Abstract:When the draghead excavates dense silt，the mechanism of using conventional high-pressure flushing to assist soil breaking is not clear. To understand the actual effect of high-pressure flushing on crushing dense silt，the conventional high-pressure flushing soil breaking test and theoretical analysis are carried out on the dense silt prepared in the laboratory by means of field test and simulation analysis. The results show that the depth and width of soil breaking by high-pressure flushing are greatly affected by the moving speed of nozzle，target distance and diameter，and show different laws.When excavating dense silt，although the auxiliary breaking effect of high-pressure flushing is not obvious，it can reduce the excavation resistance of rake head significantly，high-pressure flushing should be used reasonably according to the actual situation of the site. The results of the test can provide guidance for the design of draghead and the construction technology of dense silt.

Abstract:To seek a technically feasible，economical，and environmentally compliant dewatering treatment scheme for dredged sediment of lakes and reservoirs，this study takes the dredged sediment of Lake Baiyangdian as the research object for the experiment on electroosmotic vacuum preloading technology by systematic engineering research methods of model tests，pilot tests，and application demonstration. The results reveal that the electroosmotic vacuum preloading technology is mature and extraordinarily outperforms vacuum preloading in dewatering，and the dewatering effect of double-sided drainage is significantly better than that of single-sided drainage. In addition，the cost of electroosmotic vacuum preloading technology is about 1/3 higher than that of vacuum preloading technology. The technology meets the requirements of ecological compliance and can be used for subsequent resource utilization. The research results can provide a technical basis for engineering design and construction.

Abstract:Operating efficiency prediction of the dredger is an important basis to ensure engineering benefits. Regarding the difficulty in predicting the cutter suction dredger’s output，based on the theoretical model of specific cutting energy，this paper establishes a productivity prediction model of sand excavation by cutter suction dredger，determines the main influencing factors of sand excavation，and verifies results in combination with engineering cases. The results show that the standard penetration number is the key factor affecting the theoretical specific cutting energy. Through the mathematical model of sand standard penetration number and excavation productivity established by actual engineering，this paper better predicts the sand excavation productivity. The research results can guide and provide a reference for theoretical research on sand excavation by cutter suction dredger or on-site construction.

Abstract:Taking polluted fish ponds in Lake Baiyangdian as the research object，this paper carries out engineering tests for four different ex-situ water quality improvement processes，namely，magnetic coagulation-magnetic separation + ecological pond，magnetic coagulation-magnetic separation + reed wetland，biological ultra-deep purification treatment system，magnetic coagulation-magnetic separation + biological ultra-deep purification system + reed wetland. The results reveal that the chemical oxygen demand（COD）and total phosphorus（TP）removal rates of polluted pond water by the magnetic coagulation-magnetic separation process are 42.7% and 88.66%，respectively. Those by the biological ultra-deep purification treatment system are 60.50% and 95.59%，respectively，and after treatment，the main water quality indexes can reach the standards of Class Ⅲ in GB3838-2002. If the magnetic coagulation-magnetic separation and the biological ultra-deep purification treatment system are combined to treat the polluted fish pond water，the COD and TP removal rates are 62.96% and 94.07%，respectively. Compared with the biological ultra-deep purification system，the combination can further degrade the pollutants in the effluent produced by the magnetic coagulation-magnetic separation process，but the final effluent is not superior to that by the biological system alone. Reed wetlands can improve the effluent quality to a certain extent，and the COD and TP removal rates of the effluent of the whole treatment system are about 16.08% and 33.1%，respectively.

Abstract:The utilization of dredged soil plays an important role in promoting the harmonious development of society，building energy-saving resources and developing low-carbon economy. The properties of dredged silt in Shiqiao Lock section of the Beijing-Hangzhou Grand Canal are tested and analyzed by large deformation multi-functional geotechnical ring shear instrument，and the influence of restrained axial compressive stress on the strength of curing soil is studied. The test results show that the physical parameters such as bulk density，void ratio，liquid limit，plastic limit，liquid index and plastic index of river silt samples decrease with the increase of silt’s water content. The addition of curing agent can obviously improve the physical parameters of silt soil. The compression modulus，cohesion and internal friction angle of curing silt are significantly affected by the axial confined compressive stress. In practical engineering，it is suggested to increase the axial compressive stress of curing soil to further improve the strength of soil.

Abstract:Regarding the excavation problem of sand foundation reinforcement by DCM ship at sea，numerical simulation technology is used to establish a three-dimensional analysis model of soil cutting by agitator cutting parts and soil mixing by mixing parts. The constitutive model of soil adopts Drucker-Prager model，and the failure criterion of unit damage is used to simulate the failure process of sand，based on the explicit integral algorithm，the dynamic process of the agitator cutter cutting sand is simulated，the cutting resistance，cutting power and stirring power of the agitator are analyzed，and then the stress state of the agitator is analyzed under normal working conditions and limit working conditions. The results indicate that the maximum stress at the end of agitator is 231 MPa，which meets the requirements of strength.

Abstract:Aiming at the unreasonable power reserve setting of the cutter suction dredger equipped with the 900 mud pump and the fact that the dredger is not suitable for long-distance discharge projects，this paper determines the appropriate increase in mud pump speed and improves the lift of the cabin pump by 16.5% and that of the underwater mud pump by 17% through the CFD simulation analysis method，thereby improving the long-distance discharge performance of the dredger. After the speed of the pump body，shaft system，pump cover connecting bolts，and auxiliary sealing water pump increases，the paper analyzes their adaptability to ensure that the pump can meet the requirements of the dredger’s long-distance discharge in terms of hydraulic power，structure，and auxiliary equipment，and it can provide a reference for similar cutter suction dredgers to improve their long-distance discharge.

Abstract:Sediment ecological dredging is an important measure to reduce endogenous pollutants，control black and odorous water bodies，and improve water quality. However，traditional dredging tools will cause the spread of sediment pollution sources and secondary pollution，which will affect the dredging effect. The CCCC Tianjin Dredging Co.，Ltd. has developed a new type of ecological dredging equipment，the working principle of the machine and the dredging capacity such as production capacity，traverse speed and mud suction concentration are theoretically analyzed. Using CFD simulation technology to analyze the hydrodynamic characteristics of the tool under different working conditions，it is found that the use of screw cutting and conveying can obtain a higher concentration of mud，and a smaller pitch parameter helps to achieve more mud suction. thus confirming that the designed machine has good dredging performance.

Abstract:Cutter suction dredger is considered to be an effective dredging tool in the dredging industry，and its cutter has a great influence on the dredging capacity. At present，the cutter body is mostly manually modeled during the design process. The cutter arm，big ring，and hub are the main structure of the cutter，and their modeling faces many problems，such as massive parameters，cumbersome modeling，and low precision. In order to shorten the modeling cycle and improve the modeling accuracy，this paper proposes a parametric cutter body modeling method，uses C# programming language to realize Solidworks’s secondary development，and calls the built-in API interface to realize the parametric and automatic generation of the three-dimensional（3D）cutter body model. Based on the concept of object-oriented programming，the paper develops a modeling software for the cutter body based on the SolidWorks platform，which ensures that the cutter parameter modeling and cutter performance calculation are carried out in parallel，and it also puts forward a standardized and parametric creation of the cutter. The research results can provide a reference for the performance optimization of the cutter body.

Abstract:Gridded revetment is environment-friendly and has good durability and water permeability，which is especially suitable for bank revetment with poor geological conditions and complex water flow conditions，but there are some problems such as difficult construction management and control. To study the applicability and construction quality management of Gridded ecological revetment in the project，combined with the actual construction management experience and relying on the typical inland waterway regulation project，and focusing on the analysis from aspects of technical measures and raw material control，this paper puts forward the main construction quality control points and control measures of Gridded ecological revetment，which has been successfully used in the waterway regulation project from the Shiqiao ship lock of the Beijing-Hangzhou Grand Canal to the gate of the Yangtze River estuary，and improves the construction quality and efficiency. The results may serve as reference for similar Gridded ecological revetment construction.

Abstract:With the implementation of environmental protection dredging project in rivers and lakes，the treatment and disposal of a large amount of dredging sediment has become a social concern. To solve the problem of sediment resources，the dewatered sediment from geo-tube bag in Baiyangdian ecological dredging pilot project was taken as the research object. Based on the analysis of sediment，river sand and vermiculite were used as amendments to improve the five main control indices of sediment，including pH，salt content，organic matter，textures and soil infiltration rate. The experimental results show that both river sand and vermiculite improve the sediment，but the sediment texture does not change significantly with the addition of vermiculite. Considering also the factors of economy and engineering，river sand is selected as the amendment. It is more suitable to add 25% to 30% of the sediment mass（dry mass），the texture of the improved afforested soil is basically within the range of loam soil，which is most suitable for plant growth. Besides，the other four main control indices such as pH，salt content，organic matter and infiltration rate can all meet the requirements of planting soil for greening stipulated in the code CJ/T 340-2016. Furthermore，the project application scheme is put forward for the Baiyangdian ecological dredging pilot project，which provides a new idea for sediment resources.

Abstract:As a new water treatment technology，the super-magnetic separation and water purification technology has developed rapidly worldwide in recent years，and it is widely studied and applied in engineering. Taking the third phase of the ecological desilting project in Lake Baiyangdian as an example，this study focuses on expounding on the technical characteristics and process flow of the super-magnetic separation and water purification technology considering the engineering problems such as the massive volume of water to be treated，a short cycle，and limited land occupation. In addition，the application effect of the technology in the treatment of polluted water is obtained. The research results can provide experience and references for the treatment of polluted water in similar projects.

Abstract:Considering the difficulty in deep dewatering of dredged sediment in Haihe River in Guandu District，we carry out experiments on flocculation concentration combined with plate-and-frame filtration. Specifically，three flocculants，namely，anionic polyacrylamide（APAM，with a molecular weight of 1 500），cationic polyacrylamide（CPAM，with a molecular weight of 800），and non-ionic polyacrylamide（NPAM，with a molecular weight of 900），are used for flocculation concentration. Then，we perform pressure filtration tests on the two kinds of selected concentrated slurry separately by a diaphragm plate-and-frame filter press. Next，we use the KD20 plates to fill the slurry chamber（with a thickness of 200 mm），with continuous feeding of 10 min at the extrusion pressure of 0.8 MPa. Finally，the optimal flocculant is selected according to the plate-and-frame filtration results. The test results reveal that for the dredged sediment with a high organic content，CPAM with a molecular weight of 15 million and a degree of hydrolysis of 14% has a better flocculation effect，and upon concentration，the dewatering effect and effluent quality of the plate-and-frame filtration of slurry are better. The pressure time is 30 min，and the water content of the mud cake can be reduced to below 40%.

Abstract:When the operating waterway needs to be widened or deepened for dredging，the frequent avoidance of construction ships and operating ships often leads to high safety risks and low construction efficiency. In this situation，the ship safety avoidance and efficiency improvement measures are studied，that is，the calculation method of the effective width of the channel is adopted，and the scientific and effective avoidance measures are adopted through the construction and navigation check to solve the problem that the rake suction ship frequently leaves the channel to avoid the problem. We develop blocking rake fast mud removal device and rake head anti-slip rake device of TSHD，which respectively solve the technical problems such as the difficulty of cleaning the raking and raking in the construction of TSHD，and the low efficiency of slope construction. Practice has proved that the measures are feasible.

Abstract:We take the construction project of the extension section of the 100，000-ton level channel in Ganyu Port area of Lianyungang Port（HD-SG-2 bid section）as an example，aim at the problem of grade 4 and 5 clay mixed ginger stones when cutter suction dredger is working in long blowing distance（standard length of shore pipe is 7 km），analyze from the two aspects of excavation technology and transportation technology，use automatic dredging technology in the working conditions of clay mixed ginger stones in terms of construction parameters optimization，realize the optimal construction parameters combination of automatic dredging technology by the comparative analysis of multiple groups of parameters，and revise the construction flow rate and mud density calculation model and the Durand hydraulic gradient calculation model based on the automatic dredging data. The results show that the successful implementation of this technology can improve the calculation accuracy of the productivity of clay transported by the long distance of ultra large cutter suction dredger，determine the optimal combination of construction parameters of this kind of soil，ensure the stability of soil transportation in the pipeline，and avoid pipe blockage.

Abstract:This paper studies the damage pattern of geotextiles during construction of flexible mattress in deep water areas with strong wind and wave，and discusses the stability improvement technology of soft mattress in complex hydrological environment in combination with the characteristics of geotextile soft mattress including protection，reinforcement，filtration，isolation，integrity，and strong adaptability. The result shows that measures taken for the geogrids and soft mattress such as reinforcement，increasing buffer layers，three-layer composites，and whole-length treatment can better solve the problem of soft mattress damage due to large and frequent wind and waves and few construction days.

Abstract:How to build a permanent anti-seepage system on a new dam to ensure stable inland waters has become a key concern. Taking an artificial island in a project as an example，this paper focuses on two construction techniques including reinforced concrete anti-seepage walls engaging with deep cement mixing piles and reinforced concrete anti-seepage walls engaging with steel sheet piles on a new dam，and it compares the two techniques in terms of the anti-seepage effect and economic benefits to select the appropriate construction scheme. The results show that：1）The construction scheme of using reinforced concrete anti-seepage walls to vertically engage permanent steel sheet piles on the new dam is economically feasible. 2）On the basis of reducing the construction difficulty，the anti-seepage system of the dam is strengthened，and the effect is obvious.

Abstract:Because the slope protection and foot protection of breakwater are filled with large size stone，it is difficult to set the spiral pipe of the conventional water operation platform of cast-in-place pile，which makes it difficult to form the platform foundation system. According to the series of problems in the original design scheme of the steel platform，we carry out the optimization design，and finally adopt the foundation support system of the shore side backfilling block stone and 2 rows of beret frame and 1 row of spiral pipe piles. The results show that the stress and bearing capacity of the platform foundation system are qualified，the steel platform does not have a large slip mutation during the construction of the cast-in-place pile，and the settlement is relatively uniform. The water work platform is safe，reliable and convenient for construction.

Abstract:The multi-layer floating breakwater has the advantages of light mass，simple structure，low cost，easy to move，reusable，and not limited by water depth and geological conditions. The construction area of a dredging project in Mauritania has large swells and long period waves，which affect the dredging operation of cutter suction dredger. To solve the problem of medium and long period waves interference and reduce project budget，we use Reynolds average（RANS）equation and shear stress transport（SST）k-ω turbulence model to simulate the flow distribution based on the open source fluid mechanics platform OpenFOAM，analyze the dimensional characteristics of the multi-layer floating breakwater including plate length，plate spacing，plate thickness and the influence of different wave periods on the performance of multi-layer floating breakwater，and determine main dimensional parameters affecting wave dissipation performance of multi-layer floating breakwater. The results show that the most direct and effective way to improve the wave elimination performance of the multi-layer floating breakwater is to increase the length of board. The effect of the spacing change of board on the wave elimination performance is not completely determined，and it needs to be selected according to the actual needs.

Abstract:The bank slope of the fluctuating zone of the Yangtze River is repeatedly scoured for years as the water level rises and falls，which results in the vegetation deterioration and ecological fragility and makes the fluctuating zone lose its function of filtering and intercepting. Taking the area with the water level ranging from 160.00 m to 170.00 m in the Yangtze River in the Guangyang Bay area of Chongqing as an example，this paper studies the treatment scheme for the fluctuating zone and adopts the method of “ecological net mat for soil consolidation + vegetation” to maintain the shoreline stability. In addition，the waterfront landscape zone and a multi-level and complex compound forest system of the fluctuating zone are formed after vegetation growth. The results show that the soil retention rate is more than 98%，and the project implementation has a favorable effect.

Abstract:The pile position of pile group foundation in offshore wharf is densely arranged，so the pile sinking construction is greatly affected by environmental factors，the positioning is prone to deviation，and there is a certain risk of pile collision. In the design process，it is often necessary to check the distance between piles to reserve the working space for pile driving. The pile spacing calculation methods used in the past have certain limitations，and cannot quickly and accurately calculate the shortest space spacing and the generation position in the pile foundation，which brings difficulties to the calculation of the pile body spacing. Through the analytical geometry method，two sets of mathematical models，the ergodic method and the linear box constraint method，are developed，which can quickly calculate the shortest distance between two piles and the position where the shortest distance occurs according to the design pile parameters. To ensure the safety of the pile body during the pile driving process，these pile spacing algorithms are used to calculate the pile group foundation with various types of piles，and the results are accurate and the application effect is good.

Abstract:Regarding the requirements of high precision bathymetry in waterway engineering，this paper takes the single-beam bathymetry system as the research object and introduces the bathymetry principle and main influencing factors of bathymetric errors. Moreover，this paper analyzes the main error sources of high precision bathymetry from the perspectives such as positioning errors，bathymetric errors，water level errors，and environmental effects and puts forward corresponding reduction measures，which are subsequently verified by experiments. We recommend using RTK three-dimensional bathymetry technology to eliminate the influence of water level errors，correcting the navigation delay to reduce the influence of positioning errors，and utilizing attitude sensors to remove the influence of roll and pitch attitude angles on bathymetric errors. Finally，the influence of errors in the bathymetry process is reduced，and the accuracy of bathymetry is improved.

Abstract:The harsh construction environment of breakwater demolition projects determines that construction safety is the primary problem to be solved. Considering the difficulty of construction management in the complex construction environment of breakwater demolition projects，this paper relies on the breakwater demolition project of Tianjin Binhai Information Innovation Base for research on the application of building information modeling（BIM）technology in breakwater demolition projects. Specifically，we use three-dimensional（3D）software such as Revit，Navisworks，and Lumion on the basis of the Autodesk software platform to achieve the rapid creation of the BIM model，3D model rendering and roaming，and demolishing process display of this breakwater project. By the BIM model，the construction progress preview and engineering quantity statistics of the breakwater demolition project are realized，and the application process of BIM technology in breakwater demolition projects is summarized. The research is expected to provide a reference for similar engineering projects.

Abstract:Relying on the construction project of the third runway of Hong Kong Airport，regarding the problems of slow moving of the deep mixing vessel and the large precision deviation required for the pile sinking construction，by consulting the relevant technical data at home and abroad，this paper studies how to calculate the real-time position of the target pile through the GPS position，and the ship is moved to the target position through automatic mooring and positioning in a short time.Using a high-precision coordinate system conversion algorithm，a pile position calculation algorithm based on the ship’s space coordinate system，and a filtering algorithm to reduce the influence of the ship’s rolling period，using high-precision sensors and control units，a high-precision automatic mooring positioning system is designed，the positioning accuracy of the system is within 0.1 m，and the angle deviation is within 0.2°.The successful application of this system not only improves the construction efficiency and construction accuracy of the deep mixing vessel，but also reduces the labor intensity of construction workers，and provides an effective solution for the design of ship-moving control systems for similar ships.

Abstract:The construction process of cutter suction dredger is very complex，with more uncertainty and randomness. Regarding the problems of many impacts in dredging output，insufficient stability and low productivity，we take the slurry in the transmission pipeline of cutter suction dredger as the research object，analyze the characteristics and influencing factors of dredging construction，preprocess the historical big data of dredging engineering，compare two different flow prediction schemes of T-S model and historical data nearest neighbor，and use deviation feedback controller to independently optimize construction parameters based on big data. The results show that the accuracy of the second scheme is higher because the data are preprocessed. The flow adjusted by feedback control according to the optimization parameters is higher than the original flow.

Abstract:Regarding the characteristics of multi-process，multi-intersection，tight time and heavy tasks in river regulation projects，we establish a unified management system which is based on the BIM technology，computer technology，wireless network technology，GIS geographic information technology，and video surveillance technology，by which we can realize the whole-process monitoring and control and enable construction operation problems to be identified early and resolved quickly，forming a long-term management mechanism and making the management of river regulation projects more scientific，rational and standardized.

Abstract:When using vacuum preloading technology to treat soft soil foundations around existing roads，we should consider the influence of vacuum preloading construction on existing roadbed and ensure the safe operation of existing roads. Taking an actual project as an example，this paper summarizes and corrects the empirical formula through similar projects，and the calculation results reveal that the existing road is within the influence range of vacuum preloading. To ensure the safe operation of Dongdi Road and the effect of foundation treatment，we set a protection zone with a width of 15 m on the side of the existing road near the vacuum preloading treatment area，use long and short plates with the length of the plastic drainage plate reduced from 8.0 m to 3.0 m from the side far of the road to Dongdi Road，and adopt the stacking preloading method with the stacking height of 3.0 m. For the protection of Dongdi Road，we monitor the horizontal and vertical displacement and settlement during the construction period. Finally，under the double guarantee of the earlier scheme design and monitoring during the construction period，the foundation treatment construction has been smoothly completed.

Abstract:To accurately determine the foundation treatment parameters of the dredger fill in Binzhou Port，this paper uses permeation and consolidation as well as vacuum preloading tests to explore the relationship between the physical parameters and the consolidation pressure of the dredger fill in Binzhou Port. The results reveal that the parameters of dredger fill after the tests are only related to the consolidation pressure and is irrespective of its original state，and the change rate of physical parameters at the pressure of less than 50 kPa is faster than that at the pressure of more than 50 kPa. Moreover，in the permeation and consolidation test at the pressure of 100 kPa and the vacuum preloading test at the pressure of -100 kPa，the pressure has the same compression effect on dredger fill，and the physical parameters of dredger fill samples after the tests are consistent. When we employ vacuum preloading for foundation treatment of dredger fill and take no other measures such as stacking，the dredger fill has a limit water cut of 44%，with the void ratio of 1.23 and the density of 1.78 g/cm3.

Abstract:On the basis of the principle of effective stress in soil mechanics，the physical meanings of characterization parameters，and the analysis of the boundary conditions for geotechnical test indices，it is concluded that the shear strength of cohesive soil can be calculated using the natural density of the overlying soil layer and the shear strength of the soil layer determined by the direct shear test. This paper also put forward suggestions on the modification method of test indices for the accurate calculation of the shear strength of dredged cohesive soil. The research is of great significance to the classification of rock and soil in dredging engineering.

Abstract:Regarding the problem that the overloading caused by hoisting operation can affect the adjacent pile foundation，this paper analyzes the hoisting operation’s stability and pile foundation stress. The paper uses the empirical formula to calculate the hoisting stability and adopts the finite element method to analyze pile body stress. The results reveal that the stability coefficient of hoisting operation，pile body stress，and horizontal and vertical displacements of pile top all meet relevant requirements. The overloading exceeds the design value under the hoisting operation condition. Although the stress and displacement of the pile foundation meet the code requirements，the internal force and displacement increase significantly. Therefore，the impact of overloading on structural safety should be rechecked.