Consolidated Sediments Research Articles

Influence of tidal asymmetry on local scour near the offshore platform

An in-situ mooring measurement was conducted using a profiling sound of navigation and ranging (SONAR) system to reveal the influence of tidal asymmetry on the local scour near an artificial offshore platform, Southwest Offshore Windfarm Complex, Korea. During the mooring period, the flood tide was significantly dominated by positive tidal duration asymmetry and skewness. The lengths of scour hole were 9.8m and 5.1m along the flood and ebb directions, respectively. Flood-dominated currents intensified the horseshoe vortex, resulting in an approximately 10% deeper scour hole on the flood face than the ebb face. The periodic occurrence of bidirectional currents generated vortices that facilitated the mixing and redistribution of seabed sediments, forming a gentle slope within the scour hole. The average slope angles ranged from 14° to 16° on the flood face and 6° to 8° on the ebb face. Despite the strong influence of local scour, variations in scour depth (Ds) consistently remained around −2.15m, suggesting the exposure of the underlying consolidated sediment layer. During the intermediate period from spring to neap tide, the Ds on the lower slope of scour hole increased by 0.12m, while it decreased by 0.11m from neap to spring tide, suggesting that the net Ds gradually approached zero over the tidal cycle. These findings underscore the importance of understanding tidal impacts on the local scour morphology to enhance the stability and design of offshore wind turbine foundations.

Subsidence detection in southwest Guangdong–Hong Kong–Macao Greater Bay Area using InSAR with GNSS corrected tropospheric delays

As one of the biggest bay areas in the world, the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is subject to subsidence due to thick sedimentary. In this study, we combine 154 Sentinel-1 A/B images acquired between 2017 and 2022 with Global Navigation Satellite System (GNSS) observations to characterize the subsidence in southwestern GBA. Specifically, we use GNSS to establish the Iterative Tropospheric Decomposition (ITD) model for zenith tropospheric delay correction and the model is improved using random forest algorithm to alleviate errors caused by unreasonable interpolation methods, showing better performance than Generic Tropospheric Correction Online Service (GACOS) product. At GNSS stations with complete data, the improved model utilizing GNSS data achieves a Pearson correlation coefficient of 0.659, in contrast to a coefficient of only 0.434 using GACOS. The maximum subsidence rate detected is up to 11.32 cm/year in Zhuhai, accompanied by noticeable seasonal variations correlated with precipitation. In addition to the sediment consolidation and compaction, human activities such as agriculture, construction, and land reclamation further exacerbate subsidence in the GBA. This study enhances the utility of GNSS in improving tropospheric delay correction performance and providing more accurate observations of subsidence.

Aerobic and anaerobic mineralisation of sediment organic matter in the tidal River Elbe

PurposeThe share of microbially degradable sediment organic matter (SOM) and the degradation rate depend, among others, on the intrinsic properties of SOM as well as on the type and concentration of terminal electron acceptors (TEA). Next to its role as TEA, molecular oxygen enhances SOM decay by oxygenase-mediated breakdown of complex organic molecules. This research investigated long-term SOM decay (> 250 days) under aerobic and anaerobic conditions to (1) provide a basis for sediment carbon flux estimates from the River Elbe estuary and (2) assess the potential for carbon burial in relation to redox conditions and dredging interventions.MethodsLong-term aerobic and anaerobic SOM decay in fluid mud, pre-consolidated and consolidated sediment layers was investigated over three years along a transect of ca. 20 km through the Port of Hamburg, starting at the first hydrodynamically determined hotspot of sedimentation after the weir in Geesthacht. Absolute differences between aerobic and anaerobic cumulative carbon mineralization were calculated, as well as their ratio. Findings were correlated to a suite of solids and pore water properties.ResultsSOM decay followed first order multi-phase exponential decay kinetics. The ratio between C release under aerobic and anaerobic conditions ranged around 4 in the short-term, converging to a value of 2 in the long term. Strong gradients in absolute C release along the upstream–downstream transect did not reflect in a corresponding gradient of the aerobic-anaerobic ratio. C release was most strongly correlated to the water-soluble organic matter, in particular humic acids. Contact of anaerobically stabilized sediment with the oxygenated water phase induced significant release of carbon.ConclusionSOM degradability in the study area exhibited strong spatial gradients in relation to the organic matter source gradient but was mainly limited by the high extent of organic matter stabilization. Under these conditions, molecular oxygen as TEA provides little thermodynamic advantage. Carbon-sensitive sediment management, considering SOM reactivity patterns in stratified depositional areas, is a powerful strategy to reduce environmental impacts of dredging measures.

Resolved Simulation for the Prediction of Classification in Decanter Centrifuges

Solid–liquid separation plays a decisive role in various industrial applications particularly in the treatment and purification of suspensions. Solid bowl centrifuges, such as the decanter centrifuge, are commonly employed in these processes as they operate continuously and enable high throughputs with short processing times. However, predicting the separation performance of solid bowl centrifuges proves to be challenging due to dynamic phenomena within the apparatus, such as particle settling, sediment build-up, consolidation and sediment transport. In practice, design considerations and the dimensioning of the apparatus rely on analytical models and the manufacturer’s expertise. Computational Fluid Dynamics (CFD) offers a way to deepen our understanding of these devices by allowing detailed examination of flow phenomena and their influence on the separation processes. This study utilizes the open-source software OpenFOAM to simulate multiphase flow in a laboratory-scale decanter centrifuge, solving individual transport equations for each particle size class. The basis is the characterization of the material through targeted laboratory experiments to derive material functions that describe the hindered settling and the sediment consolidation. Furthermore, experiments on a laboratory decanter served as validation. The results demonstrate the solver’s capability to replicate clarification and classification within the apparatus. Furthermore, the solver supports the definition of geometries tailored to specific separation tasks. This research demonstrates the potential of CFD for a better understanding of complex centrifuge processes and for optimizing their design to improve performance.

Strengthening effect of nano-SiO2 on microbial induced carbonate precipitation (MICP) solidified sediment: Macro- and micro-analysis

Sediment consolidation via microbial induced carbonate precipitation (MICP) aligns with the principles of sustainable development in resource utilization. This study aimed to explore the solidification potential and mechanisms of integrating nano-SiO2 as a supplementary material in MICP-treated sediment under various conditions, employing permeability, unconfined compression strength (UCS), X-ray diffraction (XRD), scanning electron microscopic (SEM), and adsorption techniques. The results demonstrated a reduction in permeability and an increase in UCS in sediment treated with ≤0.1% nano-SiO2-assisted MICP. The factors contributing to solidification potential followed a specific order: Ca2+ concentration > OD600> nano-SiO2 dosage > biochemical reaction time. When combined with MICP, nano-SiO2 at concentrations below 0.05% promoted the transformation from aragonite to calcite. Furthermore, nano-SiO2 triggered the creation of early-stage C-S-H gels, aged viscous-like silicate gels, and spurrite [Ca5(SiO4)2CO3] to cement the sediment. Additionally, the micro filling of nano-SiO2, minerals, and gel phases significantly bolstered the sediment's strength. Finally, the impressive adsorption capacity of nano-SiO2 for Ca2+ (qm = 0.26 mol/g) alleviated the toxicity of excessive Ca2+ on urease activity, thereby facilitating urea hydrolysis and CaCO3 nucleation. The synergistic effect of nano-SiO2 with MICP, involving cementation, filling, nucleation, and mitigation of Ca2+ toxicity, provides valuable insights for the sediment reinforcement applications.

Benthic sediment disturbances by episodic human-controlled discharge in an altered estuary

In the Geum River, a representative altered estuary, in-situ mooring and erosion experiments were conducted to reveal the effects of human-controlled discharge on benthic sediment disturbances. The strong discharge through the estuarine dam increased the current velocities within the benthic boundary layer (BBL) up to 79% and 153% during spring and neap tides, respectively. During the discharge period, the suspended sediment concentration in BBL was five times higher than that during the non-discharge period. During the flood phase, a critical shear stress for erosion (τce) was in the range of 0.1278 to 0.1391 Pa. Immediately after the ebb phase with strong discharge, τce increased to 0.1848 Pa, and the erosion rate (E) decreased from 33.73 to 14.81 mg m−2 s−1. The repetition of human-controlled discharge removed the erodible sediments within BBL, exposing the underlying consolidated sediment bed with low E and high τce. The results suggest that an altered estuary is vulnerable to benthic sediment erosion under combined natural and anthropogenic forcings.

Suppression of phosphorus release and acceleration of sediment consolidation via exposure to sunlight and air (sunbathing)

Suppression of phosphorus release and acceleration of sediment consolidation via exposure to sunlight and air (sunbathing)

The Subglacial Lake That Wasn't There: Improved Interpretation From Seismic Data Reveals a Sediment Bedform at Isunnguata Sermia

AbstractRadio Echo Sounding (RES) surveys conducted in May 2010 and April 2011 revealed a 2 km2 flat area with increased bed reflectivity at the base of Isunnguata Sermia at the western margin of the Greenland Ice Sheet. This flat reflector was located within a localized subglacial hydraulic potential (hydropotential) minimum, as part of a complex and elongated trough system. By analogy with comparable features in Antarctica, the initial interpretation of such a feature was a potential subglacial lake. In September 2013 a co‐located seismic survey revealed a 1,750 m by 540 and 37 m thick stratified lens‐shaped bedform at the base of a subglacial trough system. Amplitude Versus Angle (AVA) analysis yields a derived reflection coefficient R = 0.09 ± 0.14 indicative of consolidated sediments possibly overlain by dilatant till. The bed and flank on the northern side of the trough consist of unconsolidated, possibly water‐bearing sediments with R = −0.10 ± 0.08, whereas on the southern side it consists of more consolidated material. We interpret the trough as a key component of the wider subglacial drainage network, for which the sediments on its northern side act as a localized water‐storage reservoir. Given the observation of seasonally forming and rapidly draining supraglacial meltwater lakes in this area, we interpret the lens‐shaped bedform as deposited by episodically ponding meltwater within the subglacial trough system. Our results highlight the importance of transient subglacial hydrological and sedimentological processes such as drainage events for the interaction of ice sheets and their substrates, to understand ice dynamics in a warming climate.

Submarine canyon morphology along the Chilean marine forearc (19°S–45°S)

Convergent margins host more than half of all global submarine canyons. In this environment, the lack of cognition of the canyon morphology variation and their controls in two different types of marine forearcs (erosive and accretionary) remains exists. Based on shipborne bathymetric maps, we systematically analyze width, incision depth and slope gradient of 17 submarine canyons along the Chilean marine forearc. We divide the study area into an erosive northern area, a transitional central area, and an accretionary southern area based on trench sediment cover and in line with previous tectonic interpretations. In the northern and central areas, limited sediment supply and little erosion from infrequent turbidity currents form narrow and shallow canyons that arrive at the toe of margin. Subduction erosion contributes to a simple and regular slope morphology where regional subsidence and trench-parallel faulting activities lead to vertical crustal movement and a steep thalweg of canyons' lower reach. In contrast, frequent canyon flushing/filling turbidity currents and slope failures on the canyon walls result in a wider range of canyon width and incision depth in the south. Here, the formation of an accretionary prism generates fold and thrust ridges at the seafloor that reduce the slope gradient of canyons' lower reach. Canyon morphology within the prism region has a larger range than the non-prism (backstop) region due to the higher erodibility of the less consolidated sediment. In addition, convex-up step-shaped bedforms develop along 14 canyon thalwegs, also suggesting regional uplift/subsidence and normal faulting in the north and central region but folding and thrust faulting in the south. This work not only reveals the difference of canyon morphology on active marine forearcs but also may help to understand controls on submarine canyon morphologies along the Chilean margin as well as in other convergent margins.

Capping fiberbank sediments to reduce persistent organic pollutants (POPs) fluxes: A large-scale laboratory column experiment

Deposits of contaminated wood fiber waste (fiberbanks), originating from sawmills and pulp and paper industries, have been found in the aquatic environment in boreal countries. In-situ isolation capping has been proposed as a remediation solution because it has the potential to prevent dispersal of persistent organic pollutants (POPs) from this type of sediment. However, knowledge about the performance of such caps when placed on very soft (unconsolidated), gaseous organic rich sediment is scarce. We investigated the effectiveness of conventional in-situ capping to limit POPs fluxes to the water column from contaminated fibrous sediments that produce gas. A controlled, large-scale laboratory column (40 cm diameter, 2 m height) experiment was performed over 8 months to study changes in sediment-to-water fluxes of POPs and particle resuspension before and after capping the sediment with crushed stones (≥4 mm grain size). Two different cap thicknesses were tested (20 and 45 cm) on two types of fiberbank sediment with different fiber type composition. Results showed that capping fiberbank sediment with a 45 cm gravel cap reduced the sediment-to-water flux by 91–95% for p,p’-DDD, o,p’-DDD, by 39–82% for CB-101, CB-118, CB-138, CB-153, CB-180 and by 12–18% for HCB, whereas for less hydrophobic PCBs, capping was largely ineffective (i.e. CB-28 and CB-52). Although cap application caused particle resuspension, the long-term effect of the cap was reduced particle resuspension. On the other hand, substantial sediment consolidation released large volumes of contaminated pore water into the overlying water body. Importantly, both sediment types produced large amount of gas, observed as gas voids forming inside the sediment and gas ebullition events, which increased pore water advection and affected the structural integrity of the cap. This may limit the practical applicability of this method on fiberbank sediments.

Spatial variations in the consolidation of sediments in the Neogene Miyazaki forearc basin, Southwest Japan

The Neogene Miyazaki Group comprises forearc basin sediments exposed onland in South Kyushu in Southwest Japan, and is characterized by significant spatial variations in consolidation despite the minor differences in depositional ages. The Miyazaki Group is divided into three lithofacies (the Aoshima, Miyazaki, and Tsuma facies) from south to north. To evaluate the factors controlling lithification in the basin, the physical properties of the sedimentary rocks and the calcareous nannofossil biostratigraphy were investigated. The upper parts of the Aoshima and Miyazaki facies and the lower part of the Tsuma Facies were deposited at the same time (5–6 Ma), and have minor differences in maximum paleo-temperatures (97–116, 85–99, and 80–94 °C, respectively), but major differences in porosity (15.9%, 25.5%–26.9%, and 26.1%–31.6%) and consolidation yield stress (38.2, 13.8–16.2, and 13.6–15.5 MPa). These findings indicate that the porosity reduction associated with consolidation is a more important control on the lithification than the depositional age and maximum temperature. There is a large difference in maximum burial depth between the Aoshima (>3500 m) and Miyazaki facies (<1600 m). It represents variations in sedimentary depositional environments in the Miyazaki Group: the Aoshima Facies were deposited in the deep-marine depocenter and deeply buried, whereas the Miyazaki and Tsuma facies were in the shallower marine facies and shallowly buried. After the deposition, only the southern part of the Miyazaki forearc basin was largely uplifted, making distribution of the highly consolidated sedimentary rocks there. The large amount of uplift in the Aoshima Facies was apparently due to the subduction of the Kyushu–Palau Ridge beneath the forearc basin.

The Weight of New York City: Possible Contributions to Subsidence From Anthropogenic Sources

AbstractNew York City faces accelerating inundation risk from sea level rise, subsidence, and increasing storm intensity from natural and anthropogenic causes. Here we calculate a previously unquantified contribution to subsidence from the cumulative mass and downward pressure exerted by the built environment of the city. We enforce that load distribution in a multiphysics finite element model to calculate expected subsidence. Complex surface geology requires multiple rheological soil models to be applied; clay rich soils and artificial fill are calculated to have the highest post‐construction subsidence as compared with more elastic soils. Minimum and maximum calculated building subsidence ranges from 0 to 600 mm depending on soil/rock physical parameters and foundation modes. We compare modeled subsidence and surface geology to observed subsidence rates from satellite data (Interferometric Synthetic Aperture Radar and Global Positioning System). The comparison is complicated because the urban load has accumulated across a much longer period than measured subsidence rates, and there are multiple causes of subsidence. Geodetic measurements show a mean subsidence rate of 1–2 mm/year across the city that is consistent with regional post‐glacial deformation, though we find some areas of significantly greater subsidence rates. Some of this deformation is consistent with internal consolidation of artificial fill and other soft sediment that may be exacerbated by recent building loads, though there are many possible causes. New York is emblematic of growing coastal cities all over the world that are observed to be subsiding (Wu et al., 2022, https://doi.org/10.1029/2022GL098477), meaning there is a shared global challenge of mitigation against a growing inundation hazard.

TAPHONOMIC SIGNATURES IN DEAD SHELLS OF THE INVASIVE GASTROPOD RAPANA VENOSA (VALENCIENNES, 1846) AFTER TWO DECADES IN THE RÍO DE LA PLATA, URUGUAY

ABSTRACT Rapana venosa (Valenciennes, 1846) is an invasive gastropod, the arrival of which in the Río de La Plata estuary 22 years ago is well-documented. Rapana venosa shells were collected during two sampling events from four beaches with different substrate types and wave energy regimes to compare the taphonomic attributes under different environmental conditions. We analyzed the samples by comparing frequencies of taphonomic attributes. Our results show that intermediate-reflective beaches with rocky substrates were dominated by intermediate- to highly fragmented specimens, with high corrasion, intermediate to high bioerosion, low bioencrustation, and medium to large sizes. In contrast, intermediate-dissipative beaches with sandy substrate, mobile stones, and occasional consolidated sediments were dominated by less fragmented shells, high to intermediate corrasion, scarcer bioerosion, low bioencrustation, and small- to medium-sized specimens. Results suggest that significant taphonomic differences arise within two decades under natural conditions. These findings imply that paleoenvironmental signals derived from the taphonomic attributes of fossil assemblages emerge much faster than the potential duration of time averaging of shelly fossils in shallow marine settings.

High-throughput micro-CT scanning and deep learning segmentation workflow for analyses of shelly invertebrates and their fossils: Examples from marine Bivalvia

The largest source of empirical data on the history of life largely derives from the marine invertebrates. Their rich fossil record is an important testing ground for macroecological and macroevolutionary theory, but much of this historical biodiversity remains locked away in consolidated sediments. Manually preparing invertebrate fossils out of their matrix can require weeks to months of careful excavation and cannot guarantee the recovery of important features on specimens. Micro-CT is greatly improving our access to the morphologies of these fossils, but it remains difficult to digitally separate specimens from sediments of similar compositions, e.g., calcareous shells in a carbonate rich matrix. Here we provide a workflow for using deep learning—a subset of machine learning based on artificial neural networks—to augment the segmentation of these difficult fossils. We also provide a guide for bulk scanning fossil and Recent shells, with sizes ranging from 1 mm to 20 cm, enabling the rapid acquisition of large-scale 3D datasets for macroevolutionary and macroecological analyses (300–500 shells in 8 hours of scanning). We then illustrate how these approaches have been used to access new dimensions of morphology, allowing rigorous statistical testing of spatial and temporal patterns in morphological evolution, which open novel research directions in the history of life.

Theoretical analysis for thermal consolidation of marine sediments with depth variability subjected to time-dependent loading and heating

Because the spatial distribution of energy is restricted, many energies geotechnics would build on marine sediments and the resulting thermal consolidation would pose an inevitable threat to the safety and stability of the project. In this study, a new governing equation for thermal consolidation of saturated marine sediments is proposed, by considering the depth variability of the marine sediment layer and the time-dependent external loading and temperature. The corresponding one-dimensional (1D) analytical solution for thermal consolidation of saturated marine sediments is derived. The average degree of consolidation (Ua) and the normalized excess pore water pressure (u/u0) in the saturated marine sediment layer at different depths and time durations are calculated and compared with the typical loading case. The results show that the loading rate of the external force only affects the amplitude of the excess pore water pressure u and does not affect the proportion of u with depth; the depth variability of bulk modulus has a greater effect on the distribution of Ua relative to the depth variability of permeability; the depth variability of permeability has a greater effect on the distribution of u/u0 with depth relative to the depth variability of bulk modulus when Ua = 50%; the assumption of instant thermal loading will lead to an over-assessment of Ua and u/u0. This study provides useful insights for energy geotechnical engineering design and practice.

Anthropic Influence and Heritage Value of the Quaternary Deposits of Rio de Janeiro, Brazil

This study discusses the cause of local lithification in sediments from quaternary beach ridges of Paraíba do Sul Deltaic Complex (Rio de Janeiro, Brazil) and its application to the concept of geological heritage. These beach ridges were excavated to construct the Campos - Macaé Canal, opened in the 19th century predominantly by slave labor. A detailed sedimentological, mineralogical and petrological study was performed. The consolidated material consists to fine-grained sandstone with incipient parallel lamination. Kaolinite associated with iron oxides/hydroxides is organized in thin coatings, sometimes forming meniscus and bridges. The heavy mineral assembly of the sandstone is similar to those found in the beach ridges friable samples. The sandstone granulometry increases from east to west along the canal margins and the same pattern is observed in the adjacent beach ridges. We suggest that pedogenic processes acted intensively on Canal margins after its opening, causing mechanical infiltration and translocation of clay minerals, promoting differentiated consolidation of sediments only in that part that was deepened during the excavation. The anthropic action altered the local physiography by exposing the sediments of beach ridges. Therefore, this sandstone should be considered a geological heritage due to its unique occurrence, touristic, historical, scientific and educational value.

AVA inversion for novel fluid indicator considering consolidation parameter

Abstract Geofluid identification from seismic data are crucial for understanding reservoir characteristics. However, fluid indicators based on elastic parameter combinations show strong ambiguity in terms of geofluid identification. Although the effective pore-fluid bulk modulus proves to be the superior fluid indicator in geofluid discrimination, it is limited to empirical models such as the critical porosity model. The consolidation parameter model can evaluate the consolidation and compaction of sediments and is widely used due to its better applicability. Therefore, a novel fluid indicator considering consolidation parameter is proposed and a boundary-constrained inversion strategy for geofluid identification is developed. First, the novel fluid indicator is defined based on the poroelasticity theory. Then, the linearized AVA (amplitude variation with angle) approximation equation related to the new fluid indicator is derived to directly link seismic data and properties of pore-filling materials. The model analysis verifies the accuracy of the derived approximation equation at moderate incident angles, which can be used for parameter prediction by pre-stack seismic inversion. Furthermore, the contribution of each attribute of the novel equation to the reflectivity is analyzed to validate the feasibility of new fluid indicator inversion. Finally, a boundary-constrained AVA pre-stack inversion method is presented to enhance the robustness of the inversion results of the model parameter. The reliability of the improved method is proved by accurate inversion results of synthetic seismic records. After determining the consolidation parameter using well-log data combined with BGT (Biot–Gassmann Theory), the field data further demonstrated that the proposed approach is accurate and effective.

Centrifuge and numerical modeling of the impact of sediment consolidation induced by capping on contaminant transportation

Centrifuge and numerical modeling of the impact of sediment consolidation induced by capping on contaminant transportation

A floc structure perspective on sediment consolidation in thickened tailings

Based on X-ray computed tomography measurements of aggregate macro-structure and compressive dewatering tests, this paper demonstrates that aggregate breakage and structural re-organization during mixing in the thickening process can account for some of the experimentally measured changes in solids volume fraction that have been until now attributed to aggregate densification. This paper highlights the lack of information about the micro-scale mechanisms of flocculated sediment consolidation and suggests several experimental and theoretical experiments that could be conducted to improve the situation.

Fast InSAR Time-Series Analysis Method in a Full-Resolution SAR Coordinate System: A Case Study of the Yellow River Delta

Ground deformation is a major determinant of delta sustainability. Sentinel-1 Terrain Observation by Progressive Scans (TOPS) data are widely used in interferometric synthetic aperture radar (InSAR) applications to monitor ground subsidence. Due to the unparalleled mapping coverage and considerable data volume requirements, high-performance computing resources including graphics processing units (GPUs) are employed in state-of-the-art methodologies. This paper presents a fast InSAR time-series processing approach targeting Sentinel-1 TOPS images to process massive data with higher efficiency and resolution. We employed a GPU-assisted InSAR processing method to accelerate data processing. Statistically homogeneous pixel selection (SHPS) filtering was used to reduce noise and detect features in scenes with minimal image resolution loss. Compared to the commonly used InSAR processing software, the proposed method significantly improved the Sentinel-1 TOPS data processing efficiency. The feasibility of the method was investigated by mapping the surface deformation over the Yellow River Delta using SAR datasets acquired between January 2021 and February 2022. The findings indicate that several events of significant subsidence have occurred in the study area. Combined with the geological environment, underground brine and hydrocarbon extraction as well as sediment consolidation and compaction contribute to land subsidence in the Yellow River Delta.