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Offshore artificial islands represent a novel way to develop and utilize marine space resources. Previous research has focused on predicting erosion and deposition distributions following the islands construction, utilizing laboratory experiments and numerical simulations. However, the absence of long-term continuous monitoring has hindered systematic studies on the geomorphological processes of these islands. A 20-years of underwater terrain monitoring scheme was conducted before and after construction of the Rudong Artificial Island in Jiangsu Province, China. The results were combined with on-site observations of tidal currents, suspended sediment concentrations, and surficial sediment to investigate the evolution of the water channel–sand ridge system and the development process of local scour around the artificial island. The results indicated that after the construction of the artificial island, its surrounding water channels showed an overall evolution trend of the north channel shifting towards the north, the middle channel widening and moving south, and the south channel extending westward and southward. Scour has been observed at the four corners of the artificial island, with the peak depths of 7.3 m, 5.6 m, 13.7 m, and 12.2 m at the southwest, northwest, northeast, and southeast corners respectively. The scour in the southwest and northwest corners reached an equilibrium within five years. However, in the southeast corner, continuous erosion of the shoal on the southeast side of the artificial island enhanced the local hydrodynamic force, leading to further scour development. The large-scale scour in the northeast corner was mainly caused by changes in the local flow field following the construction of water intake pipelines and their protection projects. These geomorphological changes are the joint results of the natural evolution of the radial sand ridges and local erosion and deposition from engineering construction. Currently, the sandbanks surrounding the island are still undergoing dynamic evolution following engineering construction, and local scour around the island has not yet reached equilibrium. • This paper focused on the geomorphological processes around an artificial island. • The island was built on a silty coast where tidal currents dominated its evolution. • Field terrain, hydrology, and sediment data spanning twenty years were collected. • The evolution of the radial sand ridges after the island construction was studied. • The development process and causes of local scour around the island were analyzed. [ABSTRACT FROM AUTHOR]

Hurricanes can physically transform forest ecosystems, leading to immediate and potentially long-lasting impacts on carbon dynamics. Using Forest Inventory Analysis (FIA) data from the United States Forest Service, we compared the average carbon in trees (saplings, bole, stump, tops) and foliage pre- (2001–2003) and post- (2005–2007) Hurricane Ivan for different tree categories in the Perdido Bay Watershed located in the Florida Panhandle. The log-linear regression model indicates that variables stand type (softwood/mixed/hardwood), diameter, height, physiographic class (deep sands/flatwoods/rolling uplands/small drains/swamps/bottomlands), elevation, field age and plot affected status were statistically significant (p ≤ 0.05) determinants of carbon loss from the forest stands. Results showed that plots with medium-diameter stands lost more aboveground carbon than large and small-diameter stands, similarly, softwood-dominated stands lost more aboveground carbon than hardwood and mixed wood stands. Aboveground carbon decreased in stands with large (≥ 0.15 m) and medium (≥ 0.12 m) diameter-at-breast height (DBH) by 22.74 and 30.22 metric tons/ha, respectively. We ascertained a decrease of 74.51 and 17.82 metric tons/ha of aboveground carbon in hardwood and mixed plots after Hurricane Ivan, respectively. Aboveground carbon in young (< 25 y) taller trees (> 15 m) decreased by 121.55 metric tons/ha of carbon immediately after the hurricane. These findings underscore the critical necessity of comprehending the interplay between forest structure and hurricane activity to forecast the repercussions of such disturbances on carbon stocks. Our provided framework serves as a valuable tool for researchers and policymakers to assess the vulnerability of coastal forests and facilitate strategic planning to protect forests as carbon sinks. • More than 90 % of FIA plots inside the study area were affected by Hurricane Ivan. • About 28.64 % and 62.15 % decrease in carbon in trees (sapling, stump, bole, top) and foliage, respectively. • About 1.22 % and 13.25 % carbon decreased in mixed and softwood stands; softwoods losing 51.30 % more carbon than hardwoods. • Taller trees (>10 m) lost 23.22 % more carbon than smaller trees (<10 m). • Aboveground carbon in trees and foliage decreased 18.15% and 1.36% respectively, in trees with a medium diameter (≥0.12 m). [ABSTRACT FROM AUTHOR]

Sand waves are commonly formed on the sandy seabed of the continental shelf and characterized by their regular wave-like shape. When a submarine pipeline is laid on this type of seabed, it often experiences free spans due to the unevenness of the seabed. These free spans are particularly vulnerable to vortex-induced vibration (VIV) and the resulting fatigue damage, which have been identified as the primary causes of pipeline failures in offshore oil and gas exploration. This study examines the VIV and fatigue damage of free spans in a submarine pipeline in the Lufeng oilfield, which is located in a large area of sand waves. The assessment conditions encompass the as-laid empty state, the flooded state, and the operational state. Additionally, both the minimum and maximum lay tension are taken into account during the evaluation of VIV and fatigue. The VIV onset screening conducted revealed a considerable number of pipeline free spans exceeding the VIV onset span lengths under both temporary and operating conditions for the non-trench seabed. Furthermore, the analyses indicate that the pipeline does not meet the criteria for VIV fatigue on a non-trenched seabed. Consequently, a proposed solution of implementing a 1 m trench rectification measure for the seabed is recommended. The results demonstrate that this measure effectively mitigates the occurrence of VIV and subsequently reduces fatigue damage across all conditions.

The Holocene shows rapid climatic changes associated with alternating intervals of glacier advances and retreats. The coastal regions, where beach ridges constitute common preserved landforms, are highly sensitive to register such changes and bring light into past littoral environments. Excellent marine Argentinean Holocene deposits associated with the last climate optimum are preserved at the Río de la Plata estuary (Argentina). In this beach ridge, fourteen detailed sedimentary logs were studied in order to generate an palaeoenvironmental model. The analysis of major hierarchy surfaces of the ridge was performed combined field work and Virtual-Outcrop analysis. The ridge presents internal clinoforms that subdivide it into eleven clinothems. The first two clinothems correspond to the development of a sand ridge as a response to the erosion and reworking of previous aeolian Late Pleistocene sediments. Subsequently, a bioclastic ridge was amalgamated with the sand ridge (clinothems III to XI). Simultaneously, in a landward position, a lagoon and washover deposits were developed. Finally, after the stabilization of the beach ridge the continuous sea level fall generated the actual coastal plain deposits. Six 14C ages were obtained at the base of selected clinothems, dated between 5,240 ± 110 cal BP and 3,900 ± 90 cal BP; meaning that in 1,340 years the beach prograded 290 m. Stable isotope analyses (δ13C and δ18O) allowed to infer that the temperature during the evolution of the ridge has two maximum values of 22.5 °C and a minimum of 18.5 °C. The salinity range between 32.53‰ and 33.16‰, showing short variability. The sudden change in the composition of the ridge, from sandy to carbonate sediments, may be interpreted as a combined result of an increase of carbonate productivity along with a decrease of siliciclastic supply at the coast. This stage would have been developed approximately around 5ka B.P., in coincidence with the Holocene Climatic Optimum (as recorded in Argentina) when propitious climatic conditions may have led to the proliferation of large communities of warm and warm temperate benthic organisms. We stress that, the strong activity of the Brazilian current during the Mid-Holocene thermal maximum enabled excellent conditions for the development of a carbonate warm beach similar to that occurring at tropical and subtropical areas nowadays. This study provides an example of the strong changes occurred in coastal environments as a result of climate change, particularly in the context of global warming episodes which characterized interglacial periods of the Late Quaternary in eastern South America. [ABSTRACT FROM AUTHOR]

Soil movements produced around deep excavations are one of the main issues to be addressed during design and construction of underground structures in urban environment. Several methods to predict ground movements are currently available. Semi-empirical methods correlate displacements and simple geometrical features of the excavation; these methods predict separately transversal and longitudinal settlement troughs or at least provide a conservative envelope of them and they are mainly based on empirical data of excavations in clay. Numerical methods based on the solutions of FEM or DFM models usually provide prediction of the green field subsidence. In this paper existing 2D semi-empirical methods are first shortly reviewed. Some of these methods are then modified and combined into a new 3D analytical description of the subsidence trough around a deep excavation. The proposed two variable subsidence function depends on several parameters: four independent parameters defining the overall shape and the maximum settlement acting as a scale parameter. Settlement fields reproduced by a 3D FEM nonlinear parametric study of deep excavations inspired by real case studies are thus presented and discussed. The newly proposed 3D analytical description is applied to fit the FEM results and some fundamental relationships among geometrical features of the excavation pit and the 3D shape function parameters are identified. These relationships are validated via the application to three case studies of deep excavations in sand where the subsidence was controlled by the deformation of the retaining structures finding a satisfactory and encouraging agreement. [ABSTRACT FROM AUTHOR]

The failure mechanism of biocemented sand has been largely speculated based on scanning electron microscopy images of biocemented sand after mechanical tests. However, some breakage patterns cannot be directly observed, such as the separation of CaCO3 crystals and the separation of CaCO3 crystals and sand surfaces. A study of the breakage process of biocemented sand at microscale is essential for understanding the mechanism of biocementation. In this work for the first time, a series of in situ splitting tensile tests were conducted using a tensile & compression module installed inside an SEM machine so that the breakage process of a biocemented sample under loading could be observed directly. The results showed that no breakage was observed before peak stress indicating an elastic–plastic deformation stage. Once the peak stress was reached, the stress fluctuated around the peak stress. At the end of the tests, two kinds of breakage of biocement were observed, i.e., calcite-calcite breakage and calcite-silica breakage. The detailed breakage seems also affected by the form of CaCO3. Furthermore, besides increasing active precipitates, the improvements in the strength of biocement and the bonding strength between biocement and the sand surface were suggested to improve the performance of MICP for stabilizing sand. The findings of microscale in situ observation during mechanical tests can also provide basic evidence for modeling debonding process of biotreated soils using constitutive models or numerical simulation methods. [ABSTRACT FROM AUTHOR]

This paper shows the experimental results of impact hammer tests conducted on sand and composite sand-polyurethane samples at different confining pressures. It was found that polyurethane can mitigate the propagation of waves generated by an impact, thereby influencing seismic isolation. Also, accelerations in the composite samples were reduced in relation to the percentage of polyurethane present. A theoretical lumped-mass model (calibrated based on the experimental results) interpreted the experimental results and enabled an in-depth parametric analysis. This analysis shows that the proposed isolation method is efficient, as the damping coefficient of the polyurethane and the soil/polyurethane impedance ratio increased. [ABSTRACT FROM AUTHOR]

Large-scale green tides occur frequently in summer in the Yellow Sea in recent decade. Micro-propagules, providing "seeds" for the seaweeds, play an important role in the formation of green tide. We studied the distribution pattern and genetic composition of the Ulva micro-propagules in the Yellow Sea during and after the green tide in 2019. In April, a great amount of Ulva micro-propagules was detected in the Subei Shoal, with the average density of 908 inds./L, being similar to that of previous studies. U. prolifera was found out at a low percentage (4%), and 25% of them were positive when tested by the specific marker for the floating ecotype. The percentage of U. prolifera was obviously lower than that in the same season from 2009 to 2016. Therefore, the quantity of U. prolifera micro-propagules sharply decreased. Significant variation in composition of the micro-propagules in Subei radial sand ridges was revealed in the background of the alternation of macroalgal tides in the Yellow Sea in the latest years. During the green tide in June and July, Ulva micro-propagules were detected from some nearshore sites where the floating seaweeds distributed, and U. prolifera was the dominate species. In September, when the green tide ended, no Ulva micro-propagule was detected from the open sea area of the Yellow Sea. It is indicated that the green algae micro-propagules were unlikely to exist in the open water of the Yellow Sea for a long time according to the large-scale surveys. The mechanism of preserving micro-propagules in Subei radial sand ridges, and the destination of U. prolifera micro-propagules in the open sea area of the Yellow Sea after green tide deserves further study. [ABSTRACT FROM AUTHOR]

Tidal flats are widely distributed on high-latitude coasts, where sea ice processes have been invoked to explain the abundance and distribution of boulders. This study documents the surface morphology and sediment dynamics of a Low-Arctic macrotidal system, the boulder-rich tidal flats of Koojesse Inlet, fronting the Nunavut capital, Iqaluit, on Baffin Island. This is a region of postglacial isostatic uplift and forced regression, with raised littoral, deltaic, and glaciomarine deposits. The spring-tidal range is 11.1 m and sea ice cover lasts roughly 9 months of the year. The extensive intertidal flats are up to 1 km wide, with a veneer of sand and gravel (including large boulders) resting on an erosional unconformity truncating the underlying glaciomarine mud, forming a terrace within the present tidal range. Over a 3-year study, no consistent pattern of erosion or deposition was evident. Over a longer time scale, the concave hypsometry, low sediment supply, slight ebb dominance of weak tidal currents, abrasion by wave-entrained sand, ebb-oriented ripples formed under subaerial drainage, and slumps on the terrace flanks are consistent with seaward hydraulic and gravitational sediment transport. These processes may be of greater importance than shoreward ice transport. This study underlines the importance of relict glaciomarine deposits, postglacial uplift, and falling relative sea level in the erosional development of these high-latitude tidal flats. Relative sea-level projections for Iqaluit are ambiguous, but a switch to rising sea level, if it occurs, combined with more open water and wave energy, could alter the foreshore dynamics of the system. [ABSTRACT FROM AUTHOR]

This study reports on the physical properties and geochemistry of aeolian bedform grains along the Curiosity rover traverse in Gale crater from Vera Rubin Ridge to the Sands of Forvie (Sols 1902–2995), and includes comparisons to results made earlier in the mission. Volumetrically, <150 μm grains dominate active aeolian bedforms in the study area, similar to previous findings elsewhere at Gale crater and at other locations on Mars. Coarser grains, up to 2.9 mm long, are present on larger active bedforms. The larger 1–3 mm active grains commonly are reddish or whitish in color and irregular in shape, suggesting erosion of local bedrock as sources. One inactive megaripple had a surface of dust‐covered 2–15 mm grains, with smaller <150 μm grains between and within the bedform interior. Geochemical measurements show element concentrations vary according to position on the bedform, sand activity, and grain contributions from local bedrock. A strong positive correlation between Mg and Ni is identified on active bedform surfaces, with the highest Ni always corresponding to ripple crests where the coarsest gray and clear grains were commonly found. There is also a correlation between Ti and Cr for the majority of active sands, with the finer active sands in ripple troughs and sand patches having the greatest number of red grains and highest Cr concentrations. These results show the smaller scale physical properties and geochemistry of several types of aeolian bedforms on Mars formed under current and ancient environments. Plain Language Summary: This work reports sand grain characteristics of Martian aeolian bedforms along the traverse of NASA's Mars Science Laboratory "Curiosity" rover at Gale crater from Sols 1902–2995 of its mission, and compares their characteristics to previous measurements of aeolian ripple sands on Mars. Large, active ripples have larger grains on their crests and flanks compared to smaller active ripples. Compositional variations among these grains correlate with the grain color and size. Some coarse grains on the larger active ripples are lithic fragments derived from either local Murray bedrock or from basalts. Finer grains are characteristic of smaller ripples and trough areas between large ripple crests. These finer grains are redder in color than coarser grains on larger ripples. The rover examined an inactive megaripple, which was found to be covered by coarser grains 0.3–11 mm that could have been eroded from local bedrock. Compositional differences among aeolian ripples may reflect how much of their surfaces are comprised of coarser grains that either are more resistant to erosion or are locally derived, compared with finer grains. These results provide insight into the characteristics of Martian aeolian ripples at much higher resolution than possible from orbital observations. Key Points: Larger ripples have a higher abundance of coarser gray grains compared to smaller ripples, ripple troughs, and sand patchesThe Ni concentration increases and the Cr concentration decreases as the abundance of gray grains on the ripple increasesInactive bedforms have an armor of coarse grains that can be pebbles and granules sourced from the local bedrock [ABSTRACT FROM AUTHOR]

Existing experimental evidence shows that the propagation of explosive waves in the free fields of soils is remarkably affected by the degree of saturation. In the surrounding rocks of underground protective structures, the underground water is normally unavoidable, which is supposed to reduce the isolation efficiency of a passive antiblast barrier. To investigate the effect of water saturation on the stress wave attenuation ability of infilled joints, impact tests were carried out on artificial joints filled with dry and saturated granular materials using a split Hopkinson pressure bar (SHPB). The test results revealed that under the same conditions, the stress and energy transmission coefficients of the waves crossing saturated sand-filled joints were about 3.16–4.13 times and 9.75–11.4 times those of joints filled with dry sand, respectively. The dynamic stress-strain relationship of the filling layer during the impact process and the crushing index of the infill were analyzed. The results showed that the compressibility and the granular crushing index of the dry sand were much greater than that of the saturated sand, and the dynamic stress-strain relationship of the dry sand exhibited three-stage nonlinear characteristics. The experimental results quantitatively uncovered the serious adverse effect of water on the wave absorption properties and markedly diminished the potential of the filled joints as a wave elimination barrier, which should be a matter of great concern in the design of underground protective structures. [ABSTRACT FROM AUTHOR]

The advent of lab diffuse reflectance spectroscopy (LDRS) that exploits the fundamental vibration, overtones and combination of functional groups of soil components makes the soil study easier. The present research intends to predict sand content utilizing the proximal soil sensing (PSS) tech. Thus, in accord with the supplementary data layers and stratified randomized sampling (SRS) method, eventually, 128 samples were gathered from 20 cm of soil surface of Mazandaran Province, Iran. First of all, the sample set was subdivided into two subsets: calibration (96) and validation (32). Using the multivariate regression analysis-partial least squares regression (PLSR) algorithm with leave-one-out cross-validation (LOOCV) technique and some pre-processing algorithms, such as spectral averaging, smoothing and 1st derivative (1st-D), the definitive calibration model with two & four latent vectors (LVs/LFs) and correlation coefficient (RP), determination coefficient (R2P), root mean square error (RMSEP), ratio of performance to deviation (RPDP) and ratio of performance to interquartile distance (RPIQP) respectively: 0.83&0.82, 0.68&0.67,8.68&8.83%,1.78&1.75,2.45&2.41, were validated and spotted as the most appropriate predictive model for the sand content prediction in the study region. Last, the potentiality of the visible-near infrared diffuse reflectance spectroscopy (VNIR-DRS) for sand content estimation in Mazandaran soils was proved. Also, it is feasible to upscale the sand prediction process utilizing the principal resulted model and the key spectral domains via airborne/satellite hyperspectral data, which emphatically shows the LDRS importance as a commencement point for characterizing the informative optical wavelengths. Likewise, that will be the infrastructure for spaceborne data modeling and upscaling process. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to show the contribution of artificial intelligence, namely a neural network, in reservoir characterisation to predict the clay volume in an unconventional tight sand gas reservoir. Clay volume is usually estimated using the natural gamma ray log, which can give bad results if non-clayey radioactive minerals are present in the reservoir. Our purpose is to implement a multilayer perceptron neural network machine to predict the clay volume using the conventional well-log data as an input and the measured mineralogical component, as desired output with a Levenberg-Marquardt algorithm. Application to two Ordovician reservoir intervals of a borehole located in the Ahnet basin in the Algerian Sahara shows the contribution and the efficacy of the implemented neural network machine in unconventional tight sand reservoirs characterisation. [ABSTRACT FROM AUTHOR]

The analysis of swath bathymetric data and high-resolution seismic profiles (CHIRP), combined with information from the literature, allowed the creation of an updated map of the topography of the seabed in the western part of the Sicilian Channel. This area includes the entire Adventure Plateau, the Pantelleria Graben, and the Capo Granitola- Sciacca offshore sector between the Sicilian coast, the Graham and the Terrible banks. Positive and negative bedforms (sedimentary banks, volcanoes and mud volcanoes, pockmarks) and some erosional features were recognised and analysed in the study area. The Capo Granitola-Sciacca offshore sector is a continental shelf characterised by the presence of various sand bodies that are locally cemented and interpreted as sand ridges, dunes and remnants of dune strands or barrier lagoon systems eroded by the action of bottom currents. These bodies were probably deposited during the post-LGM sea level rise, occurred from ca. 18 kyr B.P. and 6 kyr B.P. (transgressive deposits) and during the glacial phase (lowstand deposits) occurred about 20 kyr B.P., when sea level was ca. 120-130 m lower than today. In this area there are also several volcanic edifices, mud volcanoes and numerous pockmarks due to the presence of gas. The distribution of these bodies is controlled by the faults associated with the NNE-oriented active lithospheric structure called Capo Granitola-Sciacca Fault Zone, which crosses the entire western part of the Sicilian Channel. The northern margin of the rift-related Pantelleria Graben is punctuated by NW-oriented pockmarks, probably controlled by the faults bounding tectonic depression, where several scars and a broad landslide have been this also mapped. In addition, canyons were noted along the southern margin of the Adventure Plateau. [ABSTRACT FROM AUTHOR]

Shallow marine sand waves are formed on the seabed and are widely distributed within tidal environments. However, the use of multibeam echo sounding (MBES) is costly to obtain the bathymetric mapping of large complex sand waves. Therefore, we propose a new method that employs a combination of multiangle sun glint images and sparse MBES data to achieve comprehensive bathymetric mapping of large and complex sand waves. This method involves estimating sea surface roughness, automatically extracting sand-wave crests, conducting adaptive subregion partitioning, estimating the water depth at auxiliary points, and generating digital bathymetric models. The method was employed in a case study of sand waves on the Taiwan Bank. Bathymetric mapping was implemented for large complex sand waves over an area spanning approximately 350 km2 using multiangle sun glint images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer and MBES data. The results show that mapped and measured water depths were well-matched; the root-mean-square error of water depths was 1.77 m, and the relative error was 5.03%. These findings show that bathymetric mapping of large complex sand waves can be effectively conducted using the new method, and as such, the workload of MBES is reduced and efficiency is improved. [ABSTRACT FROM AUTHOR]

The seismic response of underground structures such as subway stations is critical. However, the complex underground structure experiments under a dynamic centrifuge shaking table are significantly limited. This study conducts a shaking table test of a two-story three-span underground structure under 50 g gravitational centrifuge acceleration to investigate soil–structure interaction effects (SSI). The test is performed on a sand soil-structural model using a laminar shear box with depths of 2.5 m, and the input motion is a Parkfield wave. The experimental results indicate that the central column of the two-story three-span underground structure is the weak component during the earthquake. In addition, the numerical simulations of the soil–structure system are carried out to study the effect of buried depth and foundation soil type on the seismic response of the underground structures. The experimental and numerical results proved that the performed centrifuge test can reproduce the key seismic response characteristics of the SSI in the prototype underground structure and provided guidelines to design a similar underground structure in the future development of the urban subway systems. [ABSTRACT FROM AUTHOR]

Mixtures of cohesive clay and noncohesive sand are widespread in many aquatic environments. Ripple dynamics in sand‐clay mixtures have been studied under current‐alone and wave‐alone conditions but not combined wave‐current conditions, despite their prevalence in estuaries and the coastal zone. The present flume experiments examine the effect of initial clay content, C0, on ripples by considering a single wave‐current condition and, for the first time, quantify how changing clay content of substrate impacts ripple dimensions during development. The results show inverse relationships between C0 and ripple growth rates and clay winnowing transport rates out of the bed, which reduce as the ripples develop toward equilibrium. For C0 ≤ 10.6%, higher winnowing rates lead to clay loss, and thus the presence of clean sand, far below the base of equilibrium ripples. This hitherto unquantified "deep‐cleaning" of clay does not occur for C0 > 10.6%, where clay‐loss rates are much lower. The clay‐loss behavior is associated with two distinct types of equilibrium combined flow ripples: (a) Large asymmetric ripples with dimensions and plan geometries comparable to their clean‐sand counterparts for C0 ≤ 10.6% and (b) small, flat ripples for C0 > 10.6%. The 10.6% threshold, which may be specific to the experimental conditions, corresponds to a more general 8% threshold found beneath the ripple base, suggesting that clay content here must be <8% for clean‐sand‐like ripples to develop in sand‐clay beds. This ripple‐type discontinuity comprises a threefold reduction in ripple height, with notable implications for bed roughness. Plain Language Summary: Sticky mud and sand are commonly found in estuaries and across the coastal zone. During storms, the combined effect of waves and currents can erode these sediment beds, creating undulating ripples. For sand‐only beds, ripple size depends on the strength of the waves and currents and the grain size (fine sand is easier to erode than coarse sand). However, when mud is present, ripples form more slowly and may be smaller in size. This study has identified that when waves and currents are combined (a) sediment beds with sand‐mud mixtures can form ripples with similar shapes and sizes as their clean‐sand counterparts, where mud is removed from the ripple and below it, provided the initial mud content is less than or equal to 10.6% and (b) sediment beds with initial mud contents greater than 10.6% cannot be eroded easily and form very small ripples that are prevented from growing further due to the stickiness of the mud. While the 10.6% threshold may be specific to the waves and currents tested, the findings have identified an important mud‐related ripple behavior which should help to improve the understanding of the movement of sand and mud in estuaries throughout the world. Key Points: Ripple growth rates decrease with increasing initial bed clay content in sand‐clay substrates under combined, wave‐current, flowsSmall, flat ripples occur when the clay content is above an 8% threshold below the ripple base, as strong cohesion prevents ripple growthLarge clean‐sand‐like ripples form below the clay threshold, with deep winnowing (cleaning) of clay and large equivalent clean‐sand depths [ABSTRACT FROM AUTHOR]

The decline in groundwater levels is a cause of concern in many regions of the world, including the Sand Ridge of Hungary. The causes of the regional depletion range from rising air temperatures, changes in precipitation, domestic and agricultural groundwater use and past amelioration and recent afforestation, including the effects of drilling for crude oil exploration. The relations between the decline, the soil water regime and groundwater recharge under existing aged forests remained unclear thus far. Based on our monitoring of groundwater and soil moisture we aim to clarify this interplay in a new experimental site on the hilltop of the Sand Ridge. We compared three land-uses: a 41-year-old black locust (Robinia Pseudoacacia) offshoot forest, an 83-year-old first generation black pine (Pinus nigra) forest, and a grassland control site. The observed differences in the soil moisture profiles and dynamics were connected to the use of water by the given type of vegetation. We indicated a connection between the disruption of the groundwater recharge and the loss of contact of the rooting system of the forests with the deepening of the unconfined aquifer. Even if the aged forests could locally contribute to the decline, we conclude that the decline at the hilltop site that may be more strongly driven by other regional factors. [ABSTRACT FROM AUTHOR]

In order to study the mechanism of seepage-induced geotechnical damage and characteristics of fine particle migration in sandy soil, a one-dimensional upward seepage test device was used and a series of upward seepage flow tests of sand were conducted. In these experiments, the permeability, fine particle migration and redistribution under different hydraulic gradients were investigated. The results show that local hydraulic gradient in the sand sample is larger than the critical hydraulic gradient calculated by the Terzaghi's Equation. The seepage force will induce the fine soil particles to migrate along water flow direction and then cause the redistribution and reconsolidation of sand particles. Under the test condition, fine particles (< 0.075 mm) and fine sand particles (0.075–0.25 mm) dominate in the lost soil particles. Soil particles larger than 0.6 mm are hardly to lose. [ABSTRACT FROM AUTHOR]

Past orbital parameters of the Moon are difficult to reconstruct from geological records because relevant data sets of tidal strata are scarce or incomplete. The sole Archean data point is from the Moodies Group (ca 3.22 Ga) of the Barberton Greenstone Belt, South Africa. From the time‐series analysis of tidal bundles from a well‐exposed subaqueous sand wave of this unit, Eriksson and Simpson (Geology, 28, 831) suggested that the Moon's anomalistic month at 3.2 Ga was closer to 20 days than the present 27.5 days. This is in apparent accordance with models of orbital mechanics which place the Archean Moon in a closer orbit with a shorter period, resulting in stronger tidal action. Although this study's detailed geological mapping and section measuring of the site confirmed that the sandstone bed in question is likely a migrating dune, the presence of angular mud clasts, channel‐margin slumps, laterally aggrading channel fills and bidirectional paleocurrents in overlying and underlying beds suggests that this bedform was likely located in a nearshore channel near lower‐intertidal flats and subtidal estuarine bars; it thus carries risk of incomplete preservation. Repeated measurements of foreset thicknesses along the published traverse, measured perpendicular to bedding, failed to show consistent spectral peaks. Larger data sets acquired along traverses measured parallel to bedding along the 20.5 m wide exposure are affected by minor faulting, uneven outcrop weathering, changing illumination, weather, observer bias and show a low reproducibility. The most robust measurements herein confirm the periodicity peak of approximately 14 in the original data of Eriksson and Simpson (Geology, 28, 831). Because laminae may have been eroded, the measurements may represent a lower bound of about 28 lunar days per synodic month. This estimate agrees well with Earth–Moon dynamic models which consider the conservation of angular momentum and place the Archaean Moon in a lower orbit around a faster‐spinning Earth. [ABSTRACT FROM AUTHOR]

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Sediment transport modeling (STM) is a potentially effective tool for estimating the magnitude of tsunamis and earthquakes without historical records. However, the application of STM to prehistorical tsunamis is challenging because of multiple uncertainties in topography and roughness. Along the coast of Hidaka, Hokkaido, Japan, there is potential to conduct STM even in the absence of historical records because comprehensive geological data for the coastal evolution during the Holocene are available here. The tsunami deposits in Hokkaido indicate the presence of events on a larger scale than historical tsunamis; in particular, the seventeenth‐century tsunami had multiple potential wave sources other than a Kuril Trench earthquake, inhibiting its magnitude estimation. In this study, we applied STM to paleotsunamis for the coast of Hidaka, where comprehensive geological data are available, although the wave source is unknown. The modeling parameters—paleotopography, roughness, grain size, initial sand source, sea level, and beach ridge height—were estimated using data obtained from geological surveys and sensitivity tests. The modeling of a tsunami induced by a Kuril Trench earthquake reproduced the sediment distributions and sedimentary structures of the observed sand layers better than that of extreme storms and volcanic tsunamis. Because the conventional fault model is reasonably suitable in the western area from the Kuril Trench, a much wider rupture zone is less likely. Parameters such as sand source area, roughness, ridge height, and paleo sea level are important for geologists and modelers when applying STM to paleotsunamis. Plain Language Summary: Sediment transport modeling (STM) can correctly reproduce extreme waves caused by tsunamis and storms based on sedimentary evidence. However, applying STM to prehistorical periods is challenging because of uncertainties in paleotopography. The coast of Hidaka, Hokkaido, Japan, is suitable area for STM because of the comprehensive geological data available here. These data reveal the coastal evolution during the Holocene, in addition to tsunami sediment surveys. In this study, we established realistic computational parameters for STM based on detailed geological data and estimated wave sources for the sand layers formed by extreme waves. By comparing the observed sediment distribution or sedimentary structures and those estimated from the transport processes by the modeling of tsunami and extreme storm models, most sand layers were reported to be tsunami deposits. This result allowed us to estimate the extent of the largest class of rupture zones in the Kuril Trench. Moreover, sensitivity tests for computational parameters with large uncertainties in the prehistoric period provide geologists and modelers important information that should be considered when applying STM to paleotsunamis. Key Points: Sediment transport is modeled in prehistoric periods by obtaining parameters such as paleogeography and roughness from geological dataA tsunami induced by a Kuril Trench earthquake reproduced the distribution and sedimentary structure of prehistoric sand layersSensitivity tests demonstrated parameters that significantly affect sediment transport modeling in prehistoric periods [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bioremediation is widely used to improve ground soil by introducing calcium carbonate (CaCO3). Shear wave velocity (Vs) is usually adopted to evaluate effect but the microscopic mechanism is unclear. The discrete element method (DEM), a promising tool for simulating the behaviors of cohesive and noncohesive materials, was used in this study to simulate Vs evolution and wave propagation path of sand reinforced by calcite precipitates. Two basic calcite precipitate forms are proposed for representing individual calcite precipitation (CaCO3-P) and calcite aggregation (CaCO3-C). Contact cementation between adjacent sand grain pairs was the primary association pattern for calcite precipitates at a low calcite content. At a higher calcite content, the preferential shear wave propagation pathway is the clusters cemented by CaCO3-C. With calcite content increasing from 0 to 9%, the coordination number and average contact force increased. Vs increased from 169.73 to 2132.64 m/s but had high variability due to the spatial distribution. The results suggest that the calibrated DEM model can elucidate the microscopic mechanisms and evaluate the enhancement effect of microorganism-reinforced soil. [ABSTRACT FROM AUTHOR]

Coral sand, which is an important filler resource in coastal areas, is continuously subjected to repeated waves or traffic loading. In this study, a series of oedometer tests are conducted on coral sand and silica sand under repeated loading, and the results are compared. The influence of the initial density and number and amplitude of repeated loading on the volumetric deformation, soil stiffness, and particle breakage are investigated. The results reveal that the volumetric deformation and particle breakage of coral sand mainly occur in the first loading stage and increase by increasing loading amplitude and reducing initial density. Compared to silica sand, the soil stiffness is lower and volumetric deformation is greater in coral sand during the initial loading stage. However, the opposite trend is observed for the subsequent loading. Finally, three power functions are proposed to predict the volumetric deformation and particle breakage of coral sand under repeated loading. [ABSTRACT FROM AUTHOR]

Understanding the ecological processes that affect species distribution patterns is fundamental to the conservation and restoration of rare and endangered species. Pinus kwangtungensis is an endemic and Class-II protected plant in China. However, environmental change and human disturbance result in habitat damage and population decline. In order to understand current situation of its population, spatial distribution pattern and habitat characteristics, and to guide the conservation and restoration of this species, we established a 20 hm² forest dynamics plot in the Nanling National Nature Reserve, Guangdong Province. All woody plants with diameter at breast height ≥1 cm were monitored, and multiple environmental factors, including soil and topography, were measured. We used a size-class analysis to predict population trends, the spatial point pattern analysis(L function)to reveal spatial distribution of individuals, and established a Zero-Inflated Poisson(ZIP)regression model to explore the important environmental factors that affect individual distribution. The results were as follows:(1)size-class distribution was “bell-shaped”, the number of small size-class individuals was low, indicating that population regeneration was limited. P. kwangtungensis preferred the slopes and ridges with high altitude and steep terrain, showing a strong habitat specialization.(2)Spatial point pattern analysis(L function)presented that spatial distribution was significantly aggregated compared with null models, which might cause by dispersal limitation and habitat heterogeneity.(3)The ZIP regression model showed that high soil ammonium nitrogen, available potassium and low organic matter content associated with the occurrence of P. kwangtungensis (from 0 to 1), and the abundance(from 1 to N)was positively correlated with altitude, species diversity, and mean DBH, but negatively correlated with tree height, ammonium nitrogen, total phosphorus, and total potassium. The results indicate that the unstable size-class structure and intraspecific competition caused by spatial aggregation will accelerate the decline of the population, we suggest that the habitats with low soil nutrients at high elevations should be conserved preferentially, and reduce anthropogenic disturbance to maintain the original habitats. [ABSTRACT FROM AUTHOR]

Numerous questions and problems on Earth and questions with respect to other planets arise from morphodynamic processes caused by sediment movements driven by flows of fluids, such as water, air and other gases. A sediment surface opposes the current with a resistance that is determined by its skin or grain roughness. As soon as sand waves, such as ripples and/or dunes, are formed, these bedforms cause a further resistance to the flow, the so-called form roughness. Dependent on the dimensions of the ripples and dunes, the form roughness can be much more pronounced than the skin roughness. The relevant literature provides a large number of solution approaches based on different basic ideas and different result quality. The aim of this paper is a comparative analysis of solution approaches from the literature. For this purpose, 14 approaches to bedform-related friction in the subaqueous case are evaluated using 637 measurements from laboratory and natural settings. We found that all approaches were significantly more accurate for ripples than for dunes. Since this was equally the case for all approaches tested, it is reasonable to assume that this is caused by measurement inaccuracies for dunes in the natural case rather than due to the approaches themselves. The approach of Engelund 1977 proved to be most accurate among all approaches investigated here. It is based on the Borda–Carnot formulation and an additional empirical term. An analytical derivation and justification is provided for this additional term. [ABSTRACT FROM AUTHOR]

High-frequency (HF) radar data, derived from a pair of newly developed radar stations in the Pearl River Estuary (PRE) of China, were validated through comparison with in situ surface buoys, ADCP measurements, and model simulations in this study. Since no in situ observations are available in the radar observing domain, a regional high-resolution ocean model covering the entire PRE and its adjacent seas was first established and validated with in situ measurements, and then the HF radar data quality was examined against the model simulations. The results show that mean flows and tidal ellipses derived from the in situ buoys and ADCP were in very good agreement with the model. The model–radar data comparison indicated that the radar obtained the best data quality within the central overlapping area between the two radar stations, with the errors increasing toward the coast and the open ocean. Near the coast, the radar data quality was affected by coastlines and islands that prevent HF radar from delivering high-quality information for determining surface currents. This is one of the major drawbacks of the HF radar technique. Toward the open ocean, where the wind is the only dominant forcing on the tidal currents, we found that the poor data quality was most likely contaminated by data inversion algorithms from the Shangchuan radar station. A hybrid machine-learning-based inversion algorithm including traditional electromagnetic analysis and physical oceanography factors is needed to develop and improve radar data quality. A new radar observing network with about 10 radar stations is developing in the PRE and its adjacent shelf, this work assesses the data quality of the existing radars and identifies the error sources, serving as the first step toward the full deployment of the entire radar network. [ABSTRACT FROM AUTHOR]

This article quantifies changes in primary dune morphology of the mesotidal Lower Columbia River (LCR), USA, through ~90 river kilometres of its fluvial‐tidal transition at low‐river stage. Measurements were derived from a multibeam echo sounder dataset that captured bedform dimensions within the thalweg (≥ 9 m depth; H/Hmax ≥ 0.7) of the LCR main channel. Measurements revealed two categories of dunes: (i) fine to medium sand 'fluvial‐tidal to tidal' (upstream‐oriented, simple, and two‐dimensional) low‐angle dunes (heights ≈ 0.3–0.8 m; wavelengths ≈ 10–25 m; mean lee‐angles ≈ 7°–11°), and (ii) medium to coarse sand 'fluvial' (downstream‐oriented, compound, and 2.5‐dimensional to three‐dimensional) low‐angle dunes (heights ≈ 1.5–3 m; wavelengths ≈ 60–110 m; mean lee‐angles ≈ 11°–18°). At low‐river stage, where H/Hmax ≥ 0.7, approximately 86% of the fluvial‐tidal transition is populated by 'fluvial' dunes, whilst ~ 14% possesses 'fluvial‐tidal to tidal' dunes that form in the downstream‐most reaches. Thus, throughout the majority of the deepest channel segments of the fluvial‐tidal transition, seaward‐oriented river and ebb‐tidal currents govern dune morphology, whilst strong bidirectional tidal‐current influence is restricted to the downstream most reaches of the transition zone. Two mechanisms are reasoned to explain dune low‐angle character: (1) high‐suspended sediment transport near peak tidal‐currents that lowers the leeside‐angles of 'fluvial‐tidal to tidal' dunes, and (2) superimposed bedforms that erode the crests, leesides, and stoss‐sides, of 'fluvial' dunes, which results in the reduction of leeside‐angles. Fluctuations in river discharge create a 'dynamic morphology reach' at depths where H/Hmax ≥ 0.7, which spans river kilometres 12–40 and displays the greatest variation in dune morphology. Similar channel reaches likely exist in fluvial‐tidal transitions with analogous physical characteristics as the LCR and may provide a distinct signature for the fluvial‐tidal transition zone. [ABSTRACT FROM AUTHOR]

Sand ridges are present in modern storm‐dominated and tide‐dominated shallow‐marine environments worldwide, but the number of published ancient examples is limited. The role of ocean currents in the formation of sand ridges is also poorly understood. This study investigated the lithofacies architecture of a lenticular sandstone body (ca 70 m thick and ca 30 km long) in the upper Mandano Formation (ca 0.6 Ma) on the Boso Peninsula, Japan, to establish criteria for identifying sand ridge deposits built by storm and ocean currents. The sandstone body is unconformably underlain by coastal and valley‐fill deposits and fines upward to outer‐shelf muddy deposits. It consists mainly of medium‐grained to very coarse‐grained sandstones and pebbly sandstones that are moderately to intensely bioturbated and are represented by three‐dimensional compound dune deposits. The body consists of six 10 to 20 m thick units (units 1 to 6 in ascending order), which are each defined by an erosional base and locally capped by storm‐induced fluid mud deposits. Each unit also contains low‐angle (ca 5°) large stratification inclined obliquely to palaeocurrents, indicating lateral accretion surfaces. Units 1 and 2 are characterized by south‐eastward migration (locally north‐westward), smaller dune deposits, storm‐induced sedimentary structures and cold‐water molluscs indicating a palaeowater depth of up to 50 m. The other units are represented by east/north‐eastward migration, larger dune deposits, warm‐water molluscs indicating a palaeowater depth of up to 200 m, and a general lack of storm‐induced sedimentary structures. Temporal changes in the migration directions and lithofacies features of the units indicate that sand ridge formation was initially controlled by storm‐induced currents that were subsequently replaced by the northward or north‐eastward intruding palaeo‐Kuroshio Current in response to the expansion of the shelf during an overall transgression. The initiation and development of the sand ridges may have been supported by the supply of clastic sediments eroded from the underlying coastal and valley‐fill deposits. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the effect of initial stress and heterogeneity on the propagation of torsional waves in dissipative medium. The problem consists of dry sand poroelastic half-space embedded between heterogeneous self-reinforced half-space and poroelastic medium. The frequency equation is derived in the framework of Biot's theory with some variants. Design/methodology/approach: Torsional wave propagation in dry sand poroelastic half-space embedded between self-reinforced half-space and poroelastic medium. All the constituents here are assumed to be dissipative, heterogeneous and initial stressed. Findings: Phase velocity and attenuation are computed against wavenumber for various values of self-reinforcement parameter, inhomogeneity parameter and initial stress. Particular cases are discussed in absence of dissipation. The numerical results are presented graphically. Originality/value: Initial stress and heterogeneity effects on torsional waves in dry sand half-space between reinforced half-space and poroelastic medium are investigated. The frequency equation is derived, and which intern gives the phase velocity and attenuation coefficient for various values of initial stress, self-reinforcement parameter and heterogeneity parameter. From the numerical results, it is clear that as wavenumber varies phase velocity and attenuation are periodic in nature for all the cases. Particular cases are discussed in absence of dissipation. This kind of analysis can be extended to any elastic solid by taking magnetic, thermo and piezoelectric effects into account. [ABSTRACT FROM AUTHOR]

Computing movable bed roughness plays an important role in the modeling of flood routing and bed deformation, and the magnitude of movable bed roughness is closely associated with complex bedform configurations that change with the sand wave motion. The motion of sand wave is dependent on the incoming flow and sediment conditions and channel boundary. After the operation of the Three Gorges Project, the flow and sediment regime changed remarkably in the Middle Yangtze River (MYR), followed by significant channel adjustments. A dramatic decrease in sediment concentration caused continuous channel degradation and significant variations in cross-sectional profiles of the MYR. These adjustments in the channel boundary influence the motion of sand wave, which can further affect the magnitude of movable bed roughness. A new formula for predicting the movable bed roughness coefficient is developed, which can be expressed by a power function of both Froude number and relative water depth. The proposed formula was first calibrated using 1266 datasets of measurements at five hydrometric stations in the MYR during 2001–2012. A back-calculation process shows that the roughness coefficients calculated by the proposed formula agree well with the observations, with the determination coefficient being equal to 0.88. The proposed formula was further verified using 651 datasets of measurements at these hydrometric stations during 2013–2017. Furthermore, four common roughness formulas selected from the literature were tested for comparison. The results indicate that the calculation accuracy of the proposed formula is significantly higher than that of the previous formulas, and the Manning roughness coefficients predicted by the proposed formula have the errors less than ±30% for 96% of the datasets. Therefore, the new bed roughness predictor proposed in this study can accurately calculate the roughness coefficients straightforwardly without iterative solution and graphical interpolation, and the parameters required in the roughness predictor are easily obtained from the hydrometric observations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study examines wind flow dynamics and downwind sand deposition behind engineered notches in a foredune system on a developed coast. Recent studies have examined the morphodynamics downwind of such notches, however, wind flow dynamics and sand deposition in the lee of such notches is not well understood, particularly in relation to artificial foredunes on developed coasts. Wind flow dynamics behind an excavated notch at St Kilda beach, Dunedin, New Zealand is measured using vertical arrays of ultrasonic anemometers. Field data is used to validate computational fluid dynamic flow simulations to examine flow dynamics behind a foredune section with multiple notches. Sand deposition behind the notches is measured using sand pot traps. Wind direction across the depositional lobe aligns with notch orientation and the normalized wind speed increases when the incident wind direction is >10° to the shoreline in a notch that orientates 67° to the shoreline. Wind speed in the swale downwind a notch decreases when the incident wind direction shifts from alongshore to onshore normal. Flow reversal occurs when the incident wind direction approaches onshore normal (>72° to the shoreline). Helicoidal flow appears to occur in the lee of the higher foredune section when the incident wind direction is 74° to the shoreline, while alongshore flow dominates in the lower section. Most sand deposition occurs within 5 m of the depositional lobe of the notch. The orientation of excavated notches should be less than 74° relative to the shoreline to prevent the occurrence of flow reversal in the swale, which might reduce the distance that sand can be transported inland from the notches when the incident wind direction is parallel to the notch axis. [ABSTRACT FROM AUTHOR]

In this paper, the linear stability of sand waves sheared by a turbulent flow is analyzed. The velocity distribution in the streamwise direction is considered to follow the logarithmic law. The modified pressure distribution owing to the streamline curvature induced by the sand waves is employed in the formulation. The pressure distribution is derived using the Boussinesq approximation for the variation of streamline curvature over the flow depth. The flow model is coupled with the sediment transport model to study the stability of sand waves. Both the modes of sediment transport as bedload and suspended load are considered. The linear stability analysis reveals the favorable region for the formation of dunes and antidunes on the plane formed by the Froude number and the dimensionless wavenumber. The region of instability increases with an increase in particle parameter, while it decreases with an increase in relative roughness. The analysis reveals that the sand waves form beyond a limiting Froude number corresponding to the threshold Shields number. The theoretical results compare well with the available experimental data. [ABSTRACT FROM AUTHOR]

Subaqueous sand waves have been observed where nonlinear internal waves (NLIWs) shoal on continental margins. To investigate their generation mechanisms, we propagated periodic NLIWs of depression to shoal upon a sloping bed in a laboratory flume. Following fission of the incident waves, ripple-type bedforms were observed between the point of incipient suspension and interaction point (where the quiescent pycnocline intersects the sediment bed). The largest ripples were centered on the bolus birth point, where the NLIWs of elevation, generated by fission, transform into boluses and maximum near-bed velocities occurred. The ripple height and wavelength were consistent with fluvial scaling. In two experiments, where bedload transport was not predicted, the observations showed resuspension to influence ripple generation. Net upslope sediment movement was observed beyond the turning point. • Ripple bedforms were generated beneath shoaling nonlinear waves of depression in the laboratory • Ripples formed between the point of incipient suspension and the pycnocline-bed intersection • The largest ripples were at the bolus birth point, where waves of elevation transformed to boluses • The ripple height and wavelength were consistent with fluvial scaling [ABSTRACT FROM AUTHOR]

Plate anchors are being increasingly employed to establish mooring systems for offshore floating facilities owing to their notable efficiency and cost-effectiveness. The majority of prior studies have concentrated on plate anchors, examining the vertical to horizontal orientations, particularly when embedded in single layer clay or sand. However, it is common to encounter multiple layers of soil with varying characteristics in practical engineering, leading to inaccurate estimation of pullout capacity when based solely on the properties of a single soil layer. This paper reports pullout behaviours of strip plate anchors in clay overlying sand by adopting two dimensional finite element analysis. To simulate the hardening and subsequent softening behaviour of medium to dense sand, a modified Mohr-Coulomb model is considered. The current Finite Element (FE) results are in good agreement when compared with both previous FE simulations and physical model test data. Then, the soil flow mechanisms (e.g. the accumulated plastic shear strain, the friction angle) surrounding the anchor during pullout out are revealed. Based on a series of FE results, a calculation framework considering the effect of thickness of clay layer is designed to predict the pullout behaviour of plate anchors in clay overlying sand. • The pullout behaviour of strip anchors with different inclinations in clay overlying sand is investigated by 2D FE analysis. • To simulate the hardening and softening behaviour of medium to dense sand, a modified Mohr-Coulomb model is considered. • A simple calculation framework incorporated the effect of thickness of clay layer is proposed. [ABSTRACT FROM AUTHOR]

In this paper, based on the centrifuge test of liquefied soil-pile foundation system, a numerical model of liquefied soil-pile foundation-structure system is modelled by using OpenSees platform. In the simulation model, the friction effect between liquefied ground and low pile cap is considered, and the method of establishing virtual nodes is used to deal with the non-linear contact between liquefiable soil and low pile cap. The rationality and effectiveness of the numerical simulation method adopted in this paper has been verified and evaluated by comparing with the results of centrifuge experiments. A typical liquefaction soil-pile integrated finite element model is modelled using validated numerical simulation methods. The law of seismic response of the pile foundation system with different embedding depths of pile cap, different contact modes between the pile cap and saturated sand, and the thickness of the overlying saturated loose sand layer are discussed. The results show that the pile cap and pile foundation in the high pile cap system show higher seismic response characteristics than the other three low pile cap system conditions; Under the condition of different contact modes between the pile cap and the surrounding saturated sand, the peak bending moment and residual displacement of the pile foundation calculated by the bond contact are larger than calculated by the friction contact, and the deformation of pile is more significant. By comparing the working conditions of different thicknesses of overlying saturated loose sand layer, it is found that the degree of liquefaction in shallow soils is less affected by thickness of the saturated loose sand. As the thickness of saturated loose sand layer increases, the peak bending moment and residual displacement at the top of the pile also gradually increase. The change of peak bending moment at the soil interface is more obvious. • A numerical model of liquefied soil-pile group-superstructure system is established. • The friction effect between liquefied soil and low pile cap is considered. • The non-linear contact between soil and pile cap is simulated by establishing virtual nodes. • The effects on seismic response of the contact of liquefaction soil-pile cap and are discussed. [ABSTRACT FROM AUTHOR]

• A consolidated DSL and a loose DSL occur in sandy loess and fine sand with a thickness of 3.0–3.5 cm and 1.5–2.0 cm, respectively. • The hydrochemical facies in sand media evolved from HCO 3 -Ca type to SO 4 ·Cl-Na type along the migration pathway of liquid water. • The minerals dissolved at a depth of 5–55 cm along the pathway of liquid water and deposited at surface soil. • The accumulation of dissolved solutes promotes DSL development and increases DSL thickness. • In sandy loess there is a difference between the experimental and predicted evaporation rates by Fick's law due to salt deposition. Knowledge of the parameterization of the dry surface layer (DSL) is essential for evaluating near-surface water flow and water balance in arid and semi-arid areas. Existing studies have parameterized DSL thickness and vapor flow as functions of the soil moisture content (SMC) in the surface layer to predict soil evaporation. However, hydrochemical processes related to DSL development have been ignored, including changes in hydrochemistry, the underlying hydrochemical mechanism, and the role of dissolved substances in the DSL development. Herein, we performed a series of soil evaporation experiments for 260 days and explored the factors influencing DSL development (e.g., soil texture, atmospheric temperature, SMC, solutes). Evaporation experiments were performed using silty loess, sandy loess, and fine sand with a 60-cm water table. Results showed that the cumulative evaporation of silty loess, sandy loess, and fine sand over the experimental period were 1,391.52, 460.10, and 185.53 mm, respectively, which determined by the maximum height of liquid flow continuity. The content of total dissolved solids (TDS) and major ions at the surface soil were significantly higher than the values at deep depths of 5‒55 cm, which largely depend on evaporative water loss. Evolutionary trends of chemical facies in sand media along the liquid water migration were from HCO 3 -Ca type to SO 4 ·Cl-Na type. This was attributed to mineral dissolution at a depth of 5–55 cm and their transport with liquid water, resulting in the precipitation of salt crystals at the surface soil. Furthermore, a consolidated DSL with a thickness of 3.0–3.5 cm in the sandy loess and a loose DSL with a thickness of 1.5–2.0 cm in fine sand were observed at the end of the experiments. The accumulation of solutes at the surface leads to a reduction in effective porosity and the aggregation of soil particles during continuous drying, which facilitates the consolidation of DSL in sandy loess. This overestimated the DSL thickness, resulting in a difference between the experimental and predicted evaporation rates by Fick's law. Overall, these results highlight the limitations of considering DSL thickness as a function of SMC only, providing new insights into hydrochemical processes and dissolved solutes involving DSL parameterization during continuous soil drying. [ABSTRACT FROM AUTHOR]

The overall morphological characteristics and shallow architecture of a tidal sand ridge were examined for the first time in the Beibu Gulf, northwestern South China Sea. The linear sand ridge is characterized by a unique binary feature in terms of its shape, constituents, architecture, and behavior. In the northern part, the crestline has rotated anticlockwise to the principal tidal currents, the sediment is coarse, and large active sand waves occur on the surface. In the southern part, the crestline is parallel to the principal tidal currents, the sediment is fine, and no large bedforms have developed on the crest. The sand ridge has shrunk in the northern part and elongated at its southern end in recent decades, leading to a southward or southeasterly movement. The upper strata of the northern part mainly comprise inclined bedding, whereas parallel bedding prevails in the southern part. The bedding implies historically dominant transport directions in different sand ridge parts and suggests that flow modification occurred during ridge evolution. The inclined bedding in the lower strata of the northern part dips to the south or southeast, indicating the existence of unidirectionally moving sand waves. This is unusual for a growing sand ridge where convergent sand transport should have already occurred. The present sand ridge is interpreted as a source from the joining of a sand wave assemblage and an adjoining nascent sand ridge, which has experienced stages of connection, accretion, and migration. The transformation of a sand wave assemblage to the northern part is attributed to the hydraulic change from a unidirectional residual flow regime over sand waves to a bidirectional residual flow regime. This flow regime change was not related to sea level changes but benefited from a new sand body that was produced by sand waves merging into the original nascent ridge. • The first study on sand ridge morphology and evolution in the South China Sea • The sand ridge has a unique binary feature on its north and south parts. • The sand ridge shrank in its north part and elongated in its south end. • The stacked inclined beddings suggest the flow regime change once occurred. • Sand waves can grow into a sand ridge under modern tidal conditions. [ABSTRACT FROM AUTHOR]

The ternary nature of soil texture, defined by its proportions of clay, silt, and sand, makes it challenging to predict through linear regression models from other soil attributes and auxiliary variables. The most promising results in this field have been recently achieved by Machine Learning methods which are able to derive non-linear, non-site-specific models to predict soil texture. In this paper we present a method of constructing a pair of Deep Neural Network (DNN) algorithms that can predict clay and sand soil contents from Airborne Gamma Ray Spectrometry data of K and Th ground abundances. We tested the algorithm's hyperparameters through various configurations to optimize the DNNs' performance, effectively avoiding underfitting and overfitting of the models. This led to the creation of a high-resolution 20 m × 20 m soil texture map from dense AGRS data, significantly refining the previous map's granularity. The application of the obtained DNN models to unseen sites can be supported by future training on additional textural classes. • Airborne radiometric data abundantly feed DNNs for soil texture predictions. • DNNs allow to overcome linear constraints for relations between K and clay content. • We optimized DNN hyperparameters in terms of accuracy and computational time. • We validated the DNNs for the prediction of soil texture from radiometric data. • We obtained a 20 m × 20 m soil texture map of the Mezzano Lowland (Italy). [ABSTRACT FROM AUTHOR]