Search Results (265)

This paper explores the impact of applying a powder additive in the form of halloysite and mullite on the thermal protection properties of a composite. The authors used CES R70 epoxy resin with CES H72 hardener, modified by varying the amount of powder additive. The composite samples were exposed to a mixture of combustible gases at a temperature of approximately 1000 °C. The primary parameters analyzed during this study were the temperature on the rear surface of the sample and the ablative mass loss of the tested material. The temperature increase on the rear surface of the sample, which was exposed to the hot stream of flammable gases, was measured for 120 s. Another key parameter considered in the data analysis was the ablative mass loss. The charred layer of the sample played a crucial role in this process, as it helped block oxygen diffusion from the boundary layer of the original material. This charred layer absorbed thermal energy until it reached a temperature at which it either oxidized or was mechanically removed due to the erosive effects of the heating factor. The incorporation of mullite reduced the rear surface temperature from 58.9 °C to 49.2 °C, and for halloysite, it was reduced the rear surface temperature to 49.8 °C. The ablative weight loss dropped from 57% to 18.9% for mullite and to 39.9% for halloysite. The speed of mass ablation was reduced from 77.9 mg/s to 25.2 mg/s (mullite) and 52.4 mg/s (halloysite), while the layer thickness loss decreased from 7.4 mm to 2.8 mm (mullite) and 4.4 mm (halloysite). This research is innovative in its use of halloysite and mullite as functional additives to enhance the ablative resistance of polymer composites under extreme thermal conditions. This novel approach not only contributes to a deeper understanding of composite behavior at high temperatures but also opens up new avenues for the development of advanced thermal protection systems. Potential applications of these materials include aerospace structures, fire-resistant components, and protective coatings in environments exposed to intense heat and flame. Full article

This study investigated the erosive wear of a polyurea coating with a hardness of 95 ShA and a thickness of 3 mm applied to a 3 mm thick plate made of S235 steel. The process of erosive wear was carried out using a stream of compressed air containing abrasive grains of aluminum oxide (Al₂O₃). The erosive wear was studied using different incidence angles (45°, 60° and 90°) and erosive grain sizes. Thus, the effects of the incidence angle and erosive grain size on the erosive wear of the polyurea coating were analyzed. Erosive wear was determined as linear wear: the depth of the wear trace was measured using an optical profilometer. This study showed a non-linear correlation between erosive wear, incidence angle and erosive particle size. In addition, a qualitative study of the surface of the coating after a wear test was carried out using a scanning electron microscope, which made it possible to describe the mechanisms of erosive wear of the polyurea coating. Full article

The article investigates the development of local scour downstream of a damming structure, emphasizing the dynamic equilibrium of river morphology influenced by both natural processes and human interventions like the construction of weirs. It distinguishes between clear-water and live-bed conditions, discussing how sediment transport interacts with hydraulic forces to shape the riverbed. The introduction of a damming structure disrupts sediment flow and initiates local scour formation, which varies depending on stream conditions. In the experimental section, a physical model of a damming weir was tested under controlled conditions. The laboratory model was inspired by an existing damming weir on the Radomka River in Poland. Granulometric analysis and eleven flow series were conducted to assess scour evolution over time. The results showed the fastest erosion in the first hours, followed by stabilization in scour depth but continued elongation of the scour hole. The analysis identified four phases of scour development: initiation, intensive growth, stabilization, and equilibrium. Despite depth stabilization, scour length continued to increase, indicating that full equilibrium had not been reached. The study highlights the complexity of predicting scour behavior and recommends incorporating both depth and length evolution into design analyses to improve the resilience of such damming structures. The innovative aspect of the present study lies in the inclusion of coarse sediment transport, previously accumulated in the upstream reach due to the weir’s impoundment effect, into the scour development process. This specific effect has not been addressed in the studies cited by other authors. This research provides crucial insights for the sustainable design of hydraulic structures and effective sediment management strategies, contributing to the long-term stability and safety of riverine infrastructure. Full article

Water, often described as the elixir of life, is a critical resource that sustains life on Earth. The acute water scarcity in the major basins of the Arabian Peninsula has been further aggravated by rapid population growth, urbanization, and the impacts of climate change. This situation underscores the urgent need for a comprehensive analysis of the region’s morphometric characteristics. Such an analysis is essential for informed decision-making in water resource management, infrastructure development, and conservation efforts. This study provides a foundational basis for implementing sustainable water management strategies and preserving ecological systems by deepening the understanding of the unique hydrological processes within the Arabian Peninsula. Additionally, this research offers valuable insights to policymakers for developing effective flood mitigation strategies by identifying vulnerable areas. The study focuses on an extensive investigation and assessment of morphometric parameters in the primary basins of the Arabian Peninsula, emphasizing their critical role in addressing water scarcity and promoting sustainable water management practices. The findings reveal that the Arabian Peninsula comprises 12 major basins, collectively forming a seventh-order drainage system and covering a total land area of 3.24 million km². Statistical analysis demonstrates a strong correlation between stream order and cumulative stream length, as well as a negative correlation between stream order and stream number (R² = 99%). Further analysis indicates that many of these basins exhibit a high bifurcation ratio, suggesting the presence of impermeable rocks and steep slopes. The hypsometric integral (HI) of the Peninsula is calculated to be 60%, with an erosion integral (EI) of 40%, indicating that the basin is in a mature stage of geomorphological development. Importantly, the region is characterized by a predominantly coarse drainage texture, limited infiltration, significant surface runoff, and steep slopes, all of which have critical implications for water resource management. Full article

Benggangs, a type of soil erosion widely distributed in the hilly and mountainous regions of South China, pose significant challenges to land management and ecological conservation. Accurate identification and assessment of their location and scale are essential for effective Benggang control. With advancements in technology, deep learning has emerged as a critical tool for Benggang classification. However, selecting suitable feature extraction and fusion methods for multi-source image data remains a significant challenge. This study proposes a Benggang classification method based on multiscale features and a two-stream fusion network (MS-TSFN). Key features of targeted Benggang areas, such as slope, aspect, curvature, hill shade, and edge, were extracted from Digital Orthophotography Map (DOM) and Digital Surface Model (DSM) data collected by drones. The two-stream fusion network, with ResNeSt as the backbone, extracted multiscale features from multi-source images and an attention-based feature fusion block was developed to explore complementary associations among features and achieve deep fusion of information across data types. A decision fusion block was employed for global prediction to classify areas as Benggang or non-Benggang. Experimental comparisons of different data inputs and network models revealed that the proposed method outperformed current state-of-the-art approaches in extracting spatial features and textures of Benggangs. The best results were obtained using a combination of DOM data, Canny edge detection, and DSM features in multi-source images. Specifically, the proposed model achieved an accuracy of 92.76%, a precision of 85.00%, a recall of 77.27%, and an F1-score of 0.8059, demonstrating its adaptability and high identification accuracy under complex terrain conditions. Full article

Sediment transport plays a crucial role in shaping coastal and riverine environments, influencing both natural and human activities. This study assesses sediment supply from the entire basin of a touristic zone of Cyprus, where coastal erosion and sediment deposition impact infrastructure, tourism, and environmental sustainability. Human activities, such as dam construction, further disrupt the sediment balance. This study focuses on Coral Bay and Potima Gulf, a popular tourist destination along an ~11 km shoreline in western Cyprus, fed by four small rivers draining a total area of 66.5 km². The sustainability of the Coral Bay–Potima system is threatened by the Mavrokolympos stream dam, which traps upstream sediments. Using the USLE method, mean sediment yield at the basin outlet is estimated at 888 t km⁻² yr⁻¹. These findings underscore the link between watershed processes and sustainable coastal management, emphasizing the need for integrated sediment transport assessments in touristic coastal zones. Full article

River mouths are important indicators and mediators of interactions between rivers and the sea that mark the dispersal point for catchment-based stressors and subsidies. Satellite remote sensing data products and algorithms present many new possibilities for monitoring these dynamic and often inaccessible environments. In this study, we describe a national-scale comparative framework based on proximity to river mouths and show its application to the monitoring of coastal ecosystem health in Aotearoa New Zealand. We present results from light attenuation coefficient (K_d) analyses used to develop the framework considering data products of differing resolution and the effects of coastline geometries which might obscure the influence of catchment-derived stressors. Ten-year (2013–2022) K_d values from the highest-resolution product (500 m) showed significant differences (p < 0.01) in successively larger radii (1–20 km) despite the confounding influence of adjacent river mouths. Smaller radii returned a high variability that dropped markedly > 5 km. Tests of a 10 km radius showed that coastline geometry had a significant influence on K_d (p < 0.001), which is also likely for other water quality indicators. An analytical approach stratified by coastline geometry showed significant effects of stream order on open (p < 0.01) but not enclosed coasts, differences between marine bioregions (p < 0.05), and a degradation trend in the 90th percentile of K_d on enclosed coasts, which is indicative of extreme events associated with catchment erosion or sediment resuspension. We highlight applications of the framework to explore trends across many other meaningful scales (e.g., jurisdictions and ecosystem types) in addition to tracking changes at individual river mouths. Full article

Straw incorporation is applied in sloping farmland to coordinate soil water, fertilizer, air, heat, and soil erosion control in soil loss areas. Straw incorporation is considered to significantly affect soil detachment. However, the knowledge about the influence of soil consolidation by rainfall and mechanical effect by straw incorporation in short-term on soil detachment capacity (Dc) by rill flow is still limited. The current study was carried out to quantify the impact of soil consolidation by rainfall and mechanical effect under straw incorporation on Dc. The soil samples were collected from seven different plots (straw incorporation rates of 0 (CK), 0.2, 0.4, 0.6, 0.8, and 1.2 kg m⁻² with rainfall simulation of 30 mm and without straw incorporation and rainfall simulation (CK0)) and subjected to flume scoring experiments. The results indicated that the Dc with different straw incorporation rates significantly differed and decreased by 39.16–60.04%, compared with CK. The Dc exhibited a power function relationship with hydraulic parameters and stream power was the most appropriate hydraulic variable to express Dc for different straw incorporation rates. The hydraulic characteristics, straw incorporation rates, and interaction between them have a significant impact on the Dc, and Dc was more sensitive to hydraulic characteristics. The contribution rates to Dc reduction benefits by soil consolidation exceeded those by mechanical effect of incorporated straw. The impact of incorporated straw with rainfall simulation in short-term on Dc has a threshold of a straw incorporation rate of 0.4 kg m⁻². The Dc for different straw incorporation rates could be satisfactorily simulated using the composite equation of binary power-exponential function of stream power and soil cohesion. This research reveals the impacts of soil consolidation by rainfall and the mechanical effect of incorporated straw on Dc, and offers a framework for predicting and managing soil erosion in areas susceptible to soil loss. Full article

During urbanisation, extensive production and construction activities encroach on ecological spaces, leading to changes in environmental structures and soil erosion. The issue of yellow muddy water caused by rainfall in cities with high construction intensity has garnered significant attention. Taking Guangzhou City as the research area, this study is the first to propose a risk assessment model for yellow muddy water in cities with high construction intensity, and the influence of construction sites on yellow muddy water was fully considered. Rainfall and construction sites were used as indicators to assess the hazards of yellow muddy water. Elevation, slope, normalised difference vegetation index (NDVI), soil erosion modulus, stream power index (SPI), surface permeability, and roads represent the exposure evaluation indicators. Population number and GDP (Gross Domestic Product) were used as vulnerability evaluation indicators. Based on the analytic hierarchy process (AHP) method, the weights of each evaluation indicator were determined, and a risk assessment system for yellow muddy water was established. By overlaying the weighted layers of different evaluation indicators on the geographic information system (GIS) platform, a risk degree distribution map of yellow muddy water disasters was generated. The evaluation results demonstrated that the disaster risk levels within the study area exhibited spatial differentiation, with areas of higher risk accounting for 14.76% of the total. The evaluation results were compared with historical yellow muddy water event information from Guangzhou, and the effectiveness of the model was verified by the receiver operating characteristic (ROC) curve. The validation results indicate that this model provides high accuracy in assessing the degree of risk of yellow muddy water in high-construction-intensity cities, offering effective technical support for precise disaster prevention and mitigation. Full article

The goal of this study is to investigate the surface morphology changes induced by the cavitation erosion of a coating based on cordierite with an epoxy matrix for an aluminum substrate. The literature review shows a certain lack of knowledge regarding the coating’s resistance to wearing induced by water flow, which is a highly important property of the material immersed in or in contact with water streams. The main idea behind the investigation is that such a protective coating will also improve the cavitation erosion resistance of metal substrates. The protective coatings were based on cordierite filler (88 wt.%) and epoxy resin (7 wt.%). The filler, made of a mixture of kaolin, alumina, and talc, is obtained by a sintering procedure that took place at 1350 °C. X-ray diffraction analysis and scanning electron microscopy were employed in the characterization of the produced filler. The adherence of the obtained epoxy-based protective coating and resistance to water flow were tested by the ultrasonic vibration method (i.e., cavitation erosion testing). Scanning electron microscopy was used for analysis of the coating’s morphology upon cavitation erosion. Based on the value of the cavitation erosion rate and the analyzed final surface damage, it was assessed that the investigated protective coating is resistant to cavitation erosion. Full article

During shale gas field production, wellhead throttle valves are prone to erosion caused by solid particles carried in the gas stream, posing significant safety risks. Existing studies on erosion primarily focus on simple structure like elbows and tees, while research on gas–solid two-phase flow erosion in needle throttle valves remains limited. This paper establishes a numerical model based on the CFD-DPM approach, integrating actual shale gas field production conditions to investigate the erosion behavior of needle throttle valves under varying openings, particle sizes, inlet velocities, and particle mass flow rates. The results show that the valve spool consistently exhibits the highest erosion rate among all components, with the most severe erosion localized at its front end. At a 1/4 opening, particles colliding with the spool exhibit significantly increased frequency and energy when re-entering the upstream pipeline, raising the risk of blockages. Furthermore, when the opening exceeds 2/4, the valve chamber experiences higher erosion rates than the upstream and downstream pipelines. This study provides critical insights for optimizing valve design and maintenance strategies, thereby enhancing service life and ensuring safe shale gas production. Full article

Gravel coverage on slopes influences overland flow and soil erosion. However, the effect of different gravel sizes on the soil erosion process remains underexplored. In this study, a runoff scour test was performed to examine the effects of gravel coverage on the hydrodynamic characteristics of slope runoff and sediment transport capacity (T_c). The slope gradient varied from 18% to 84%, the unit flow discharge ranged from 0.27 × 10⁻³ to 1.11 × 10⁻³ m² s⁻¹, and gravel coverage was adjusted from 0% to 90%. The results reveal that water depth, shear stress, and stream power increased with gravel coverage. However, once coverage exceeded 20%, flow velocity and unit stream power decreased and stabilized. As gravel coverage increased, the hydraulic regimes transitioned from laminar to turbulent flow and shifted from supercritical to subcritical. Consequently, T_c first increased and then decreased with the increase in gravel coverage, reaching a peak at 20% coverage (1.66 kg m⁻¹ s⁻¹). Moreover, the degree of coverage indirectly influenced T_c through grain shear stress. The new equations, based on the Box–Lucas function, incorporated slope, grain shear stress, and flow velocity, thereby effectively simulating T_c for runoff on gravel-covered slopes (R² = 0.94, NSE = 0.94). These findings provide a basis for modeling soil erosion on gravel-covered slopes. Full article

Critical shear stress and erosion rate are two key factors for the prediction of the incipient motion of sediment and the transport of sediment. Seabed seepage can significantly alter the pore pressure gradient within the soil and the hydrodynamics around the surface of the seabed, further affecting erosion processes. Previous studies attempted to theoretically clarify the effect of the seepage force on sediment incipient motion. In this study, a newly designed erosion–seepage system (ESS) that considers the effect of seepage under steady or oscillatory flow is used to simulate the erosion process. Through the designed ESS, the erosion height per unit time was measured directly on the Yellow River sand, and the upward seepage force was applied at the bottom of the soil sample in the process. Then, the relationship between the erosion rate and seepage was established.The experimental results show that upward seepage reduces the critical shear stress of the sand bed and increases the erosion rate of the soils under both steady flow and oscillatory flow conditions. The erosion coefficients in the erosion models decrease with increasing seepage gradient. The effect of seepage on erosion is more obvious when the flow velocity of the steady stream is large, while the effect of seepage on erosion is relatively small under the oscillatory state with a shorter period. However, when violent erosion of soil samples occurs, seepage under both flow conditions greatly increases the erosion rate. Full article

Acid mine drainage (AMD) generated during the exploitation and utilization of mineral resources poses a severe environmental problem globally within the mining industry. The Xiaomixi Stream in Ziyang County, Shaanxi Province, is a primary tributary of the Han River, which is surrounded by historically concentrated mining areas for stone coal and vanadium ores. Rainwater erosion of abandoned mine tunnels and waste rock piles has led to the leaching of acidic substances and heavy metals, which then enter the Haoping River and its tributaries through surface runoff. This results in acidic water, posing a significant threat to the water quality of the South-to-North Water Diversion Middle Route within the Han River basin. According to this study’s investigation, Xiaomixi’s acidic water exhibits yellow and white precipitates upstream and downstream of the river, respectively. These precipitates stem from the oxidation of iron-bearing minerals and aluminum-bearing minerals. The precipitation process is controlled by factors such as the pH and temperature, exhibiting seasonal variations. Taking the Xiaomixi Stream in Ziyang County, Shaanxi Province, as the study area, this paper conducts field investigations, systematic sampling of water bodies and river sediments, testing for iron and aluminum pollutants in water, and micro-area observations using field emission scanning electron microscopy (FESEM) on sediments, along with analyzing the iron and aluminum content. The deposition is analyzed using handheld X-ray fluorescence (XRF) analyzers, X-ray diffraction (XRD), and visible–near-infrared spectroscopy data, and a geochemical model is established using PHREEQC software. This paper summarizes the migration and transformation mechanisms of iron and aluminum pollutants in acidic water and proposes appropriate prevention and control measures. Full article

Polyurethane coatings are widely used as protective layers against wear, mainly abrasive wear. They have recently been applied to surfaces exposed to erosive wear, such as wind turbine blades. This study investigated the abrasive and erosive wear of polyurethane elastomeric coatings with hardness values of 55 ShA, 75 ShA, and 95 ShA. The abrasive wear test was carried out using loose abrasive grains. The erosive wear test was carried out using a pressurized stream of gas containing abrasive particles. Both tests were carried out using aluminum oxide grains of five different sizes to evaluate the effect of particle size on wear behavior. Microscopic and profilometric analyses of the surface of the wear tracks were carried out. The mechanism of abrasive and erosive wear of polyurethane elastomeric coatings was determined. The results of the tests show a non-linear dependence of abrasive and erosive wear on the grain size. Furthermore, polyurethane elastomer coatings with a higher hardness exhibit a lower abrasive wear resistance but higher susceptibility to erosive wear. These findings provide insight into the trade-offs between hardness and wear performance, offering practical guidance for selecting polyurethane coatings in applications requiring resistance to combined abrasive and erosive wear. Full article