Search Results (205)

The integration of glass fibre-reinforced polymer (GFRP) and steel reinforcement in hybrid RC beams offers durability benefits, yet the specific influence of GFRP surface treatments on bond mechanics remains critical. This study experimentally investigates the performance of hybrid GFRP-steel-reinforced beams under three-point bending, comparing sand-coated and ribbed GFRP bars, while maintaining a constant total reinforcement ratio of 1.4% to isolate interface mechanics. Due to the exploratory nature of the study and the specific specimen matrix, the results are interpreted as observed experimental trends rather than statistically generalised performance metrics. The results indicate that ribbed GFRP bars provide enhance mechanical interlocking; in this specific experimental program, the ribbed GFRP hybrid beam exhibits an observed load capacity approximately 11% greater than the sand-coated specimen in this study and surpassing comparable steel-only beams. Additionally, ribbed configurations demonstrated an observed 15% higher toughness. In contrast, sand-coated hybrid beams exhibited signs of premature bond degradation, quantitatively captured by strain gauge monitoring; sand-coated bars plateaued at 14,000 µε, reaching only 79% of their theoretical rupture capacity. This strain limitation indicates failure by internal slippage rather than material rupture, further evidenced by a 50% reduction in crack propagation compared to ribbed beams. While energy-based ductility indices suggest a marginal 6% advantage for sand-coated bars, both hybrid systems exhibited relatively low energy-based ductility indices (μ < 2), reflecting the linear-elastic nature of GFRP reinforcement. These findings suggest that the mechanical interlock of ribbed surface treatments is more resilient under the combined stress states typical of hybrid configurations, providing a foundational baseline for the development of future numerical models and reliability-based design frameworks for hybrid GFRP-steel-RC systems. Full article

Existing studies have extensively investigated sand-rich shallow-water deltas. However, the sedimentary characteristics and internal architecture of mud-rich deltas remain poorly understood. In this study, two comparative flume experiments were conducted with sand–mud ratio as the key variable. High-resolution topographic data were acquired using a laser scanner to extract geometric parameters of the architectural elements. Three-dimensional architectural models were established and validated against the Ganjiang Delta (sand-rich) and the Ouchi River Delta (mud-rich) in China. The results reveal contrasting depositional styles: sand-rich deltas develop dense, laterally migrating braided channels with broad fan-shaped morphologies, forming blanket-like geometries that consist of vertically stacked and laterally amalgamated channel complexes with good connectivity; mud-rich deltas are characterized by stable channels with limited bifurcation, forming elongated finger-like morphologies with isolated, ribbon-like channel–mouth bar complexes that exhibit strong lateral heterogeneity and poor connectivity. These contrasting behaviors are governed by sediment cohesion: non-cohesive sands promote channel migration and dispersion, whereas cohesive silt and mud stabilize channels and focus sediment transport along main conduits. The experimental models successfully reproduce natural delta end-members, confirming the universal control of the sand–mud ratio. The established quantitative relationships provide a predictive basis for subsurface reservoir characterization and the formulation of differentiated development strategies. Full article

This study investigates the bond–slip behavior of glass fiber-reinforced polymer (GFRP) bars embedded in concrete and exposed to alkaline environments at different temperatures. Although GFRP reinforcement is increasingly adopted for its corrosion resistance, the long-term bond performance of the bar–concrete interface in high-pH conditions is still not fully understood. To help close this gap, a comprehensive database of 84 pull-out tests from the literature was assembled, focusing on three key parameters: bar surface configuration, exposure duration, and conditioning temperature. The comparative analysis highlights the dominant role of surface treatment in bond degradation and reveals substantial variability across existing results. To complement the literature review, additional pull-out tests were carried out on sand-coated GFRP bars conditioned in an alkaline solution (pH = 12) for 1.5 months at ambient temperature and at 60 °C. These tests showed average reductions in bond strength of approximately 28% and 32%, respectively, compared with unconditioned specimens, together with marked changes in the post-peak portion of the bond–slip response. An analytical formulation was also applied, not as a novel bond–slip law but as a consistent mechanical framework to interpret durability-induced degradation effects, to describe the local interface shear stress–slip law, and to assess the resulting stress and slip distributions along the bonded length. Overall, the combined experimental and analytical findings emphasize the need to account for environmentally induced degradation when evaluating durability and defining design criteria for GFRP-reinforced concrete structures. Full article

The deep reservoir of the K gas field in the Xihu Depression of the East China Sea Basin has ample storage space and a vast reserve scale. However, these deep intervals remain poorly explored and developed, and their reservoir attributes and key controlling factors are not yet well constrained. Using integrated analyses of cores, cast thin sections, scanning electron microscopy, petrophysical statistics, grain-size data, high-pressure mercury intrusion, and nuclear magnetic resonance imaging, together with conventional well logs, we evaluate the roles of sedimentation, diagenesis, and overpressure in the development and distribution of high-quality reservoirs. Based on clastic grain texture and composition, authigenic minerals, diagenetic types and intensities, pore architecture, petrophysical properties, and gas saturation, two types of high-quality deep sandstone reservoirs are identified: rigid, moderately porous sandstones and strongly compacted, low-porosity sandstones. Compaction is the dominant diagenetic process controlling reservoir quality in the Eocene Pinghu Formation. Overpressure prolongs kaolinite stability and promotes precipitation within pore throats, enhancing fluid sealing and retention, yet does not significantly reduce porosity. Rigid moderately porous reservoirs mainly occur in subaqueous distributary channels, whereas strongly compacted low-porosity reservoirs are concentrated in mouth bars and sheet-sand microfacies. This distribution pattern provides guidance for exploring high-quality deep sandstone gas accumulations. Full article

This study investigates seawater coral sand engineering cementitious composites (SC-ECCs) characterized by multi-crack propagation and strain-hardening properties, utilizing seawater and coral sand as the primary matrix materials. The research systematically evaluates the interactions between polyethylene (PE), co-polyoxymethylene (POM), calcium carbonate whiskers (CW), and basalt fiber (BF). Quasi-static mechanical tests and split Hopkinson pressure bar (SHPB) dynamic impact experiments were conducted to analyze fiber bridging characteristics, dynamic stress–strain behaviors, and failure morphologies. The results indicate that while the PE-BF hybrid system optimized static tensile performance with a maximum strain capacity of 7.5%, and the multiscale fiber system delivered superior compressive and impact capabilities. Specifically, the multiscale configuration achieved a quasi-static compressive strength of 119 MPa, representing a 33% improvement over the single-doped PE control group. Under high-strain-rate impact loading, the multiscale reinforced HSC-ECC exhibited outstanding impact resistance, reaching a peak dynamic compressive strength of approximately 160 MPa—28% higher than the control group. These findings demonstrate that multiscale fiber reinforcement significantly enhances energy absorption and damage control, providing a robust technical basis for the application of SC-ECC in marine infrastructure subjected to impact loads. Full article

Sediment transport in alluvial channels is strongly controlled by the grain-size distribution of bed and suspended materials. This, in turn, influences river morphology by modifying the cross-sectional area and course of the channel. Statistical parameters such as mean, standard deviation, skewness, and kurtosis provide quantitative indicators of the energy conditions that control sediment transport and deposition. This study examines the depositional characteristics of sediments in the Ganga River in Varanasi City, India, employing a novel combination of linear discriminant function (LDF) and sediment transport index (STI). The LDF results reveal distinct depositional environments: Y₁ and Y₂ values indicate deposition in a low-energy fluvial environment similar to beaches, Y₃ values suggest shallow marine settings, and Y₄ values point to mixed deltaic and turbid current depositional environments. Additionally, CM diagrams show rolling and suspension as the dominant sediment transport mechanisms. Shear stress analysis combined with STI highlights significant depositional features, with minimal erosion observed throughout the study area. The study provides an operational framework for mapping erosion-deposition patterns on alluvial point bars that are transferable to other sand-bed rivers worldwide where detailed hydraulic data are limited but detailed grain-size and DEM information are available. Full article

This study systematically investigates the lithofacies, sedimentary microfacies, vertical evolution, and spatial distribution of the braided river delta–shallow lacustrine carbonate mixed sedimentary rocks of the Upper Ganchaigou Formation in the Huatugou Oilfield of the Qaidam Basin, China. This study integrates data from field outcrops, core observations, thin section petrography, laboratory analyses, and well-logging interpretations. Based on these datasets, the sedimentary characteristics are identified, and a comprehensive sedimentary model is constructed. The results reveal that the study area contains five clastic facies, three types of mixed sedimentary facies, and ten sedimentary microfacies. Two distinct modes of mixed sedimentation are recognized: component mixing and stratigraphic mixing. A full lacustrine transgression–regression cycle is formed by the two types of mixed sedimentation characteristics, which exhibit noticeable differences in vertical evolution. Component mixing, which occurs in a mixed environment of continuous clastic supply and carbonate precipitation during the transgression, is the primary characteristic of the VIII–X oil formation. The mixed strata that make up the VI–VII oil formation show rhythmic interbedding of carbonate and clastic rocks. During the lacustrine regression, it shows the alternating sedimentary environment regulated by frequent variations in lacustrine levels. The planar distribution is affected by both intensity of sediment from the west and the changes in lacustrine level. During the lacustrine transgression, it is dominated by littoral-shallow lacustrine mixed beach bar and mixed sedimentary delta. On the other hand, during the lacustrine regression, it is dominated by laterally amalgamated sand bodies in the braided-river delta front. Based on this, a mixed sedimentary evolution model controlled by the coupling of “source–lacustrine level” is established. It offers a guide for reconstructing the sedimentary environment in basins that are similar to it and reveals the evolution path of mixed sedimentation in the short-axis source area of arid saline lacustrine basins. Full article

Pb (II) contamination in wastewater represents a grave threat to the environment and ecosystems. Consequently, there is an urgent need to prepare low-cost and highly efficient Pb (II) adsorbents. To address this need, abundant and low-cost natural silica-based desert sand (DS) was innovatively utilized as a carrier to develop efficient and selective Pb (II) adsorbents. Modified desert sand (MDS) was first prepared via 1 M HCl pretreatment for 2 h and subsequent KH550 silane modification. Pb (II)-imprinted composites (Pb (II)-IIP@MDS) were then fabricated via ion-imprinted polymerization, using Pb (II) as the template ion and N-hydroxymethacrylamide (NHMA)/hydroxyethyl methacrylate (HEMA) as dual functional monomers with a molar ratio of 1:1. The synthesized Pb (II)-IIP@MDS was comprehensively characterized by X-ray photoelectron spectrometer (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The adsorption capacity, selectivity, and reusability of this material for lead ions were evaluated through three experiments conducted within the optimized pH range of 6–7, with error bars indicated. In adsorption isotherm experiments, the initial Pb (II) concentration ranged from 50 to 500 mg·L⁻¹, conforming to the Langmuir model (R² = 0.992), with a theoretical maximum adsorption capacity reaching 107.44 mg·g⁻¹; this indicates that the adsorbate forms a monolayer adsorption on the homogeneous imprinted sites. Kinetics data indicate that the process best fits a quasi-first-order kinetic model (R² ≥ 0.988), while the favorable quasi-second-order kinetic fit (R² ≥ 0.982) reflects the synergistic effect of physical diffusion and ion-imprinting chemistry, reaching equilibrium within 120 min. Thermodynamic parameters (ΔH⁰ = 12.51 kJ·mol⁻¹, ΔS⁰ = 101.19 J·mol⁻¹·K⁻¹, ΔG⁰ < 0) confirmed endothermic, entropy-increasing, spontaneous adsorption. In multicomponent systems, Pb (II)-IIP@MDS showed distinct Pb (II) selectivity. It retained 80.3% adsorption efficiency after eight cycles. This work provides a promising strategy for fabricating low-cost, high-performance Pb (II) adsorbents, and Pb (II)-IIP@MDS stands as a practical candidate for the remediation of Pb (II)-contaminated wastewater. Full article

The meandering river reservoirs of the Ng3–Ng4 members of the upper Guantao Formation in northern Middle Block 2, Gudao Oilfield, exhibit sand bodies with rapid lateral variation, complex contacts, and strong heterogeneity. Previous characterization using sparse well patterns showed deviations in depicting sand body boundaries and internal architecture with insufficient accuracy for optimizing development plans and tapping remaining oil. Additionally, small-scale lateral accretion mud interlayers within point bars—which are hard to trace between wells—limited fine characterization of point bar architecture. Using the high-resolution data and dense inter-well control of the study area’s dense well pattern, we traced 3–10 cm thick lateral accretion mud interlayers within point bars between wells, overcoming the challenge of characterizing thin interlayers with sparse well patterns, and dissected reservoir architecture. Results indicate the study area is dominated by meandering river deposits, with four architectural units: channels, abandoned channels, overbanks, and flood plains. Meander belts range in width from 450 to 1900 m with an average of 1420 m; point bars measure in length from 310.6 to 1754 m with an average of 1036.2 m and in width from 323.4 to 1586 m with an average of 1000.8 m. Lateral accretion mud interlayers show sub-oblique profiles, with dips of 3–6° and a thickness of 3–10 cm; individual lateral accretion bodies are 1.5–5.7 m thick and 32–255 m wide horizontally. Based on channel-point bar scale relationships, an empirical formula for quantitative characterization was established, enabling the prediction of single sand body scales in sparsely well-patterned areas to support well placement and remaining oil prediction. Combined with contact relationships of sand bodies across architectural hierarchies, the main architectural models of composite meander belts were developed. This study provides a reliable geological basis for dissecting meandering river reservoir architecture and tapping remaining oil under sparse well patterns. Full article

The federally threatened Puritan tiger beetle (Ellipsoptera puritana; PTB) inhabits Upper Chesapeake Bay bluffs, beaches and Connecticut River point bars. This study focuses on Maryland’s Chesapeake Bay population (Calvert County and Sassafras River), where adult PTBs prey on beach arthropods but establish larval habitat on the adjacent bluffs. A combination of panoramic photography, GIS mapping, and field and laboratory measurements of sedimentological and ecological characteristics were measured across 17 high- and low-density Maryland beetle sites to identify the geologic and biological controls on population distribution and abundance. Results indicate that temporal and spatial fluctuations in PTB abundance are governed by bluff face quality, which in turn, is shaped by antecedent geology (medium-compacted, fine-to-medium, well-sorted sands) and bluff dynamics. We present a four-stage, multi-decadal geomorphodynamic conceptual model in which long-term bluff recession and short-term storm-driven colluvium removal periodically expose fresh bluff surfaces required for larval establishment. By integrating geomorphic, geologic, and ecological perspectives, this study highlights the role of sedimentary processes in maintaining critical estuarine habitats and provides a framework for predicting species persistence in dynamic coastal landscapes. Full article

The shallow-water delta-front reservoir in Member II of the Oligocene Dongying Formation (Ed2), located in an oilfield within the Bohai Bay Basin, is a large-scale composite sedimentary system dominated by subaqueous distributary channels and mouth bars. Within this system, reservoir sand bodies exhibit significant thickness, complex internal architecture, poor injection–production correspondence during development, and an ambiguous understanding of remaining oil distribution. To enhance late-stage development efficiency, it is imperative to deepen the understanding of the genesis and evolution of the subaqueous distributary channel–mouth bar system, analyze the internal reservoir architecture, and clarify sand body connectivity relationships. Based on sedimentary physical modeling experiments, integrated with core, well logging, and seismic data, this study systematically reveals the architectural characteristics and spatial stacking patterns of the mouth bar reservoirs using Miall’s architectural element analysis method. The results indicate that the study area is dominated by sand-rich, shallow-water delta front deposits, which display a predominantly coarsening-upward character. The main reservoir units are mouth bar sand bodies (accounting for 30%), with a vertical stacking thickness ranging from 3 to 20 m, and they exhibit lobate distribution patterns in plan view. Sedimentary physical modeling reveals the formation mechanism and stacking patterns of these sand-rich, thick sand bodies. Upon entering the lake, the main distributary channel unloads its sediment, forming accretionary bodies. The main channel then bifurcates, and a new main channel forms in the subsequent unit, which transports sediment away and initiates a new phase of deposition. Multi-phase deposition ultimately builds large-scale lobate complexes composed of channel–mouth bar assemblages. These complexes exhibit internal architectural styles, including channel–channel splicing, channel–bar splicing, and bar–bar splicing. Reservoir architecture analysis demonstrates that an individual distributary channel governs the formation of an individual lobe, whereas multiple distributary channels control the development of composite lobes. These lobes are laterally spliced and vertically superimposed, exhibiting a multi-phase progradational stacking pattern. Dynamic production data analysis validates the reliability of this reservoir architecture classification. This research elucidates the genetic mechanisms of thick sand bodies in delta fronts and establishes a region-specific reservoir architecture model. This study clarifies the spatial distribution of mudstone interlayers and preferential flow pathways within the composite sand bodies. It provides a geological basis for optimizing injection–production strategies and targeting residual oil during the ultra-high water-cut stage. The findings offer critical guidance for the efficient development of shallow-water delta front reservoirs. Full article

With the development of infrastructure construction, seawater sea–sand concrete (SWSSC) is expected to solve the shortage of freshwater and river sand. Polyoxymethylene (POM) fiber, owing to its excellent corrosion resistance, provides a novel approach to enhancing the bond performance of SWSSC. This study systematic study of the bond properties of bimetallic steel bars (BSBs) in POM fiber-reinforced SWSSC and develops a predictive model. Mechanical property tests of SWSSC and pull-out tests of BSB and SWSSC were conducted with various POM fiber contents. The results showed that the optimal volume fraction of POM fibers was 0.6%. At this fraction, the compressive strength and splitting tensile strength of SWSSC were improved by 17.7% and 20.3%, respectively, compared with the group without fibers. All pull-out specimens experienced splitting failure. The bond strength increased monotonically with the increase in relative cover thickness and exhibited a trend of first increasing and then stabilizing with rising POM fiber volume fraction. In addition, a bond stress–slip prediction model between BSBs and POM fiber-reinforced SWSSC was established based on the test results, which can provide theoretical support for the numerical simulation and design of BSB-SWSSC structures. Full article

Climate change in Mediterranean regions is projected to cause declines in rainfall and higher temperatures and evaporation, which will enhance the formation of barriers at the mouth of low-inflow estuaries and potentially also in the riverine reaches. This review uses data from estuaries in south-western Australia across a rainfall gradient to describe how these barriers form and the effects they have on environmental conditions and biotic communities. The formation of barriers disconnects the estuary from adjacent freshwater and marine environments, prohibiting the movements of fauna and lowering taxonomic and functional diversity. Moreover, the longer periods of bar closure can result in increased frequency and magnitude of hypersalinity, hypoxia and nutrient enrichment. These conditions, in turn, act as stressors, often synergistically, on the floral and faunal communities. In some cases, mass mortality events occur, and some estuaries dry completely. To ensure the functioning of such systems in the future, regular monitoring across a wide range of estuaries is needed to understand how climate change is impacting different types of estuaries. A range of management options are discussed that may help mitigate the effects of increased barrier formation but should be employed as part of a whole-of-catchment approach and regularly evaluated. Full article

The complexity of tight sandstone reservoirs challenges effective oil and gas exploration. The Chang 8 Member of the Yanchang Formation in the Longdong area of the Ordos Basin has significant exploration potential. However, its reservoir characteristics are controlled by two distinct provenance systems and diverse sedimentary microfacies. The specific impacts of these factors on reservoir quality and their relative importance have remained unclear. This study employs an integrated analytical approach combining casting thin sections, conventional porosity-permeability measurements, and Nuclear Magnetic Resonance (NMR) to systematically investigate the petrological characteristics, pore structure, and physical properties of the Chang 8 reservoirs. Our findings reveal that the entire section of Chang 8 is a delta front subfacies, with sub sections of Chang 8¹ and 8² developing microfacies such as underwater distributary channels, underwater natural levees, sheet sand and mouth bars. The tight sandstone reservoir is mainly composed of lithic arkose and feldspathic litharenite, with its porosity dominated by dissolution and intergranular types. These secondary pores, particularly those resulting from feldspar dissolution, are of great importance. The underwater distributary channels have the best pores, followed by sheet sands, and underwater natural levees the worst. Compaction in Chang 8² is stronger than in Chang 8¹, leading to smaller pores. The northwest provenance is characterized by high clay content and small pores, while the southwest provenance has coarser grain size and better-preserved intergranular pores. Reservoir properties improve toward the lake but deteriorate at the lake-proximal end due to more small pores. This study reveals the control laws of sedimentary microfacies, provenance, and diagenesis on the pore development of tight sandstone in the Longdong area, providing theoretical guidance for the exploration and development of tight sandstone oil and gas in the region. Full article

The prediction of thin-bedded, favorable sand bodies within the Triassic Baikouquan Formation fan delta on the western slope of the Mahu Sag is challenging due to their strong spatial heterogeneity. To address this, we propose an integrated workflow that synergizes seismic sedimentology with geologically constrained seismic inversion. This study leverages well logging, core data, and 3D seismic surveys. Initially, seismic attribute analysis and stratal slicing were employed to delineate sedimentary microfacies, revealing that the fan delta front subfacies comprises subaqueous distributary channels, interdistributary bays, and distal bars. Subsequently, the planform distribution of these microfacies served as a critical constraint for the Seismic Waveform Indicative Inversion (SWII), effectively enhancing the resolution for thin sand body identification. The results demonstrate the following: (1). Two NW-SE trending subaqueous distributary channel systems, converging near the BAI65 well, form the primary reservoirs. (2). The SWII, optimized by our workflow, successfully predicts high-quality sand bodies with a cumulative area of 159.2 km², primarily located in the MAXI1, AIHU10, and AICAN1 well areas, as well as west of the MA18 well. This study highlights the value of integrating sedimentary facies boundaries as a geological constraint in seismic inversion, providing a more reliable method for predicting heterogeneous thin sand bodies and delineating future exploration targets in the Mahu Sag. Full article