Search Results (671)

Water jet scouring technology is extensively applied in marine engineering, harbor maintenance, river training, and various other fields, showcasing a broad spectrum of potential applications. However, achieving a comprehensive understanding of the transient sand scouring characteristics of water jets remains challenging due to the inherent complexity of the coupled flow structure involving submerged jets and environmental fluids, along with the intricate dynamics of two-phase flow. This study, rooted in numerical simulation and experimental validation, introduces pulse characteristics into a submerged jet. A thorough investigation is conducted to explore the transient sand scouring characteristics and sand transport laws of the submerged jet under diverse working conditions. The results of this study revealed that the main reason for the asymmetry of the sand pit morphology is not the non-uniform distribution of sand grains, but more likely caused by turbulence effects. Simultaneously, within the initial 0.25 s of the pulse cycle, suspended sediment resulting from the pulsed jet in the preceding cycle gradually transports to the dune and its surrounding areas. Subsequently, from 0.25 s to 0.5 s, sediment on both sides of the pit’s bottom undergoes movement and amalgamation with the sediment that remained unsettled during the previous cycle. The findings reveal that higher jet velocities significantly enhance sediment suspension, migration, and redeposition, leading to deeper erosion and the rapid formation of the sand pit’s outline within 2 s. Additionally, the jet velocity and the impact distance are identified as critical factors influencing erosion depth and sediment dynamics. These insights advance the understanding of erosion mechanisms driven by pulsed jets, highlighting their impact on sediment transport processes. The research findings provide important guidance for dredging and ocean engineering fields and offer a theoretical basis for improving the understanding of submerged jet scouring mechanisms. Full article

The Carboniferous–Permian coal deposits in the western margin of the Ordos Basin are known for their unique geological characteristics and potential enrichment of trace elements; however, there have been limited studies on the complex geological genesis of these elements, hindering the development of effective strategies for mineral resource exploration in this region. This study aims to investigate the distribution characteristics of trace elements in Carboniferous–Permian coal from the western margin of Ordos Basin, focusing on their complex geological genesis using techniques such as optical microscopy, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry. The results show that the average maximum vitrinite reflectance values in the Helanshan coalfield, Zhuozishan coalfield, and Ningdong coalfield are 1.25%, 0.83%, and 0.69%, respectively. Compared with the world’s hard coals, Li and Ga in Carboniferous–Permian coal from the western margin of the Ordos Basin are mildly enriched (CC, concentration coefficients; 2 < CC < 5) or enriched (5 < CC < 10). On the basis of revealing the response of the geochemical characteristics of coal to the geological development of the basin, the composite genetic model of terrigenous clastic supply, fault structure, low-temperature hydrothermal fluid and coal metamorphism have been established in Carboniferous–Permian coal in the western margin of the Ordos Basin. In this complex genetic model, folds and faults are very well developed. Although the provenance may have provided sufficient detrital sources for the study area, frequent tectonic changes, denudation, or scour led to the loss of detrital supply, and the provenance did not ultimately cause the enrichment of elements in the study area. However, the widely developed fault structure provided channels for sulfur-containing hydrothermal fluids, and the increase in coal metamorphism resulted in the enrichment of trace elements in the Carboniferous–Permian coal in the western margin of the Ordos Basin. Full article

Protecting coastal regions is crucial due to high population density and significant economic value. While numerous strategies have been proposed to mitigate scouring and protect coastal structures, existing techniques have limitations. This paper introduces a novel approach, SEAHIVE^®, which enhances the performance of engineered structures by utilizing hexagonal, hollow, and perforated concrete elements externally reinforced with glass fiber-reinforced polymer (GFRP). Unlike conventional steel bars, GFRP offers superior durability and requires less maintenance, making it a sustainable solution for any riverine and coastal environment. SEAHIVE^® aims to provide robust structural capacity, effective energy dissipation, and preservation of natural habitats. Although some research has addressed energy dissipation and performance in riverine and coastal contexts, the structural performance of SEAHIVE^® elements has not been extensively studied. This paper evaluates SEAHIVE^® elements reinforced with externally bonded GFRP longitudinal strips and pretensioned GFRP transverse wraps. Testing full-size specimens under compression and flexure revealed that failure occurred when the pretensioned GFRP wraps failed in compression tests and when longitudinal GFRP strips slipped in flexure tests. Strength capacity was notably improved by anchoring the GFRP strips at both ends. These findings underscore the potential of the SEAHIVE^® system to significantly enhance the durability and performance of coastal and riverine protection structures. FEM simulations provided critical insights into the failure mechanism and validated the experimental findings. In fact, by comparing FEM model results for cases before and after applying GFRP wraps under the same compression load, it was found that maximum stresses at crack locations were significantly reduced due to compression forces resulting from the presence of pretensioned GFRP wraps. Similarly, FEM model analysis on flexure samples showed that the most vulnerable regions corresponded to the locations where cracks started during testing. Full article

Owing to their excellent water-absorption and swelling properties, polymer microspheres have been extensively applied as deep profile control agents in oilfields. These microspheres effectively seal large pore-throat channels in reservoirs, optimizing the water-absorption profile. In this study, a composite system was developed, comprising polymer microspheres and polyacrylamide polymers, with the inclusion of a cross-linking agent. The system leverages the synergistic effects of polymer microspheres and other plugging techniques to efficiently seal fractured reservoirs. Results indicate that the composite system exhibits strong blocking and scour resistance due to enhanced network integrity, higher viscosity, and improved elastic strength. Additionally, the composite system demonstrates a notable self-repairing capability, maintaining a high sealing efficiency even after a waterflood breakthrough. Full article

Reservoirs deliver vital ecological services, including water storage and drainage. However, these functions are increasingly compromised by the dual pressures of climate change and human activities. Among the most pressing concerns is reservoir sedimentation, highlighting the urgency of investigating hydrodynamic sediment scouring. This study focuses on the plain reservoirs of Liaoning Province, using the Shifo Temple Reservoir as a case study. An optimized sediment scouring scheme was developed based on the reservoir’s hydrodynamic characteristics to improve water and sediment management. A coupled hydrodynamic and sediment transport (ST) model was constructed to simulate runoff dynamics and sediment distribution within the Liao he River Basin, while the MIKE21 model was applied to simulate the interaction between the hydrodynamics and sediment transport. The study analyzed groundwater dynamics across different runoff scenarios, seasons, and representative years, offering a scientific foundation for optimizing water and sediment allocation strategies. The results demonstrated a strong correlation between simulated and observed data during validation, confirming the accuracy of the hydrodynamic simulations. Utilizing the coupled HD and ST modules, the study proposed a sediment transfer scheme. The analysis revealed that flow rates between 165 and 190 m³/s significantly enhance sediment scouring in the long term (2029–2039) compared to the short term (2024–2029), effectively reducing sedimentation, minimizing deposition length, and lowering silt removal costs. The findings offer critical insights for predicting reservoir evolution and conducting risk assessments, thereby contributing to the sustainable management and ecological restoration of water systems in Liaoning Province. Full article

The geotextile mattress with floating plate (GMFP) is an innovative scour protection device. This study examines the potential for seepage failure under the GMFP, which has been previously documented. The effects of flow velocity and GMFP configuration on the potential for seepage failure were analyzed. The variation pattern of the sloping angle was first revealed in flume tests, and the bed pressure near the GMFP with various configurations in steady currents was thereafter simulated. The average hydraulic gradient across the GMFP was observed to increase with an increase in the Froude number before reaching a plateau, which can be explained by the coupled effects of the rising Froude number and the decreasing sloping angle. The average hydraulic gradient was approximately inversely proportional to the mattress length upstream of the floating plate. With the decreasing mattress length downstream of the floating plate, the average hydraulic gradient initially rose and then declined when the downstream mattress was relatively short. This trend can be associated with the amplification of the vortices in the top vortex zone downstream of the GMFP with the shortened downstream mattress, which pushed the bottom vortex to the leeside. The shortened downstream mattress could increase the risk of overturning and slipping of the GMFP, although the average hydraulic gradient decreased. Full article

The impact of an ice-covered environment on the local flow characteristics of a bridge pier was studied through a series of flume tests, and the dominant factors affecting the scour pattern were found to grasp the change laws of the local hydrodynamic characteristics of the bridge pier under the ice cover. At the same time, because the scour problem of the pier foundation is a technical problem throughout the life-cycle of the bridge, to determine the optimal anti-scour protection effect on the foundation of the bridge pier, active protection scour plate was used to carry out scour protection tests, and its structural shape was optimized to obtain better anti-scour performance. The test results show that the jumping movements of sediment particles in the scour hole around the pier are mainly caused by events Q2 and Q4, which are accompanied by events Q1 and Q3 and cause the particle rolling phenomenon, where Q1 and Q3 events are outward and inward interacting flow regimes, and Q2 and Q4 events are jet and sweeping flow regimes, respectively. The power spectral attenuation rate in front of the upstream pier is high without masking effects, while strong circulation at the remaining locations results in strong vorticity and high spectral density, in particular, when the sampling time series is 60 s (i.e., f = 1/60), the variance loss rates under ice-covered conditions at the front of the upstream pier, between the two piers, and at the tail end of the downstream pier are 0.5%, 4.6%, and 9.8%, respectively, suggesting a smaller contribution of ice cover to the variance loss. Full article

Scouring is a major concern affecting the overall stability and safety of a bridge. The current research investigated the effectiveness of the various artificial intelligence (AI) techniques, such as artificial neural networks (ANNs), the adaptive neuro-fuzzy inference system (ANFIS), and random forest (RF), for scouring depth prediction around a bridge abutment. This study attempted to make a comparative analysis between these AI models and empirical equations developed by various researchers. The current research paper utilized a dataset of water depth (Y), flow velocity (V), discharge (Q), and sediment particle diameter (d50) from a controlled laboratory setting. An efficient optimization tool (MATLAB Optimization Tool (version R2023a)) was used to develop a scour estimation formula around bridge abutments. The findings of the current investigation demonstrated the superior performance of the AI models, especially the ANFIS model, over empirical equations by precisely capturing the non-linear and complex interactions between these parameters. Moreover, the result of the sensitivity analysis demonstrated flow velocity and discharge to be the most influencing parameters affecting the scouring depth around a bridge abutment. The results of the current research highlight the precise and accurate prediction of the scouring depth around a bridge abutment using AI models. However, the empirical equation (Equation 2) demonstrated better performance with a higher R-value of 0.90 and a lower MSE value of 0.0012 compared to other empirical equations. The findings revealed that ANFIS, when combined with neural networks and fuzzy logic systems, produced highly accurate and precise results compared to the ANN models. Full article

Examining scouring around bridge piers is crucial for ensuring water-related infrastructure’s long-term safety and stability. Accurate forecasting models are essential for addressing scour, especially in complex water systems where traditional methods fall short. This study investigates the application of the HEC-RAS 2D sedimentation model, which has recently become available for detailed sediment analysis, to evaluate its effectiveness in predicting scoring around various pier shapes and under different water conditions. This study offers a comprehensive assessment of the model’s predictive capabilities by focusing on variables such as water velocity, shear stress, and riverbed changes. Particular attention was paid to the influence of factors like floating debris and different pier geometries on scour predictions. The results demonstrate that while the HEC-RAS 2D model generally provides accurate predictions for simpler pier shapes—achieving up to 85% precision—it shows varied performance for more complex designs and debris-influenced scenarios. Specifically, the model overpredicted scouring depths by approximately 20% for diamond-shaped piers and underpredicted by 15% for square piers in debris conditions. Elliptical piers, in contrast, experienced significantly less erosion, with scour depths up to 30% shallower compared to other shapes. This study highlights the novel application of the HEC-RAS 2D model in this context and underscores its strengths and limitations. Identified issues include difficulties in modeling water flow and debris-induced bottlenecks. This research points to the improved calibration of sediment movement parameters and the development of advanced computational techniques to enhance scour prediction accuracy in complex environments. This work contributes valuable insights for future research and practical applications in civil engineering, especially where traditional scour mitigation methods, such as apron coverings, are not feasible. Full article

Microbially induced carbonate precipitation (MICP) technology is employed to reinforce the surface soil of a dam, aiming to prevent erosion caused by water flow and damage to the dam slope. The relationship between penetration depth, calcium carbonate content, and bonding depth was investigated at eight measuring points on the sand slope surface of a mold under different reinforcement durations. It was observed that as grouting reinforcement times increased, there was a gradual increase in calcium carbonate content but a rapid rise in penetration resistance. Moreover, the bonding depth of sand on the bio-reinforced sand slope increased with higher levels of calcium carbonate content. Microbial grouting reinforcement enhanced soil particle bonding force, requiring water flow to overcome this force for activation of sand particles. Consequently, microbial grouting reinforcement significantly improved shear strength and critical starting flow velocity on sand slope surfaces. The experimental results demonstrated that after MICP surface treatment through spraying, a dense and water-stable hard shell layer composed of bonded calcium carbonate and soil particles formed continuously on sample surfaces, effectively enhancing the strength and erosion resistance of sandy soils. These findings provide reliable evidence for silt slope reinforcement and dam erosion prevention. Full article

Gas pipelines are buried and installed across rivers to supply the gas necessary for daily life. When crossing rivers, gas pipelines are typically installed on bridges; however, when installation on bridges is not feasible, the pipelines are buried in riverbeds. This study utilized both a one-dimensional model (HEC-RAS) and two-dimensional models (SMS) to simulate river flow and estimate the potential for scour and deposition around buried pipelines. The hydrodynamic simulations considered critical factors, including sediment transport, river discharge, and geological characteristics, to derive the maximum scour depth and assess the risk of pipeline exposure. The findings from the long-term and short-term simulations confirmed that riverbed changes due to natural hydrological events do not exceed the minimum burial depth standards, thereby ensuring pipeline safety. In addition, the study proposed specific reinforcement measures tailored to local site conditions, addressing concerns of continuous subsidence and ensuring long-term structural stability. This research offers important insights into pipeline risk management and contributes to the development of more effective regulatory standards for gas pipelines buried in riverbeds, enhancing both their safety and environmental sustainability Full article

The stability of bridge foundations is affected by local scour, and the formation of ice jams exacerbates local scour around bridge piers. These processes, particularly the evolution of ice jams and local scour around piers, are more complex in curved sections than in straight sections. This study, based on experiments in an S-shaped channel, investigates how various factors—the flow Froude number, ice–water discharge rate, median particle diameter, pier spacing, and pier diameter—affect the maximum local scour depth around double piers in tandem and the distribution of ice jam thickness. The results indicate that under ice-jammed flow conditions, the maximum local scour depth around double piers in tandem is positively correlated with the ice–water discharge rate, pier spacing, and pier diameter and negatively correlated with median particle diameter. The maximum local scour depth is positively correlated with the flow Froude number when it ranges from 0.1 to 0.114, peaking at 0.114. Above this value, the correlation becomes negative. In curved channels, the arrangement of double piers in tandem substantially influences ice jam thickness distribution, with increases in pier diameter and spacing directly correlating with greater ice jam thickness at each cross-section. Furthermore, ice jam thickness is responsive to flow conditions, escalating with higher ice–water discharge rates and decreasing flow Froude numbers. Full article

Recent studies have revealed that the frequency and magnitude of floods tend to increase due to climate change. Hence, excessive scouring due to flood events puts river bridges at greater risk of failure. This paper presents the initial findings of an experimental study to improve the understanding of the main characteristics of bridge pier scour under pressurized flow encountered during flooding. The experiments were carried out in four main groups according to two deck alignments with circular and oblong pier shapes. For each group of experiments, thirty-six tests were conducted under partially and fully pressurized flow conditions using four approach flow depths and three discharge values. The validity of the structured design approach for pier scour estimation implemented in the guidelines was investigated. The results showed that the bridge pier scour depths were up to 29.4% and 49.4% greater than the sum of the vertical contraction and local scour depths for 100 L/s for partially and fully pressurized flow conditions, respectively. However, as the discharge increased to 120 L/s, the bridge pier scour depth became 38.3% and 17.8% smaller than the sum of the vertical contraction and local scour depths for partially and fully pressurized flow, respectively. So, the structured design approach was determined to be safe for high discharge values. Furthermore, it was found that tests with a circular pier resulted in higher bridge pier scour depths than the sum of the vertical contraction and local scour depths up to 19.3% even for 120 L/s. Conversely, smaller bridge pier scour depths than the sum of the vertical contraction and local scour depths were observed up to 17.8% for tests with oblong piers. Thus, it can be concluded that the pier shape has a profound effect on scour holes and oblong piers cause smaller scour depths than circular piers in pressurized flow conditions. This study showed that the flow–pier–deck interaction significantly affects the depth and width of the scour hole, especially for small discharges and fully pressurized flow conditions. Full article

Microfibers are small fiber particles that separate from larger textiles through wear abrasion or home laundering. Pervasive accumulation of synthetic microfibers in the environment is motivating efforts to quantify them, and to gain a better understanding of the factors that lead to their release from garments. Automated imaging systems have been previously employed for the quantification of synthetic and natural microfibers. In the current study, a rayon standard and microfibers sourced from scoured cotton HVI calibration standards were examined with the Fiber Quality Analyzer-360 (FQA) automated imaging system. Mechanically stirred suspensions of six cotton microfiber standards showed significantly lower fiber counts than those obtained with a rayon standard. Probe sonication of the sample suspensions significantly increased observed fiber counts for the cotton standard samples, by 105% on average. Mean length determinations decreased by, on average, 5% for the sonicated samples, an indication that count increases were not due to sample fragmentation. No significant change was observed for the fiber counts or length measurements of the sonicated rayon samples. The sonicated cotton samples showed an average of 95% detection by the FQA. These results highlight the importance of proper microfiber suspension for accurate detection and quantification using the FQA system. Full article

Spontaneous vegetation within a managed green space is often regarded as unwelcoming and insignificant weeds. This perception is still deep-rooted among green-space managers and the general public worldwide; they are generally uncertain about the management needs after allowing these groups of flora to take root. The short-term growth dynamics of both spontaneous and planted vegetation should be analyzed, and a widely acceptable, feasible management plan to balance aesthetic and ecological functions should be formulated with the backing of data and analysis for such fast-growing flora in tropical and subtropical regions. A manicured, extensive green roof with only seven (two native, five exotic) plant species was transformed into a renaturalized biotope by replacing 15 native ferns and forb species over 15 months. After planting, a baseline plant survey was conducted, with 54 plant species representing spontaneous growth and 14 planted species alive (7 planted native species survived, plus 7 species planted prior to renaturalization revived). Three quarterly plant surveys recorded the cover-abundance of each species, and the growth dynamics of the planted and spontaneous plant species were evaluated over the first year of study. During each quarterly survey, the number of planted and spontaneous plant species remained stable (ranging from 14 to 16 species and 51 to 54 species, respectively), with a constant turnover of 11 to 12 die-out species and 11 to 12 newly colonized or revived species. Plant coverage of different plant forms fluctuated slightly (within 7%) in the quarterly surveys according to seasonal changes, except for ferns, which outperformed (12% increase in coverage in a year) all the other plant forms. The height of the planted vegetation fluctuated in a year, being shorter during the summer, while the height of spontaneous vegetation remained stable throughout the year, exhibiting resilience to scouring heat. The seasonal growth tendencies of both planted and spontaneous plants were illustrated in relation to their species ranks, and further hierarchical cluster analysis was conducted for the clustering of spontaneous species. Their differential growth patterns provided comprehensive information or supported decisions regarding plant selection and maintenance, which is a scientific novelty within this unexplored topic. Management recommendations based on the findings were suggested to fulfill both aesthetic and ecological needs. Species with stable and less stable growth patterns could be useful to meet maintenance efficiency and biodiversity enhancement needs, respectively. These findings provide insights to form guiding principles for choosing plant species for renaturalization projects. Full article