In the decarbonization of container terminals (CTs), one of the important items is the decarbonization of cargo handling equipment equipped with onboard diesel engine.At present, electrification of the energy source for drive system is considered to be the most effective countermeasure, but tire-type gantry cranes (RTGCs) are not suitable for shore powered crane due to the need to maintain operational flexibility, cost and area constraints. Some CTs are unable to develop infrastructure for power supply. On the other hand, by making RTGC hydrogen-powered, a large decarbonization effect can be expected without changing the conventional operation pattern, but at present there are recognized technical and operational issues with the use of hydrogen.

 In the present study, we manufactured a hydrogen powered RTGC and conducted tests that simulate actual cargo handling to evaluate the operating conditions and hydrogen consumption characteristics that can be used for cargo handling operations similar to conventional RTGC. Also, we identify issues in hydrogen filling and propose method to manage them.

 The estimation of the construction period and cost for marine construction is based on the utilization factor calculated from the wave frequency distribution table. However, there may be discrepancies between the actual construction operation rate. In a port on the Pacific coast, marine construction was carried out inside the breakwater, but the construction operation rate was lower than expected based on the utilization factor. This study estimated the factors causing the suspension of breakwater marine construction at the target port and examined new criteria for suspending construction.

 Based on construction records and continuous wave height estimation results, it was suggested that in the target port, the decision to proceed with construction is great case of influenced not only by wave height but also by wave direction, with more suspension days occurring in the NE to ENE wave directions. It is presumed to be due to reflections from the breakwater and the effects of waves along the breakwater, which lowered the construction operation rate within the port. Additionally, a proposal for new construction suspension criteria considering both wave height and wave direction was made.

 Dredged soil solidification composite used for blocks and artificial rocks for marine construction is manufactured by mixing dredged soil with steelmaking slag, ground granulated blast furnace slag and/or blast furnace cement, which is one of the effective utilization technologies for dredged soil. Nowadays, cementless solidification technology is often required due to the needs of fishermen and decarbonization, but in that case, it is necessary to reduce the mixing ratio of dredged soil and increase that of the binder, which consequently poses a problem of high costs of the solidification composite. In this paper, we examine the factors that reduce strength when dredged soil is mixed in high ratio, but also show that the above problem can be solved by adding slaked lime as an alkaline stimulant. In addition, we will report on the results of manufacturing real artificial rocks of dredged soil solidification composite using five types of compositions with varying mixing ratio of dredged soil, as well as the results of quality control tests.

 Focusing on the possibility that nutrients contained in dredged sediment may function for the growth of eelgrass and Japanese eelgrass, field investigation, soil properties analysis, and chemical analysis were conducted in Oshima tidal flat. Vertical transport fluxes associated with consolidation were obtained from the average concentrations of ammonia nitrogen and phosphate phosphorus in the pore water of dredged soil and the volume of consolidation drainage during the consolidation process. The maximum diffusion transport fluxes were obtained from the ammonium nitrogen and phosphate phosphorus concentration gradients in the pore water. The amount of nutrients required for eelgrass growth from the subterranean stem was significantly insufficient for the amount of nutrients supplied by the dredged soil through pore water due to compaction subsidence and diffusion after convergence. It was suggested that sources other than the dredged material may contribute to maintain enough nutrient concentrations in the surface sediment, or that direct uptake from the overlying water through the leaves was the main source of nutrients.

 Pumice ejected from a submarine volcanic eruption at Fukutoku Okanoba in August 2021 drifted into the sea. They spread throughout Okinawa and had a tremendous impact on daily life. Agencies are considering using the collected drifting pumice for reclamation by mixing it with other soils. There are few examples of recycling pumice ejected from undersea volcanoes as a construction material. The engineering properties are not yet known. In this study, various tests were conducted to understand the engineering properties and particle breakage characteristics of drifting pumice. The results show that drifting pumice is a sample that does not easily increase in density as a characteristic. Strain-hardening behavior was observed under low confining pressure in monotonic shear. In cyclic shear, the liquefaction strength is comparable to that of compacted sand. A positive correlation was found when the particle breakage rate was organized using normalized cumulative dissipation energy and accumulated shear strain.

 In this study, SST (sea surface temperature) from 36 GCMs in the CMIP6 historical experiment and three GCMs in the CMIP6 OMIP2 experiment were used to assess the accuracy of reproducing past IOD events. The comparison was made by using the IOD phenomenon reproduced by COBE-SST2 and HadISST in order to indicate the accuracy of IOD in GCMs. The results for the historical experiment showed that the reproducibility varied significantly from model to model, with no significant results obtained from the correlation coefficient and RMSE. On the other hand, it was confirmed that the OMIP2 experiment reproduced the occurrence of past IOD events with relatively higher accuracy for all of the three GCMs. This indicates that the OMIP2 SST data can be effective for evaluating the reproduction of past IOD events, and that the SST from the OMIP2 experiment can reproduce temperature changes in the tropical Indian Ocean with higher accuracy than the data from the historical experiment of CMIP6.

 The consequence of anthropogenic global warming is more pronounced in the Arctic area. This has resulted in the melting of sea-ice in the Arctic Ocean. It also leads to the availability of northern sea route, making sea-ice future prediction a more important problem. In this study, we performed a series of past and future sea-ice predictions by applying the concept of pseudo global warming experiment to CESM2 in order to predict Arctic sea-ice area under future warmer climate. Although, the prediction of sea-ice in summer season was somewhat underestimated, the results showed that the past reproductions of the sea ice conditions were generally in good agreement with the observation. Our future prediction result showed a decrease in sea-ice compared to the past historical simulations, which was consistent with the other GCM results.

 Consideration of wave-induced motion and wave forces on a floating structure moored along a seawall is complicated by the presence of reflected waves from the seawall. If these are evaluated by directly modeling the seawall in a numerical analysis, a sufficiently long seawall model is required, and calculation load becomes large. Therefore, in general, analysis codes that mainly target moored floating structures use a mirror image modeling method that does not require a seawall model. On the other hand, general-purpose analysis codes for offshore floating structure generally don’t include such function. Therefore, in this study, we applied an analysis method that corresponds to a mirror image modeling method by considering two symmetrical floating structures. And we examined its validity by comparing it with the results of hydraulic model experiments and with the results of analysis using a seawall model. As a result, it was confirmed that in the analysis using the direct modeling of the seawall, stationary wave of modes corresponding to the length of the seawall developed. And the waves were also confirmed to influence the wave forces acting on the floating structure. On the other hand, such stationary waves don’t occur in the analysis using the mirror image modeling which assumed an infinite length of seawall. The reproducing calculation of the experimental results by the mirror-image modeling showed good agreement with the experimental results, in the both cases of the barge-type and semisubmersible-type. And we confirmed the validity of the calculation by mirror-image modeling. In a future work, we plan to improve the accuracy of the calculation by taking into account the effects of nonlinearity such as drag and drift forces acting on the floating body, which were not taken into account in the present analysis.

 Remote-controlled underwater drones have been developed for special purposes such as deep-sea research, and in recent years, relatively inexpensive underwater drones for commercial and leisure use are also becoming popular, but most of them are operated by wired communication, which imposes various operational limitations. In this study, a small wireless underwater drone using M-sequence acoustic pulse signals is fabricated, and its controllability is examined through experiments in extremely shallow water areas such as bays. In addition, a basic experiment was conducted to study the possibility of identifying the location of a drone by passive ranging method based on the observation of time differences in the path of M-sequence pulse sound waves emitted from the drone.

 To model the behavior of a tsunami debris object, repeated experiments were conducted for 63 cases with varying aspect ratios (AR) and initial orientation angles (𝜃) of the objects, as well as wave heights (𝐻) of acting waves. This paper focuses on the object displacement (y_d) oriented perpendicular to the tsunami flow. Since y_d exhibits uncertainty, this study examined its mean (y_dm) and standard deviation (y_sd). For objects positioned diagonally relative to the flow, y_dm became significant. During the down-stream process, y_dm became most significant in the initial phase after the object began to move, with the maximum occurring at 45° within the range of 𝜃 = 0° to 90°. While y_sd increased with smaller H, no distinct characteristics were found concerning AR or 𝜃, leading to the modeling of its maximum value. The maximum spreading angle was defined and modeled based on y_dm+ 2y_sd to estimate the area affected by a tsunami debris object.

 To expand the uses of coal ash, artificial stone mixed with coal ash has been developed. In this study, the stability and scour prevention effect of foot protection bags using artificial stone mixed with coal ash installed around the foundation of an offshore wind power generation facility was investigated through hydraulic model experiments. As a result, it was confirmed that the foot protection bags are stable in the planned field experiment area. And it was also confirmed that it can be expected to have the same scour prevention effect as in previous research.

 The monopile is used as the main type of foundation of offshore wind power generation. As the countermeasure to reduce vibration during earthquakes, a new structure has been proposed, by attaching a cylindrical underwater seismic control panel to the monopile. In this study, numerical simulation of flows around monopile type foundation with underwater seismic control panel is carried out, using a 3D flow model in generalized curvilinear moving coordinate system. Through comparison with the experimental results, it was confirmed that the sloshing in the seismic control panel generates a fluid force to suppress vibration.

 Digital transformation (DX) of ports and harbors has been promoted with the aim of solving the issues of efficiency and decarbonization of port operations. The efficiency of RTGs and other container handling machinery operations is largely dependent on the operator's skill, and there is a lack of visual representation of the technology. There is a lack of efforts to visually express these techniques. On the other hand, it is important to analyze the characteristics of skilled operators' skills and apply them to the development of remote automated loading/unloading machines in order to realize loading/unloading efficiency comparable to that of skilled operators in the remote and automated operation of loading/unloading machines. In this study, we utilized data from the Programmable Logic Controller (PLC) that controls the RTG to visualize and compare the characteristics and energy consumption of loading and unloading operations performed by skilled and inexperienced operators.

 Anaerobically decomposed organic matter in the sediment layer, where oxygen supply is limited, releases electrons and protons, reducing the sediment (organic mud) in which organic matter has accumulated. As reduction progresses, microbial activity decreases, and nutrients are fixed together with organic carbon. It is difficult to expect nutrients elution from dredged mud in current tidal flats. In contrast, lactic acid bacteria and nutrients contained in crushed bamboo powder (BP) are expected to promote nutrient elution fixed in the mud layer. In this study, we investigated the nutrients elution from organic mud by mixing BP with the mud. It was elucidated that bamboo powder dissolved in water has the characteristics of organic acid formation and elution of N, P and when mixed with oxidized organic mud, it enhances the reactivity of the organic mud and functions as a reducing agent.

 In this study, we evaluated the effect of gravel beaches on beach formation by analyzing trench excavation surveys and various monitoring data for gravel beaches in the Katayamazu construction area on the Ishikawa coast, where the amount of longshore drift sand is small. As a result, it was confirmed has formed upstream of the convex point on the longshore sand drift. Analysis of the trench cross section showed that about 2.3 years’ worth of gravels remained in the surface layer, and the remaining gravels were mixed with local sand and gravel, contributing to the formation of the beach in the lower layer. The remaining gravels were mixed with local sand and gravel and contributed to the formation of the lower layer. The “jami” material (2.5 to 10 mm) and gravel (5 to 40 mm) used as beach nourishment material were less discharged offshore during the high wave period and easily stayed on the shore side, indicating that they are suitable as beach nourishment materials in this construction area.

 It has been reported that spatial variation in the properties of the improved ground is caused by variations in the properties of the original soil and the degree of compaction of the sand piles during construction using the sand compaction pile method. Recently, the spatial heterogeneity of ground strength of ground improvement methods has been studied by Monte Carlo simulation using random field theory to understand the seismic behavior. In this paper, the seismic behavior of non-uniform SCP improved ground is evaluated using the above method. As a result, (1) the coefficient of variation of settlement after 100 MCS cycles is 0.129 for the unimproved ground and 0.018 for the improved ground, and it is confirmed that the coefficient of variation of settlement is reduced. (2) The correlation coefficients between the settlement of the unimproved soil and the liquefaction rate defined by the excess pore water pressure ratio and shear strain in the elements at the center of the improvement (x = 40-60m, y = 2.5-7.5m) were 0.743 and 0.881, respectively, suggesting that the behavior of the central elements affects the settlement behavior.

 Effective use of maritime transport is needed as a solution to the effects of logistics disruptions caused by the 2024 problem and to the realization of a carbon-neutral society in 2050. In addition, domestic trade unit loads have become larger in recent years and are expected to serve as a means of receiving a modal shift from truck transport. Based on the above, the purpose of this study is to obtain a guideline for the acceptable modal shift capacity of domestic ferries, and to estimate the transport capacity of domestic ferries from the replacement interval and transport capacity increase rate. A future trial calculation is made, and a model formula for the occupancy rate is calculated based on the relationship between the number of years of domestic ferry operation and the occupancy rate, and the model formula for the occupancy rate is applied to the predicted future transport capacity. By doing so, we estimated the cargo volume transported by domestic ferries in the future.

 At construction sites of rubble mounds, the concern arises over the vulnerability of these mounds to high waves. To investigate the damage to rubble mounds, both hydraulic model experiments and numerical analyses are considered. Numerical analyses typically involve methods such as the finite element method or particle methods, which can impose heavy computational loads. In this study, the authors focused on the resemblance of the damage process of rubble mounds to advection-diffusion phenomena and initiated repeatability calculations using analytical solutions of advection-diffusion equations. From the results of hydraulic model experiments, relationships between diffusion coefficients and advection velocities with wave conditions and mound conditions became evident, allowing for the determination of advection velocities and diffusion coefficients from wave conditions and mound conditions. Therefore, an attempt was made to reproduce the damage process of rubble mounds using advection-diffusion equations. It was possible to effectively reproduce the decrease in the height of the top of the rubble mound. However, there were remaining challenges as the calculated results underestimated the offshore slope shape.

 Nearshore high waves induce wave runup, overtopping and beach deformation, and cause not only damages of coastal structures but also severe coastal flooding. Although it is important to quickly assess such damage induced by high waves, it has been a challenge to assure reliable and robust nearshore monitoring system of such high wave events. In this study, we developed a coastal monitoring method using an inexpensive waterproof and dust-proof LiDAR (Light Detection And Ranging) system that enables us to monitor nearshore geometry for long period of time even under severe coastal environments. The developed monitoring system was tested at the winter coast on Japan Sea. Through the field test, we confirmed that the developed system can obtain synchronized geometric data of structures, beach deformation, wave runups and overtoppings. The method is robust and has a promising potential to be a future nearshore monitoring system.

 There is worldwide concern about the impact of microplastics on marine ecosystems, surveys of the state of pollution in oceans and rivers are being conducted. In this study, we conducted a sampling survey of 13 sandy beaches in Osaka Bay to understand the contamination status of an inner coastal bay located between rivers and the ocean. Microplastics were distributed at several locations from the shoreline to coastline, and most tended to be deposited at elevations higher than the highest monthly tide level. The amount of microplastics deposited varied from 50 to 9,500 pieces/m², and the maximum difference was about 100 times. The results of the microplastic deposition rate for each coast considering the distribution condition showed that the average value for the beaches of Osaka Bay was 52.0 microplastics/m², whereas the value for the beaches at inner part of the bay area was 253.0-312.6 microplastics/m², indicating a high degree of contamination.

 Seamless Asia is of great importance, as stated in the National Spatial Strategy. On the other hand, Japan is an island nation, and in terms of international logistics, shipper companies are always faced with the choice of port routes. In order to improve the environment for seamless Asia, it is important for port managers and related policy makers to know the evaluation of the frequency of port calls by shipper companies, but there is a lack of analysis. In this study, we conducted an empirical analysis of shipper firms' evaluation of vessel call frequency in their choice of domestic ports for international maritime container logistics with neighboring Asian countries (Korea, China, and Taiwan). The results indicate that the frequency of vessel calls by shipper firms tends to deviate from the average waiting time when the number of vessel calls is small. This tendency can be explained by the rationalization of logistics by shipper firms.

 Approximately 40% of the overseas transshipment cargo from Japan to North America in foreign trade containerized cargo uses Strategic International Port. In order to maintain and expand the direct trunk routes, which is a policy goal, it is necessary not only to encourage the use of direct routes by overseas transship cargoes using ports other than Strategic International Port, but also to encourage the use of direct routes by overseas transship cargoes using Strategic International Por. From this perspective, this study conducted a factor analysis of cargoes using Strategic International Port by route choice, such as direct route use and overseas transship use. The results of the analysis revealed a variety of findings. In particular, it was shown that the use of overseas transshipments is affected when the final cargo unloading port is on the east coast of North America, when the consignor company is a commercial wholesaler of various types, and when the cargo commodity is light industrial goods.

 Mizushima Port is facing the problem of a lack of a disposal site for dredged sediment due to the deepening of the channel, and in order to extend the life of the disposal site and increase its receiving capacity, construction has been carried out to reduce the volume of dredged sediment through consolidation settlement. At that time, in order to formulate an appropriate construction plan from dredging to soil disposal, we attempted to accurately understand the state of volume reduction through UAV surveying using a green laser that is not easily absorbed by water. Specifically, we investigated a method that enables high-precision surveying without installing adjustment points as instructed in previous manuals. We also investigated the characteristics of the green laser in terms of bottom quality, water quality, and transparency, which are unique to sediment disposal sites, and investigated methods to improve sounding ability. We have developed a monitoring method using UAV surveying by increasing the accuracy by introducing the PPK post-processing kinematic method and improving the sounding ability by expanding the laser divergence angle.

 Vibro-hammer method is frequently used for installing steel pipe piles which are often used for the foundation of port facilities. Recently, bearing capacity estimation method for the bearing capacity of open ended piles installed by vibro-hammer method is disappeared from official technical standards. Main reasons of disappearance is in short of the evidences of the bearing capacities of it.

 To evaluate the bearing capacity of an open-ended pile installed by vibro-hammer, model pile penetration experiments under dry model sandy ground were conducted. In the experiments, three types of installation methods including vibro-hammer method were applied. As a result, only the piles installed by vibro-hammer were fully plugged and gave large end bearing capacity as that of closed-ended piles.

 Tsunami analyses based on 2D planar numerical models consider the flow preservation associated with overtopping of seawalls, but do not take into account the 3D effect of water masses overtopping. It may underestimate the tsunami damage at just behind the seawall. In this study, the wave forces around the seawall under three types of shapes, model heights and overtopping depths were estimated. It clarified that the water mass overtopping the erect-type seawall may cause more damage to the inside land than that of slope-shaped seawall, and that the maximum flow velocity was estimated around at the behind seawall. Furthermore, the results of scale model experiments were converted to real scale to calculate the wave force on 2-stories house. And, it was clarified that the combination of seawall shape, seawall height and overtopping depth showed the differences of the extent of house damage.

 Submerged horizontal plates cause a phenomenon called wave focusing, in which the waves are refracted to collect and amplify the wave height. This wave focusing effect amplifies the wave energy density in a specific area and is expected to improve the power generation efficiency without increasing the size of the wave power generation system. In existing research, numerical analysis using the doublet distribution method and the boundary element method has been conducted in conjunction with experiments, and the results are generally in agreement.

 In this study, the wave focusing effect of a crescent-shaped plate was analyzed using the SPH method, which can consider complex fluid behavior such as wave breaking and wave peak splitting, and it was confirmed that the wave focusing position can be adjusted by controlling the installation angle. The results suggest that the crescent-shaped plate can efficiently collect wave energy by adapting to the seasonal variation of wave period.

 Elastic mooring lines always exert tension, enabling the stable position holding of floating bodies. However, there are no examples of their application to superlarge floating bodies, and guidelines for mooring design do not seem to include descriptions regarding the mooring design of elastic mooring lines. In their previous research, Sugawara et al. prepared a superlarge floating body moored by a mooring systemcomposed of multiple elastic mooring lines. They clarified the relationship between the restoration force characteristics of the elastic mooring systemand the motion response characteristics of the floating body.They also presented a series of procedures to assist in the design of an elastic mooring system, which enables designers to select the specifications of elastic mooring lines that satisfy the allowable motion amplitude determined by their application and operation methods.We conducted a study to verify the applicability of this series of procedures even when the characteristics of rubber ropes or water depth are altered, using the proposed workflow, enabling designers to freely select the specifications of mooring lines for elastic mooring systems according to the intended use when designing floating bodies.

 Tsunami-induced pressure and force acting on an elevated slab inside a building with openings were investigated numerically. Numerical results showed that the cross-shore distribution of the maximum pressure acting on the ceiling of the first floor depended on wave conditions, opening ratios, and installation heights of openings. If the wave condition and the opening ratio of the seaward wall were same, the maximum force acting on the slab between the first and second floors increased with an increase in the ratio of the opening ratio of the seaward wall to that of the landward wall. This suggested that the slab can be subjected to larger tsunami force if openings in the wall on the side facing the tsunami are larger than those in the opposite wall.

 In January 2024, an earthquake struck the Noto Peninsula, causing a tsunami that reached the coastal regions of Niigata Prefecture. In Joetsu City, the tsunamis breached seawalls and flooded coastal parks and beaches, leading to damages such as the destruction of beachfront properties. In this study, with the aim of comprehensively understanding the tsunami's impact, we conducted field surveys and numerical tsunami propagation experiments. Field surveys spanned Joetsu City, extending westward towards Itoigawa City and northeastward towards Kashiwazaki City. During the surveys, tsunami inundation heights were measured using laser rangefinders and RTK-GNSS. Additionally, aerial photography via unmanned aerial vehicles provided terrain data, aiding in pre- and post-tsunami topographical assessments and inundation height evaluations. In numerical experiments, fault displacement was computed to simulate water level changes caused by the tsunami using a two-dimensional plane model. This facilitated the estimation of tsunami arrival times at various locations. Subsequently, the obtained results were compared with observational data for validation.

 During the construction of Runway D at Haneda Airport, strain gages and fiber-optic instruments were installed on 15 steel pipe piles, and the results of these measurements have been utilized for maintenance.It has been about 16 years since the installation of them, and it is important to continuously utilize the long-life fiber-optic measurement for continued maintenance. The authors conducted Rayleigh backscattering measurements in addition to conventional Brillouin backscattering measurements with currently installed optical fibers, and ensured that Rayleigh measurement is an effective measurement method for maintenance. In addition, since fiber optic measurement is not a temperature-compensated measurement method, the evaluation of measurement results in sections with temperature changes has been a problem so far. To overcome this problem, they ensured the effectiveness of a temperature compensation method based on the results of both measurement methods with currently installed optical fibers.

 The seismic loads on monopile-type offshore wind turbines are evaluated by combining the aerodynamic elastic analysis for wind and waves and seismic response analysis for earthquakes. This may result in unfavorable design sections economically, emphasizing the importance of evaluating the response of offshore wind turbines considering wind, waves, and seismic events simultaneously. Therefore, in this study, we investigated the wind turbine responses under wind, wave, and seismic actions using a coupled analysis considering the effects of seismic forces and the soil-structure interaction. As a result, it was found that while wind turbine responses tend to increase with larger seismic forces and smaller soil stiffness their impact depends on the timing of external forces, and that depending on the seismic waves and soil properties, maximum responses may occur at altitudes other than the mudline.

 The pumice resulting from a volcanic eruption poses severe problems for society and economic systems. Previous studies have indicated that waves, currents, and winds influence the drifting and accumulating of pumice in coastal areas and structures. However, few studies have been done on the redrifting and re-accumulating of pumice between structures in shallow water, largely due to the challenges in replicating the phenomenon. In this study, we utilize a wind tunnel tank to replicate the accumulation of pumice between structures and examine the impact of wave and wind fields on its re-drifting and re-accumulating. As a result, (1) The air density of pumice can be used to calculate its drift period. (2) Wind and structures influence re-drifting pumice more than waves. (3) Pumice may form rafts during windy conditions. (4) The rate of pumice accumulation in structures can be calculated using wind velocity and pumice particle size.

 When assessing the feasibility of marine operations, alpha-factor, a correction factor on the operational limit for wind speed and wave height, is used to consider the effect of weather forecast uncertainty. In this study, the Japanese version of the alpha-factor is calculated based on wave forecast data in the Japan Region, since the alpha-factor used by Det Norske Veritas (DNV) is based on the data of European waters. The alpha-factors for three locations in Japan are found to be larger than those of DNV, and results show seasonality and spatial variations of alpha-factors. To evaluate the validity of the alphafactor, the rate of missing operational risks and the rate of misjudging whether to cancel the operation are calculated. The Japanese version of the alpha-factor, which has larger values than DNV, enables the rate of misjudging whether to cancel the operation 3-4% lower than that of DNV. On the other hand, the number of missed risks is similar regardless of the alpha-factor used. These results suggest the potential for improved feasibility assessment of marine operations through the establishment of the Japanese version of the alpha-factor.

 In recent years, coastal facilities have also been required to consider the landscape and the environment, and buildings with high design quality are increasingly being constructed along the coast. In this study, we proposed a curved seawall as a new type of seawall with a high level of design that harmonizes with such buildings and the landscape. Hydraulic model tests and numerical analyses using CADMAS-SURF/3D and OpenFOAM were conducted to understand the wave resistance characteristics against wave pressure, wave force, wave overtopping flow rate, etc., acting on the structure for the purpose of contributing to its future design.

 The results showed that although both the maximum horizontal wave force and the maximum uplift pressure exceeded the Goda’s wave force in high waves, rational design was possible by considering the simultaneity of each wave force component, and that the overtopping flow rate was suppressed by the wave return effect of the curved seawall. The applicability of both analysis methods to wave resistant design of curved seawalls was also demonstrated.

 The importance of preserving blue carbon and biodiversity is being reaffirmed, and the government is recommending that the creation of tidal flats be promoted as a way to achieve this goal. By maintaining tidal flats for clams, which are decreasing all over the country, we can increase the value of tidal flats not only in terms of fishing, but also in multiple ways, such as environmental education and clam picking. In order to effectively apply fertilizers to effectively propagate clams, a method is needed to quickly verify the effects of fertilization. Therefore, we investigated a method to appropriately monitor diatoms in the environment, which are the food for clams and proliferate with firtilizing. We also considered appropriate fertilization conditions. The results suggested that environmental DNA analysis targeting the rbcL gene, which targets photosynthesis-related enzymes, enables more detailed analysis than microscopy methods. In addition, it has become clear that chicken manure fertilizer is effective for fertilization, and that it is important to choose appropriate times.

 In the event of a large-scale earthquake that causes extensive damage, it is necessary to immediately judge availability which mooring facilities can be used for the transport of emergency supplies. However, there are few reports of such decisions being made in the initial survey after an earthquake, when the survey equipment and time to make a decision are extremely limited. In the case of a large-scale earthquake that is expected to occur in the future, it will be necessary to quickly make similar decisions on a large number of mooring facilities over a wide area and in multiple ports. As a reference for such a situation, the paper discusses the items that should be verified for mooring facility in advance, based on the knowledge obtained from initial survey after the 2024 Noto Peninsula earthquake（M7.6）.

 The purpose of this study was to estimate of carbon storage in sediments at tidal flat, salt marsh and seagrass bed in the coastal area of Osaka Bay. The characteristics of the sediments varied with depth at each site. The carbon storage in sediment at a depth of 1 m was estimated to be 36-117 tonC/ha, with the highest carbon storage on the Yodo River tidal flat. The presence of vegetation with sediments promoted the sedimentation and deposition of particles, which resulted in carbon storage. It suggested that carbon storage by sediments occurs in addition to carbon storage by vegetation itself. This study was able to estimate carbon storage at a depth of 1 m for sediments in the study areas in the coastal area of Osaka Bay, which has different environments.

 BIM/CIM models become popular for the newly built port facilities. Also, BIM/CIM models are expected to improve the productivity of the maintenance of the existing port facilities. However, the requirement for LOD (level of details) and LOI (level of information) of BIM/CIM models is determined mainly for the newly built port facilities and can be too much specification for the existing port facilities. The present study conducts the interview surveys to the people familiar with port facility maintenance. Based on the results of the interview surveys, the minimum requirement for LOD and LOI of BIM/CIM models regarding the maintenance is proposed. Furthermore, BIM/CIM model of the existing pier is made by two different methods. One method is based on LOD and LOI for the newly built port facilities, and the other method is based on the proposed minimum LOD and LOI. The comparison of the production time for two BIM/CIM models shows the efficiency of the proposed method.

 This study has systematically investigated the performance of a two-layer filter using rock debris as a countermeasure against internal erosion of sea sands surrounding coastal facilities such as seawalls and quay walls. The applicability of rock debris as a filter material was comprehensively examined through a series of sand filtration tests and prototype-scale experiments under various dynamic external forces acting at the waterfront. As a result, in cases where sea sands with low grain sphericity are used as backfilling sands, the rock debris showed a sufficient deterrent effect under various external forces involving tides, waves, seepage flows, rainfalls, overtopping waves, and earthquakes, when the uniformity coefficient of the filter (DF₆₀/DF₁₀) was higher than 2.5, and the median particle diameter ratio (DF₅₀/DS₅₀) was less than or equal to 25.

 The introduction of floating offshore wind turbines is expected to expand, and one of the floating types is the TLP type. In this study, cyclic pull-out loading tests were conducted using large piles in an actual sea area to establish a method for evaluating the stability of TLP mooring foundation piles. Static pull-out tests were conducted on the first of the three test piles to determine the ultimate uplift resistance of the pile in the ground. For the remaining two piles, two types of cyclic pull-out tests were conducted at various loading levels. In both of the two types of cyclic pull-out tests in this study, the displacement of the piles during the loading process was small, and we have concluded there was no effect on the stability of the piles. When these results were plotted on a stability evaluation diagram from previous studies, the results were consistent with the proposed stability region and the load levels near its boundaries. This demonstrated the validity of the stability evaluation at the load levels assumed for the actual wind turbines.

 It is seriously concerned that the wave-overtopping disasters will increase due to the climate change accompanied by the sea level rise and intense typhoons in the near future.As a countermeasure, Nakatani et al. (2019) proposed a low-cost and simple mooring type wave-overtopping prevention method by utilizing a cylindrical body for the vertical seawall.The both ends of the cylindrical body are moored using ropes to the front face of the seawalls. This mooring allows that the cylindrical body moves following the wave motion in front of the seawall.This method has several merits, e.g., low cost, ease of construction and maintenance, and so on. They conducted model experiments and confirmed that the proposed method can efficiently reduce the wave-overtopping quantity. Furthermore, ongoing investigations through numerical simulations have been conducted, and Sakamoto et al. (2023) have confirmed the ability to reproduce the tension acting on the mooring ropes and the wave-overtopping rate in the moored wave-overtopping prevention method. However, the numerical simulations revealed an issue of empty space soccurring between the surface of wave and the cylindrical body or the front face of a seawall, indicating room for improvement in computational accuracy.

 In this study, we aimed to improve the reproducibility of numerical simulations by enhancing the boundary treatment and focusing on accurately reproducing the tension exerted on the mooring ropes, which is crucial for investigating mooring-type wave overtopping prevention structures.

 As a result, the application of Modified Dynamic Boundary Conditions (mDBC) to the boundary treatment between the fluid and the seawall surfaces, as well as the prevention structures, confirmed an improvement in the accuracy of reproducing wave overtopping and the tension exerted.

 In the verification of reinforcing embankments behind caissons, the concepts of caisson sliding, bearing capacity failure of the mound and caisson edge pressure have been presented, but studies on caisson overturning have not progressed. In this study, loading tests were carried out using a centrifuge on a caisson overturning by an inclined loading plate, with the aim of understanding the basic characteristics of the resistance to overturning of the caisson reinforced by embankment made of rubble stones. The results of the loading tests showed that the relationship between the resistance force of the reinforcing embankment and the inclination angle of the loading plate was non-linear, and the relationship changed with repeated loading. However, as the inclination angle increased, the moment due to the resistance force of the reinforcing embankment increased and the resistance force of the embankment was more tenacious. On the other hand, it was also found that the resistance of the embankment to small loads decreased with experience of loading with large loads.

 It is important to grasp the scour depth and shape around the foundation when designing offshore wind turbine foundations. In this study, we propose a numerical method that can predict scour depth and shape by coupling CFD with optimization algorithm. Wave basin experiments were conducted employing monopile and suction foundations in order to validate the proposed numerical method. It was observed that the discrepancy in the maximum scour depth obtained from the numerical method and measurements was approximately 20 to 30%. Although the error was somewhat large, the wall shear stress distributions on the bottom surface in the CFD results showed consistency with the scour locations in the experiments.

 The authors have developed a method for evaluating the residual structural performance of piers using artificial intelligence technology. The problem was that the AI sometimes did not recognize the shape of the pier correctly when evaluating the residual structural performance from the image of the deterioration assessment result of the pier, because it was necessary to fit the deterioration assessment image to a fixed size. Therefore, the authors proposed two methods: (1) a method that correctly outputs the pier shape by fitting the pier to a fixed size without margins using a scaling algorithm and using nearest neighbor interpolation (SE method), and (2) a method that sequentially predicts the concern member and its surrounding members as explanatory variables (NB method). The NB method is a sequential prediction method that includes the predicted member and its surrounding members as explanatory variables.

 The results of the damage prediction showed that the NB method had an average of more than 80% correctness for all predictions, but the SE method requires caution for practical use because the correctness rate varies greatly depending on the ratio of vertical to horizontal expansion of the pier.

 Dense fog advisory information was used to discuss the selection of maintenance dates for offshore wind farms. Dense fog advisories from 2013 to 2022 were obtained from Disaster Prevention, DB, and the information (fog advisories) whether the advisories were announced every six hours was calculated at six locations. The number of days per month calculated from the fog advisory information shows seasonal variations and exceeds 1000 days per decade in Akita, Choshi, Iwaki, and Miyako. By scheduling maintenance in months with fewer average days per month, these sites will have fewer postponements, resulting in a cost benefit. Classification approaches for fog advisories from weather data using the threshold (Ex1) and using a neural network (Ex2) were investigated to show that Ex2 achieved higher accuracies than Ex1, resulting in better and longer estimates of fog advisories available for trend analysis. The accuracies for Ex1 and Ex2 indicate that humidity information is important for estimating the fog advisories as input data.

 The study aimed to examine the effect of the artificial seaweeds on the population of Japanese spiny lobster Panulirus japonicus in the small holes of artificial reefs. The artificial seaweed (1.0 m long, 20 cm wide) consisted of three ropes with polypropylene fibers is used to create habitats for pueruli of P. japonicus. The artificial reefs consist of three surfaces, one of which has 20 small holes with diameters of 15 to 37 mm. A total of nine diving surveys were conducted along the coast of Uchinoura Bay, Kagoshima to measure the number of P. japonicus at small holes of artificial reefs with and without artificial seaweeds from 24 May 2023 until 4 December 2023, for 43-194 days after installation. Five P. japonicus were observed in small holes of artificial reefs with artificial seaweeds on 6 July, 43 days after installation. The population of P. japonicus increased, reaching a maximum of 57 individuals on 7 September, 106 days after installation, and decreased to 21 individuals on 4 December, 194 days after installation. In contrast, only one P. japonicus was found at the small hole of artificial reef without artificial seaweed. The results of the study suggest that the artificial seaweeds are adjoined to the artificial reefs for increasing the population of P. japonicus at small holes of artificial reefs.

 A preloading method is one of the typical soft ground improvement technologies. This method is often used in combination with vertical drains. The amount of residual settlement after the start of service is determined by conventional calculation methods or consolidation analysis using the finite element method. However, the calculation of settlement after preload removal is not necessarily accurate. Therefore, predicting the final settlement based on observations during construction is generally performed. To predict the residual settlement with high accuracy, it is necessary to evaluate the long-term settlement including secondary consolidation. For model experiments on preload removal, it is important to consider the self-weight of soft ground with thick layers. In this study, centrifuge model tests were conducted focusing on the deformation behavior after the preload is removed to improve the accuracy of residual settlement calculations. To predict the behavior after preload removal, a simple calculation method using a finite difference method based on the isotache concept was proposed. This method enables the evaluation of behavior after unloading including secondary consolidation.

 We analyzed the occurrence trends of rainfall clusters formed around typhoons based on rainfall analysis data from the Japan Meteorological Agency's MesoScale Model. The possibility of identifying characteristic rainfall clusters by coordinate transformation and binarization was demonstrated. The rainfall clusters decrease with distance from the center of the typhoon, and are more common in the north-northeast direction. The rainfall intensity statistically depends on latitude and central pressure, and the location of the center of gravity of rainfall clusters also depends on the central pressure. The azimuthal angle of rainfall clusters was found to be dependent on the moving speed, latitude, and on the month of onset. Rainfall clusters predominantly move counterclockwise away from the typhoon, but within a radius of 200 km, radial movement is not as pronounced. Additionally, there appears to be a certain level of persistence in the movement of rainfall clusters in the circumferential direction and away from the typhoon at successive times.

 In this study, hydraulic experiments were conducted on a semisubmersible floating foundation of an offshore wind turbine. In the experiments, the elemental floating model as a side column cut out of a semisubmersible floating foundation was forced to move up and down with various periods in a basin, and the vertical force acting on the elemental floating model was measured to estimate the drag coefficient Cd, which is considered to be damping due to vortices and viscosity. The results were almost the same as the drag coefficient during descent of the elemental floating model calculated by the previously proposed and validated formula. However, it is necessary to develop a new formula for the drag coefficient during ascent of the elemental floating model. In addition, we performed numerical simulations using OpenFOAM to reproduce the hydraulic experiments, and they were compared and the agreements were verified, suggesting the use of CFD as an alternative to hydraulic experiments.

 The dynamics of marine microplastics in Tokyo Bay, which have been a concern for marine organisms, were analyzed using a mathematical model. In this paper, three equations (dissolved form, small particles with sedimentation rate, and large particles adsorbed form) are constructed for microplastics loaded from rivers in Tokyo Bay, and the number density analysis method is developed by considering adsorption/desorption, mineralization, and sedimentation effects among them. The distribution coefficients of microplastics were parameterized with reference to dioxins. When the distribution coefficient was 20 times larger than that of dioxins, the number density analysis of microplastics in Tokyo Bay showed high reproducibility compared to the measured data. The analysis results show that the discharge of microplastics into the bay is about 30%.