Abstract:The influences of input parameter dimension on prediction accuracy of the neural network model are investigated based on the data of wave overtopping at sloping breakwaters of block revetment from the European CLASH Project Database.For the selected three types of breakwaters with varying structural complexity,which are simple double-slope breakwaters,double-slope breakwaters with smooth berm and complex double-slope breakwaters with crown wall,three neural network(ANN)wave overtopping models(ANN1,ANN2,ANN3)are established and their prediction accuracies are compared and analyzed.For these models,the random forest method is used to rank the importance of the input parameters such as design wave factors,breakwater geometry and position and revetment characteristics.The results indicate that the roughness coefficient γf is a primary influencing parameter shared by the three models ANN1,ANN2 and ANN3.The relative crest freeboard significantly affects model ANN1,while the relative berm width has a notable impact on model ANN2.By comparing the contribution of roughness coefficient γf to predicted values of different structural types,it is found that different structural types exhibit various sensitivities to γf.A single roughness coefficient value is not enough to reflect reasonably the influences of the changes in geometric shape of revetment blocks,number of block layers and other structural characteristics on the wave overtopping.

Abstract:By using the wave data observed in-situ at 5 representative stations in the Bohai Sea,the applicability of ERA5 reanalyzed wave data in the Bohai Sea is evaluated from three aspects including wave height,wave period and wave direction.The results show that the temporal variation trend of ERA5 wave elements is basically consistent with that of the data observed in-situ,but differences in magnitude are present.The statistical results of different elements at different stations vary also to some extent.Between the ERA5 wave data and the data observed in-situ,the correlation of effective wave height is the highest,being roughly above 0.9,followed by peak wave period and the correlation of mean wave direction is the worst.The correlation between the effective wave height and the peak wave period is the lowest at the station nearest to the coast.The error between the two elements is also largest at the station nearest to the coast.At the stations far away from the coast,the performance of wave elements shows better on the whole.As far as the data use of the three representative elements is concerned,the ERA5 wave elements require some correction in terms of magnitude,especially the wave direction data.The wave products from ERA5 have certain applicability in the Bohai Sea.Therefore,it is feasible to analyze the statistical characteristics of waves based on the ERA5 products.

Abstract:For understanding the variations of the response of seafloor soft clay strength to different loading rates,the non-drainage shear strength characteristics of seafloor shallow soft clays in an offshore wind farm area in Shandong are tested and analyzed under various shear rates by using a high-precision soft-solid rheometer.The results show that the shear rate does not affect the characteristics of the non-drainage shear stress-strain relationship of seafloor soft clays.Under different shear rates,the initial non-drainage shear strength of all seafloor soft clays shows strain-softening collapse characteristics,while the remodeling non-drainage shear strength shows plastic collapse features.There is a positive correlation between the peak non-drainage shear strength of seafloor soft clays and the shear rate,whereas the residual non-drainage shear strength is almost not affected by the shear rate.Under different conditions,the average residual strength is about 1 700 Pa.The sensitivity of seafloor soft clays trends to increase slowly with the increase of the shear rate.The results of the study can provide a reference for selecting reasonably the strength parameters of seafloor soft clays under different loading rates in marine engineering.

Abstract:The completion of the Pinglu Canal,the main channel connecting the Xijiang main river and the Beibu Gulf,can not only greatly shorten the route to the sea and reduce transportation costs,but also provide irrigation and flood drainage services for the banks of both the tributary and the mam stream of the Qinjiang River.The Pinglu Canal entering the sea through the Qinjiang River can cause the runoff of the Qinjiang River to increase,and then affect the variations of salinity and silt content in the estuary and adjacent coastal waters.Based on the tidal current model FVCOM and its sediment module,the influences of the launch of the Pinglu Canal on the sediment content and salinity in Qinzhou Bay are analyzed by means of numerical simulation.The results show that with the increase in water diversion the salinity decreases significantly in the northeastern part of the Maowei Sea,with the magnitude of salinity decrease being increasing.The envelope area of the salinity reduction also expands continuously and extends gradually towards the neck of the bay.Because there is freshwater floating on the surface,the salinity reduction in the surface layer of Qinzhou Bay is significantly greater than that in the bottom layer.The high suspended sand concentration and siltation areas in Qinzhou Bay are mainly concentrated in the three channels of the Qinjiang River and the estuarine area.With the increasing in water diversion the increment in the river channels and the estuary area is significant and that in the central area of the Maowei Sea shows a small change.

Abstract:Dredging project plays a critical role in the constructions of port channels and marine exploitation.As a main working equipment,the cutter suction dredgers(CSDs)are commonly used for conveying the excavated sediments to the designated discharge sites by pipelines.Therefore,to optimize the sediment-conveying efficiency of the CSDs,it is critical to monitor key factors such as flow velocity in the pipeline in real time.However,the challenging working environment imposes great constraints to the wild applications of the traditional physical sensors due to their high cost and complex maintenance requirements.For measuring the flow velocity in the pipeline,therefor,a soft sensoring method ICBFormer is proposed.This ICBFormer integrates the Interactive Convolutional Block(ICB)and the Transformer Model in order to replace the traditional flowmeters,in which the ICB is used to capture the complex inter-variable relationships and extract multiscale temporal features.Subsequently,the dynamic relationships among variable data sequences are high-effectively handled with the help of the advantages of the Transformer Model in long-sequence feature extraction,thus achieving the accurate prediction of flow velocity in the pipeline.This soft sensoring method has been evaludated through data collecting by building a simulation experiment platform for conveying by dredging mud pump.The results show that the ICBFormer proposed in the study has a significant advantage in the flow velocity prediction and provides a new solution for reducing the sensor cost and maintenance expense of the dredgers.

Abstract:In the design of offshore wind power foundation,the key to ensure the safety and stability of the structures is to analyze the force characteristics and destruction modes of pile-cylinder foundation under composite loading modes.This study is aimed to investigate the destruction modes of pile-cylinder foundation of a 3 MW wind turbine in homogeneous soft clay ground,for which a finite element analysis tool ABAQUS is used to establish the model for simulating the combination of different composite loading modes and a normalized foundation destruction envelope within two-dimensional load space is obtained by using method of load-displacement loading.The results indicate that under the composite loading modes,an appropriate vertical load can be helpful for improving the bearing capacity of the foundation,whereas the synergistic actions of horizontal load and bending moment load can exacerbate the destruction of the foundation.With different loading modes,the pile-cylinder foundation shows a variety of destruction modes.Under V-H and V-M loading modes,for instance,the destruction of the pile-cylinder foundation exhibits the following stages:vertical scoop-shaped destruction,spherical rotation destruction,horizontal wedge sliding and overturning destruction.In contrast,under the H-M loading mode,the destruction mode of the pile-cylinder foundation is more complex and displays 4 stages,including overall rotation,scoop-wedge shaped destruction,horizontal sliding and backward overturning.

Abstract:Residual currents play a significent role in long-term transport and diffusion of pollutants in water bodies,and the field of residual currents can be altered by the shoreline changes caused by reclamation activities in the Bohai Bay.In order to investigate the changes of residual current field in the Bohai Bay before and after the reclamation,the hydrodynamic field and the Lagrangian particle moving trajectories in the Bohai Bay before and after the reclamation are simulated by using the hydrodynamic model and Lagrangian particle tracking model of software MIKE21,and the Eulerian residual current field and the detailed circulation structures in the Bohai Bay are obtained.By comparing the changes in hydrodynamic field,residual current field and Lagrangian particle trajectories before and after the reclamation,it can be concluded that after the reclamation the velocities of the maximum flood and ebb currents in most areas of the Bohai Bay are all decreased compared to those before the reclamation,and the directions of the maximum flood and ebb currents are changed in the waters near the reclamation area.The velocities of the residual currents are changed greatly in the waters near the shore and ports.The residual current field in the Bohai Bay exhibits four circulation structures,among which the clockwise circulation located near the Huanghua Port and the Binzhou Port and the counterclockwise circulation located at the southern bay mouth are significantly affected by the reclamation activities.The overall circulation structure in the Bohai Bay follows a pattern of inflow from the north and outflow from the south.After entering the bay from the northern part of the bay mouth,the currents flow inward and diverge into three branches in the southeastern sea area of Caofeidian,which flow southward,southeastward and southwestward,respectively.Of them,the southwestward branch further diverges near the Tianjin Port during the process of its flowing into the bay,and then these branches join the circulation structures on the north and south sides of the Tianjin Port.

Abstract:Reclamation is an important way to solve the shortage of land resources.A new round of large-scale reclamation has been raised in China since entering the 21st Century.However,the negative effects caused by the reclamation are getting more and more attention.As one of the most common reclamation projects,the coastal reclama-tion has still no systematically theoretical system and technical methods for its environ-mental impact assessment.In order to provide references for the development and man-agement of the coastal reclamation,the latest research methods and achievements of the coastal reclamation environmental impact assessment are summarized from the following two aspects:One is the single environmental impact assessment,which has focused on research of the methods for the hydrodynamic and sedimentary environmental impact as-sessment and the contaminant transport impact assessment;another is the comprehen-sive environmental impact assessment,which has mainly focused on research of the methods for integrated benefit evaluation,suitability evaluation,bearing capacity evalu-ation and vulnerability evaluation.

Abstract:The scouring and breaking of waves to the structure of sloping breakwaters are affected by many factors, such as wave elements, water depth, slope angle, armor block types, and so on. In studying the armor blocks of some sloping breakwaters, we found that the stability of an artificial block depends mainly on the changes of wave height and wave period when the sectional structure of breakwater is determined. Usually, the value of wave height has been paid enough attention in calculating and designing the armor block stability. However, the effect of wave period on the armor block stability is commonly ignored. This article is, by means of physical model testing, to summarize and analyze the influences of wave period on the armor block stability of the sloping breakwaters, and to provide references for the design of breakwaters.

Abstract:Seepage field produced in the penetration of bucket foundation under a nega- tive pressure was analyzed by means of ABAQUS, a FEM analysis software. The fea- tures of the seepage field around the bucket foundation and the influences of different parameters on the seepage were discussed. Combining with the analysis of an example, the differences in the seepage around the bucket foundation were analyzed between the multi-layered and the single-layered soils.