Abstract:Against the complex domestic and international environment faced by Yangtze River shipping during the 15th Five-Year Plan period,as well as the higher requirements set by national strategies such as the Chinese path to modernization and the cultivation of new productive forces,and focusing on the existing problems in Yangtze River shipping,this study analyzes the current situation of Yangtze River shipping,combines the phased characteristics of the 15th Five-Year Plan period and domestic and international economic development policy requirements,conducts a situation analysis,and proposes targeted development countermeasures.It is concluded that Yangtze River shipping still faces issues such as bottlenecks and congestion in main channels,prominent market supply and demand contradictions,and insufficient momentum for green and intelligent transformation.During the 15th Five-Year Plan period,it is faced with requirements such as channel security,economic and social circulation support,pioneering demonstration as a transportation powerhouse,and innovation leading industry upgrading.It is necessary to vigorously develop in terms of enhancing infrastructure capabilities,strengthening transportation service quality,improving transportation organization efficiency,and promoting green and intelligent transformation.The research results can promote the construction of a modern system for Yangtze River shipping,fully leverage the hub role of the golden waterway,provide strong support for the construction of a transportation powerhouse and the dual circulation development pattern at home and abroad,and assist in demonstrating and leading high-quality development of inland navigation.

Abstract:In view of the limitations of the traditional “port-industry-city” three-dimensional analytical framework in capturing the synergy mechanisms among key elements such as routes,shipping enterprises,information,and finance,a “seven-in-one” synergy development analytical framework is proposed comprising port,route,shipping enterprise,cargo,information,finance,and government.Within this framework,the intrinsic interrelationships are systematically examined from three dimensions:infrastructure,operational optimization,and institutional safeguards.By a multi-case comparative approach,Guangzhou Port,Ningbo-Zhoushan Port,and Rizhao Port are selected as representative cases for empirical analysis.The results indicate that the seven-in-one synergy mechanism can substantially improve overall port efficiency.Specifically,Guangzhou Port reduces customs clearance time by 60% through the “bay area one-port access” model;Ningbo-Zhoushan Port shortens average vessel waiting time to 8 h by leveraging the “port brain” platform;Rizhao Port reduces port clearance time to 12 h via the “smart port cloud brain” system.The “seven-in-one” synergy mechanism extends the scope of the traditional “port-industry-city” tripartite framework by incorporating a more multidimensional and dynamic perspective.It provides a more systematic analytical framework for enhancing port performance,strengthens the competitiveness of Chinese ports within global supply chains,and offers both theoretical insights and practical references for port development under the Belt and Road Initiative.

Abstract:To address the inaccuracy in predicting the motion responses of moored ships caused by the traditional overall wave representation method,which neglects the bimodal spectral characteristics of mixed waves,this study investigates the motion response characteristics of moored ships based on the multimodal wave representation method.Numerical simulations are performed,with field-measured wave data from Chancay Bay,Peru,as input.Three representative mixed wave spectra are reconstructed to systematically analyze the differences in the simulated results of moored ship response characteristics between the overall and the multimodal wave representation method.The results indicate that the overall method oversimplifies wave energy distribution.In conditions dominated by short waves,this approach artificially concentrates wave energy,resulting in an overestimation of the calculated motion response.Conversely,in scenarios involving long-period swells,the multimodal wave representation method can accurately isolate the long-wave components causing low-frequency resonance of the moored ship,effectively avoiding underestimation risks.The multimodal wave representation method can more accurately capture the hydrodynamic impact of mixed waves on mooring systems.Thus,it is recommended to replace the traditional overall representation method with it in engineering designs for complex sea states to enhance safety margins.

Abstract:To address the issue of insufficient ecological functionality in traditional coastal armor units,we develop a novel ecological armor block that integrates effective wave protection with enhanced ecological benefits.The core innovation lies in the structural groove design,which maintains engineering safety and durability while significantly improving the block’s capacity to promote marine organism colonization and habitat formation,thereby achieving a synergistic optimization of protective performance and ecological value.We evaluate its hydrodynamic stability by physical model tests based on gravity similarity laws.The results indicate that the stability coefficient KD value of blocks is 10.0-14.6.The blocks remain stable under more severe marine conditions (significant wave height Hs=11.8 m),with a KD value exceeding 24,indicating a notable performance enhancement from model to prototype.The effectiveness of the proposed structural groove design scheme is proved,which can provide a new technical pathway and practical basis for constructing environmentally friendly and resilient coastal protection engineering.

Abstract:To mitigate the erosion of Qianshuiwan Beach affected by artificial islands and make full use of the existing shielding effect of artificial islands,two models are proposed on the southern side of the wave shadow zone behind the artificial islands.Model 1 adopts “beach shoulder sand replenishment+jetty+underwater sand bar+offshore submerged dike+sand dike”,Model 2 adopts “berm nourishment+jetty+artificial sand bars”.Numerical simulation software including Mepbay,XBeach and GENESIS are used to carry out beach profile design,stability assessment and morphological evolution prediction for the two models.Considering factors such as the protection length and secondary erosion hotspots,Model 1 is selected as the optimal basic scheme.The research finds that due to the influence of diffracted waves,there exists a problem of secondary erosion hotspots.It is necessary to change the jetty in Model 1 to an offshore submerged dike nearly parallel to the shore,and an optimized model of “beach shoulder sand replenishment+underwater sand bar+offshore submerged dike+sand dike” is proposed.The physical model test results indicate that compared with Model 1,the beach erosion rate of the optimized model decreases from 30 m over 5 years to nearly 0 m within one year.The proposed model can serve as a reference for beach restoration projects in similar coastal areas.

Abstract:In response to the frequent occurrences of mooring line breakage accidents at global ports and the fact that existing research often focuses on single hydrodynamic factors or relies on numerical simulations,making it difficult to reveal the coupling effects of multiple hydrological factors on tension variation,a study is conducted on the identification of sensitive factors for cable tension and environmental risk forecasting.The orthogonal experimental design combined with range analysis and variance analysis is employed to screen environmental factors highly sensitive to cable tension changes.A polynomial response model is constructed using MATLAB software to fit the mathematical relationship between cable tension and key environmental factors,thereby establishing an environmental risk forecasting model.The results indicate that wave factors exhibit higher sensitivity to cable tension changes compared to current and wind conditions.The revealed influence laws of combining wind and wave actions on the maximum tension of mooring lines under extreme once-in-a-century current velocities superimpose with the most unfavorable flow directions.On the basis of this,an early warning mechanism using critical tension thresholds is developed.The cable tension values predicted by this risk forecasting model show an error within 10% compared to those simulated by the numerical model.

Abstract:Aiming at the problems of low terminal throughput and low equipment utilization caused by reliance on experiential judgment and the lack of systematic quantitative analysis tools in traditional dry bulk terminal design,this paper constructs a discrete event simulation modeling framework based on dynamic stockpile shape data.Taking the two core processes of unloading and ship loading as the main line,the framework proposes a three-layer object system consisting of physical objects,abstract objects and logical objects,which realizes the refined modeling of terminal operation elements.Key innovations include:a real-time yard stacking construction algorithm based on B-spline surface fitting that dynamically calculates retrieval operation time according to real-time stacking information.A vessel berthing algorithm is developed to comprehensively evaluate vessel tonnage,berth water depth,and yard accessibility.A process selection strategy oriented to “minimizing process switching” is formulated for unloading and loading operations,which preferentially unload cargo into stockpiles in the same row to reduce equipment switching times.The framework is applied to a coal terminal case with an annual design throughput of 9 million tons.The simulation results show that the berth utilization rate reaches 54.3%,the average vessel turnaround time is 36.37 hours,and the dumper utilization rate is 31.5%.The findings verify the framework’s capability in quantitatively evaluating terminal throughput,equipment utilization rate and vessel turnaround times,and can provide a scientific basis for terminal planning and design,operational optimization and decision-making support.

Abstract:To address the problems of high empty-load rates,delayed responses,and over-reliance on manual experience in the scheduling of shunting vehicles at bulk dry bulk cargo ports,a multi-objective bi-level optimal scheduling model is constructed to improve operational efficiency,reduce operating costs,and realize intelligent scheduling.The upper level of the model optimizes revenue equilibrium,the timeliness of high-priority tasks,and vehicle waiting time by associating work teams with operation plans.The lower level implements vehicle assignment with the objectives of proximity dispatching,revenue maximization and allocation fairness,and adopts Fully Loaded Both Ways strategy to reorganize homogeneous operation plans into closed-loop routes to reduce empty running mileage.Numerical experiments are conducted using Python and Gurobi based on actual port operation data.The results indicate that when the plan revenue weight is set between 0.4 and 0.6,the system achieves a balance among revenue fairness,the completion rate of high-priority tasks,and equipment configuration rationality.When the fairness weight ranges from 0.1 to 0.3,the system maintains an operational efficiency above 85% and realizes reasonable load distribution.Compared with traditional single-plan scheduling,Fully Loaded Both Ways strategy reduces travel distance by 30%-44% in 29 instances.The proposed model provides an effective optimization approach for the intelligent and low-cost operation of port transfer operations.

Abstract:With the ever-increasing functional requirements of wharves,many existing wharfs can no longer meet the berthing demands of large vessels and are in urgent need of renovation and upgrading.Aiming at a series of problems in the renovation and upgrading of existing wharves,such as limited construction sites from simultaneous operation and renovation,tide-dependent construction caused by water level fluctuations,and the 100-year durability requirement for the structure,this paper introduces the application of a new precast breast wall in the renovation and upgrading of existing wharves.By comparing the combined precast and cast-in-place breast wall scheme with the traditional full cast-in-place breast wall scheme,carrying out theoretical calculation and analysis,and citing practical engineering project examples,this paper concludes that the combined precast and cast-in-place breast wall scheme can effectively solve construction difficulties caused by limited construction site space,water level variation,structural durability and other factors.Meanwhile,it eliminates the time consumed by working procedures such as formwork erection and removal on the seaward side during concrete pouring as well as concrete hardening,thereby shortening the construction period.The research results can provide a practical basis for subsequent similar reconstruction and renovation projects of existing wharves,and promote innovation and development in the field of wharf upgrading and reconstruction.

Abstract:Due to the flammability and explosiveness of loading and unloading materials,the high risk of fire hazards,and the difficulty in extinguishing fires,the fire protection design requirements for oil ＆ gas and chemical terminals are higher than those for other terminals.Therefore,strict requirements have been made for both domestic and foreign standards.In response to the limited research on the design of oil ＆ gas and chemical terminals under the American standard system in China,as well as the relatively broad design requirements of NFPA30 and ISGOTT standards,this paper relies on a case study of an oil and gas chemical terminal project in Africa.It compares and analyzes the similarities and differences in the configuration requirements of JTS158 and American standards.By referring to other relevant NFPA standards,it clarifies the layout requirements and parameter values for fire monitors,foam monitors,fire hydrants,international shore connection,and pump-in points for fire-fighting boats.Drawing on the water curtain separation function of JTS158,and based on NFPA13,it proposes the design requirements for water curtains in oil ＆ gas and chemical terminals under the American standard system.To reasonably determine the flow parameters of fire pumps,scenario analysis is used to obtain the maximum fire protection design flow rate for the terminal.The research results can provide reference and guidance value for the fire protection design of oil ＆ gas and chemical terminals under the American standard system.

Abstract:Current comparisons of shed forms for bulk cargo storage yards often focus on structural safety indicators or initial metrics such as construction duration and investment costs,without conducting a comprehensive assessment across the entire lifecycle,including construction,operation,and maintenance.Based on the new bulk cargo storage yard shed project at Huanghua Port,and considering a design working life of 50 years for the yard shed,this study analyzes and compares three structural forms:air-supported membrane structures,flat grid roof with windbreak net structures,and arched prestressed truss structures.The comparison is conducted from three perspectives:design and construction,production and operation,as well as usage and maintenance.The results show that the arched prestressed truss structure outperforms the other two in seven out of nine comparative items.It provides the large storage capacity for bulk cargo,the suitability for production and operation,the low usage and maintenance costs,the excellent environmental performance,and the favorable occupational health and hygiene conditions.Therefore,it represents a rational choice for optimizing economic indicators and environmental performance over the 50-year design working life.The itemized comprehensive comparison system and methodology established in this study can serve as a reference for similar yard shed projects.

Abstract:In the process of capacity expansion and renovation of navigation facilities,two key issues are involved in the renovation plan:the scientific quantification of key indicators and the reasonable determination of weight coefficients.Through the analytic hierarchy process (AHP),the indicators are quantitatively analyzed，and the weights are calculated,establishing an evaluation method suitable for the capacity expansion and renovation of navigation facilities.Taking the capacity expansion and renovation of the Weishan third-line ship lock as an example,the necessity,economic feasibility,technical feasibility,environmental impact,and social impact of the capacity expansion and renovation of the Weishan third-line ship lock are comprehensively analyzed through the fuzzy comprehensive evaluation method.The results show that in the process of capacity expansion and renovation of navigation facilities,the sum of the weight ratios of five indicators,namely the economic internal rate of return (EIRR),the degree of cargo volume exceeding the passing capacity,ecological and environmental impact,terrain conditions,and geological conditions,has reached 0.43,approaching 0.5,and should be regarded as key indicators for the capacity expansion and renovation project.The necessity of the capacity expansion and renovation of the Weishan third-line ship lock is relatively strong.During the argumentation of the renovation plan,attention should be paid to the feasibility of the technical plan and the environmental impact.

Abstract:Aiming at the complex hydraulic issues arising from shared approach channels of double-line ship locks with significant scale differences under space-constrained conditions,we conduct a systematic study using a comprehensive physical model with a geometric scale of 130,on the basis of the double-line ship lock project of the Jiantan navigation hub.The results show that the ship lock chamber width has the controlling role on ship mooring conditions,revealing that narrow ship lock chambers experience intense jet impact during unilateral filling,leading to transverse mooring forces prone to exceeding code limits,whereas wide lock chambers provide ample space for water flow diffusion.The flow superposition effect during simultaneous filling and emptying of the double-line ship lock,which significantly influences the flow conditions in the mooring sections of both upstream and downstream approach channels.By implementing an optimized measure that staggered scheduling is not shorter than the valve opening time,water level fluctuations in the mooring sections of the upstream and downstream approach channels can be effectively controlled within 20 cm,while mooring forces also comply with code requirements.

Abstract:Many hydropower hubs in the central and western regions have design heads above 100 m,making single-stage ship locks unable to meet their navigation requirements with current technology.To address this major technical challenge of increasing the design head of single-stage ship locks,we conduct a study on 100-meter class ship locks on the basis of the Xiangjiaba hydropower hub on the Jinsha River.In accordance with the actual terrain and geological conditions of the site,as well as the requirements of relevant codes and model test results,we complete the general layout,make preliminary plans for the division of water levels,the parameters of water-saving basins,peak flow rates during filling and emptying,and energy dissipation facilities within the ship lock chamber,and use finite element numerical calculations to analyze the stability,strength,displacement,and foundation bearing capacity of the hydraulic structures.The results indicate that the general layout of the 100-meter class giant water-saving ship lock is reasonable,and the conveyance system is feasible.Under controlled conditions,the structure is stable,with foundation stresses less than the bearing capacity of the bedrock.During earthquakes,structural deformation remains within allowable limits,and stresses (after excluding local singular points) can be achieved with reinforcement.Overall,the hydraulic structure is implementable.The navigation head of single-stage ship locks has been successfully increased from the 40-meter class to the 100-meter class,demonstrating feasibility in terms of general layout,water conveyance systems,and hydraulic structures.

Abstract:Seepage prevention of structural joints in hydraulic structures such as ship locks is a crucial issue related to the safe operation of structures.Surface water-stopping with polyurea coating has emerged as one of the effective methods for seepage control of structural joints in recent years.Focusing on the water-stopping protection system of flat-covering polyurea coating for structural joints,we investigate the deformation of the surface polyurea water-stopping and the bonding performance between polyurea and concrete through opening deformation tests of structural joint specimens,and analyze the failure modes of the specimens,load-deformation behavior,strain distribution law,and interfacial bonding characteristics in detail.The results show that all specimens show tensile failure of the polyurea coating without interfacial cracking or debonding phenomena.Relative humidity and bond length have little effect on the deformation and peak bond stress of the surface polyurea water stop,while the deformation and peak bonding stress increase correspondingly with the increase of polyurea thickness.The deformation of the polyurea coating in the bonding area is mainly concentrated within the range of 40 mm at the loading end,and a bonding length of 50-100 mm can ensure reliable interfacial bonding.

Abstract:To address the issue of excessive transverse flow velocity caused by the northward water diversion from the Huai’an River intake gate on the left side of the downstream approach channel of the Huai’an fourth-line ship lock on the Beijing-Hangzhou Grand Canal,where space for layout is limited,an optimization study on the arrangement of diversion embankments is conducted.Adopting a hydraulic physical model test,an integral physical model with a scale of 1:60 is established for the downstream area of Huai’an ship lock to conduct tests on navigation flow conditions.The results show that:When independent pier-type structures are used for the berthing sections of the fourth-line and second-line locks,water flow tends to pass through the berthing sections,resulting in excessive transverse flow velocity.By adding bottom elevation-gradient perforated baffles at the middle 100 m of the berthing section of the second-line ship lock and the middle-lower 250 m of the fourth-line ship lock to form perforated flow separation dike,water diversion and flow obstruction are achieved,gradually dispersing the flow.Comparative tests on multiple schemes reveal that the transverse flow velocity of the approach channel drops to the specified limit of 0.15 m/s at a porosity of 40%.The proposed bottom-gradient perforated diversion structure effectively resolves the issue of excessive transverse flow in the approach channel and entrance zone,providing valuable insights for the construction and operation of high-grade ship locks under complex working conditions.

Abstract:Aiming at the problems of insufficient width of the approach channel,complex water flow conditions in curved sections,and high local flow velocity at the discharge outlet of the Weituo Ship Lock reconstruction and expansion due to spatial limitations,an optimization study on the hydraulic characteristics of the ship lock water conveyance system is carried out.By establishing a hydraulic physical model with a scale of 130,the applicability of the dispersed water supply system for the side support holes of the gate wall corridor is systematically evaluated,and key improvement measures are proposed.The results show that the operation method of advancing the water head by 0.5 m and closing the valve for 2 min can effectively improve the problem of inertia induced high drop in the water level of the gate chamber.The adjustment of the width of the energy dissipation open ditch has limited effect on improving the berthing conditions of ships,but it cannot be completely eliminated.Optimizing the outlet into a “combined top and side outflow” grid type energy dissipation chamber structure significantly improves the uniformity of discharge in the gate chamber.The layout of the filling and emptying system is reasonable,and the optimization measures effectively improve the hydraulic performance of the ship lock under complex boundary conditions in the lower approach channel.The research results provide reference solutions and technical basis for the design of ship lock projects that are similar to those constrained by space.

Abstract:In view of the situation where the original revetment structures fail to meet the requirements of relevant standards after the upgrading of inland restricted waterways,this paper studies the current renovation and reinforcement types of revetments using existing pile foundations.Considering the mechanical performance of existing pile foundations and the integrity of retaining wall structures,an approach is proposed to reinforce the revetment again by forming a “T-shaped” composite pile structure with existing and newly-built piles.By arranging foundation piles intermittently behind the original retaining wall,the original single-row pile force-bearing system is transformed into a spaced “portal frame” system,which optimizes the stress on pile foundations,reduces the deformation of the pile foundations,and meets structural requirements.For a typical project,the PLAXIS 3D finite element software is used to conduct numerical simulation of the soil excavation process in front of the piles of the re-reinforced revetment structure,and the characteristics such as pile foundation deformation and internal force are analyzed.The calculation results show that the safety factor of the re-reinforced revetment structure is increased by about 21%,the bending moment distribution of existing pile foundations is more uniform,the peak bending moment is reduced by about 23%,and the pile top displacement is decreased by about 58%,all of which satisfy the relevant standard requirements.Meanwhile,the re-reinforced revetment does not occupy waterway areas or require additional land,demonstrating good feasibility and applicability.This study can provide a reference for similar waterway upgrading projects.

Abstract:Weituo water control project on the Fujiang River is located in a sharp bend section of a mountainous river.To address the problem that the upper approach channel and entrance area of the expanded ship lock are jointly affected by curved flow and dynamic-static water,resulting in strong oblique flow,we conduct physical model and ship model experiments to study the navigation conditions of the upper approach channel and entrance area under different layout schemes,and propose engineering measures to improve the navigation flow conditions.The results show that due to the influence of the water flow in the upstream bend,the flow velocity in the upper approach channel and its entrance area of the ship lock in the design scheme is relatively large,failing to meet the safety requirements for ships entering and exiting the ship lock under all navigable discharges.Through measures such as adding a division wall and submerged spur dike,excavating the riverbed on the opposite bank of the upper approach channel,translating the ship lock and adjusting the axis angle of the ship lock,all flow velocity indicators in the upper approach channel and area of the final modified scheme basically meet the specification requirements at Q≤5,000 m3/s.Combined with the ship model experiments results,ships can smoothly enter and exit the ship lock via the upper approach channel at Q≤5,000 m3/s.

Abstract:Addressing challenges in marine dredging,such as dispersed data sources,positioning gaps from signal disconnection,compliance risks from manual judgment,and delayed quantity calculations,this study investigates key technologies including master-slave collaborative data fusion,electronic fence navigation,and dynamic quantity calculation technologies.Adopting a four-layer architecture of “perception-transmission-service-application”,it integrates multi-source data,such as vessel monitoring,automatic identification system, video,geospatial,and meteorological data,and develops a full-process intelligent management system.The system achieves continuous output of positioning data through a master-slave collaboration mechanism.Millisecond-level regional judgment is achieved by means of double-layer electronic fences and an optimized ray casting method.Daily automatic accounting of engineering quantity is completed based on the cabin capacity utilization model.The application in a large-scale project shows that the system has processed 1.826 9 million pieces of data,supported 27 vessels to achieve zero-accident and zero-violation operations,shortened the accounting cycle from monthly to daily,and reduced the regional judgment response time to within 0.3 seconds.This research provides a practical technical scheme for the digital transformation of marine dredging enterprises,and has practical significance for improving the industry’s safety standards and construction efficiency.

Abstract:To address the problems of geometric gaps and seam color distortion that commonly occur in the transition zones during the integration of terrestrial realistic 3D models and underwater terrain point clouds due to scale inconsistency,texture differences,and geometric topological discontinuities,a water-land integrated realistic 3D data fusion technique is investigated.A method combining multi-scale geometric seamless processing and face-primitive-based Poisson color blending is adopted.Through boundary detection and adaptive meshing,geometric cracks in the water-land junction areas are eliminated,and abrupt color differences are reduced.In demonstration applications,the proposed method effectively resolves geometric incompleteness in the junction regions and achieves continuous and smooth color optimization across seams while preserving the gradient structural characteristics of the source imagery,resulting in a geometrically continuous and visually coherent water-land integrated realistic 3D model.The results demonstrate that the fusion strategy is suitable for high-quality integration of multi-source water-land realistic 3D data in complex navigation waterway environments,and can provide reliable technical support for the refined construction and application of the realistic 3D China initiative in the field of smart waterway.

Abstract:To address the problems of multiple weak failure surfaces,unclear failure mechanisms and complex instability modes existing at the interface between bucket foundations and soil in deep composite foundations,the finite element strength reduction method is adopted.The numerical model is validated by field measured data and geotechnical in-situ test results,and the effects of parameters such as the area replacement ratio of sand columns,the penetration depth of the lower bucket and the compartment arrangement of the lower bucket on foundation stability are systematically analyzed.The calculation results indicate that the failure surface at the bottom of the lower bucket is not a horizontal sliding surface as assumed in the specification,but a curved surface intruding into the bucket compartments.The depth of the lower bucket penetrating into the sand column composite foundation has a significant impact on the overall stability,when the penetration depth reaches 1 m,the safety factor is increased by about 1 time compared with the non-penetration condition,and the stability reaches the optimal level at this time.The increase in the sand column replacement ratio can improve the safety factor,but the growth rate tends to flatten out when it exceeds 35%,indicating that 35% is the optimal replacement ratio.Reducing the compartment width is conducive to improving stability.When the width decreases to 13.3 m,the growth of the safety factor slows down,and 10.0 m is the optimal compartment setting.This study reveals the curved failure mechanism of the bucket foundation and provides a theoretical basis for the optimization of key parameters.

Abstract:In the construction projects of ports and docks in coastal areas,the ground soil types formed by landfill are mostly coarse-grained mixture or sand-clay mixture,with high water content,large porosity,and high pore water salinity.In the construction projects of ports and docks in coastal areas,the foundation soil formed by hydraulic reclamation mostly consists of sand-clay mixtures with coexisting coarse and fine particles and discontinuous particle size gradation,which are characterized by high water content,large void ratio,and relatively high salinity of pore water.The deformation law of soft soil foundation is closely related to its compression characteristics.However,there is little research reported on the influence of sand content on the compression characteristics of saline soft clay.To address this problem,sand-clay mixtures with varying sand contents and pore water salinity levels are prepared.One-dimensional consolidation tests combined with numerical simulations are performed to investigate the effect of sand content on the compression characteristics of saline soft clay and reveal its micro-mechanism.The results indicate that the presence of both salt and sand reduces the compressibility of soft clay.A sudden inflection occurs on the compression curve when the consolidation stress approaches approximately 400 kPa.Numerical analysis reveals that banded stress zones emerge at this stress level,which demonstrates that a sand skeleton is formed inside the sand-bearing soft clay.Before the sand skeleton forms,pore water salinity affects compressibility by promoting the agglomeration of clay particles.Once formed,the sand skeleton bears the major load of sand-clay mixtures and further governs the compression performance.This study clarifies the action mechanism of salt and sand particles on the compressive behavior of soft clay.

Abstract:To address the issue that most existing studies mainly focus on the sulfate attack resistance of cement-stabilized soil,while insufficient attention has been paid to soil reinforced by new curing agents,this paper conducts a comparative experimental study on the sulfate erosion resistance of soil stabilized with the two materials.With different sulfate concentrations and two erosion modes adopted,systematic tests are carried out on the two stabilized soils at different erosion ages.By observing surface morphology,testing unconfined compressive strength,calculating the sulfate resistance coefficient,and analyzing microstructure via scanning electron microscopy (SEM),the performance evolution law and erosion failure mechanism are comprehensively revealed.The results show that low sulfate concentrations (≤3,000 mg/L) have little effect on both types of stabilized soil,with performance degradation rates all less than 20%.Under high-concentration sulfate erosion (≥8,000 mg/L),cement-stabilized soil deteriorates rapidly,and the degradation intensifies with erosion age,its unconfined compressive strength decreases by up to 100%,and the sulfate resistance coefficient drops to a minimum of 0.In comparison,stabilized soil presents superior erosion resistance,with its minimum corrosion resistance coefficient reaching only 0.49 under long-term semi-immersion conditions.Stabilized soil overall outperforms cement soil in erosion resistance.This is mainly attributed to the lower content of aluminum-phase hydration products inside stabilized soil,which effectively inhibits the formation of expansive secondary ettringite in the later stage.

Abstract:Research on the load transfer mechanism and bearing capacity of grouted steel pipe composite piles in moderately weathered mudstone strata is insufficient.Based on a port project in Peru,this study investigates the bearing performance of composite piles in moderately weathered mudstone strata through axial compression static load tests on the composite piles.The results indicate that:1) The theoretical calculated ultimate axial compressive bearing capacity of a single composite pile is no less than 23,000 kN.In comparison with the maximum axial compressive bearing capacity of 18,000 kN of test piles,the safety factor is not lower than 1.28.2)Mobilized shaft friction resistance of moderately weathered mudstone inside steel pipe piles is no less than 258.10 kPa,with further values exceeding 270.45 and 1,845.65 kPa observed for cast-in-place piles under both mobilized shaft friction resistance and pile end bearing resistance.3)Axial force within the pile diminishes incrementally with increased embedded depth,exhibiting reduced attenuation in the steel pipe section relative to the cast-in-place section.Pile end bearing resistance approaches 0 kN when test loads are below 14,000 kN.However,it progressively develops as load increases beyond this threshold.4)When the pile-soil relative displacement exceeds 14.37 mm,the growth rate of pile end bearing resistance of moderately weathered mudstone piles decreases,but it still does not reach its peak value.The research results can provide reference for engineering practices under similar geological conditions.

Abstract:As a new type of structure,the application of insertable large-diameter steel cylinders in China is still in its infancy,and there is an urgent need to conduct in-depth research on the applicability and stability of large-diameter steel cylinder foundations under super-thick soft soil foundations.We carry out the stability research of steel cylindrical structures under different water depth conditions,different penetration depths and different geological conditions by numerical simulation calculation methods.The results show that when the depth of the rotation center is less than the burial depth,the mechanical mechanism of the large-diameter steel cylinder is mainly manifested as rotational overturning,which is a deep-insertion structure.When the depth of the rotation center is greater than the burial depth,the mechanical mechanism of the large-diameter steel cylinder includes rotational overturning and horizontal sliding,which is a shallow-insertion structure.The failure mode of steel cylinders is related to dimensions,burial depth,load magnitude,and soil parameters,etc.Under the condition of super-thick soft soil geology,the steel cylinder structure can still be applied.When the S/H (S is the horizontal displacement of the top of steel cylinder,and H is the height of the cylinder body above the mud surface) of the steel cylinder is 1.5%,the load value increases with the increase of the insertion ratio,the cohesion of the soil,the internal friction angle of the soil,and the backfill depth,and decreases with the increase of the load height.

Abstract:The performance of dredging equipment exerts a decisive impact on the regulation effect of suspended rivers.To investigate the performance of the high-pressure flushing system for typical suspended river dredging equipment,a numerical simulation method is adopted to study the flow field inside the pipelines and nozzles of the system.The results show that the structural layout of the original high-pressure flushing pipeline and nozzles is unreasonable.The difference between the maximum and minimum outlet velocities of all nozzles is 3.86 m/s,and the relative deviation of the outlet velocity of No.9 nozzle reaches 17.35%.The outlet velocity distribution of each nozzle is extremely non-uniform.In view of the above findings,a targeted structural optimization scheme for the towed harrow high-pressure flushing system is proposed and verified by numerical simulation.After optimization,the outlet velocity of each nozzle becomes highly uniform.The velocity difference between the maximum and minimum outlet velocities is only 0.33 m/s,and the relative deviation of the outlet velocity for all nozzles is within 1.10%.The overall flow field of the towed harrow high-pressure flushing system is significantly improved.The research results can provide a reference for the design of dredging equipment used in suspended river regulation.

Abstract:To address the sliding problem of the berthing structure in an artificial island with tied-back sheet piles,we build a 3D finite element model using the“Nanshui”double-yield surface elasto-plastic constitutive model.Then we systematically simulate structural responses under various construction loading processes,water level conditions,and service loads,thereby revealing the mechanical mechanism of sliding and proposing corresponding treatment solutions.The results indicate that sliding primarily stems from insufficient bearing capacity of the weak silty clay foundation and an imbalance in lateral earth pressure caused by asynchronous filling and rock dumping during construction.Under the design low water level condition,the peak tensile stress at the southeast retaining wall reaches 1.60 MPa;while this does not exceed the material strength,it poses a potential threat to long-term durability.Moreover,the non-slip dominant factor of the design load has a much smaller increase in the structural response than the influence of filling and water level changes.The proposed remediation measure of supplementary counter-pressure dumping enhances the bearing capacity of soil in the passive zone and lateral constraints,increases the anti-sliding safety factor to 1.050 under extreme low water level conditions,and meets code stability requirements.

Abstract:Large trailing suction hopper dredgers may experience pronounced layer-thickness fluctuations and discontinuous strip coverage when conducting backfilling over deep soft-soil foundations.To address this engineering problem,a quality database for layered sailing side-casting backfilling is established based on high-precision RTK-GNSS vessel tracks and multi-period multibeam bathymetric surveys from the Pasay backfilling project in the Philippines.Statistical indicators,including mean thickness,unit-area thickness,thickness coefficient of variation,and effective coverage width,are employed to systematically investigate the coupled effects of bottom-door opening,sailing speed,and flushing-water flow rate on backfilling thickness and uniformity,and to summarize adaptive rules for on-site parameter adjustment.The results show that within a practical control window with a bottom-door opening of 30% to 50%,a sailing speed of 1.2-1.8 kn,and a flushing water flow rate of approximately 2,000 m3/h,the single-layer thickness can be maintained at 0.45-0.60 m,the measured total thickness ranges from 1.88 to 2.14 m,the thickness coefficient of variation is generally below 0.12,and the final construction surface elevation deviation is controlled within ±0.15 m of the design value.This study clarifies the quantitative relationships between key operational parameters and backfilling thickness-control indicators,and proposes an optimized parameter window and an on-site control method for layered moving discharge backfilling by trailing suction hopper dredger over deep soft-soil foundations,providing technical support for process selection and construction quality assessment in similar projects.

Abstract:On the basis of an offshore infrastructure project,the fatigue damage characteristics of a large-diameter steel cylinder structure ultra-deep into foundation soil are analyzed under the vibration force during the sinking construction stage and the wave load after installation.The performance test is carried out through continuous long time vibration force input during the sinking of the test steel cylinder,and the mechanical performance of the structure-equipment system under extreme conditions is tested and verified.The E2 fatigue curve and parameter value obtaining method are presented,and the fatigue analysis results are in good agreement with the actual test.An intermittent continuous vibration force input method is proposed together with the achievement of accurate vibration input control based on force feedback,which can effectively reduce the total vibration time and fatigue damage,and make the fatigue safety of the structure reach nearly 2.0 during vibration sinking construction.According to the test data obtained from physical models under regular and irregular wave conditions,the fatigue damage factor of the steel cylinder caused by sea wave load is less than 0.1,and the irregular wave is less than the regular wave,which accounts for a relatively small proportion in the total damage factor.