects of sand concentrations (SC) and flow velocities (FV) on HAE behaviors of high-velocity oxygen-fuel (HVOF) sprayed carbide-based cermet (i.e. Cr3C2–NiCr and WC–Cr3C2–Ni) coatings were studied using a rotating disk rig facility. The obtained results revealed that the WC–Cr3C2–Ni coating possessed lower porosity value, higher hardness (H) and elastic modulus (E) values, superior HAE resistances, and appeared less influenced by SC as well as FV compared with the Cr3C2–NiCr coating. Higher SC and FV caused more severe HAE degradations for both carbide-based cermet coatings, while FV had a greater influence on HAE resistances for both coatings than SC. With the increase of the SC and FV, the Cr3C2–NiCr coating experienced the HAE process of the isolation of hard phase grains as well as the scouring, the connection of micro-cracks as well as severe plastic deformations, and the crater formation as well as deep scour marks, while the HAE process of the WC–Cr3C2–Ni coating mainly included the micro-cracks, the erosion pits, and the scour marks.

Seepage Performance of Fibre Bundle Drainage Pipes: Particle Flow Simulation and Laboratory Testing

Mining coal, oil and other energy will form much slope engineering, such as open-pit mine slope and oil depot slope. The groundwater seepage seriously affects the stability of these slope engineering projects. Drainage pipes are commonly used in slope engineering projects to reduce the risk of moisture decreasing soil stability. Such pipes are prone to blockage by soil accumulation after a period of operation, resulting in decreased drainage or complete failure. By installing fibre bundles in drainage pipes, drainage can be maintained under soil ingress. This paper conducted particle flow simulations of the influences of soil particles on the clogging of geotextile filters and drainage pipes under various influences and estimated their seepage rates. Higher water pressure, smaller flower hole intervals in the pipe, greater soil friction angles and smaller pipe inclination angles are less conducive to drainage. Under silting conditions, the seepage and drainage performance of a drainage pipe can be improved by installing a fibre bundle. Five types of fibre bundles were tested with plastic rope providing the best drainage effect. With plastic rope and cotton rope, the best drainage is achieved using uneven arrangements of fibre bundles. In contrast, nylon rope, hemp rope and polyester rope perform best when uniformly arranged. The greater the number of fibre bundles per unit cross-sectional area of pipe, the better the seepage conductivity. Seepage is also greater when the soil in the pipe has a higher sand content. These results provide a reference for the design and construction of more reliable drainage systems for slope engineering in wet areas.

Neural net detection of seismic features related to gas hydrates and free gas accumulations on the northern U.S. Atlantic margin

Bottom-simulating reflections (BSRs) that sometimes mark the base of the gas hydrate stability zone in marine sediments are often identified based on the reverse polarity reflections that cut across stratigraphic layering in seismic amplitude data. On the northern U.S. Atlantic margin (USAM) between Cape Hatteras and Hudson Canyon, legacy seismic data have revealed pronounced BSRs south of the deepwater extension of Hudson Canyon and more subtle ones from offshore Delaware south to Cape Hatteras, where the reflections sometimes follow stratigraphic layering. Using high-resolution seismic data acquired during the 2018 Mid-Atlantic Resource Imaging Experiment and a supervised neural net, we identify seismic features associated with gas hydrates and/or the top of gas between Hudson Canyon and Cape Hatteras. Using seismic attributes especially sensitive to the presence of gas, we train a neural network algorithm on seismic data from an area with strong BSRs and then apply the model to the rest of the data set. The results indicate that gas hydrate and/or shallow free gas are significantly more widespread on the northern part of the USAM than previously known. Seismic indicators of gas extend landward from the 2000 m isobath to the upper continental slope in sectors with (offshore Virginia) and, to a lesser extent, without (offshore New Jersey) pervasive upper slope methane seeps. Higher sand content and intermediate sediment thickness, factors related to the container size and gas charge in a petroleum systems framework, are associated with more robust gas indicators.

Conversion Factors for Electrical Conductivity of 1:5 Soil-Water Extracts to Saturated Paste of Reclaimed Tideland Soils are Affected by Sand Contents

Electrical conductivity (EC) of saturated soil paste extracts (ECe) is a standard measure for soil salinity assessment. However, due to the difficulty of ECe measurement, EC of the extracts of 1:5 soil:water ratio (EC1:5) is widely used, and thus conversion of EC1:5 to ECe is often required. However, the conversion factor varies widely being affected by many soil factors including soil texture though such variation has rarely been investigated. This study was conducted to explore the effect of soil texture (particularly sand content) on the EC conversion factor using soil samples (n = 628) from 19 reclaimed tidelands (RTLs) located in the coastal areas of Korea. The conversion factors ranged from 4.6 to 9.9 (average 7.5) and the conversion factors were positively correlated with the average sand content of the RTL (r2 = 0.48, P < 0.001) except for three RTLs which have extremely low sand contents. The increased EC conversion factors for soils with higher sand contents should be ascribed to decreased saturated water contents for ECe. Our results demonstrate the critical influence of sand content on the EC conversion factor by highlighting the necessity of consideration of sand content for EC conversion factor.Correlation between EC1:5 and ECe of soils collected from reclaimed tideland. The slope (7.5) indicates that the conversion factor from EC1:5 to ECe is 7.5.

Manufacturing Technique of the Avalokitesvara Bodhisattva Mural Painting in Geungnakjeon Hall, Daewonsa Temple, Boseong

The manufacturing technique was studied through the structure and material characteristics of the walls and the painting layers of the Avalokitesvara Bodhisattva mural of Geungnakjeon Hall, Daewonsa Temple. The mural is painted and connected to the earthen wall and the Junggit, and the wall is composed of wooden laths as a frame, the first and middle layers, the finishing layer, and the painting layer. The first layer, middle layer, and finishing layer constituting the wall were made by mixing weathered soil and sand. It was confirmed that the first layer had a high content of loess below silt, and the finishing layer had a high content of fine-sand and very fine sand. For the painting layer, a ground layer was prepared using soil-based mineral pigments, and lead white, white clay, atacamite, minium, and cinnabar (or vermilion) pigments were used on top of it. The Avalokitesvara Bodhisattva mural was confirmed to belong to a category similar to the soil-made buddhist mural paintings of Joseon Dynasty. However, it shows characteristics such as a high content of fine sand in the finishing layer and overlapping over other colors. Such material and structural characteristics can constitute important information for future mural conservation status diagnoses and conservation treatment plans.