Search Results (300)

The Hechangzhou Anabranching Reach is a typical tidal anabranching segment of the Yangtze River with intense riverbed evolution driven by altered water-sediment regimes and channel regulation. Submerged dikes stabilize river regimes and navigation yet trigger differential local clear-water scour; most prior studies only adopt short-term bathymetric data and lack long-term quantitative analysis across diverse hydrological scenarios, so the synergistic geomorphic mechanism under the control of the submerged dike group remains unclear. This study integrates the 2002–2025 flow division ratio series and multi-period bathymetric data from 2018 to 2026 to quantify spatiotemporal deep-channel adjustments, scour-deposition patterns and cross-sectional deformation of the two anabranches, and evaluate morphological effects of river training structures and relevant potential scour risks. The submerged dike group regulates diversion patterns and keeps the left anabranch’s flow division ratio below 70%. The right anabranch deep channel undergoes persistent vertical incision and reverses its historical deposition trend, while the left anabranch features spatially uneven scour: intense scour zones migrate within the SD1–SD2 reach, and persistent landward erosion occurs between SD2 and SD3. The reach’s polarized evolution of intensified scour and attenuated deposition arises from the joint control of the submerged dike group, bank protection and reduced basin sediment supply. This study reveals the spatially differentiated riverbed evolution driven by engineering-induced hydrodynamic redistribution, offering scientific support for refined waterway management and scour prevention in analogous tidal anabranching rivers. Full article

Fluvial terraces represent important geomorphological archives for reconstructing the effects of climatic fluctuations, tectonic activity, and base-level changes during Quaternary times. This study investigates the geomorphological and stratigraphic evolution of the Bradano, Basento, and Salandrella River systems within the Bradanic Foredeep of southern Italy, by means of field observations, geomorphological mapping, aerial-photo interpretation, and GIS analyses. Four relative morphostratigrafic orders of Pleistocene fluvial terraces (T₁–T₄) have been identified and correlated across the three drainage basins. No absolute ages are available for these surfaces. The terraced deposits consist of alternating sandy and conglomeratic bodies recording multiple episodes of incision and/or aggradation overlaying erosional surfaces developed on Pre-Quaternary bedrock. Morphometric analyses revealed significant differences in terrace elevation and relative height above the modern channels, among the three investigated basins. The Salandrella basin preserves some of the highest terraced remnants, a pattern compatible with a possible tectonic contribution related to its proximity to the Apennine mountain front. Conversely, the Basento and Bradano basins evidenced a greater influence of lithological conditions, sediment supply, and climate-controlled variations in fluvial dynamics. The results indicate that the evolution of the staircase fluvial terraces reflects the combined influence of glacio-eustatic sea-level fluctuations, Quaternary climatic oscillations, local geological controls, and a possible contribution from regional tectonic deformation. The regional correlation of terraced surfaces highlights the role of the external forcing in shaping landscape evolution, while local differences emphasize the importance of catchment-scale controls within the Bradanic Foredeep. Full article

Conventional full-span movable weirs may require complete lowering for sediment or debris release, reducing upstream water-level control and limiting operational efficiency. This study evaluates a smart rubber and steel (SRS) movable weir that enables selective gate operation through a one-way coupled hydraulic–structural framework using the Environmental Fluid Dynamics Code (EFDC) and MIDAS Civil. Four gate-operation scenarios and gate heights of 0.5, 1.0, 1.5, and 2.0 m were analyzed to characterize flow redistribution, hydraulic loading, gate response, longitudinal-rib performance, and the safety of anchor bolts, clamping plates, and the airbag system. Selective lowering substantially altered flow distribution, with side-gate lowering producing the most critical condition and increasing maximum velocity by approximately 267% relative to the fully raised condition at a 2.0 m gate height. Hydraulic demand became strongly localized near the lowered and adjacent raised spans, although the governing static load remained dominated by hydrostatic loading. Rib comparisons showed that redistributing stiffness through additional longitudinal stiffeners reduced stress and deformation without relying solely on gate thickening, while all component-level static checks satisfied the adopted safety criteria. The results demonstrate that integrating span-specific hydraulic redistribution with structural response provides a practical basis for structurally safe and material-efficient river-infrastructure design. Full article

Earthquake-induced fracturing and microcrack development in subsurface strata are widely recognized as important processes influencing seepage and the hydrological behaviour of surface water bodies, particularly in tectonically active mountainous terrains. However, the hydrogeological response to repeated low-magnitude (<4) seismic events remains poorly understood. This study presents an integrated geoelectrical and remote sensing investigation of the Nagi Lake region in the Sikkim Himalaya, India, based on Vertical Electrical Sounding (VES) surveys conducted in May 2022 and March 2026, following a seismic sequence of 74 low-magnitude earthquakes recorded during February 2026. Comparative analysis of four VES profiles (VES1–VES4), supported by validatory factor analysis, reveals spatially heterogeneous changes in subsurface electrical characteristics between the two survey periods. VES1, VES2, and VES3 indicate reduced signatures of pre-existing microcracks that are consistent with sediment densification and partial sealing, whereas VES4 suggests localized development or persistence of microfractures. Because the surveys span approximately four years, these changes likely reflect the combined influence of long-term hydrogeological, environmental, and geomorphic processes, with the February 2026 seismic sequence representing one potential contributing factor rather than the sole driver. To further evaluate ground deformation, Sentinel-1A Synthetic Aperture Radar (SAR) data acquired between January 2019 and March 2026 were analysed using Persistent Scatterer Interferometric SAR (PS-InSAR). The results indicate cumulative Line-of-Sight (LOS) displacements ranging from −17.9 cm (movement away from the satellite) to +3.5 cm (movement toward the satellite) in the vicinity of Nagi Lake, reflecting localized surface deformation with millimetre-scale precision. These observations provide complementary evidence of ongoing subsurface adjustment that may promote sediment compaction and microcrack modification. Overall, the study demonstrates measurable temporal changes in the subsurface structure of the Nagi Lake area and suggests that repeated low-magnitude seismicity may contribute to subsurface restructuring alongside other environmental processes. The findings highlight the value of integrating geophysical monitoring and satellite-based deformation analysis for understanding groundwater–surface water interactions and supporting the sustainable management of vulnerable Himalayan water bodies. Full article

Pumping stations serve as critical hydraulic infrastructure for water conveyance and irrigation. Sediment deposition in forebays can deteriorate intake flow conditions, increase hydraulic losses, reduce pumping efficiency, and consequently impair the long-term operational performance of pumping systems. To accurately predict sediment deposition in complex three-dimensional flow fields, we developed a dynamics-driven boundary-responsive numerical model that integrates sediment particle dynamics with real-time bed evolution. This model adopts the near-bed vertical velocity of sediment particles as the deposition discrimination criterion and dynamically updates bed topography via a mass-conservation-based boundary response strategy. The proposed method was validated against open-channel experimental data. The simulated flow structures, deposition patterns, and temporal variations in deposition thickness agreed well with the measurements, with average deviations below 4%. Compared with conventional static-boundary numerical methods, the proposed model reproduces the coupled evolution of sediment transport, flow redistribution, and bed deformation with higher fidelity. The developed framework provides an effective numerical tool for sediment deposition prediction and offers practical support for hydraulic structure optimization, maintenance scheduling, and energy-efficient operation of pumping stations with sediment-laden flow. Full article

Seafloor undulations are common on continental shelves and slopes, but their origin is often difficult to determine because similar ridge-and-trough morphologies may originate from depositional processes, post-depositional deformation, or a combination of both. This study investigates seafloor undulations offshore the Sinni River mouth, southern Italy, to assess their depositional, deformational, or hybrid origin, using high-resolution bathymetry, sparker seismic profiles, sub-bottom profiler data, and morphometric analysis. Bathymetric data reveal a seaward-deepening shelf-to-slope system affected by submarine canyons, troughs, slide scarps, crests/ridge, and fields of undulated seafloor. Seismic profiles show that the undulations are mainly developed within the shallow sedimentary wedge, where continuous to gently wavy reflectors pass laterally and downslope into sectors characterized by reduced reflector continuity, local reflector bending, minor reflector offsets, low-angle reflector surfaces, disturbed sediment bodies, vertical to subvertical acoustic anomalies, and locally chaotic to semi-transparent seismic facies. Deeper stratified deposits are generally more continuous, indicating that deformation is mainly confined to the upper sedimentary succession. Morphometric analysis of 65 seabed features distinguishes broader seafloor undulations, characterized by longer wavelengths, low relief, and higher L/H ratios, from shorter, steeper deformation-related sectors with lower L/H ratios. The integrated evidence indicates that the Sinni undulation field is best interpreted as a hybrid depositional–deformational system. Broad, low-relief undulations record depositional accumulation and seabed reworking within the upper sedimentary wedge, whereas shorter, steeper, and more asymmetric sectors indicate localized post-depositional deformation, possibly favored by weak fine-grained deposits, gas/fluid-related acoustic disturbance, slope steepening, and local sediment remobilization. Full article

This paper presents a critical review of surface protection strategies for refurbished hydropower components, with emphasis on the manufacturing and materials-processing logic that links damage mechanisms, substrate condition, deposition route, microstructure, and service performance. The literature indicates that cavitation erosion, sediment abrasion, corrosion, and their synergistic interactions are intensified by flexible and off-design hydropower operation, making refurbishment decisions increasingly surface-sensitive rather than purely bulk-material problems. Thermal spray and laser cladding remain the dominant industrially relevant routes, while cold spray and emerging multi-principal-element, high-entropy, and Fe-based amorphous systems expand the design space for lower heat input, better defect control, and improved cavitation resistance. Across the considered studies, the most consistent conclusion is that hardness alone is not a reliable selection criterion; porosity, interfacial integrity, crack susceptibility, residual stress, and the ability to accommodate local deformation govern real durability. Chemical pre-treatments, sealants, and hybrid finishing routes appear less mature as standalone hydropower solutions, but are important enablers for substrate activation, coating densification, and corrosion mitigation. Therefore, the review proposes a refurbishment-oriented framework in which route selection is based on the initial damage state of the component, the admissible thermal load on the substrate, the required build-up thickness, and the expected cavitation/slurry/corrosion regime. Full article

In the Western Anti-Atlas, the stratiform copper mineralisations of the Tabia Member are distinctly hosted within sedimentary rocks, forming deposits comparable to the sediment-hosted stratabound copper (SSC) type. In Tizert, Ouarmdaz, and Talat n’Ouamane, the sandstones and clays host primary sulphides as disseminations and copper carbonates occurring as small continuous or lenticular beds, small geodes, and coatings on clay laminations. In Tiferki, the conglomerates are more mineralised; sulphides are represented by chalcopyrite and bornite, locally altered into chalcocite. Copper carbonates appear as malachite and azurite coating pebbles and deeply impregnate the granular matrix. From a sedimentological and sequence-stratigraphic perspective, the conglomeratic level at Tiferki represents a low-sea-level prism (LST) formed during a stage of maximum platform exposure allowing erosion products to accumulate at the base of the slope. By contrast, the silty–sandy complex known as the “Talat n’ Ouamane level” corresponds to a prograding sedimentary sequence (Highstand Systems Tract, HST) that developed after a relative regression where the platform was only partially exposed. In both cases, relative sea-level fall promoted the emergence of the hinterland and active erosion, supplying the depositional environment with coarse detrital during the maximum drops in sea level and sandy-to-micro-conglomeratic deposits during less pronounced regressions. This detrital supply probably brought copper in the form of grains and especially dissolved copper, which is largely deposited at the bottom of slopes and in marine environments where microbial communities contribute to the precipitation of copper. The selective distribution of sulphides within the Tabia Member shows that only the low-sea-level and high-sea-level prisms are enriched in stratiform copper, while the transgressive and maximum flooding systems tracts lack significant mineralisation. This suggests that sea-level variations played a controlling role in copper deposition. The regressive trend of the high sea-level suite continued until emergence, reflected by the invasion of the environment by red or ochre siltstones from the alluvial plain. The emergence at the transition from sandstones to dolomites, and the “Red Beds”-type mineralisation embedded in these subaerial facies, support the syngenetic origin of the sulphides in the Tabia Member. After this main emplacement of stratiform copper, the sulphides would have undergone remobilisation and alteration during a significant episode of vertical water escape that deformed the host facies and enhanced mineral concentration within permeable sandstones. Even the clays were delaminated and coated with a thin films of copper carbonates on their surfaces. In the Tamjout dolomites, carbonates are percolated by acidic solutions, contributing to the brecciation and silicification of the stromatolitic layers. Copper mineralisation accompanies this silicification and fills the karstification pockets. Full article

The Raša Fault is a prominent seismically active strike-slip fault within the Dinaric Fault System in SW Slovenia, seismotectonically estimated to be capable of producing earthquakes up to Mw = 7.4. Since the surface exposure of fault-related markers is discontinuous, and the near-surface expression of deformation is poorly constrained, there is a need to improve the detection of fault-related features in complex sedimentary environments. In such settings, signal attenuation, complex stratigraphy, and irregular fault-zone geometries often obscure subtle deformation features, limiting the interpretability of standard 2-D geophysical profiles. A pseudo 3-D Ground-Penetrating Radar (GPR) survey, along with complementary Electrical Resistivity Tomography (ERT) surveys and reprocessing of LiDAR (light detection and ranging) data to obtain high-resolution Digital Elevation Models (DEMs), was conducted in selected environments dominated by low-resistivity karstic deposits and highly heterogeneous fluvial sediments to assess and improve the capability to detect and characterize subtle shallow deformations associated with the Raša Fault. Tectonic geomorphological mapping facilitated the recognition of potentially active fault traces and the identification of Quaternary sedimentary and erosional features, where recent deformations are usually preserved and can be dated in further paleoseismological investigations. The analysis of dense GPR data and complementary ERT profiles enabled us to clearly image the fault deformation pattern and obtain quantitative information about the subsurface, showing details of faulting and related deformation structures not evident at the surface. Furthermore, it enabled the detection of fault zone complexity, revealing it as an irregular and laterally changing area with sediment infillings, rather than a single vertical discontinuity. The complexity of faulting in the near surface depends on many factors, including the competence and age of the faulted material, as well as the local geomorphology. This study has demonstrated the applicability of pseudo 3-D GPR surveying, combined with ERT profiles, for subsurface mapping of active strike-slip faults in karstic and fluvial sedimentary environments. The methodology can be recommended in particular for rapid and cost-effective investigation of sites with subtle surface evidence of active faulting in order to determine near-surface fault splaying. Full article

Autonomous subterranean mobility remains one of the least unified domains in robotics because locomotion emerges from coupled interactions among deformable geomaterials, structural mechanics, energy dissipation, and environment-dependent sensing constraints. This foundational pioneer technical review synthesizes 35 years of research on burrowing and underground robotic systems through a terradynamic and multiphysics perspective. Following PRISMA guidelines, 143 peer-reviewed studies were analyzed across granular soils, cohesive sediments, saturated media, fractured geomaterials, and extraterrestrial regolith analogs. The review evaluates six dominant locomotion classes, including peristaltic, undulatory, fluidization-assisted, excavation-based, tip-extension, and hybrid architectures. Results demonstrate that locomotion performance is governed primarily by regulation of substrate response rather than propulsion generation alone. Across all architectures, mobility depends on the coupled evolution of confinement-dependent stress redistribution, yielding mechanics, pore-pressure dynamics, fracture propagation, structural stability, thermomechanical loading, and energy partitioning. The analysis further reveals a convergence toward stress-regulated locomotion, where successful systems minimize drag accumulation, control force-chain evolution, and adapt to changing terradynamic conditions. Major unresolved challenges include the absence of transferable scaling laws, standardized benchmarking methodologies, predictive terradynamic models, and multi-medium autonomy. The review concludes by proposing the foundations of a unified multiphysics terradynamic robotics paradigm capable of linking robot design, substrate mechanics, control, and deployment across terrestrial and planetary subsurface environments. Full article

Freely meandering rivers flow through gently sloping plains composed of loess and fluvial sediments. Low-gradient alluvial plains are formed without the influence of landscape features such as rock outcrops or other features that distort the flow path. The channel configurations of such rivers, and in particular the size of meanders and oxbow lakes, depend on the average long-term water discharge. Large rivers form large meanders, while small rivers form correspondingly small ones. Morphological analysis of river channel configurations can offer a metric for estimating the average long-term water discharge of a river based solely on the sinuosity of its channel. The study examined six freely meandering rivers in Kazakhstan, with discharges ranging from 4.5 to 760 m³/s and channel slopes from 0.005 to 0.06%. The morphological analysis of river channels was based on the Relative Elevation Model, specifically its version based on the Copernicus Global Digital Elevation Model, with a spatial resolution of 30 m. River channel configurations were approximated using a set of inscribed circles, the diameters of which formed the basis for the river’s average long-term water discharge metric. The largest diameter circles, which could support the river channel with a sector of at least 135°, were expertly inscribed into river bends. The diameters of the inscribed circles within these sets varied from four times for small rivers to ten times for large rivers. These sets of circles, sorted by size, can characterize the average long-term water discharge of the analyzed rivers. For example, a sample of average median values of inscribed circle diameters has a high correlation with the average long-term water discharge, with a linear approximation reliability of R² = 0.997. The scope of the developed method for assessing the average long-term water discharge of freely meandering rivers includes retrospective analysis of changes in average long-term average long-term water discharge. This can provide significant historical depth of analysis, spanning centuries and millennia, since the analysis is based on describing the results of very slow processes of natural deformation of river channels. Thus, the method proposed in this study for assessing the average long-term water discharge of freely meandering rivers based on morphological analysis of their channel configurations expands the arsenal of tools for reconstructing certain paleoclimate elements related to the hydrology of territories. Full article

Variable sediment supply and widely graded bed materials modify boulder–bar development, sediment transport and bar evolution in mountain mixed-size reaches. To elucidate the evolution characteristics of bars in boulder-strewn mountain river segments, this study conducted flume experiments. By adjusting parameters including discharge, boulder position, and boulder protrusion height, the paper analyzes bed scour and deposition deformations under various conditions. Results show discharge growth intensifies bed deformation: Both bar area and volume increase with rising discharge, with longer downstream bar extension and a positive correlation between bar length–width ratio and velocity. Higher boulder protrusion height and exposure amplify scour depth, expand bars laterally and reduce scour pit width–depth ratios. Boulders at bar heads migrate furthest downstream; moving boulders toward bar tails increases bar area/volume while bar height peaks then declines. Bar scale follows mid-channel bar head > bar tail > side anabranches. Boulder embedding depth linearly rises with exposure, both parameters positively linked to post-scour bar volume loss. The stable co-evolutionary relationship between scour depth and extent (R² = 0.849) confirms their synchronized development under varying flow and boulder conditions. Boulders limit downstream bar elongation, flat beds boost scour diffusion, and scour pit width–depth ratio positively correlates with flow velocity. This work offers experimental and mechanistic references for mountain river geomorphic prediction. Full article

Tracked deep-sea mining vehicles (DSMVs) interact strongly with soft seabed sediments during seafloor operations, which may cause excessive sinkage and vehicle instability. Variations in mineral loading and initial pitch angle are important factors affecting operational safety. In this study, the “Kunlong 500” tracked DSMV was selected as the prototype, and a coupled Eulerian–Lagrangian (CEL) numerical model was established to simulate vehicle–sediment interaction. The Drucker–Prager elastoplastic model was adopted to describe sediment yielding and plastic deformation. Different mineral loading levels and initial pitch angles were considered to investigate vehicle sinkage, local Mises stress in the track–sediment contact region, and attitude response. The results show that increasing mineral loading significantly increases body sinkage and rear-track Mises stress, causing the vehicle response to evolve from overall sinkage to rear-biased sinkage. Under the present model parameters, the reference critical loading for local rear-track sinkage was estimated to be approximately 5.8 t, with a sensitivity range of approximately 4.5–7.1 t under ±10% variation in the equivalent bearing term. Under the present model conditions, loading conditions of 8 t and above should therefore be treated as key risk-control cases. The initial pitch angle further aggravates asymmetric sinkage, especially under the 4 t loading and 4° pitch condition. These findings provide a reference for load control and attitude regulation of DSMVs. Full article

Gas-insulated switchgears (GISs) and gas-insulated transmission lines (GILs) are essential for large-capacity power transmission in demanding environments, such as high drops, large spans, and heavy pollution. As the core components providing both electrical insulation and mechanical support, ultra-high voltage (UHV) epoxy-based insulators often suffer from high internal residual stress. This issue, compounded by a lack of reliable detection methods, frequently results in equipment being commissioned with hidden defects. To address this, this review first examines the formation mechanisms of curing deformation and residual stress in oversized insulators based on cure kinetics and thermo-chemical coupling models. Subsequently, it provides a comprehensive summary of current residual stress measurement techniques, comparing the applicability and limitations of embedded sensors, direct mechanical measurements, and indirect non-destructive testing (NDT) methods. Finally, by coupling residual stress with filler sedimentation, the stress distribution patterns and mechanical reliability of epoxy-based insulators across different life-cycle stages are analyzed. These insights offer valuable theoretical references for the structural design, process optimization, and performance evaluation of oversized epoxy-based insulators, ultimately contributing to the intrinsic safety of UHV power equipment. Full article

Kelvin–Helmholtz (K–H) instabilities play an important role in mixing and entrainment processes in stratified and sediment-laden flows, while their development can be affected by particle properties and rheological contrasts. In this study, a two-phase numerical framework is used to investigate the onset and nonlinear evolution of K–H billows in sediment-laden shear layers. The governing equations are solved using a finite-volume approach with second-order TVD discretization, and the effects of the Richardson number ($Ri$), sediment particle size, and viscosity ratio (W) are examined systematically. In addition to concentration, vorticity, and interphase slip-velocity fields, a box-counting dimension (BCD) diagnostic is introduced as a complementary measure to quantify the instability onset time, the effective growth-start time, and the maximum geometrical growth rate of the sediment–water interface. The results show that, within the tested parameter range, coherent instabilities develop for $Ri\lesssim 0.25$. Decreasing $Ri$ leads to earlier BCD-based onset, shorter effective growth intervals, larger BCD growth rates, and stronger vortical structures. Sediment granulometry also affects the instability evolution: fine silt-like particles delay the onset and produce broader, more diffuse vortical structures, whereas fine-sand-like particles promote earlier destabilization and more compact billows. The viscosity ratio W modifies the vortex morphology, with high viscosity contrast reducing peripheral deformation and concentrating vorticity within the core region. These findings complement classical descriptions of stratified shear instabilities by highlighting the additional effects of sediment granulometry and rheological contrast. The proposed BCD-based diagnostic provides a practical quantitative tool for comparing interfacial growth in sediment-laden shear flows relevant to estuarine, coastal, and hydraulic engineering applications. Full article