Termites build nest systems within embankments,damaging the integrity of the soil structure,which is one of the main causes of major engineering accidents such as piping and landslides,seriously threatening the safe operation of China's water conservancy projects.According to statistics,the direct economic losses caused by termite damage in China exceed 2.5 billion yuan annually.Moreover,with climate warming of the climate and the northward shift of the rain belt,the activity range of termites continues to expand,affecting 18 provinces including Jiangsu,Zhejiang,Anhui,and Henan.The prevention and control of termite infestation in embankments is urgent.Ground-penetrating radar technology,with its rapid,non-destructive,and high-resolution imaging capabilities,demonstrates significant advantages in detecting termite nests and has become an important research direction in this field.However,this technology still faces many challenges in practical applications.This paper systematically explains the technical principles of ground-penetrating radar for detecting termite nests,introduces the core detection method of reflection and the basis for equipment selection,and analyzes the structural characteristics(including the main nest,secondary nests,and tunnel network)and geophysical properties(conductivity,dielectric properties,density differences)of termite nests,clarifying their physical property basis for detection.Based on this,the paper comprehensively reviews the research and application progress from four aspects:detection influence mechanisms,data processing and analysis,integrated geophysical exploration techniques,and intelligent detection systems.In terms of detection influence mechanisms,existing studies have revealed the constraining relationship between antenna frequency and detection depth,clarified the rule that high water content leads to intensified signal attenuation,and summarized the differences in signal characteristics between nests and tree roots,cavities,etc.However,understanding of the combined effects of multiple factors remains insufficient,and the fidelity of numerical simulations is limited.In terms of data processing and analysis,techniques such as singular value decomposition have been applied for signal denoising,and indicators such as reflection coefficient and peak frequency can be used for nest identification,but the clata processing still relies on experience and lacks dedicated algorithms and a multi-parameter joint discrimination system.In terms of integrated geophysical exploration technology,the joint application of ground-penetrating radar and the high-density resistivity method has been preliminarily implemented,effectively reducing the misjudgment rates,but standardized technical procedures are still lacking.In terms of intelligent detection systems,deep learning algorithms have achieved classification and recognition of nests and interference objects,but the model generalization remains limited,and the recognition accuracy for deep and small-sized nests needs improvement.In response to the above technical bottlenecks,this paper proposes the following five future research directions and corresponding solutions:first,promote coordinated innovation in detection equipment and methods,develop a composite antennas integrating low-frequency penetration and high-frequency resolution,and enhance detection capability for medium-and shallow-depth nests;second,deepen the research on environmental coupling mechanisms,use CT scanning and 3D printing technologies to construct a high-fidelity physical models of nests,and establish a quantitative relationship between nest parameters and radar spectral characteristics;third,improve data processing and multi-parameter analysis capability by extracting multi-dimensional features such as amplitude,phase and frequency,and establish a dedicated discrimination system for termite nests;fourth,advance integrated geophysical exploration technologies by establishing a three-level detection system"general survey-detailed survey-precise survey",and formulating data fusion and interpretation standards;fifth,develop end-to-end intelligent detection systems by integrating deep learning from data acquisition to risk assessment to achieve automation and intelligence.The coordinated advancement of above research directions is expected to overcome existing technical bottlenecks and provide a theoretical basis and technical reference for achieving precise and efficient detection of termite nests.
Existing water resource system simulation and scheduling models fall short in meeting the demands of"forward and reverse pre-rehearsal"in water resource allocation and management.These demands entail multi-element simulation and forecasting,integrated with the flexible and efficient optimization of complex regulation rules.To address these challenges,this study first reviews the pre-rehearsal requirements for basin-level water resource management.On this basis,it proposes a novel approach that divides the water resource system into core units by twinning key nodes.The study outlines system generalization principles and unit modeling methodologies,and introduces a comprehensive simulation model for basin water resources.This model simulates the dynamic interactions of various elements—available water,inflow,demand,usage,and shortage—across multiple scheduling schemes,capturing the full lifecycle of water resource dynamics within the basin.Further,based on this simulation model,the study develops a method for constructing optimization-based scheduling models adaptable to diverse scheduling goals,thereby providing a framework for efficiently deriving optimal operational rules.The proposed methods are implemented on the digital twin platform developed for the Huanglei River Basin(Shandong Peninsula,China).Validation is carried out through two key case studies:Retrospective Analysis of a Typical Drought Year(2015):The model accurately reproduced historical drought conditions,validating its capability for historical scenario reconstruction("reverse pre-rehearsal").Dynamic Assessment of a Real-time Water Shortage Event(May 2023):The platform dynamically evaluated a live water shortage scenario,demonstrating its utility for real-time awareness and forecasting("forward pre-rehearsal").The findings confirm that the proposed approach enables:Full-process simulation of multi-element water dynamics throughout the basin;highly efficient optimization of scheduling rules for key infrastructure—including surface reservoirs,sluices/dams,and water diversion works—under various goals.Significance and Support Capabilities:The integrated modeling framework offers robust computational support for pre-rehearsal functions in three key domains:(1)Identifying Issues under Routine Schemes:Facilitates early detection and diagnosis during evaluations of conventional scheduling plans.(2)Pre-rehearsing Decision Impacts during Consultations:Supports assessment of anticipated impacts prior to implementing decisions during coordination meetings.(3)Deriving Optimized Schemes for Specific Targets:Enables generation of scientifically grounded,optimized scheduling strategies for defined management goals(e.g.,maximizing supply reliability,minimizing shortages,or preserving ecological flows).In sum,this research delivers a robust,adaptable modeling foundation essential for enhancing the precision and effectiveness of water resource pre-rehearsal within digital twin-based basin management systems.
The intake and drainage system of cooling water is a key component of coastal power plant projects.In recent years,as China's nuclear power development has steadily expanded and shifted toward offshore islands,increasingly complex wave conditions in open sea areas have made wave forces a primary factor affecting the safety of drainage structures.The steel cap-type variable cross-section drainage riser structure is a commonly employed configuration in the drainage engineering of coastal power projects.In this study,a three-dimensional(3D)wave physical model test was conducted to simultaneously measure the inline force,transverse force,and uplift force acting on the steel cap-type variable cross-section drainage riser.The temporal variation of the forces on the variable cross-section drainage riser was analyzed,the effects of water discharge and submergence depth on the forces were examined,and calculation methods for the inline and transverse forces of the variable cross-section drainage riser were developed.The 3D wave physical model test was performed in the wave basin of Nanjing Hydraulic Research Institute,which has dimensions of 50.0 m in length,17.5 m in width,and 1.2 m in depth.Wave-absorbing slopes or plates were installed around the basin to reduce wave reflection.The results of the 3D wave physical model test indicate that under the combined action of waves and water discharge,the forces on the drainage riser display periodic variations,with the force variation period corresponding to the wave period and accompanied by high-frequency fluctuations.These high-frequency fluctuations may be attributed to the turbulent state of the discharged water inside the pipe and the pulsating behavior of water particle motion.By comparing the peak values of the uplift force,inline force,and transverse force on the drainage riser structure,it is found that the uplift force is the largest,followed by the inline force,while the transverse force is slightly smaller than the inline force.The influence of the transverse force on the drainage riser structure cannot be ignored and must be highlighted in future engineering design.Regarding the timing of the peak values of the uplift force,inline force,and transverse force on the steel cap-type variable cross-section drainage riser structure,the peaks of the inline force and transverse force occur simultaneously,indicating no phase difference between them.However,the peak of the uplift force does not coincide with that of the inline force or transverse force,showing a phase difference of approximately π/2 between the uplift force and the inline or transverse forces.Water discharge has almost no effect on the phase relationship among the inline force,transverse force,and uplift force.Water discharge significantly amplifies the uplift force,with an increase ranging from 25%to 75%.The uplift force under the combined action of waves and water discharge exceeds the linear superposition of the force due to waves alone and the force due to water discharge alone.In contrast,water discharge has no significant amplifying effect on the inline force and transverse force of the drainage riser.The relative submergence depth is a key parameter affecting the forces on the drainage riser.The relative maximum inline force and transverse force occur at a relative submergence depth of zero,while the relative maximum uplift force occurs at a relative submergence depth of 0.013.For small-scale variable cross-section drainage riser structures,the Morison equation can be applied for segmented calculation.However,for the force calculation of the perforated structure,a void ratio reduction coefficient should be introduced.By incorporating this coefficient,the wave force on the perforated structure can be calculated with a maximum error of less than 4%.The wave force calculation method for variable cross-section perforated drainage riser structures proposed in this study can serve as a reference and validation for future similar engineering designs and numerical simulations.
The widespread construction of hydropower projects worldwide represents a double-edged sword,providing essential energy while simultaneously causing profound ecological disturbances by erecting impassable barriers that severely fragment riverine habitats.This fragmentation critically disrupts the longitudinal connectivity required by numerous rheophilic fish species to complete their essential life-cycle migrations—such as movements to and from spawning,feeding,and overwintering grounds—inevitably leading to the decline of native riverine fish populations.To mitigate these adverse ecological impacts,the installation of fish passage facilities has become an indispensable component of modern dam design and river restoration strategies.Among these engineering solutions,the fishway(or fish ladder)is particularly prevalent,owing to its relatively simple structure,lower construction cost,and ease of maintenance,making it a primary tool for restoring connectivity.Despite their widespread use and apparent necessity,fishways suffer from a critical deficiency:the lack of rigorous,quantitative assessment of their actual ecological effectiveness.The success of a fishway is seldom measured by the number of fish that successfully pass the barrier,making it difficult to distinguish a functional facility from a mere structural appendage.This difficulty in achieving quantitative evaluation is multifaceted,arising from the substantial variability in fish community structures across different rivers,the markedly diverse migratory behaviors and swimming capabilities of target species,the broad spectrum of existing fishway structural designs(e.g.,vertical-slot and pool-and-weir types),and the highly dynamic hydraulic conditions governed by fluctuating hydropower operational regimes.Consequently,making meaningful cross-system comparisons of passage efficiency remains exceptionally challenging,firmly establishing the development of robust,standardized,and quantifiable metrics as a priority for future ecological engineering research.To address this pressing need and enhance the effectiveness of existing infrastructure,this comprehensive study conducted a detailed investigation into the hydraulic characteristics and attraction efficiency of the Jiacha fishway during its peak migratory season.The research employed a rigorous methodology,beginning with intensive fishery surveys conducted both within the fishway structure and in the immediately downstream river reach.This effort successfully characterized the local fish community,unequivocally identifying the three dominant species of Schizothorax—namely the Schizothorax waltoni,Schizothorax oconnori,and Schizothorax macropogon—as the primary migratory targets.Collectively,these three species accounted for approximately 78.9%of the total fish encountered,underscoring their critical ecological and conservation significance.Building upon this biological foundation,the research proceeded to the critical hydraulic analysis.By synthesizing physiological data on the species'swimming performance—including both prolonged and burst speeds—the suitable flow velocity range permitting successful and non-exhausting upstream movement within the fishway was theoretically determined to be 0.2 to 1.9 m/s.This range is essential for guiding operational limits.Furthermore,to fully characterize the flow dynamics,a detailed two-dimensional(2D)hydrodynamic model was developed specifically for the complex geometry of the fishway's entrance pool and initial channel segment.This model was then employed to perform numerical simulations of the flow field across a comprehensive matrix of operating scenarios,encompassing varied fishway discharge rates in combination with different downstream river water levels(tailwater depths).The key findings from the simulations provided actionable insights for adaptive management.The research conclusively established that downstream river water level is the most influential factor controlling flow velocity at the fishway entrance.Notably,the simulations indicated that during periods of significantly low river levels,the maximum velocity generated at the narrow vertical slot of the entrance often exceeds the burst swimming capacity of the target Schizothorax species.This condition creates an overpowering velocity barrier,or an"impassable jet,"effectively preventing or severely deterring fish from successfully detecting and entering the facility.Based on these findings,the study proposes a refined,adaptive operational strategy essential for optimizing the fishway's performance.To manage this velocity barrier effectively,the operational recommendation is clear:during periods of low downstream water level,the fishway discharge must be systematically reduced.This measure is intended to directly control the water head drop(energy dissipation)at the entrance,thereby ensuring that the resulting flow velocities remain safely within the ecologically determined optimal range of 0.2 to 1.9 m/s.By implementing this dynamic operational adjustment,the Jiacha fishway can substantially minimize hydraulic interference with the natural migratory behavior of the fish.In conclusion,this research not only provides a concrete,scientifically supported optimization plan for the Jiacha fishway—significantly enhancing its ecological effectiveness—but also establishes a robust,quantitative methodology that can be readily transferred and applied to the assessment and adaptive management of fish passage facilities across diverse river systems worldwide.
The Qinghai-Tibet Plateau,a region highly sensitive to global climate change,hosts the headwaters of the Yangtze River.The dynamics of its cryosphere,particularly snow cover,are critical to regional water resources and ecological security.Given the observed high variability of snow cover under climate warming,a quantitative analysis of its response mechanisms to temperature and precipitation anomalies at the sub-basin scale'is essential for accurate hydrological projections.To better reveal the spatial heterogeneity and climate-driven mechanisms of snow cover change in the source area of the Yangtze River,the region was divided into four sub-regions based on sub-basins:Tuotuo River,Dangqu,Chumar River,and other sub-regions,and the variation characteristics of snow cover indices in each sub-region and their relationships with climatic factors were explored.Based on snow cover,temperature,and precipitation data from 1980 to 2020,the spatiotemporal variation characteristics of snow cover in sub-regions were analyzed,using the Mann-Kendall test to detect monotonic trends and the ESMD method to identify nonlinear and non-stationary oscillations in the time series.The relationship between snow cover and climatic factors was analyzed using the partial correlation method to isolate the individual influence of temperature and precipitation by controlling for the other.To move beyond traditional statistical correlations and explore the physical mechanisms,the XGBoost-SHAP model was employed,leveraging its strong predictive performance and the SHAP framework's interpretability to reveal nonlinear thresholds and interaction effects.The results showed that snow cover changes exhibited significant spatial heterogeneity:during the snow accumulation period in the source area of the Yangtze River,average snow depth and snow water equivalent showed an increasing trend in southeastern and high-altitude peripheral areas,while other areas showed a decreasing trend.Snow depth and snow water equivalent increased in high-altitude areas of the Tuotuo River,the margins of Dangqu,the northwest of the Chumar River,and small southeastern parts of other regions,while most other areas generally decreased,and snow cover extent was mostly declining.This spatial pattern can be attributed to the fact that high-altitude and southeastern peripheral regions,with persistently lower temperatures,are less susceptible to warming-induced melt,allowing potential precipitation increases to dominate snow accumulation trends,whereas lower-lying and central areas are more vulnerable to temperature-driven ablation.Correlation analysis showed that snow cover changes in the four sub-regions were not consistent with changes in precipitation and temperature,overall,snow cover was positively correlated with precipitation;snow depth and snow water equivalent were negatively correlated with air temperature in the Tuotuo River and Dangqu,while a few areas in the northwest of the Chumar River and southeastern parts of other regions showed positive correlations,and most other regions showed negative correlations;snow cover extent was mostly negatively correlated with temperature,indicating spatial differences in the impact of climate warming and humidification on snow cover in cold regions.The XGBoost-SHAP model shows that historical precipitation conditions have a greater effect on current snow depth than instantaneous precipitation.Precipitation in low-temperature ranges contributes positively to snow cover,but as temperature rises,this positive contribution gradually weakens until it disappears,with SHAP values approaching 0 when the temperature is at-15℃to-10℃.Thereafter,the interaction between temperature and precipitation leads to snow reduction,and even increased precipitation cannot further increase snow.When the temperature is at-5℃to 0℃,snow change reaches another critical point,beyond which further temperature increases no longer significantly intensify snow reduction.The stronger influence of historical precipitation indicates that snow has a"memory effect",whereby prolonged wet or dry conditions affect subsequent accumulation or melting.The nonlinear relationship between temperature and snow characterizes phase change processes more accurately than linear assumptions,helping to improve traditional hydrological models,enhance snow prediction accuracy,and better assess the impacts of climate change on the cryosphere.
When a ship navigates in restricted waters,the complex interaction between the moving hull and the confined water body generates a distinctive flow structure.The spatial distribution of the time-averaged flow velocity near the hull directly affects the ship's maneuverability and stability,and plays a critical role in ensuring operational safety.In this study,high-resolution Particle Image Velocimetry(PIV)technology was employed to conduct open-channel turbulence tests using a scaled ship model in a restricted water environment.The distribution characteristics of time-averaged velocity around the hull were examined,focusing on the effects of varying cross-sectional coefficients and inflow conditions.The influence of these two key factors on the longitudinal and vertical components of the time-averaged velocity was analyzed.Results show that the maximum longitudinal velocity U in restricted waters appears beneath the ship.Influenced by the descending flow at the bow and the ascending backflow behind the stern,the vertical velocity V peaks near the bow and downstream of the stern,with the most significant velocity changes occurring near the bow.The dimensionless longitudinal time-averaged velocity beneath the hull exhibits an asymmetric"⊃"-shaped distribution along the vertical axis.The vertical flow velocity initially increases and then decreases from the hull bottom to the channel bed,approximating an"S"-shaped pattern within the stern vortex region.The longitudinal time-averaged velocity decreases with an increasing cross-sectional coefficient,with its maximum value reaching approximately 1.35 times the average cross-sectional velocity.However,the position of the velocity peak remains largely unaffected.As the inflow velocity rises,the longitudinal time-averaged velocity increases accordingly,and the dimensionless profile reveals distinct zoning:the high-velocity zone beneath and in front of the hull expands,the low-velocity zone near the bow contracts,and the stern backflow zone enlarges.Nonetheless,variations in inflow velocity do not significantly alter the location of maximum flow velocity.These findings provide a scientific basis for the design and maintenance of restricted waterways and the safe navigation of vessels.
From the perspective of systems science,this article systematically examines the multi-layered systemic characteristics of river systems and river governance.It argues that river systems are typical natural geographical systems,exhibiting integrated features of morphological systems,cascading systems,process-response systems,and control systems.These characteristics reflect the holistic and dynamic nature of river systems,in which matter and energy are transferred along upstream-downstream and main-tributary networks,continuously driving their evolution.On this basis,human development and utilization of rivers—through reservoirs,dams,and inter-basin water transfer projects—further transform river systems into civil engineering systems with clear objectives,autonomy,and constraints,exerting profound impacts on river morphology,hydrological processes,ecological environments,and social structures.The article further emphasizes that river governance is not a matter of isolated projects or single factors,but a complex multi-variable,multi-mechanism system involving natural,engineering,economic,social,and ecological elements.The overall system state is determined by direct and indirect interactions among elements,feedback mechanisms,and their fully coupled pathways.Through analysis of system structures and mechanism pathways,the author highlights that effective river governance must adopt a systems-thinking approach:clarifying governance objectives,constructing a comprehensive system framework,accurately identifying key elements and their interactions,and closely monitoring system evolution trends.Only under an integrated,coordinated,and forward-looking governance framework can river systems evolve toward sustainable harmony between humans and nature.
Since the completion of the Three Gorges Dam, navigation conditions in the Three Gorges section of the Yangtze River have become increasingly complex, and the assessment of navigation risk is critical to the safe operation of the reservoir area. Existing studies have primarily focused on environmental, managerial, vessel, and human factors, relying on theoretical assumptions and expert experience, which may introduce subjective bias. Additionally, previous assessment studies have not given sufficient attention to vessel navigation and accident data in the Three Gorges section of the Yangtze River. To address these problems, this study collects data on the waterway conditions of the Three Gorges section and expert judgments regarding its navigational conditions to establish a risk assessment indicator system. Subsequently, on the one hand, data from the Automatic Identification System (AIS) are collected to extract vessel count and design deadweight tonnage, which are incorporated into the risk assessment indicator system. The Analytic Hierarchy Process (AHP) is employed to determine the weights of individual evaluation indicators. Combined with the Fuzzy Comprehensive Evaluation (FCE) model, and through calculation of a three-tier evaluation matrix, the navigational risk value for the Three Gorges section using the original model is derived. On the other hand, accident data are systematically collected, cleaned, sorted, and subjected to preliminary statistical analysis. An Information Value-Logistic Regression (IV-LR) integrated model is then introduced to analyze the accident data, enabling quantification of the correlation between influencing factors and accident occurrence. These quantified correlations are integrated into the indicator system to form more objective factor weights, thereby improving the fuzzy comprehensive evaluation model. The three-tier evaluation matrix is then recalculated to obtain the improved navigational risk value for the Three Gorges section using the improved model. Finally, a comparative analysis is conducted on the navigational risk assessment results for the Three Gorges section obtained respectively from the original and improved models used in this study. The evaluation results of the original model showed that the overall navigation safety level of the Three Gorges section in 2024 was rated as “Basic Safety”, while the segmental risk assessment found that the safety levels of the Chongqing–Fuling section and the Fuling–Fengdu section were rated as “Needs Attention”, indicating that the model failed to fully reflect the actual conditions of local navigation segments in the overall risk assessment. The evaluation results of the improved model revealed that the integration of the IV-LR model indicated the overall navigational safety level of the Three Gorges section in 2024 was at the “Needs Attention” level, which more accurately reflected the actual conditions of local segments. The model also identified meteorological conditions, waterway complexity, and vessel design tonnage as major factors significantly affecting navigation safety. Additionally, safety awareness and the completeness of the supervision system were identified as potential high-risk factors requiring continuous attention. Factors such as vessel composition, anchorages, berthing areas, and port operation zones were classified as extremely high-risk sources in Section IV. However, their odds ratios showed negative correlations, indicating that existing control measures had already mitigated the risks associated with these factors. The results demonstrate that the improved model can provide evaluation outcomes that account for both overall and local risks, offering stronger practical guidance for navigation safety management in the Three Gorges section. This approach integrates objective accident data with traditional expert knowledge, thereby enhancing the objectivity of risk assessment. The proposed methodology provides valuable support for decision-making related to waterway safety management, early warning system development, and accident prevention strategies. Furthermore, this method is applicable to navigational risk assessment in other complex inland waterway systems, contributing to the broader field of waterway transportation safety research.
With the development of inland waterway and sea-river interconnection projects,underwater borehole blasting is essential to channel improvement,harbor basin dredging,and cofferdam demolition.In waterway engineering projects,over and under excavation affect excavation quality,dredging workload,and slope trimming.Compared with tunnel blasting,underwater blasting is more difficult to measure and control because the blasting face is concealed,rock mass and water depth exhibit spatial variability,and blasting effects are influenced by drilling accuracy,charge structure,delay timing,subdrilling depth,and construction management.Therefore,a refined management approach integrating sensing,modeling,calculation,visualization,and feedback control is needed.Taking the Pinglu Canal waterway excavation project as the background,this study establishes a digital twin-based framework for controlling over and under excavation in underwater borehole blasting.Based on the five-dimensional digital twin model,the Pinglu Canal digital twin system was structured into the physical,perception,transmission,virtual,and application layers.The physical layer includes blasting equipment,survey instruments,monitoring devices,construction personnel,and the site environment.The perception layer acquires geospatial,geological,construction-process,safety-management,and blasting-performance information.The transmission layer is responsible for data cleaning,storage,and exchange,while the virtual and application layers support model reconstruction,over and under excavation calculation,three-dimensional visualization,parameter optimization,and construction quality management.To establish the digital twin data foundation,high-precision scanning equipment was used to acquire terrain and bathymetric point-cloud data in the blasting area.An unmanned aerial vehicle equipped with LiDAR collected above-water slope and ground data,while an unmanned surface vessel equipped with a single-beam echo-sounding system collected underwater channel-bed data.The raw point-cloud data were processed according to the characteristics of waterway excavation projects.First,obvious outliers caused by mechanical vibration,floating objects,dust,or construction equipment were removed through denoising.Then,an octree-based thinning method was adopted to reduce data density while preserving the main terrain features,thereby improving processing efficiency.Finally,moving least-squares smoothing was applied to reduce local irregularities and improve surface continuity.On this basis,ContextCapture was used to generate a realistic three-dimensional scene model,and MATLAB was employed to construct a Delaunay triangulation model suitable for volume calculation.A mesh-based automatic algorithm was developed to calculate over and under excavation volumes.For each triangular element,the relative position between the measured terrain surface and the design surface was determined.Elements above the design surface were classified as under excavation,whereas those below it were classified as over excavation.Mixed elements intersecting the design surface were further decomposed into geometric bodies so that positive and negative excavation volumes could be calculated separately.The results were visualized in three dimensions,enabling engineers to identify the spatial distribution and concentration zones of over and under excavation after each blasting cycle.In the control stage,the digital twin platform stored over and under excavation results together with geological conditions,hole spacing,row spacing,charge per hole,subdrilling depth,hole depth,hole inclination,construction teams,and other key process parameters.Manual parameter adjustment was first conducted during the early blasting cycles to establish a training dataset.Artificial-intelligence-assisted analysis was then introduced to optimize multiple blasting parameters simultaneously and feed the updated results back into the dataset,forming a closed-loop process of measurement,evaluation,parameter adjustment,construction,and re-evaluation.The platform also supported refined management by recording borehole quality and construction responsibility by zone and team,which helped distinguish parameter-induced deviations from systematic deviations caused by construction management.The proposed scheme was applied to the underwater borehole blasting project of the Pinglu Canal.The results show that the digital twin system improved the quantification,visualization,and feedback efficiency of blasting quality.Compared with the initial construction stage,the over and under excavation volume was reduced by 80.25%after digital twin-supported parameter optimization and refined management were implemented.This study demonstrates that digital twin technology provides a feasible pathway for refined underwater blasting control in large-scale waterway engineering projects and offers a practical reference for intelligent blasting construction and quality management.
Understanding the impacts of different types of sudden events on shipping networks and their recovery mechanisms is of critical importance for ensuring maritime stability and advancing the sustainable development of ports.This study takes the Guangdong-Hong Kong-Macao Greater Bay Area(GBA),one of China's most economically dynamic regions,as a case to systematically analyze the structural vulnerabilities and resilience mechanisms of its shipping network under various disruptive scenarios.Drawing on complex network theory,the GBA shipping network is constructed,and key topological metrics such as network efficiency,connectivity,and the number of independent paths are quantified,providing a rigorous framework for evaluating network performance under stress.Four disruption scenarios are designed to simulate potential real-world shocks:degree-based attack(DA),betweenness-based attack(BA),strength-based attack(SA),and random attack(RA).The results indicate that the ports of Hong Kong,Shenzhen,and Guangzhou serve as core nodes,and their resilience directly shapes the overall stability of the network.Although the initial network exhibits high connectivity and efficiency(connectivity:10.300;efficiency:0.295),the failure of these core ports substantially degrades both metrics,demonstrating that network vulnerability is highly concentrated in critical hubs.In particular,attacks targeting node degree and strength cause the most pronounced declines in network performance,underscoring the system's dependence on highly connected or high-throughput ports.During the recovery phase,four strategies are evaluated:degree-based recovery(DR),betweenness-based recovery(BR),strength-based recovery(SR),and random recovery(RR).The analysis shows that under DA disruptions,the SR strategy proves most effective,achieving network connectivity resilience of 0.76 and independent path resilience of 0.54.Conversely,under BA and SA scenarios,the BR strategy performs better,particularly in restoring network efficiency,with resilience reaching 1.00 and 0.83,respectively.These results suggest that recovery strategies should be tailored to the type of disruption,and that prioritizing the restoration of critical nodes is more effective than random or uniform recovery in strengthening network resilience.Furthermore,the exponential random graph model(ERGM)is employed to examine the network's formation and evolution mechanisms.The findings reveal that the GBA shipping network is shaped by a combination of endogenous structural effects,node attribute effects,and exogenous relational effects.Structural tendencies such as reciprocity and clustering highlight the importance of bilateral cooperation between ports and the emergence of a"core-periphery"hierarchy,in which core ports like Hong Kong and Guangzhou radiate connections to secondary ports,facilitating efficient cargo flows and reducing redundant routes.The network also exhibits negative transitivity,consistent with practical shipping strategies that prioritize direct routes to minimize multi-hop transit time and handling costs.Node attribute analysis indicates that ports with similar shares of international cargo are more likely to cooperate,while throughput alone does not significantly influence edge formation.Geographic proximity and international partnerships further reinforce collaborative ties,demonstrating that spatial and strategic factors jointly shape network resilience.The dual mechanisms of route optimization and port cooperation are central to enhancing network robustness.By reducing the vulnerability of multi-hop transportation and fostering reciprocal cooperation between core and secondary ports,the network establishes multi-level redundant paths,improving its capacity to withstand systemic risks.These findings provide scientific guidance for port management,route optimization,and regional emergency recovery planning,emphasizing the importance of prioritizing and rapidly restoring core ports,optimizing shipping routes,and strengthening cooperative frameworks to build adaptive and resilient maritime systems.Such insights are particularly valuable for responding to global trade fluctuations,natural disasters,and operational disruptions.Overall,the study not only elucidates the structural and functional dynamics of the GBA shipping network but also establishes a transferable analytical framework applicable to other regional and global shipping systems.
Climate change has profoundly altered hydrological processes and the spatiotemporal distribution of water resources at both regional and global scales.The Yangtze River Basin,as the largest river basin in China,is particularly sensitive to climate-driven changes in precipitation patterns,temperature regimes,and evapotranspiration dynamics.Accurately projecting future runoff trends within the basin therefore carries significant scientific value for the sustainable development and rational allocation of regional water resources,as well as for informing long-term water security strategies and disaster risk management policies.This study employs the RCCC-WBM(Research Center for Climate Change-Water Balance Model)to construct a spatially distributed runoff simulation framework encompassing 14 sub-units across the entire Yangtze River Basin,capturing the pronounced spatial heterogeneity in climate,topography,and hydrological response characteristics across the basin.The model was rigorously calibrated and validated against long-term observed streamflow records,with the Nash-Sutcliffe Efficiency(NSE)coefficient exceeding 0.9 for total basin-wide runoff simulation during both the calibration and validation periods,confirming the model's high reliability and strong capability to reproduce observed runoff dynamics.To drive future runoff simulations,the study incorporates ensemble-mean climate forcing data from 19 General Circulation Models(GCMs)participating in the sixth phase of the Coupled Model Intercomparison Project(CMIP6).Four Shared Socioeconomic Pathway(SSP)scenarios were selected to represent a broad range of plausible future greenhouse gas emission trajectories:the low radiative forcing pathway(SSP1-2.6),the intermediate radiative forcing pathway(SSP2-4.5),the medium-to-high radiative forcing pathway(SSP3-7.0),and the high radiative forcing pathway(SSP5-8.5).Together,these scenarios provide a robust multi-scenario framework for assessing the sensitivity of basin hydrology to varying levels of anthropogenic climate forcing over the projection period from 2015 to 2100.The study yields four principal findings.(1)Under all four SSP scenarios,both mean annual temperature and total annual precipitation across the Yangtze River Basin exhibit statistically significant upward trends throughout the 21st century.The magnitude of warming and precipitation increase scales consistently with the level of radiative forcing,indicating a warmer and wetter future in the basin with important implications for runoff generation,flood frequency,and water availability.(2)The RCCC-WBM model demonstrated robust performance in simulating the hydrological regime of the Yangtze River Basin.NSE values exceeding 0.9 during both the calibration and validation periods confirm a high level of simulation accuracy,lending strong confidence to the reliability of subsequent future projections.(3)Future annual runoff across the Yangtze River Basin is projected to increase significantly under all four scenarios relative to the baseline reference period of 1995-2014.Mean annual runoff is projected to increase by approximately 2.4%to 9.6%by the 2035 horizon year,3.9%to 13.5%by the 2050 horizon year,and 11.1%to 16.6%by the 2080 horizon year.The progressively widening inter-scenario range toward the end of the century reflects growing divergence between low-and high-emission futures,highlighting that the extent of future runoff increase is critically dependent on global emission trajectories.(4)Intra-annual runoff across all seasons also exhibits significant increasing trends,with summer contributing most substantially to the total annual runoff increase,likely driven by intensified monsoon precipitation and accelerated glacial melt under warming conditions.Spatially,projected runoff increments display a downstream-decreasing gradient along the mainstream Yangtze River,with the upper reaches experiencing the largest absolute increases.The Two Lakes Basin—encompassing the Dongting Lake and Poyang Lake sub-basins—exhibits the smallest projected runoff increments among all sub-units,suggesting that future hydrological benefits may be unevenly distributed across the basin.The findings of this study provide important scientific evidence for climate change impact assessment,long-term water resource strategic planning,integrated flood and drought risk management,and the formulation of adaptive disaster prevention strategies in the Yangtze River Basin,contributing to evidence-based water governance under an increasingly uncertain climate future.
Sediment discharge scheduling in reservoirs often requires lowering water levels,which conflicts with the higher levels needed for power generation.Therefore,a reasonable scheduling scheme is essential to ensure long-term operation and maximize benefits.This study focuses on the Xiaolangdi Reservoir,aiming to enhance its siltation reduction and power generation benefits.By integrating a one-dimensional hydrodynamic and sediment transport model with the Non-Dominated Sorting Genetic Algorithm Ⅲ(NSGA-Ⅲ),an optimization scheduling model for water,sediment,and power generation was developed.The model simultaneously considers sediment and power generation objectives,employing a refined one-dimensional hydrodynamic and sediment transport model that offers more accurate sedimentation calculations than empirical sediment discharge efficiency formulas.The Preissmann scheme discretizes the governing equations,solved via the double-sweep method.The hydro-sediment model calibration involved analyzing the effects of parameters in the sediment transport capacity formula on predicted sedimentation.In the NSGA-Ⅲ algorithm,an individual represents a series of daily-averaged outflow discharges from the reservoir,which serve as outlet boundary conditions driving the hydro-sediment model.Predicted water levels and updated bed elevations at each cross-section evaluate the objective functions of power generation and siltation reduction.Initial population generation was improved by considering total released water volume.Uniform crossover and polynomial mutation are applied,with mutation amplitude constrained by reservoir discharge capacity.Results show the hydro-sediment model accurately simulates water levels at multiple stations,with Nash-Sutcliffe efficiencies from 0.77 to 0.99.Predicted outflow sediment concentration aligns well with measurements,and sedimentation volume error is within 4.3％.The proposed model optimized Xiaolangdi Reservoir outflow discharge from April 20 to October 20,2012.Initial crossover and mutation probabilities were set at 0.4 and 0.02,respectively,dynamically reduced to 0.2 and 0.01 over iterations.The target pool level matched the actual level at the operation period's end.Population distribution in objective space was observed across generations.The Pareto optimal solutions from NSGA-Ⅲ highlight the conflict between siltation reduction and power generation,with Pareto front solutions outperforming the original plan.Holding sedimentation constant,power generation increased by 11.4％;conversely,with constant power generation,sedimentation volume reduced by 48％.Keeping the ratio of objectives constant,power generation increased by 13％,and siltation reduction by 50％.The minimum siltation plan and the turning point on the Pareto front were compared with actual operations regarding pool level processes.All optimal solutions converge to states maintaining pool levels below the flood-limited water level,satisfying flood control constraints.The minimum achievable siltation is about 0.74×108 m3 and the maximum power generation is 5.82×109 kW·h.This model enables quantitative analysis of trade-offs between power generation and siltation reduction,supporting multi-objective optimal scheduling of reservoirs in heavily sediment-laden rivers.
Accurately identifying and quantifying variation trends in hydro-meteorological variables in alpine and high-cold regions is of great scientific and practical significance for addressing the multifaceted challenges posed by climate change,optimizing regional water resource allocation,and promoting sustainable watershed management.As one of China's most important hydropower bases,the hydrological evolution of the upper and middle reaches of the Yalong River directly affects downstream hydropower development,operational scheduling,and long-term energy security.In this study,based on a comprehensive analysis of long-term observations from 1960 to 2020,we employed the Pettitt non-parametric change-point detection method and linear trend analysis to investigate the temporal variation characteristics of annual streamflow,precipitation,air temperature,and potential evapotranspiration(PET).The study further incorporated snow dynamics and examined the runoff-precipitation relationship at a monthly time scale to explore the hydrological response of the regional water cycle under a warming climate.The results indicate several key findings.(1)The change-points of different hydro-meteorological variables occurred at different times,reflecting the asynchronous nature of climate-related shifts in the basin.Precipitation exhibited the earliest abrupt change in 1978,followed by air temperature and PET,which shifted significantly in 1997 and 2005,respectively.After these change-points,the warming rate accelerated markedly(0.50℃per decade),accompanied by a substantial increase in PET(42.2 mm per decade),indicating a pronounced intensification of atmospheric evaporative demand.(2)From 1979 to 2018,mean snow depth exhibited a persistent decreasing trend,while the date of maximum snow depth was delayed by approximately 1.9 days per decade.This delay suggests a prolonged snowmelt season,which may have important implications for spring runoff timing,reservoir refill cycles,and water availability.(3)Monthly runoff generally increased,with a notable enhancement in cold-season runoff contributions and a decline in runoff concentration during the warm season.Such changes are likely linked to shifts in precipitation phase(from snow to rain)and earlier snowmelt under a warmer climate,which together lead to altered intra-annual runoff distribution patterns.(4)The region exhibited an overall wetting trend,as evidenced by a decreasing aridity index and an increasing runoff coefficient.In particular,the increase in precipitation emerged as the dominant driver of water cycle intensification,while the occurrence and magnitude of extreme precipitation events further enhanced the efficiency of rainfall-to-runoff conversion,amplifying short-term hydrological responses.These findings provide new evidence of the complex interplay between climatic forcing,cryospheric processes,and hydrological responses in alpine basins.The observed wetting tendency and altered runoff seasonality underscore the necessity for adaptive water resource management strategies.For example,the shift toward increased cold-season runoff may challenge existing reservoir operation rules,which are often optimized for historical seasonal flow patterns.Moreover,the intensification of extreme precipitation events poses greater risks for flood management and infrastructure resilience in the Yalong River Basin.From a broader perspective,this study highlights the importance of integrating snow and glacier monitoring,precipitation phase discrimination,and high-resolution hydrological modeling to better predict future changes under continued warming scenarios.Overall,our results not only deepen the understanding of hydrological response processes in high-altitude cold regions but also provide scientific insights for sustainable hydropower development,flood control,and climate adaptation in the Yalong River Basin and similar alpine watersheds worldwide.The multi-decadal dataset used in this work offers a valuable reference for detecting long-term climate signals and developing robust regional adaptation policies.By linking statistical change-point detection with physical interpretations of snow-runoff processes,the study demonstrates that climate-induced changes in temperature,precipitation,and snow dynamics are reshaping the seasonal and inter-annual water cycle in ways that will require proactive and flexible water management approaches in the coming decades.
Alluvium sand-gravel(SG)foundations are among the typical foundation conditions for dams,and the mechanical behavior of the foundation materials directly determines the stress and deformation characteristics of the dam.These mechanical responses influence both the safety of dam deformation coordination and the effectiveness of long-term deformation control.However,due to the heterogeneous composition of sand-gravel mixed with fines such as mud,their stress-strain behavior under external loading remains complex and difficult to characterize using conventional soil mechanics models.To provide reliable technical support for the accurate estimation of dam deformation on alluvium foundations,this study focuses on the stress-strain characteristics of alluvium SG materials containing different mud mass fractions under triaxial compression.A series of consolidated drained triaxial shear tests were conducted in the laboratory.Specimens were prepared with controlled relative density to minimize variability,and confining pressures covering typical in-situ ranges were applied to simulate different stress conditions within a dam foundation.The mud mass fraction was considered a key influencing factor,and tests were carried out under various combinations of mud mass fraction and confining pressure.Through these experiments,the effects of mud mass fraction and confining pressure on stress-strain curves,nonlinear shear strength indices,and volumetric strain behavior were systematically analyzed.The test results indicate clear and consistent trends.With decreasing confining pressure and increasing mud mass fraction,specimens with the same relative density exhibited a reduction in peak strength,showing an increased tendency to yield at lower stress levels.The phenomenon of strain-softening becomes more pronounced under lower confining pressures,where specimens reach a peak stress and then experience a notable drop in strength with continued deformation.Regarding volumetric strain behavior,specimens with higher mud mass fractions show a greater propensity for shear contraction at the same confining pressure.At relatively low confining pressures,specimens initially exhibit dilatancy before transitioning into contraction,and the dilatancy effect is more prominent as the confining pressure decreases.These findings highlight the dual role of mud:while it weakens the structural strength of the gravel matrix,it also modifies the deformation mode from dilation to contraction,thereby influencing the shear resistance mechanism.Based on these test results,the applicability of the classical Duncan-Chang model to alluvium SG materials containing mud was assessed.Although the Duncan-Chang model can represent general nonlinear stress-strain behavior,its limitations become apparent when applied to alluvium SG materials exhibiting significant strain-softening and dilatancy effects.To overcome these shortcomings,an improved constitutive model is proposed in this study.The new model incorporates mechanisms that explicitly capture strain-softening and dilatancy,making it more suitable for describing the instantaneous deformation behavior of SG materials under triaxial shear conditions.A methodology for determining the model parameters is provided,and regression relationships between mud mass fraction and the key model parameters are established.These regression functions allow the model to dynamically adjust with varying mud fractions,enhancing its predictive capacity.Finally,the performance of the proposed model was evaluated using the laboratory tests presented in this paper as well as data from existing studies,indicating that the model can accurately reflect the stress-strain characteristics of alluvium SG specimens under triaxial shear conditions.This study provides a theoretical basis for the accurate estimation and coordinated control of dam deformation on alluvium SG foundations.
As one of the sub-centers of Guangzhou,Nansha District has long been a critical area for managing flood and storm surge risks due to its distinctive location at the Pearl River estuary and its exposure to both fluvial flooding and coastal surges.With the growing impacts of climate change and intensified human activities,the district now faces increasing threats from sea level rise,land subsidence,and extreme weather events—factors that collectively heighten flood risk and threaten regional development.Enhancing Nansha's flood and storm surge resilience is therefore essential to safeguarding local populations and infrastructure.This study establishes a two-dimensional hydrodynamic model using TELEMAC,focusing on the Pearl River Delta's river network and Nansha's low-lying zones.Based on this model,scenario simulations were conducted to quantitatively evaluate the inundation characteristics and defense performance under different conditions,including current design standards and projected future scenarios that account for sea level rise,land subsidence,and extreme storm surge events exceeding standard thresholds.The simulation results show that,under current standard conditions,the inundation area in Nansha District reaches about 59 square kilometers in the storm surge-dominated scenario and 48 square kilometers in the upstream flood-dominated scenario.This highlights the dual influence of coastal and riverine flooding on inundation risks,underscoring the need for integrated defense strategies.To address these challenges,two flood protection schemes were assessed:a standalone levee system and a combined sluice-levee system.Under current standard conditions,the levee-only scheme effectively prevents inundation across the study area,demonstrating its adequacy for the existing hydrodynamic environment.However,in future scenarios that include sea level rise and land subsidence—anticipated to intensify over the next 30 years—the effectiveness of the levee-only scheme diminishes.Specifically,in the storm surge-dominated future scenario,the inundated area expands to 22 square kilometers,indicating that levees alone may no longer provide adequate protection.In contrast,the combined sluice-levee system,which incorporates gated hydraulic structures alongside embankments,performs better,especially under storm surge conditions.While its impact is limited in upstream flood-dominated scenarios,it notably improves water level regulation and flow patterns during storm surges.This results in enhanced protective performance,particularly in the northwestern polder areas of Nansha,where storm surge risks are most acute.Quantitative analyses further highlight the advantages of the combined scheme:compared to the pure levee approach,the sluice-levee configuration reduces inundation extent by up to 50%under future scenarios involving sea level rise and land subsidence.Even under extreme storm surges exceeding current design thresholds,the reduction in inundated area ranges from 12%to 18%,demonstrating the added value of flexible and adaptive infrastructure in addressing uncertain future conditions.Overall,this research underscores the importance of incorporating dynamic environmental changes into flood risk management.Through the application of advanced numerical modeling and scenario-based evaluation,it provides scientific support for selecting optimal flood defense strategies in estuarine urban settings like Nansha.The results serve not only as a reference for local decision-makers and planners but also offer broader insights for other coastal cities confronting similar flood and storm surge adaptation challenges.
With the continuous expansion of the scale and number of earth-rock dams in China,challenges related to deformation control and structural safety have become increasingly prominent.Accurate monitoring data provide a direct and reliable means of capturing the actual deformation behavior of dams.Compared with deformation measurements at individual monitoring points,full-plane deformation across a characteristic plane of the dam offers a more comprehensive understanding of its structural response,encompassing both local and global deformation trends.To enhance the reliability of deformation and crack analysis for high core rockfill dams(HCRDs),it is necessary to construct a detailed full-plane deformation model of the dam crest.Using the HCRD at Pubugou as a case study,this paper proposes a methodology for constructing and analyzing full-plane deformation at the dam crest based on multi-point monitoring data and statistical analysis.Settlement data from each monitoring point along the dam crest are first processed using a sectional statistical analysis method to establish individual settlement models.This approach enables temporal variations in settlement at different sections of the crest to be effectively captured,providing a foundation for subsequent spatial modeling.Finally,the relationship between the parameters of each settlement model and their corresponding spatial coordinates is examined to construct a statistical model representing the overall settlement of the entire dam crest plane.By integrating data from all monitoring points,the model can estimate full-plane deformation at different time intervals,providing a comprehensive representation of the dam's deformation process.This method bridges the gap between localized point measurements and the global deformation pattern,enabling more accurate assessment of structural behavior.To further quantify deformation characteristics,the gradient of the full-plane settlement model is calculated to derive the deformation inclination of the dam crest.This facilitates identification and analysis of areas prone to differential settlement or excessive tilting,which are closely linked to crack formation and potential structural risks.The results demonstrate that the proposed methodology constructs a reliable full-plane deformation model of the dam crest.The predicted deformation and crack distributions show good agreement with field observations,confirming the effectiveness and applicability of the approach.By extending deformation analysis from individual monitoring points to a comprehensive characteristic plane,this study enhances the utilization of monitoring data and improves the interpretability of dam deformation patterns.The methodology provides a quantitative and spatially continuous basis for assessing both settlement and crack development,which is critical for structural safety evaluation,maintenance planning,and early warning systems.Moreover,the integration of multi-point data and statistical modeling captures local variations as well as overall trends,facilitating informed decision-making in dam operation and risk management.In conclusion,the approach presented in this paper enables detailed and accurate characterization of full-plane deformation in high core rockfill dams.By combining multi-point statistical analysis with spatial modeling,it offers an effective and reliable tool for monitoring,predicting,and analyzing dam deformation and associated crack development.The method is generalizable and applicable to other large-scale embankment dams,providing a solid foundation for engineering evaluation,operational optimization,and safety management.Overall,this study advances the analytical framework for earth-rock dam deformation,improves monitoring efficiency,and supports the sustainable and safe operation of such infrastructure.
In recent years,China's installed nuclear power capacity has grown steadily.According to the latest statistics,the total installed capacity of nuclear power units in operation and under construction has reached the highest level in the world.Meanwhile,the thermal impact of heated discharges generated during nuclear power plant operation on receiving water bodies has become increasingly prominent.Therefore,accurately predicting and assessing such thermal impacts is not only a key prerequisite during the feasibility demonstration stage of new nuclear power projects,but also an important basis for evaluating the environmental and ecological effects of thermal discharges from operating reactors on adjacent aquatic ecosystems.This study systematically reviews and analyzes the key factors influencing the thermal effects of cooling water discharge.These factors can be broadly categorized into two groups.The first group relates to engineering operational modes,including cooling methods(e.g.,once-through direct cooling and recirculating cooling using cooling towers)and discharge configurations(e.g.,open-channel discharge and culvert discharge).The second group involves natural marine environmental conditions,including hydrodynamic conditions(tides,tidal currents,residual currents,and waves);shoreline and bathymetric characteristics(water depth,seabed slope,coastline curvature,and island distribution);meteorological conditions(wind speed,air temperature,and solar radiation);as well as physical properties of the water column(ambient water temperature and salinity).These factors play critical roles in the diffusion,mixing,and heat dissipation processes of thermal discharges.This study further examines the major methodologies used to assess the thermal impact range of heated discharges and summarizes the advantages and limitations of four representative approaches:field observations(which provide real environmental background data but are costly and limited by spatial and temporal coverage);physical models(which are intuitive and controllable,capable of reproducing complex three-dimensional processes,but tend to underrepresent vertical diffusion and have difficulty in fully simulating surface heat dissipation and boundary heat recirculation);numerical simulations(which are flexible,cost-effective,and capable of simulating complex hydrodynamic and thermal processes,but are highly dependent on parameter selection and boundary condition settings);and remote sensing techniques(which provide broad spatial coverage at relatively low cost,but can only reflect surface temperature distributions and are susceptible to atmospheric absorption,scattering,and cloud interference).It is worth noting that no single method can fully characterize the dispersion process of thermal discharge.Therefore,research should comprehensively consider factors such as engineering characteristics,simulation scale,accuracy requirements and project schedules,and adopt a multi-method framework for investigation and validation,thereby leveraging the complementary advantages of different approaches to achieve effective integration.In view of the current large-scale development of nuclear power and increasingly stringent environmental protection requirements,this study identifies several future research directions that warrant further attention.First,it is necessary to investigate the synergistic regulation mechanism of wave-current coupling on the transport and dispersion of thermal discharge,and to propose a parameterized characterization method for diffusion coefficients that integrates the combined effects of tides and waves.Second,methods should be developed to distinguish the respective contributions of thermal discharges from adjacent outlets after the superposition of thermal impacts.Third,comparative studies should be conducted on the nonlinear thermal mixing behavior of multiple thermal discharge plumes and their cumulative thermal impacts on the ambient water body.Fourth,predictive models for long-term thermal impacts should be established to enable analysis of the spatial and temporal extent of temperature rise impacts.This study will help improve the accuracy of prediction and the precision of assessment regarding the thermal impact zone of warm-water discharge from nuclear power plants,thereby enabling more reliable evaluation of discharge impact ranges.
A comprehensive scientific research and testing platform serves as the core infrastructure driving technological innovation,with its composition and effectiveness directly affecting the level of national water security.This article seeks to systematically elucidate the logical inevitability and strategic pathways for building a comprehensive testing platform for water conservancy,hydropower,and water transport disciplines.This platform is characterized by deep integration of prototype observation,physical model testing,and mathematical model simulation(hereinafter referred to as the"three-type platform").Historical logic demonstrates that the synergistic evolution of the"three-type platform"has been a decisive force in advancing China's water conservancy,hydropower,and water transport engineering technologies from a phase of catching up,to running abreast,and now taking the lead in certain areas.Drawing on the 90-year practical trajectory of a national-level research institution as an example,this article argues that the synergistic evolution of the"three-type platform"is not only the cornerstone supporting the successful construction of major projects but also the fundamental driver behind the leapfrogging advancement of water conservancy engineering technologies.Theoretical logic indicates that the"three-type platform"forms a closed loop of"understanding-reproducing-predicting-optimizing"for complex hydraulic engineering systems.It serves as the methodological foundation for exploring the inherent complex laws of hydraulic systems and ensuring engineering safety.The interconnected,synergistic,and referential research within this framework ensures the scientific rigor,safety,and economic efficiency of the construction,operation,and maintenance of major projects,including"national strategic projects."Practical logic indicates that,in the face of intertwined challenges posed by both traditional and emerging water-related issues,as well as the strategic demands for national water security,the"three-type platform"is an inherent requirement and strategic fulcrum for developing new quality productive forces in water conservancy,achieving high-level self-reliance and strength in science and technology,and safeguarding flood control security,water supply security,food security,ecological security,and navigation security.Drawing on cutting-edge practices,this article proposes construction pathways such as strengthening whole-chain innovation,deepening the integration of"industry,academia,research,and application,"and innovating scientific research mechanisms.It aims to provide insights for scientific and technological innovation and high-quality development in China's water conservancy,hydropower,and water transport sectors.
The continuous advancement of inland waterway infrastructure has led to the emergence and growing prominence of a distinct type of navigation structure—ship navigation tunnels.These specialized passages,designed to enable vessel transit beneath natural or artificial barriers,present unique challenges for fire safety management.A central issue lies in accurately predicting the critical ventilation velocity required to prevent smoke back-layering during a fire.Focusing on this key parameter,the present study examines its determination in ship tunnel environments using advanced numerical simulation techniques.The methodology involved constructing three detailed simulation models representing tunnels for 1,000-ton,8,000-ton,and 10,000-ton vessels.In each model,a fire source was located at the tunnel center.A comprehensive series of numerical experiments was then conducted for each configuration,with the heat release rate(HRR)systematically varied from 20 MW to 90 MW.The initial longitudinal ventilation velocity in each simulation was set according to established empirical formulas.The smoke dispersion patterns were meticulously analyzed based on the resultant data.Subsequently,an iterative procedure was employed:the longitudinal ventilation velocity was adjusted in increments of 0.1 m/s until smoke back-layering was effectively suppressed(i.e.,no upstream smoke reflux was observed).The velocity meeting this condition was identified as the critical velocity for the corresponding scenario.A comparative analysis between the critical velocities obtained from simulations and those calculated using existing empirical formulas reveals notable discrepancies and uncertainties.The values predicted by the Li formula are generally overestimated across all cases.For tunnels accommodating 1,000-tonne and 8,000-tonne vessels,the Xu and Wu formulas consistently yield lower predictions than the simulation results.Conversely,for the 10,000-tonne tunnel,the values from the Xu and Wu formulas predominantly exceed the numerical results.Moreover,the divergence between the empirical predictions and simulation outcomes increases progressively with the heat release rate of the fire source.In terms of applicability,the Li formula demonstrates relatively satisfactory performance for the 1,000-tonne and 8,000-tonne tunnels,whereas the Wu formula exhibits superior suitability for the 10,000-tonne tunnel design.These identified deviations underscore a significant finding:existing empirical models and standard provisions—originally developed for conventional road or rail tunnels—are not directly applicable to ship navigation tunnels.The geometric proportions,ventilation dynamics,internal surface characteristics,and ambient boundary conditions inherent in large,navigable waterway tunnels differ substantially from those of their land-based counterparts.Consequently,traditional approaches often yield inaccurate estimates of the airflow required for effective smoke control in these unique environments,thereby limiting their practical reliability in design and safety engineering.Building on these findings,the study further examines the fundamental parameters governing critical velocity in ship tunnels.Through rigorous statistical analysis and regression modeling,it is demonstrated that the critical velocity exhibits a strong correlation with three primary variables:(1)the heat release rate(HRR)of the fire source,(2)the net cross-sectional perimeter(L)of the tunnel,and(3)the net clearance height(H),or headroom,available within the tunnel.These parameters exert a dominant influence on the minimum ventilation threshold required to prevent back-layering and maintain tenable conditions.To more effectively integrate the defining geometric attributes of ship tunnels into a predictive framework,this study introduces a novel dimensionless parameter—the tunnel cross-sectional coefficient,ω.This coefficient is defined as the ratio of the net cross-sectional perimeter(L)to four times the net clearance height(4H),i.e.,ω=L/(4H).The introduction of ω offers a unified metric that encapsulates the combined influence of tunnel shape and scale.Drawing on the dataset generated from the simulations and the insights derived from the correlation analysis,a new empirical formula for predicting the critical velocity in ship navigation tunnels is developed.This proposed model incorporates the principal influencing factors,including the fire's HRR,the tunnel cross-sectional coefficient ω,and the geometric parameters L and H.Comparative validation indicates that the new formula achieves markedly higher predictive accuracy than the existing models evaluated in this study.In summary,this research highlights the limitations of conventional fire safety engineering models when applied to the emerging typology of ship navigation tunnels.It systematically identifies the governing factors affecting critical velocity in such structures and introduces a tailored predictive approach centered on a new geometric coefficient.The findings and the proposed model provide a refined analytical tool for improving the design and safety assessment of future waterway transport infrastructure.
Partition dikes between sluices and locks of hydropower projects are an effective measure to improve navigable flow conditions.Traditional partition dikes adopt impermeable or dike-opening structures.The upgrading of locks and the increasing complexity of operating conditions lead to difficulties in meeting specifications for navigable flow conditions in the approach channel and entrance area.Permeable partition dikes,such as bottom-permeable structures and diversion piers,have therefore come into use.However,it is still often necessary to reduce the maximum navigable discharge to ensure navigation safety.To meet the conditions required for safe vessel maneuvering within the approach channel,separation dikes of sufficient length should be arranged between the ship lock and structures such as overflow dams,sluice gates,and power stations.It is recommended that when the longitudinal flow velocity exceeds 0.5 m/s,the length of the separation dike on the outer side of the approach channel should extend to cover the area beyond the braking section.The proposed Huai'an East Ship Lock is an important component of the supporting navigation project for the second phase of the Huaihe River Seaward Waterway.A comprehensive physical model with a geometric scale of 1∶90 was established to conduct experimental research on downstream navigable flow conditions,and the downstream separation dike was optimized accordingly.The structure adopts a pile-cap and pier-slab configuration.Optimization tests focus on the length of the pier-slab separation dike,the type of bottom openings,and the opening height.If a fully enclosed separation dike is adopted,the flow regime in the approach channel and entrance area becomes relatively disordered,manifested as large-scale crossflow and backflow in the entrance area.Downstream of the Huai'an East Ship Lock,the measure of extending the separation dike to cover two-thirds of the braking section has been implemented.The total length reaches 360 m,with the lower 320 m gradually transitioning to a permeable structure from bottom to top.The porosity ranges from 25%to 8%,with an average porosity of 15%.It can effectively eliminate the backflow in the entrance area.A weak backflow exists within the approach channel,with the maximum crossflow traversing the channel reaching 0.15 m/s.Based on the existing physical model,comparative tests were conducted under the same flow conditions for five structural types:fully enclosed baffle plates,bottom-section gradual porosity,uniform porosity at a consistent bottom height,and full-section uniform porosity.A new type of full-section uniformly permeable structure is proposed(slit height 0.3 m,porosity 20%),and the improvement effect is investigated by physical model tests.The results indicate that the new structure of permeable partition dike can make the mainstream and the flow in the approach channel mix gradually and evenly,effectively improve the flow regime in the approach channel and the entrance area,and reduce the intensity and range of crossflow and backflow.Under this scheme,the maximum crossflow generated by the backflow within the approach channel is only 0.10 m/s,with a backflow length of 230 m—exceeding one time the length of the designed single vessel.This has relatively minor impact on navigation safety and significantly improves the flow regime.If the separation dike serves solely as a flow-dividing structure,a uniformly permeable structure across the entire cross-section can be adopted.Its placement should avoid the design highest navigable water level and the normal water level to the extent possible.Under the same conditions,it significantly increases the maximum navigable flow of the ship lock,ensures the number of navigable days and navigation safety,and provides a new method for the design of diversion channel separation dikes under complex boundary conditions.
