As the global movement toward decarbonization is gaining momentum, the importance of low-carbon construction is becoming increasingly important for port construction in Japan. In this study, as a fundamental study for low-carbon port pier construction, CO₂ emissions during construction were compared between conventional in-situ casting and PCa pier construction methods. As a result, the most effective method for low-carbon pier construction was to reduce the quantity of steel materials such as steel pipe piles and rebar. It was confirmed that factory PCa is a superior construction method not only in terms of process shortening and productivity improvement, but also in terms of supply chain for port pier construction.

 In order to effectively promote the low-carbonization of the construction of port structures, it is necessary to estimate CO₂ emission levels during the planning and design phases, and then to implement appropriate and effective low-carbon measures. The estimation of CO₂ emissions at that point in the construction process, however, has some inherent uncertainties as the details of the construction work would not yet have been finalized. In this paper an estimation method of CO₂ emissions performed during the design stage of the construction of caisson-type breakwaters is investigated. The effects of the differences in the specifications of the cross-section and the construction conditions on the trends in CO₂ emissions are analyzed for three facilities, and an estimation method based on cross-sectional specifications is then formulated using these results.

 The COVID-19 pandemic since 2020 has caused diverse impact on the economy and maritime transport. In the same year, achieving carbon neutral by 2050 was declared in JAPAN, and the conversion of fossil fuel to renewable energy has rapidly developed. In the cargo estimation of port planning, it is necessary to consider the impact of these structural changes since 2020.

 This study estimated prospects for future change of maritime trade volume based on impact analysis of COVID-19 pandemic and decarbonization on Japanese maritime trade volume. As a result, it was revealed trade volume of 18 items will possibly change their trends: export of agricultural, forestry, fishery products and foods, import of woody biomass, export and import of storage battery, export of semiconductor manufacturing equipment will increase; and import of crude oil, export of video equipment, import of pulp and paper will decrease.

 Cargo handling machinery at container terminals (CTs) is a major source of CO₂ emissions. This paper examines the availability of big data analysis and cargo handling simulation from the perspective of improving efficiency of cargo handling operations in order to decarbonize CTs. In the big data analysis, the distance traveled by cargo handling machinery and the number of operations by work type were identified, and it was found that rehandling considered to be the cause of cargo handling inefficiency accounted for approximately 40% of the total. For the cargo handling simulation, a model was developed to simulate the specific behavior of external chassis, and CO₂ emissions were estimated from the obtained distance traveled. Thus, big data analysis and cargo handling simulation could be a tool for the decarbonization of CTs.

 The movement of fishing boats with fishing lights has been investigated around the Oki Strait from spring to fall using nighttime light satellite images. Fishing boats were distributed in and around the Oki Strait and along the coast of Honshu. They were distributed east-west along 100 m isobaths. The first branch of the Tsushima Warm Current bypasses the Oki Strait and forms a weak circulation current off the southeast of the Oki Islands. Fishing boats tend to be distributed in the area converged by this circulation current and the tributary of the first branch of the Tsushima Warm Current. Since these areas have the potential to be good fishing grounds where plankton and other organisms tend to accumulate, it is important to understand the characteristics of the current field off the southeast of the Oki Islands.

 Water transportation is not only a means of transportation, but also has the characteristic of being able to enjoy the waterfront scenery. It is necessary to pay attention to the waterfront scenery in rainy weather in order to further improve the attractiveness of the water transportation. Based on this point of view, the purpose of this study is to clarify the characteristics of favorable waterfront scenery by comparing sunny and rainy weather conditions through the Tokyo Port cruise. This paper clarified six waterfront scenery elements and their spatial characteristics by cruise experiments of the Tokyo port.

 In March 2019, Cyclone Idai made landfall near the city of Beira, Mozambique, causing extensive damage. During Cyclone Idai attack, the tide level was relatively low, resulting in no significant storm surge damage. However, severer damage can be assumed with high tide levels. This study analyzed storm surge characteristics based on the damage caused by Cyclone Idai in the city of Beira and developed a storm surge hazard map considering the cyclone class and tidal conditions.

 It was found that cyclones in the area move very slowly and are likely to coincide with high tide levels, and that the simultaneous occurrence of a cyclone and a high tide has a significant impact on the damage situation. Furthermore, the worst cyclone course for Beira was identified as WNW. The hazard map developed in this study was widely published in May 2021 and are used for the related plans and capacity building of the Mozambiquan government.

 The Nansei Islands in Japan have been frequently hit by strong typhoons, causing significant damage due to high waves. On remote islands, precise forecast information is essential to protect people from unexpected high waves.Although the factors such as central pressure and wind speeds are already addressed in the wave forecast, the dependency of typhoon path on high waves needs to be more investigated because typhoons approach these islands from almost all directions. In this study, a statistical classification of typhoon path is proposed to quantify its dependency on high waves. In addition to the JMA typhoon best track data, measured wave data at the five ports of Naze, Naha, Nakagusuku Bay, Hirara, and Ishigaki derived from the NOWPHAS network were used as objective variables to apply multiple regression analysis among various typhoon parameters and wave heights at each location. The present analysis shows that there exists significant dependency in mean wave heights on typhoon path, suggesting that improvement of wave forecasting may be possible by incorporating such a typhoon path classification procedure.

 In this study, we conducted a pseudo-warming experiment of the storm surge in Tokyo Bay associated with Typhoon Hagibis (2019) using SSP585 scenario proposed by the IPCC AR 6. Two types of meteorological data, FNL and GFS, were used as initial boundary conditions, and the accuracy of the reconstruction of typhoons and storm surges was examined by comparing the results of the two types of data. As a result, the case employing GFS showed better results of intensity and track of the typhoon. In the pseudo-warming experiment, spectral nudging was used to make the track of typhoons under global warming close to that under present climate. By setting the appropriate coefficient of nudging intensity when using spectral nudging, it is possible to appropriately mimic the path of the typhoon without suppressing the reduction in typhoon intensity. As a result of storm surge simulation forced by the simulated typhoon, storm surge height was nearly 2 m in the Tokyo Bay under SSP585 scenario.

 The characteristics of meteorological tsunamis generated by northeastward propagating micro-pressure waves are analyzed by varying the wavelength and speed of the pressure waves and the resolution of the numerical model. The results suggest that the distribution characteristics of the maximum tide level anomaly vary greatly depending on the wavelength and speed of the pressure wave due to the mode change of the bay water oscillation and the harbor amplification, and that the influence of the water level fluctuation propagating from outside Osaka Bay is also significant. The effect of resolution of numerical simulation was relatively small at the harbor mouth, while it had a large effect at the inner part of harbor, but the results were stable at resolutions of 30 m or less. Besides, our results indicate that even when water level fluctuations due to meteorological tsunamis are relatively small, current velocities in coastal areas can be large.

 A spectrum of quasi-deepwater wave which is defined in deeper shallow water can be only obtained by calculating the deformation of offshore wave spectrum in shallow water. Therefore, to estimate design waves of harbor facilities for the quasi-deepwater wave, the inverse estimation of offshore wave condition which may require several repeated trials of calculation of wave transformations from offshore is necessary. Moreover, the estimation accuracy may depend on the bathymetry and the surrounded topography of the point of the quasi-deepwater wave.

 To support that, we propose a simple inverse estimation method of offshore wave height and direction for quasi-deepwater waves, while it is assumed that offshore wave period is not varied in shallow water. And, diagrams of both wave refraction coefficients and angles and wave diffraction coefficient and angles are newly drown to be applied in the proposal method. It is confirmed that the offshore wave parameters can be estimated by using this method with a few trials of estimation of wave transformations.

 Wave observation results are organized based on the water surface displacement data estimated from the pressure information obtained by an instrument installed on the sea bed in the deep water and the intermediate water region. However, there has been little research on the water surface displacement estimated based on the pressure gauge installed in the chamber of a wave absorb caison. In this study, an estimation method is investigated from the pressure gauge installed in the chamber of the slotted breakwater, following the existing method for organizing wave observation data. In addition, the validity of the wave characteristics is clarified by comparing the estimated wave characteristics in the slotted breakwater with those at NOWPHAS (Port of Kobe).

 In recent years, powerful typhoons such as Typhoon JEBI(1821) and Typhoon FAXAI(1915) have hit the densely populated areas of the inner bay, causing enormous damage due to storm waves. Therefore, in order to support quick and reliable evacuation activities in the event of typhoons, we have developed storm waves forecasting system that can take into account the uncertainty of the typhoon forecast using the ensemble forecast distributed by the Japan Meteorological Agency. This system can provide users with the detailed information at an early stage by combining the coarse predictions and the fine predictions. We also examined the applicability of this system for Typhoon FAXAI(1915) and Typhoon HAGIBIS(1919). As a result, it was found that the ensemble forecast can predict the storm waves risk more reliably. However, we have shown that the predicted wave height may underestimate in case of using GEPS(Global Ensemble Predict System) for small typhoons or when the initial time is 12 hours before the peak.

 This study clarified the relationship between wind speed and run-up height of irregular waves on a coastal revetment focusing on the presence or absence of wave breaking in front of the revetment. In the study, a two-dimensional wave tank with a wind tunnel was used to measure the wave run-up height under wind blowing conditions. The characteristic of wave run-up height differs depending on the existence of wave breakings in front of the revetment. Under the non-wave breaking condition, the relative run-up height increases exponentially as the wind speed increases. On the other hand, the wind speed shows almost no influences on wave run-up height under the wave breaking condition. Increasing or decreasing characters of wave run-up height against the steepness of incident wave differ depending on the wind speed. The probability distribution of the wave run-up height under wind blowing conditions follows Rayleigh distribution.

 It is normal that the breakwater foundation mound will be protected by armor layer as necessary to ensure stability against waves. The conventional method in such cases is that armor layer satisfying the required mass calculated for the top of the mound surface are installed down to the bottom of the foundation mound slope. A concern here is the leveling of the foundation mound that is required prior to the installation of the armor layer. When breakwater is installed in deep sea, the leveling work should be performed in deep water, which significantly reduces the efficiency of the work and raises concerns about the impact on the overall construction schedule. Therefore, it was necessary to consider how to appropriately set the range of armor layer that had normally been installed down to the bottom of the slope in deep sea. In view of the above, this study was conducted to understand water current and flow at the foundation mound surface by numerical analysis, to identify the extent to which the conventional method should be applied via comparative verification with the conventional calculation methods, and eventually to clarify the applicability of these to the project site.

 In the future, there is concern that the risk of storm surge inundation due to wave overtopping and overflow will increase by the influence of global warming. As an adaptation measure against storm surge inundation, a double parapet seawall where a new parapet was installed on the land side of the existing seawall has been examined. Although there have been application examples of the double parapet seawall in the past, most of them are permeable between parapets, and there are few studies where the relationship between the overtopping flow rate and the related parameters evaluated quantitatively. In this study, hydraulic and numerical experiments were conducted to investigate the relationship between the overtopping flow rate and the specifications of waves and seawall. As a result of the experiments, it was shown that the double parapet seawall is effective as a countermeasure against wave overtopping, and that the overtopping flow rate can be calculated by the parameters of the seawall and waves.

 To calculate the wave forces acting on the monopiles for offshore wind turbines, two methods are available: one is the method using the numerical wave flume, CADMAS-SURF, which compute nonlinear wave field as a direct solution of fluid dynamics. The other is the constrained wave method which is based on a linear irregular wave train in which a finite amplitude wave solution is embedded in the maximum wave. This study focuses on the applicability of the two methods in the calculation of the wave force by Morrison equation which calculates the drag and inertia from the water particle velocity and acceleration. From the computations of two depth conditions, 10m and 40m, the followings are made clear: 1) Since the waves in the deep water can be assumed mostly linear, the constrained wave method, which has a smaller calculation load than CADMAS-SURF, is more reasonable for computations of deep irregular wave motions. 2) In shallow water where wave breaking and wave nonlinearity are dominant, the analysis of nonlinear irregular wave fields by CADMAS-SURF with appropriate grid resolution is desirable.

 In the harbor tranquility, the reflection coefficient of the slipway in a fishing port is set with that of reference to the natural beach. In this study, for the purpose of rational setting of the reflection coefficient of the slipway, we try to understand the hydraulic characteristics by calculation under irregular wave condition for the slipway. As a result, we confirm that the reflection coefficient tends to increase as the wave steepness decrease in the same slope gradient. we also affirm that the reflection coefficient increases as the slope becomes steeper in the same steepness. we formulate the method of calculating the reflection coefficient of the slipway by a quadratic function using the surf similarity parameter with reference to previous studies. From the viewpoint of inundation, we indicate that it is important to evaluate the wave overtopping rate by numerical calculation when the runup height calculated by the formula proposed by Mase is larger than the ground height behind the slipway. Furthermore, for long-period waves such as the harbor surging, we suggest that the reflection coefficient of the slipway should be set to nearly 1.0.

 Gravity type breakwater is commonly applied to deep water area to ensure harbor calmness. In the case of Wajima Port, a sloping breakwater is applied because there is need for seawater exchange despite the deep water depth. A sloping breakwater covered with wave-dissipating blocks allows deformation. However, improvement method of the breakwater is studied through hydraulic model experiments taking into account the change of wave condition and the deformation of breakwater. The improvement method in this study is proposed to use a structure with a berm on the seaward side. Furthermore, the stability and hydraulic characteristics are confirmed through the experiments. The conclusions of this study are as follows: 1) By changing the height of berm, the stability of the breakwater is improved. 2) By installing a berm, reflection coefficient is reduced. 3) There is no increase in the transmission coefficient by installing a berm. In addition, numerical analysis with CADMAS-SURF is carried out, and the changed condition of the wave overtopping by the berm installation is reviewed.

 Slit type seawalls have been constructed in order to decrease wave overtopping for the safety of coastal areas, because of their good cost performance. However, the rectangular members of slit type seawall were seriously damaged by abrasion due to wave action on gravel coast. In this paper, the differences of hydraulic performances between cylindrical and rectangular slit type seawall were examined by irregular wave tests with the model scale of 1/40. The wave splash height of cylindrical slit type seawalls can be decreased than that of rectangular ones for shorter wave period conditions. The motion of spherical model due to wave action was reproduced by dam-break type tests with the model scale of 1/10. The relationship between the collision force and the flow rate was shown for both slit types. The collision force distribution of the cylindrical slit wall was shown, and the collision force at the top position was found to be 1.3 times larger than that of the rectangular slit wall. It was found that the collision force of the backwall was smaller than that of the slit wall. The effect of slit opening ratios and water levels were also discussed for cylindrical slit type. Based on the test results, the calculation methods of the abrasion speed of cylindrical slit wall were proposed for the typical wave and period conditions.

 The present study examined the effect of barrier height on the mitigation effect of perforated barriers on wave overtopping and wave forces. Hydraulic model experiment was carried out for the extremely high wave condition where the wave overpass the top of the wave barrier mounted on a vertical seawall covered with wave-dissipating blocks. The experimental results showed that the wave force acting on the perforated barrier was reduced to about the shield rate compared to the force on the unperforated wall. However, if waves frequently overpass the top of the barrier, the rate of reduction in wave force on the perforated barrier has increased by up to 20% from the shield rate. The ratio of the wave overtopping discharge of the perforated barrier to the discharge of the unperforated wall depended on the relative wave height or the relative runup height and the shield ratio.

 In recent years, the number of upright coastal dikes installed on the landward side of the shoreline has been increasing. The applicability of the CERC’s formula and Tominaga and Kutsumi’s formula to the calculation of the wave force acting on the upright coastal dike on the landward side of the shoreline was investigated by conducting hydraulic model tests for regular and irregular waves. The expected wave attenuation effect of the rubble mound breakwater which is a temporary structure constructed on the shoreline in front of the construction yard during the construction of such coastal dikes was also determined.

 As a result, it was found that the scope of application of Tominaga and Kutsumi’s formula is limited to regular waves, and that Mase's formula and Goda's method should be applied to irregular waves. Based on this, the modified Tominaga and Kutsumi’s formula and the modified CERC’s formula were proposed. In addition, the reduction coefficients of runup height and wave pressure by the structure were evaluated.

 In shallow water, it is confirmed that complex distributions of wave height and overtopping rate are formed along a vertical wall while an oblique wave penetrates with a small angle to the wall face. Though that is caused by a scattering wave generated on the end of wall and a stem wave propagating along the wall, both model experiments and numerical simulations are less conducted in deep water for a berth. In this study, they are done to investigate characteristics of wave transformation and verify calculation accuracy of a Boussinesq model for much oblique regular waves and uni-/multi-directional irregular waves.

 Based on a case of road slope sinking behind a retaining wall due to high waves that occurred in december 2014 on the T coast of Hokkaido, the authors have conducted experiments to reproduce the damage pattern based on the wave conditions at the time of the damage and the results of field surveys. A similar disaster occurred in a nearby area in November 2021. Based on the results of the field survey, numerical wave estimation, and previous studies, we analyzed the factors of the two types of damage and found that there were differences in the actual damage conditions and mechanisms between the 2014 disaster and the 2021 disaster, depending on whether or not there was wave overtopping. In particular, it was inferred that the sinking behind retaining walls has a significant impact on the extent of the sinking due to the expansion of the area affected by wave overtopping. On the other hand, it was also found that when high waves, which occur frequently without wave overtopping, act for a long period of time, the underside of the retaining wall is sucked out and the road slope is caved in as a result. It was shown that it is effective to provide both countermeasures against wave overtopping of the road slope behind the retaining wall and countermeasures against suction out of the underside of the retaining wall.

 The evaluation of wave forces acting on caisson breakwaters with deformed wave dissipation works is important to maintenance. In the past, the experiments on a low-crested caisson breakwater covered with wave-dissipating blocks were carried out. In this study, with reference to that experiment, an experiment on a caisson breakwater with higher crest. The wave forces acting on the caisson increased when the magnitude of the deformation of the wave dissipation works increased. It was also found that the maximum wave force was not necessarily caused by the maximum wave height. These results had the same tendency as the past experiments on a low-crested caisson breakwater. In addition, it was shown that the breakwater with a higher crown height induced a larger acting wave force.

 In recent years, the design offshore waves has been revised nationwide, and as a result, the design wave will become larger, which will increase the demand of wave-dissipating works. Currently, when estimating the amount of wave overtopping of a seawall in design, there is no choice but to use Goda's overtopping estimation chart, even if the conditions do not match. Matsushita et al. proposed a wave overtopping discharge estimation chart for wave and cover conditions corresponding to the example of implemented construction, but the results were obtained on a gentle slope beach with a slope of 1/30. Since there are many beaches with a seabed slope of 1/10 in Japan, verification on a steep slope beach is also necessary. This study conducted hydraulic experiments on a steep slope beach with the same crown height of the seawall and the wave absorber, and the fully cross-sectional covered type of seawall. The results were compared with those of Goda's chart and the effect of seabed slope was discussed. Furthermore, the applicability of the Integrated Formula of Overtopping and Runup Modeling (IFORM) to a wave-dissipating seawall was examined.

 In this study, we conducted significant wave height forecast for 14 sites along the Japanese coast using LSTM, a neural network that can retain time series features, combined with an error correction process using Markov chains. The applicability of LSTM-Markov chain forecasting was verified by comparing the forecasting accuracy of LSTM stand-alone models with that of LSTM-Markov chain models. As a result, the combination of the Markov chain model significantly improved the forecast accuracy when the forecast time was about 3 hours, but the accuracy did not improve when the forecast time was longer than 3 hours. It can be said that the LSTM-Markov chain forecast can be applied with high accuracy in short-time forecasts. Forecast accuracy on the Pacific Ocean side is lower than that on the Sea of Japan side due to the effect of swell, so the LSTM-Markov is useful to predict the waves on the Sea of Japan.

 Real-time wave prediction is used to determine the feasibility of marine construction work, but the numerical models currently in use have the disadvantage of being computationally expensive. Recently, a prediction model using machine learning has been proposed, which enables prediction at low computational cost. However, because observed data is used as the teacher data for machine learning, it is not possible to make predictions at locations different from the observation points, making it difficult to use machine learning to make decisions on marine construction work, which requires wave prediction at arbitrary points. Therefore, we developed a real-time wave prediction method that can predict waves at arbitrary locations by using a data assimilation method to create highly accurate spatial wave distributions from numerical model results and using them as teacher data. The results of wave prediction in Tsuruga using this method showed that the method was able to quickly obtain predictions that were more accurate than numerical models, confirming the usefulness of the method.

 In winter, the big height waves are occurred by the strong wind from the big low pressure. However, the low pressure in winter ordinary moves east in the Japan Sea, and Port of Fushiki Toyama places the inner part of Toyama bay and the base of Noto peninsula. Therefore, there is semi enclosed and calm even though the low pressure moves east. However, this area sometimes be damaged by the undulating waves. Therefore, some countermeasures have been considered as before. However, this area was damaged by a typhoon. This typhoon in 2019 moved north above Kanto plain, furthermore, the incident wind and wave entered from the not common direction. Therefore, some structures of the port at Shinminato district and Fushiki district of Fushiki Toyama port were damaged by the big waves

 Firstly, we grasped the weather feature when the wave increased. Secondary, we grasped the frequency of passed similar weather pattern over 10 years. And we grasped the conditions for increasing wave height in Toyama Bay.

 Empirical typhoon models are often used to create wind fields as external forces in storm surge simulations. The empirical typhoon model is computationally inexpensive and can easily calculate hypothetical typhoons, but has the disadvantage that it does not take into account the effects of topography and does not produce accurate wind fields. Therefore, we compared the results of the JMA Mesoscale Model, which is computationally expensive but highly accurate, with those of typhoon models, and constructed a neural network model (wind field correction model) to correct the wind field of the typhoon models. Furthermore, the wind field correction model was applied to the winds estimated by the typhoon model by changing the intensity and/or path of Typhoon No. 10 in 2020, which had been warned of a special warning before its arrival, to realistically possible hazardous conditions to investigate storm surge in the Ariake Sea. As a result, it was found that the designed high tide level of the levees was exceeded in a wide area in the western part of the inner part of the Ariake Sea, and there was a risk of inundation.

 In marine an port construction, wave forecasting one day to one week ahead is indispensable to determine whether construction is feasible, to manage the process, and to ensure safety. In recent year, many studies on wave prediction have been conducted using deep learning, showing the potential for practical, accurate, and low-cost wave prediction models. In previous studies, spatial and temporal learning of weather fields have been found to be effective, respectively, but no study has yet taken both into account. In this study, we proposed a model that can learn both in space and in time and clarified its effectiveness. Furthermore, we attempted to forecast wave in the coastal areas of Japan for 11 days by using the forecast data from the GPV global numerical prediction model of the Japan Meteorological Agency (JMA).

 Sea level rise expected during climate changes is one of the important issues in future coastal protection. To estimate the sea level at coast with tectonic activity, the observed sea level records need to be collected with the ground displacement. This paper presents a regression analysis of the sea level rise estimated by tidal records collected with ground level observations along coasts of Hokkaido. The error analysis provides conditions to extract available datasets observed at local sites with tectonic displacements. Future projections of the current estimations are consistent with predictions by the previous climate-ocean models, which ensures appropriate analysis for future sea level rise.

 In order to predict sheltering effects by permeable breakwaters in a harbor of variable water depth, an approximate method has been developed to be able to analyze wave height distributions around a harbor with multiple permeable breakwaters. Wave interactions among multiple permeable breakwaters and landside seawalls on the sea bed of variable water depth are treated approximately by use of the vertical line source Green’s function method. Numerical tests on sheltering effects of the harbor of variable water depth protected by several permeable breakwaters have been carried out to check the validity of the analysis.

 Avariety of satellite remote sensing has been used to investigate ocean dynamics affected by typhoons in Northwest Pacific Ocean (NPO). At present, the Copernicus Marine Environment Monitoring Service (CMEMS) can provide 6-hourly wind and daily ocean data through a blend between multi-satellite remote sensing, oceanographic observation and reanalysis. CMEMS data were used in this paper to investigate the oceanic response under the condition of existing Kuroshio Current during the 2019 super typhoon HAGIBIS. The use of 6-hourly wind speed data in CMEMS can provide that wind-induced vertical mixing (P_w) was formed around both left and the right semicircle of the typhoon, while Ekman pumping velocity (EPV) was formed at the center of the typhoon. As a result of them, daily physical oceanic changes in sea surface temperature (SST), salinity (SSS), and mixed layer depth (MLD) under HAGIBIS were biased by each strongly influenced area by P_w on the left and right sides, and EPV in the center of the typhoon. Further, massive cooling SST was caused by the upwelling effect of HAGIBIS in combination with pre-existing cyclonic eddy induced by the Kuroshio Current, and the low SSS concentration area was detected on the left side of the typhoon track as an effect of the heavy rainfall accompanied by HAGIBIS.

 The tsunami generated by the 2011 Great East Japan Earthquake far exceeded previous predictions. Buildings, automobiles, and ships were swept away, and the large amount of drifting debris caused catastrophic damage. A method of evacuation using a floating tsunami evacuation shelter was proposed in the event of a tsunami. In this study, an acceleration sensor was attached to a drifting object model to measure the angle at the time of tsunami impact. Wave forces were calculated by measuring changes in draft and correcting for water pressure caused by the model's behavior. The results showed that the timing of the maximum wave force varies with the depth of inundation, but becomes progressively smaller in drifting conditions.

 On January 15, 2022, a large-scale eruption occurred at a submarine volcano (Hunga Tonga-Hunga Ha'apai Volcano) in Tonga. This paper is a preliminary report of the water level fluctuations observed along the Pacific coast of Tohoku-area in Japan due to the eruption of this volcano. Tsunami analysis was conducted using the water level profiles at the tide gauges, seabed wave meters and GPS-mounted buoys of NOWPHAS. The maximum tsunami anomaly varied greatly from location to location, with the largest anomaly being 105.9 cm at the Kuji tide gauge. The East Aomori and North Iwate GPS-mounted buoys recorded an air pressure fluctuation of about 2 hPa at 20:40 on January 15. The tidal anomaly occurred after the air pressure fluctuation, suggesting that the recent tsunami was caused by the air wave. However, the mechanisms of the occurrences were unclear, such as the large tsunami height relative to the air pressure fluctuation, and these subjects remain as future issues.

 A three-dimensional debris model utilizing a physics engine “Bullet” was developed for the purpose of developing a numerical simulation tool that can assume complex debris damage during typhoon action. Two-phase gas-liquid model CADMAS-SURF/3D-2F is used for the fluid model, and the connection is made to take into account the interaction between the fluid and the solid object. In the validation of the physics engine and the interaction model, it was confirmed that appropriate results were obtained. In addition, simulations of the collapse of stacked containers due to wind and the moving of multiple movable objects with fixed obstacles on a wharf were performed, and it was confirmed that complex conditions for debris simulation can be easily set up and that stable calculations can be performed by employing the physics engine. Further validation of this coupled model through comparison with experiments is required for future application.

 In the coastal area of the Izu Peninsula, the "Tsunami Countermeasures Council" has been established, which is divided by regional characteristics. The purpose of this study is to clarify the implementation measures of the tsunami countermeasure discussion process considering regional characteristics in "Tsunami Countermeasures Councils" of 37 districts. This paper clarified the following; 1) Three regional types were derived from the issues of the district and the characteristics of the discussion process, 2) In each of the three regional types, the characteristics of measures to coordinate residents' opinions and tsunami countermeasure plans are shown in chronological order.

 Steel slag-dredged soil mixtures, which is an effective utilization technology for dredged soil, is organized as a viscous soil (a material designed only with adhesive strength c) as its soil characteristics. On the other hand, the steel slag-dredged soil mixtures is composed of solidified dredged soil mixed with aggregate, and the effect of the mixture of aggregate on the shear behavior is unclear. Therefore, we examined the uniaxial compression strength and triaxial compression test. As a result, it was confirmed that Steel slag-dredged soil mixtures, which is a material in which aggregate is mixed with solidified soil, exhibits an internal friction angle φ as compared with solidified soil due to the mixing effect of aggregate. However, the conditions for the strength development level are not clear, and various factors such as the properties of the soil to be solidified, the aggregate ratio, the aggregate properties, the strength development level, and the restraint conditions have an effect, and it has been confirmed that the strength decreases depending on the conditions. Therefore, elucidation of the mechanism of the aggregate mixing effect is a future task.

 The port and airport facilities constructed on the landfill sites whose ground is usually contains large particles such as gravel and shell fragments. Because, the strength of the chemically improved soil decreases with larger soil particles, it is important to identify the factors that influence the strength development of the improved soil in order to develop the strength for such materials. Because, the homogel strength of the chemical solution for liquefaction countermeasures used in recent years is considerably lower than before, it was unclear whether the previous research results could be applied. Therefore, in this study, the factors affecting strength development were confirmed by measuring the pore water pressure generated inside the specimen during the unconfined compression test. From the test results, it was found that the unconfined compressive strength of the chemically improved soil consists of two strengths caused by the adhesive force of the soil particles and the generated negative pore water pressure. It was also observed that the surface area of the soil particles, the internal friction angle and the negative pore water pressure during loading affect the unconfined compressive strength.

 To increase the passive resistance of the ground in front of retaining walls, the quantitative evaluation of the improvement effect is important in the practical design. In particular, when the front of the steel pipe sheet pile is stabilized in the normally consolidated clayey ground to increase the passive resistance to earth pressure from the ground behind the quay wall, the mechanism of passive resistance and the relationship between the improvement range and the improvement effect should be clarified. A simple design method using a beam-spring model was proposed for stabilization of the ground in front of sheet pile walls. However, this method was validated for sandy soil, and its applicability to cohesive soil is not yet confirmed. In our research group, the applicability of the design method using the beam-spring model to cohesive soil ground for deepening the existing gravity-type quay wall using steel pipe sheet piles was examined using centrifuge model experiments. In this study, to investigate the mechanism of passive resistance and the relationship between the improvement range and the improvement effect, reproduction analysis and parametric study are performed.

 In recent years, there has been a chronic insufficient capacity of dredged material disposal sites. On the other hand, there is concern about the shortage of the supply of rock used for port construction. As one of the techniques to effectively utilize dredged soil, a manufacturing technique of artificial rock material using dredged soil as a base material has been developed. In this paper, we investigated the composition of artificial rock, which has the strength equivalent to that of semi-hard rock, by mixing cement and additives with dredged soil. As a result, it was shown that artificial rock equivalent to semi-hard rock can be produced by adding cement and a small amount of quicklime to dredged soil with a high water content. In addition, the artificial rock material produced has the similar shear characteristics as natural rock material and is a very lightweight material, so it is expected to reduce earth pressure by using it as a backfill material for revetments. Therefore, a series of centrifuge model test was conducted with the aim of using the artificial rock as a backfill material for revetment. The test results confirm that the conventional method (seismic coefficient method) of stability analysis can be applied.

 Horizontal loading experiments of the pile were conducted with the aim of evaluating changes in subgrade reaction behavior due to differences in deformation mode of the pile from the distribution of subgrade reaction coefficients. As a result, there was no significant difference in the behavior of the subgrade reaction when the horizontal external force loading position on the pile was higher than the ground surface. However, it was found that the value of the coefficient of subgrade reaction appears small when the loading position is deeper than the ground surface. Then, such a distribution of subgrade reaction coefficient was applied to the behavior of piles used in steel pile reinforced breakwater. As a result, the validity of this method was confirmed when the deformation mode of the pile was relatively similar to that of the horizontal pile-head loading experiment. It was also considered necessary to take into account that if the deformation mode of the pile is significantly different from that of the horizontal pile-head loading tests, the coefficient of subgrade reaction should be smaller, as confirmed by the horizontal pile-head loading experiments.

 The upheaval control and the improvement effect of the new CPG method (U/D method) were verified under various experimental conditions in which the fine fraction content and the plasticity and nonplasticity of fine fraction were changed.

 As a result, at fines contents up to about 30%, regardless of the plasticity or non-plasticity of the fines contents, the U/D method has provided a high upheaval control as equivalent to or higher than the result of application to conventional sandy soils.

 The improvement effect was such that the static cone penetration resistance rose to 6.7 times at maximum and 3.8 times on average, in the case of U/D method, in comparison to those exhibited in the conventional CPG construction in sandy grounds that contained non-plastic fines. For sandy grounds that contained plastic fines, a maximum of 4.7 times and an average of 1.9 times the static cone penetration resistance of the conventional CPG construction were obtained in the case of the U/D method.

 In this study, the consolidated and undrained triaxial compression tests were conducted on relatively low strength slag-clay mixtures with low addition rate, and the results were evaluated and discussed together with the triaxial compression properties of the base material clay.

 The main characteristics obtained were as follows: i) the isotropic consolidation property of the slag-clay mixtures is the existence of consolidation yield stress as with the compressive property of ordinary clays; ii) the ratio of consolidation yield stress to uniaxial compressive strength for slag-clay mixture is 1.4, which is slightly larger than 1.2 for clay; iii) normalizing the relationship between the differential stress and the consolidation pressure by the consolidation yield stress, a failure line with a different slope can be drawn between the overconsolidation and normal consolidation regions; iv) the failure line in the normal consolidation regions is higher than that of the original clay.

 The permeability of cement-treated soil is significantly reduced compared to the untreated soil by filling the voids with cement hydrate. However, recently it has been clarified that cement hydrates are decomposed by chemical erosion by seawater. Therefore, it is considered that the permeability of cement-treated soil changes when seawater infiltrates. In this study, Mg solution was permeable to cement-treated sandy soil as a substitute for seawater, and changes in permeability were investigated. As a result, it was shown that the permeability of cement-treated soil was significantly reduced. The decrease in permeability of cement-treated soil is caused by the decomposition of cement hydrates and the precipitation of magnesium hydroxides due to the Mg salt infiltrated into the treated soil. It is presumed that the pore volume decreased and the void with a small diameter that was difficult to penetrate increased.

 Authors have been developing a countermeasure using shallow vertical drain (PVD) to prevent destruction owing to sand boils induced by liquefaction. This method aims to protect the ground surface from large deformation or unevenness induced by sand boils, in order to ensure the transportability of vehicle used for human rescue and post-earthquake recovery activities. In our previous studies, the application of the vertical drain (spacing of 1.2m; length of 3.0m) showed a sufficient effect on preventing sand boils caused by the upward propagation of pore water pressure. Since the vertical drain is only applied in the shallow soil layer in this method, in contrast to the conventional countermeasure against liquefaction, the less use of PVD would result in a lower construction cost. The effect of the method on reducing the ground surface deformation/unevenness by 90% has been demonstrated in this study.

 Cellular-bulkhead quaywalls, which are a relatively economical form of quay structure, are often used in the construction of large depth quays, but the large water depths require large construction costs. Further reduction of construction costs is needed. On the other hand, high seismic performance is required for deep-water quays, and it is necessary to ensure this performance. In this study, shaking model tests were carried out using a centrifuge to investigate the seismic behaviors of a cellular quaywall structure using a solidification method behind the cellular-bulkhead quaywall, with the aim of making the structure more economical and effective. Shaking model tests showed that the displacement of the cellular-bulkhead quaywall was similar in the block- and grid-type improvement cases, suggesting that the improvement rate of the solidification method could be reduced. Some cracks were observed locally in the cement treated soil, but the displacement was reduced by 0.4–0.7 m compared to the unimproved case, indicating that the solidified method was effective in improving the ground behind the cellular-bulkhead quaywalls.

 A method has been proposed and adopted whereby the ground is cemented by the deep mixing method and the cemented-treated soil is used as the main body of quay walls (earth retaining structure for the backfill ground). In this paper, the seismic behaviour of this type of quay walls is investigated with a view to generalising this structure. Specifically, the seismic behaviour was parametrically investigated by centrifuge model tests, varying the dimensions and shape of the main body. The results showed that it was desirable for the main body of quay walls to have a certain width (more than the depth of the improvement) and to land on a non-liquefied layer. The seismic stability assessment method was also clarified by using the Newmark method to estimate the amount of sliding of the quay wall.

 Rubble are used to make caisson-type breakwaters more tenacious, and the method for assessing the stability has already been proposed. On the other hand, the structure in which dredged soil is added in addition to rubble has also been adopted, but its stability has not been investigated. In this study, the reproducibility of FEM was first confirmed for the existing centrifuge model test results on the breakwaters reinforced by rubble, and the characteristics of the deformation and resistance force of the backfill were determined by FEM. In addition, the calculation of resistance force using a circular slip analysis was verified.