After the 2011 off the Pacific coast of Tohoku Earthquake and Tsunami, coastal structures such as breakwaters and coastal dikes have been required to have “resiliency” against large tsunamis exceeding design level, and research has been vigorously carried out. To realize resilient structures, it is important to develop methods to predict the stability limit and deformation amount against the assumed instability factors and to develop effective countermeasures for these factors. This report reviews past studies concerning resilient breakwaters and coastal dikes focusing on the stability of the armor units.

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 This paper discusses the experimental findings pertaining to a failure mechanism and the resilient structure of composite breakwaters brought by the instability of a foundation mound due to the seepage flow induced by a huge tsunami. Centrifuge tsunami testing using a drum channel was applied to reproducing the reduction of the bearing capacity of a mound under seepage flow leading up to the failure of the mound. It is important to place rubble on the back of a caisson for stability of the foundation mound against tsunami-induced seepage flow. The effects of the resiliency structure with the units packed gravels are also examined in the light of stability of a mound as well as a foundation bed under the seepage flow.

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 Tohoku-Pacific Ocean Earthquake on March 11, 2011 caused great damage to the port on the Pacific coast in Tohoku Region. Many breakwaters were damaged by devastating tsunami, which made us reconsider tsunami resistance design for the breakwater. The idea of the “tough structure” of the breakwater is intended to make a breakwater that can withstand the large tsunami exceeding the tsunami occurring frequently (design tsunami) and would not collapse even after deformation. In this study, the restoration construction of breakwaters damaged by tsunami in the port of Tohoku region based on the idea of the tough structure is described by referring to a prior example, the disaster recovery of breakwaters in Hachinohe Port.

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 On the southern coast of Sendai Bay, coastal levees damaged due to the Great East Japan Earthquake Tsunami on 11^th March 2011 were restored as the "Resilient Coastal Levee". In Idoura area located on the northern side of the Natori River estuary, the restoration work with "CSG coastal levee" was completed in consideration of the precious natural environment such as landscape and ecosystem, as well as land acquisitions and availability of materials for levees etc.
 This paper reports case studies employed in Idoura area including process of solutions of challenges in construction of CSG coastal levee, design approaches applied for loose geological conditions, and adoption of CSG containing maximum 70% sand with diameter of 5mm or less (unit cement amount is 40kg/m³).

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 This paper is aiming at reviewing current status of the Northern Sear Route. In the paper, historical back ground, geographical features, recent activities of cargo shipping, actual navigation in ice infested waters, and characteristics of shipping cost is described.

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 It was 2008 when the study of US Geological Survey pointed out that the Arctic region is blessed with huge oil and gas potential. Now the energy industries especially in Russia have been tackling Arctic oil and gas development and have so far accomplished a number of results, i.e. the first oil production at the Prirazlomnoye offshore oil field in the Pechora Sea, the first LNG project at the northeast Yamal Peninsula, which will start production late 2017, and the first oil discovery in the Kara Sea beneath the gas bearing horizons. As the oil price fell down and the activities in the Artic will shrink for a certain period but a new exploration activity will be made even at the low oil price to prepare the field development in the future.

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 Ongoing sea ice retreat in the Arctic Ocean eases the navigability of the Northern Sea Route. However, it should be utilized under sustainable manner. This paper aims at over viewing recent research activities, which have been carried out under the national research project of GRENE and ArCS for the purpose of investigating issues on sustainable Arctic shipping.

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 It is well known that the current method designing a reinforcing embankment for a caisson type breakwater has some problems such as underestimating the load bearing capacity of the embankment. Thus, the present study established a new design method for the reinforcing embankment, based on the past research results. There are three features of the proposed method: 1) a new calculation method for load bearing capacity of the embankment, 2) introducing load distribution effects excerted by the embankment, and 3) relaxation of the present prescribed minimum size of the embankment. The size of embankment calculated by the proposed method would be smaller than one by the current method, and it was confirmed that it was sufficiently safe compared with model experiment results. Additionally, sensitivity analyses were conducted to understand the effect of the embankment shape change on the bearing capacity. Those showed that the increment of the height and width of the embankment were effective for the failures of sliding and bearing capacity, respectively. By employing the proposed method and understanding the results of sensitivity analysis, it would enable a more rational design of the reinforcing embankment.

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 Phan Thiet is a coastal city located in Vietnam. Recently, the coastal areas of the city have been suffering from severe coastal erosion due to a rapid coastal development such as land reclamations and port constructions. Without receiving a sufficient financial relief from the government, the local people have resorted to wood piles as a wave-breaking countermeasure to prevent coastal erosion. Particularly in developing countries, usage of low-cost countermeasures such as wood piles could be very beneficial. However, its effectiveness has yet to be scientifically proven. This study aims at confirming the effectiveness of a three-dimensional hydrodynamic analysis in evaluating the performance of wood piles. The present study performed a 3D numerical simulation, considering the offshore irregular waves and bathymetric conditions in Phan Thiet, Vietnam. The wave-energy dissipation and durability of wood piles were simply evaluated by two criteria: 1) wave run-up distance and 2) bending stress on pile. It is worth noted that remarkably large water levels could be generated because of multiple mechanisms such as the overlap of incident and reflected waves, stagnant water behind the piles, and intensified flow through the gap of the piles. These mechanisms cannot be adequately evaluated by a common 2D-numerical model with regular waves, demonstrating the benefit of the use of the 3D model.

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 In many ports, it has been reported that long-period waves and wind waves cause trouble in cargo handling. As a countermeasure to this, wave absorbing structures installed on the harbor side are employed. For long-period waves, we have already proposed submerged type wave absorbing structure and shown that it works effectively. However, the effectiveness of submerged type for wind waves is unclear.
 In this study, a series of hydraulic model experiments was conducted to evaluate the wave absorbing performance of the submerged structure for wind waves. Furthermore, the stability of wave dissipating concrete blocks used for the submerged structure was examined. Throughout this study, it become clear that submerged structures display a higher wave absorbing performance for wind waves than conventional structure whose crown is situated above the still water level. Finally, methods to estimate the required crown width and the mass of wave dissipating concrete block are proposed.

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 This study conducted a series of hydraulic model experiments using honeycomb structure blocks which possess hexagonal aperture as armour blocks of an artificial reef. The experiments evaluated stability performance of honeycomb blocks and effects of relative water depth h/L to the stability number N_s. The procedure of experiments follows “A Manual on Hydraulic Model Test to Evaluate the Stability of Artificial Reef Blocks against Waves” issued from the National Institute for Land and Infrastructure Management in 2016. The results clearly show honeycomb blocks have higher stability number N_s than the existing blocks. In addition, h/L has an effect on the stability performance because the smaller h/L is, the smaller N_s is. Furthermore, in case that the relative crown depth R/H is high, the wave transmission coefficient of the artificial reef covered by honeycomb blocks becomes lower than by rectangular blocks. As a result of experiment on the processes of expansion of damage, it occurred from wave breaking point. Honeycomb blocks has remarkable stability performance even in the surf zone where armor blocks are easily lifted up.

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 Concrete blocks have been constructed alone in the bottom of the sea to build artificial algae reefs. In this study, Clarify the properties of the wave force acts on the concrete blocks in actual survey by the physical model experiment. As a result, as for the blocks, resistance force (F₀) which decreased by lift force (F_Z) is less than drag force (F_x), it make slide and move. Wave force calculated by Morison eq. (evaluated from experiment) almost accords with measured value (F_xmax).

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 In this paper, we investigated the influence of mortise and rubber mat on the vibration characteristics using rectangular parallelepiped block model with mortise and rectangular parallelepiped block model without mortise. In addition, because the similarity rule of the shaking table experiment by the block model does not match the actual situation, the similarity rule applicable to the block model was also examined. The models are two types of wave absorbing block models with different scales. We could make sure that the mortise had the effect of improving the earthquake resistance from the shaking table test of a rectangular parallelepiped block model and the similarity law suitable for the block model existed from the shaking table experiment of the two kinds of wave absorbing block models.

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 This study investigated the effects of wave forces on the detached-breakwater that consisted of an upper structure and a pile foundation. In this study, structure stability was also considered on the results obtained from previous studies on the instability of seabed induced by wave force. When a wave force acted on the structure, an external force acted on the pile foundation as if pulling out the foundation on the outer harbor side and pushing it in on the inner harbor. The effective stress in seabed was increase so the pile foundation was considered to maintain sufficient bearing capacity. Subsequently, when the bearing capacity of the ground was decreased because the water pressure in the ground surface layer was decrease, the pile foundation will be aggravated settled down. The external force acting on the pile foundation was not same on outer harbor and inner harbor with the form of the upper structure. As a result, we found that the strain will be generated on the structure.

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 On April 18, 2015, field observation was carried out on the Kenbutsu coast in front of Katanagiri Shrine, which is located on the south shore of Tateyama Bay. A park was constructed by land reclamation in a shallow sea with reefs and narrow sandy beaches, and a seawall was built in front of the reclaimed land. Near the seawall surrounding the park, the backyard of the seawall was stable at a place with rocky reefs in front, but in an area with a large water depth between the rocks, wave overtopping was severe and sinking of the ground was found. In this study, the seabed topography was measured near the seawall together with the observation of wave overtopping. Then, the wave overtoppoing was calculated by using the VOF method.

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 In the 2011 Tohoku tsunami, the number of oil tanks in petrochemical complexes along the coast were damaged by its huge hydrodynamic forces. The detailed mechanism how the tsunami force acts on a specific point or specific member of the grouped tanks has not been sufficiently clarified. The aim of this study is to investigate hydrodynamic tsunami forces acting on oil tanks arranged in a grid system. The possibilities that the hydrodynamic pressure inside the grouped tanks become greater than that acting on a single tank are revealed, and the characteristics of the pressures are found to be depending on the position and arrangement of the grouped tanks. It is also noted that the starting time of water level rise is much affected by the spacing conditions of the tank arrangement.

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 It is known that piloti-type structures, which have open space on the ground floor, have an advantage for tsunami hitting because tsunami can pass through the ground floor. There is a basic guideline for the design of piloti-type structures for tsunami forces but detailed information such as tsunami forces acting on the elevator hall or the ceiling is not speculated. It was also reported that tsunami forces acting on members of piloti-type structures such as the elevator hall or the ceiling estimated by the existing guideline were occasionally much smaller than the tsunami forces measured by the hydraulic physical model tests.
 In the present study, hydraulic physical model tests were performed by using the tsunami wave generator in the wave basin in order to investigate the characteristics of tsunami force acting on the elevator hall of the piloti-type structures. As a result of the physical model tests, the tsunami forces acting on members of the structure could be estimated by the Froude Number of the incoming tsunami, same manner as in the case of a vertical wall. When the elevator hall of the piloti-type structures is located in the landward side, the tsunami forces acting on the elevator hall becomes larger because the tsunami flow is restricted at the ceiling in front of the elevator hall. This tsunami forces could be estimated by the momentum of the incoming tsunami.

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 After the 3.11 earthquake, the design of tenacious tsunami breakwaters is required in Japan. The steel piles and widening works construction method proposed for tenacious breakwater. These methods increase the construction cost. It is a problem to pay expenses to external forces beyond design wave. In this research, we propose a tenacious tsunami breakwater design with low cost.
 The proposed design method sets a low safety factor for some of the breakwater caissons. The breakwater will collapse locally against the tsunami over design waves and escape from complete destruction. We conducted a model test of a tsunami breakwater with locally lowered safety factor. As a result, it was confirmed that this method is effective for the tsunami of 1.4 times the design tsunami.

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 In order to improve the stability of breakwater due to tsunami-induced overflow and seepage flow, it is effective that putting armor blocks on the harbor-side mound of breakwater. A hydraulic model experiment for the model of Kamaishi Bay breakwaters under tsunami condition was conducted to evaluate the extent of armor block damage focusing on the weight, the height ratio (the ratio of the armor block height to the armor block diameter) and the open ratio of the armor block (the ratio of the open volume to the armor block volume). As the result from this study, following conclusions were obtained. Although it was confirmed that the armor blocks slips downward due to seepage flow before occurring overflow, the armor blocks were stable against overflow. Although the damage of armor blocks with the weight of 0.29N was noticeable, the damage ratio was below 3.5% for armor block having the weight more than 0.29N. In the experimental conditions of this study, the damage of armor blocks with the triangle arrangement was smaller than that of the square arrangement. Stability ratio against surface slip was defined. This shows the tendency of damage of armor blocks.

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 Tsunami-induced flow fields around the landward toe of a coastal dike and the effectiveness of countermeasures against local scouring were investigated from full-scale numerical simulations. Numerical results showed that the flow fields were classified into two patterns, i.e., a submerged flow which ran down on the landward slope and submerged under a hydraulic jump, and a clockwise vortex which was formed from a flow separated at the landward edge of protection blocks and a return flow along the surface of a scour hole under the separated flow. Furthermore, the submerged flow was formed when bottom flow velocity at the landward edge of protection blocks was directed downward. This suggested that it is essential to reduce the downward component of the bottom flow velocity in order to prevent the formation of the submerged flow, which increases the depth and width of a scour hole.

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 A new tsunami disaster mitigation scheme named here “Three-Level Disaster Management”, includes three disaster scenarios i.e., 1)Disaster Prevention Level, 2)Disaster Mitigation Level, 3)Maximum Evacuation Level. The Maximum Evacuation Level is to ensure safe evacuation and to minimize tsunami casualties (i.e., possibly Zero Tsunami Casualties) even for the case. The Disaster Mitigation Level is to ensure early recovery by reducing the damage and preparing for the recovery.

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 The importance of breakwater stability for giant tsunami has been increasing since 2011 East Japan Disaster. Miyazaki Prefecture, located in south-east of Kyusyu Island has also major potential of large tsunami induced by Nankai trough earthquake. This study aims at studying countermeasures for resilient breakwater against tsunami and clarifying the effects by conducting the physical model test.
 The examination of armor block stability with the hydraulic experiments clarified that consideration of slope angle in the Isbash formula can overestimate the minimum weight of armor blocks. The results of the physical model tests revealed the effects of friction-increasing asphalt mat to the stability of armor blocks. The paper concluded that the optimum countermeasure in the breakwaters are to set 8 tons blocks on the rubble mounds with cost comparison of countermeasures.

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 If an earthquake occurs nearby a breakwater, the breakwater damaged by the earthquake would be attacked by Tsunami. Therefore, the breakwaters have been required “Persistence” against the complex disaster composed of the earthquake and Tsunami. In this paper, the behavior of a gravity caisson type breakwater reinforced with steel piles has been estimated by finite element analysis. At first, the seismic analysis FLIP (Finite element analysis program of Liquefaction Process) has been conducted. As a result, the settlement of reinforced breakwater has become smaller than that of non reinforced breakwater, because the pile would prevent liquefied soil deformation. After that, the deformed section by the seismic analysis has been applied for the lateral loading analysis presented Tsunami force. The reinforced breakwater has shown the persistent resistance. These results indicate that the pile has the effect which prevents the caisson settlement during earthquake and the effect which resists against Tsunami persistently.

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 There is fear that coastal levees will sink by liquefaction due to large earthquake such as Nankai Earthquake in Japan. To overcome this damage, as one of major countermeasures, the application of double sheet-piles wall to coastal levees has been proposed. Authors confirmed that the settlement of coastal levee was reduced remarkably using partition walls connected to double sheet-piles, based on model tests and 2-D numerical analyses. However, the influence of the interval of partition walls has been discussed in the framework of 2-D numerical analyses. So, in this study, authors investigated 3-D behavior of levee deformation during earthquake using 3-D numerical analysis. As a result, authors confirmed that long interval of partition walls increased settlement near the center of levee between partition walls.

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 The empirical typhoon models or the advanced mesoscale meteorological models are often used to calculate wind and pressure fields as external forces of storm surge simulations. The conventional typhoon models can calculate wind field of a virtual typhoon with low computational cost. However, the typhoon models do not include the influences of the land topography. On the other hand, the advanced mesoscale meteorological models can calculate highly accurate wind field with considering the geographical features, while it requires huge computational cost and is difficult to simulate virtual typhoons. The aim of this study is to propose a correction method of wind field obtained by a conventional typhoon model using correction coefficients based on the wind field by an advanced mesoscale meteorological model. First, wind fields were simulated with both the conventional typhoon model and the advanced mesoscale meteorological model under the same typhoon conditions. Then, comparing the both numerical results, the correction coefficients were determined by the least-square method for each grid of computational mesh depending on the wind speed and direction (octas). In addition, storm surge simulations were performed using a coastal circulation model to investigate the effect of the correction of wind field.
 The wind speed is affected by the influence of the geographical feature like the advanced mesoscale meteorological model. In the time series of the corrected wind speed during typhoon, both the maximum wind speed and its occurance time it occurs agree well with the result of the advanced mesoscale meteorological model. Furthermore, the result of the storm surge estimation is improved by the proposed correction method. The results indicate that the correction method is valuable for getting the wind field data with accuracy and low computational cost.

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 For further accuracy verification of MSM(Meso Scale Model)-based winds data samples released by JMA(Japan Meteorological Agency), buoy-based measurement data samples acquired by KMA(Korea Meteorological Administration) at 9 stations deployed along almost all offshore areas of Korea are used, in cases where the period of hourly data sample ranges from 4 to 13 years. The comparison between both samples is conducted using the wind statistics such as mean value and standard deviation of wind speed and the error indices such as correlation coefficient, slope value in correlation diagram and root-mean square error. Main conclusions are that 1) MSM winds are in overall agreement with measurement winds at 9 stations, 2) in details, MSM wind speeds tend to be slightly smaller than measured speeds at the East and South stations and slightly greater at the West stations and 3) the error indices also suggest somewhat lower accuracy at the West stations than at the East and South stations.

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 For a coastal structure in shallow water, it is important to estimate the probability of wave height with storm surge because the tidal level much affects the situation of wave transformation. In this study, the return periods of both the storm surge without wave set-up and the wave with storm surge are estimated, respectively and their relation is discussed. To do that, each wave set-up at the peak of storm surge is calculated by using the Boussinesq model in which wave breaking and runup model are installed, and it is removed from the observed tide of storm surge. Finally, it is suggested that the tidal level for design wave can be estimated with the superposition between the probability of atmospheric surge and the wave set-up calculated for the probability of wave height.

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 A hindcast wave model was built using the SWAN model to estimate wave fields in front of the Ida beach. To verify its accuracy, estimated hindcast results were compared with NOWPHAS wave data. From numerical results, it was found that the hindcast results were in good agreement in terms of the significant wave height. Although the mean wave period and direction had lower statistical quality than the significant wave height, their tendency was estimated reasonably well. Using hindcasted wave data, the characteristics of wave fields at the Ida beach and their relationship with Owase's buoy data were analyzed. The significant wave height at Ida was smaller than that at Owase. However, the significant wave height with 2 to 4 m in the east direction was similar between Ida and Owase. Finally, the relationship between wave fields and beach profile change under high wave conditions was analyzed using the hindcasted wave data and DEM data. From these results, it was shown that the hindcasted wave data at the Ida beach can be used to assess the characteristics of beach profile change more appropriately than Owase's buoy data.

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 Typhoon and storm surge are considered the biggest hazards that threaten coastal communities in Vietnam. The possibility of a large typhoon taking place in Southern Vietnam is considerably smaller than in the northern and central parts of the country. However, this does not necessarily mean that Southern Vietnam is less vulnerable against typhoons. In this paper the authors tried to analyze typhoon track data during the last six decades to analyze how frequently typhoons made landfall on southern coast, particularly focusing on the Mekong Delta. The analysis reveals that the chance of typhoons making landfall is not negligible, although the frequency is substantially lower than that in Northern or Central Vietnam. A questionnaire survey was also carried out to investigate disaster awareness amongst local inhabitants in the Mekong Delta. To do this, the authors visited many small coastal towns and the regional capital, Can Tho city, whose population is well over 1.2 million. The events of the worst storm in recent times, severe tropical storm Linda in late October 1997, which claimed more than 3,000 lives and caused severe damage in the delta and the remote islands, were also investigated by conducting interviews with local people who directly experienced the typhoon. The key objective of this paper is thus to understand the awareness and concern about typhoons and storm surges in the delta. The results show that the local population tend to have a high degree of awareness about the dangers posed by those events, contrary to the authors' original hypothesis. However, it is also noticeable that it is necessary to improve preparedness against coastal disasters in Vietnam, especially in term of the education of the younger generation, and the elaboration of a mitigation plan.

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 Laboratory experiment and numerical simulation were carried out to grasp the vertical mixing with the artificial mound reef in stratified flow with the thermocline. It was revealed that the structure of stratified flow with the thermocline depended on densimetric Froude number F_r by the laboratory experiment results, and it was similar to past knowledge. Under conditions of F_r<1, internal waves were generated and mixing occurred in a thermocline over the artificial mound reef or on the downstream side. Under conditions of F_r>1, the internal wave was not generated, but mixing produced in a thermocline on the downstream side of the artificial mound reef was observed. The laboratory results were compared with results by three-dimensional LES numerical simulation. It was confirmed that the numerical simulation could successfully reproduce the laboratory results.

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 A numerical flow model applicable to the Okinawa sea was developed on the Okinawa project 2012 to 2014. This numerical model simulates the flow fields at offshore to coral coastal areas. In addition, this model is systemized to run easily by mouse operation on the personal computer.
 This report shows some functions and performances of the system and shows the validation by observational data.

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 The rip current occurs at the wave breaking area near the beach, and the accident that is related to the rip current occurs every year in the world. Some generation mechanisms of the rip current are known. For example, about the rip current at the sand beach that has the cusp topography. However, the rip current occurs near the structures such as the groins or the detached breakwaters. In Niigata, there is not many large beach, and ordinary the beach is semi-enclosed by the groins or the detached breakwaters those were built to protect from the coastal erosion.
 This study tried to know the current regime of the rip current at the semi-enclosed beach by detached breakwaters. Firstly, this study made the field survey, and comprehended the scale and velocity of the rip current. In this method, the rip current was pigmented by the sea water colorant, and the pigmented current was observed by the UAV. Secondary, this study reproduced the rip current by the numerical simulation. Finally, this study concerned that the rip currents occur at both end of the cusp topography, and the wave conditions will be decided whether the both currents will merge or not.

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 At Numakawa-daini floodway located on the Fuji coast, a plan converting the ordinary-type floodway into a setback-type floodway was made, by which the mouth of the floodway is moved from offshore of the shoreline to landward of the berm. To realize the plan, the influence of the conversion of the type of the floodway to the nearby coasts should be predicted beforehand. In this study, a numerical simulation using the contour-line-change model was carried out to predict beach changes when the floodway type is converted from ordinary-type to setback-type. As a result, it was predicted that the shoreline retreated in an area of approximately 1.5 km upcoast of the floodway, and the maximum shoreline recession was 15 m in 10 years.

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 The total extension of the Cambodian shoreline is approximately 500km. However this region has the abundance of natural piscatorial resources by reason of the semi-enclosed, calm, shallow sea and the enormous mangrove grown coast. The Cambodian Environmental Impact Assessment Law was put a law into force, recently. For perform the environmental impact assessment, flow mechanism, water quality and another physical quantities are known, however the almost observed data in this region do not supplied in the present.
 The authors have concerned in the assessment about this region since 2008, and made many observations, for example, geographical map, water flow mechanism, weather and etc. This study reports the observation result and feature of geography, tidal change and weather. And furthermore, this study simulate the tidal flow and wind-driven flow. Ultimately, this study try to know the flow mechanism of this region, and contribute about the make the method of deliberate development project.

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 After the East Japan great earthquake disaster occurred, it came to be predicted that the tsunami which was considerably huger than a previous assumption. It was pay attention to the hybrid refuge technique that was used together with the floating type tsunami evacuation shelter in addition to conventional high place refuge. The behavior of the shelter is divided into 3 patterns in previous study.
 In this study, data was put in order by the Froude number and the wave force was measured to act on a shelter. Then it was performed an evaluation for the refuge using the shelter. Therefore, Pattern 1 was stable from photointerpretation and behavior analysis, and patterns two or three was unstable. However, Pattern 1 was shown great value from wave force, it was thought the risk that a shelter was destroyed. In addition, pattern two or three shows a relatively small value. From these reason, examination of the most suitable setting position will be important in the future.

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 There was the refuge technique that was hybrid which combined Floating Type Tsunami Evacuation Shelter with conventional high place refuge as technique to plan the improvement of the survival rate from a tsunami. Basic motion of Floating Type Tsunami Evacuation Shelter properties at having installed it on low land and a building are clarified in the previous study. However, there are many studies for the first wave of the tsunami. Therefore there is a possibility that it was not intend for the maximum tsunami wave height
 In this study, it was performed experiments with the behavior of the Floating Type Tsunami Evacuation Shelter when the tsunami becomes maximum wave height after the second wave. Then, it was investigated the behavior of the Floating Type Tsunami Evacuation Shelter and examination about the wave height. As a result, it was able to classify the behavior of the shelter in 6 patterns. It was revealed that a change of the still water depth of the water greatly affected the behavior of the shelter. Because even the same condition might show different behavior, it will be necessary to perform wave height, speed, wave force and the analysis in future.

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 During a scenario earthquake with M_J7.8 nearby Ryukyu Trench, not only strong motion but also huge tsunami with the maximum water level and run-up height of 6m and 15m, respectively is predicted in central Ishigaki City, Okinawa Prefecture, Japan. In this paper, seismic waveforms in the tsunami attack area were first predicted with very high density based on the SMGA models and microtremor measurements. Walking times from the prediction sites to the designated refuge places were then measured. Using non-evacuation time based on the time history of instrumental seismic intensity and measured time based on results of the walking experiment, finally, we evaluated the difficult area for tsunami evacuation in central Ishigaki City.

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 During a large scale scenario earthquake, huge tsunami with early travel time is striked in Tobishima, Sakata City, Japan. In this study, ground shaking characterisrtics in the tsunami attack area were evaluated using microtremor measurement with high density. The strong motions in Tobishima were then estimated based on the asperity models considering the ground shaking characteristics. Furthermore, the difficult time for tsunami evacuation during the earthquake was calculated using instantaneous instrumental seismic intensity. Finally, we discussed the influence of the strong motion on the tsunami evacuation based on the relationship between the travel time and the difficult time.

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 This paper presents a simulation based experience system in evacuation building using OpenFOAM and VR device. To estimate tsunami propagation and forces against a building, 3-D simulation based on VOF method which involves the OpenFOAM solver was applied. Study of aperture ratio of building was carried out to compare tsunami forces around building and inundation of each floor inside building. These results can be shown the validity of not only planning for building design but also education and training for disaster prevention.

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 After the Pacific coast of Tohoku Earthquake in 2011, the necessity of tenacious coastal/harbor structure has been suggested. Although, it's necessary to experimentally examine its effects to make it in practical design. Some features of a self-propelled wavemaker proposed by the authors have been clarified, but generation of arbitrary waveforms has not been studied. In this study, the feasibility of arbitrary waveforms by a self-propelled wavemaker was examined using CADMAS-SURF/3D which is combined with the immersed boundary method. As a result, the following findings were obtained: 1) Reproducibility of an arbitrary waveform at an arbitrary point is very high by utilization of wavefront velocity and water particle velocity by shallow water wave theory, consideration of wave deformation using wavefront velocity, and correction of wave travel time. 2) As for arbitrary overflow on the structure, it was confirmed that arbitrary overflow is also sufficiently possible by considering the reflectance by the structure and the lowering of the water level due to the overflow.

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 In order to examine mechanisms and countermeasures of destruction caused by the tsunami attacks, it has been developing tsunami wave generators which generate various types of tsunami waves after the Great East Japan Earthquake. This study has developed a new tsunami wave generator using an electric sluice gate. It can make various types of tsunami waves using ordinary wave flume. The tsunami wave generator was investigated about the characteristics of the waves. As a result, it turned out that it can make the tsunami bore and the dispersive waves.
 It also examined the control method of the tsunami bore height and the first dispersive wave height. A simple model was created to make the target height of the tsunami bore using the tsunami wave generator. This model can calculate the opening value of the gate for making the target tsunami bore. The first dispersive wave height varies with the distance from the gate. Therefore, it is possible to select the target wave height. The relation between the distance from the gate and the wave height was calculated using T-STOC.

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 Although we can sense the power of tsunami instinctively by watching the high wave as it surges or by listening to the loud report of the wave as it collides with a retaining wall, we have an incomplete understanding of the combination of circumstances in which a wave occurs and the relation to wave pressure.
 In this study, we measured the height and volume of the splash and the pressure to the vertical wall when a solitary wave crashes into the wall. We changed the stroke of the wave plate to shift the position of the breaking wave and checked the condition when the solitary wave crashed into the wall. The study enabled dividing conditions into Wagner, Bagnold, and Transitional types, and revealed the difference in the splash height and the wave pressure of the three types.

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 Traffic hindrances were often caused by driftwood run-up due to wave overtopping under storm wave conditions on coastal roads behind gently sloping seawalls. In this study, the driftwood patterns around a gently sloping seawall were revealed by the field observation data. Hydraulic model tests with irregular waves of 1/40 scale were carried out in order to disclose the relationship between driftwood run-up ratio and wave overtopping rate for three wave period conditions. The characteristics of driftwood run-up were also shown for different driftwood thicknesses, lengths and densities for the longest wave period condition. The effect of increasing the crest height of wave-dissipating blocks was clarified as for countermeasures of driftwood run-up on gently sloping seawalls. In addition, tests of 1/5 scale were conducted to confirm the stability of a transmissive fence. Based on the test results, the hydrodynamic force when driftwood collided with the transmissive fence can be estimated for design wave conditions.

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 Design waves and water depth at a construction site are important factors in a seawall design, but the seawall design excludes factors such as wind speed and direction. It is easy to image that a gale increases the volume of water that gets over a seawall more than an expected overtopping rate. In order to achieve a safety land use on a coastal area, the wind speed and direction should be included in the seawall design process to estimate the wave overtopping rate properly. This study aims to clear the effect of wind speed on wave overtopping phenomenon to construct a methodology that could evaluate the wave overtopping rate under the gale condition. Furthermore, this study evaluates the effect of a wave dissipating work with lower crown height to reduce the wave overtopping rate on Flared shaped seawall less than an upright seawall covered with wave dissipating blocks under the gale condition.

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 This study presents a new generalized liquefaction prediction and assessment method that takes account of the influence of the waveforms and durations of earthquakes. The new method facilitates universal applications to various types of liquefaction charts. The predicted results were compared and validated against case histories at Sendai Port, Onahama Port, Chiba Port, Haneda Airport and Urayasu City under the 2011 Off the Pacific Coast of Tohoku Earthquake. The results show the validity and effectiveness of the new method for the level 2 earthquakes. This study also presents and discusses its applicability to sequenced earthquake motions.

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 The liquefaction resistance of sand under sequenced earthquake motions was investigated by a series of stress-controlled, undrained hollow cylinder cyclic torsional shear tests. The ordinary sinusoidal cyclic shear stress was first applied to the specimen to a certain extent simulating the pore pressure generation in the first shock. Under such conditions with various degrees of excess pore pressure, the liquefaction resistance was evaluated against 3 different aftershocks. When the equivalent CSR* is estimated based on the effective number of waves, the test results are clearly categorized into the 2 groups with and without liquefaction. The effective number of waves well characterize the irregular loadings in the cases with residual excess pore pressure. The presented simple approach allows one to predict the risk of liquefaction during aftershocks.

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 The present study aimed at developing a new concept of countermeasure against liquefaction-induced damage by utilizing artificial drain materials. A series of model tests and 3D seepage analyses were performed to investigate the spread of liquefaction and associated sand boils. The results demonstrate that the drain method is capable of suppressing the spread and propagation of liquefaction, while allowing the occurrence of liquefaction underneath the bottom of the drain installed. This resulted in preventing flows in and boiling above the ground effectively, giving rise to no significant surface deformations. It is a subject for future study to establish a design of this countermeasure against liquefaction-induced damages.

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 The Compaction grouting (CPG) method is one of the liquefaction countermeasures to increase the density of improved ground by injecting mortar statically into the ground. CPG can be often applied just below or near the existing structures, and accordingly ground upheaval often becomes a problem. In this study, regarding Up and Down (U/D) method of a new upheaval control type CPG method, field demonstration experiment was carried out by changing actual construction machines and various parameters.
 Consequently, in field verification, the same upheaval control as model tests was obtained by the new U/D method. The proposed U/D method has proven itself in reducing the ground upheaval quantity by more than 90 %. Moreover, by using the concept of the equivalent improvement rate, it is possible to predict the upheaval amount and the density increase of the improved ground by the new U/D method, thereby facilitating a rational design based on the conventional CPG method.

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 The Fukushima Daiichi Nuclear Power Station suffered great damage due to the Tohoku Regional Pacific Offshore Earthquake that occurred on March 11, 2011 and the accompanying tsunami. Due to the influence of the leakage of contaminated water including high concentrations of radioactive materials, Radioactive substances were detected from the seabed soil in the harbor. In order to prevent seabed soil containing radioactive material from diffusing out of the harbor, seabed soil was coated with cement mixed soil. In FY 2012, we covered 72,600 m² in the first construction and covered 180,600 m² in the second construction in FY 2014. In the 2nd construction work, cement mixed soil mainly composed of sand was selected, as it required earlier strength than the cement mixed soil used in the 1st construction. Material separation at underwater casting, which is a problem of cement mixed soil mainly composed of sand, was solved by developing special additives and casting jigs.

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 Vertical seawalls around the offshore waste landfill should be constructed as the revetment and impervious wall. Using box-shaped steel sheet pile is considered one of the most effective methods, because the sheet pile has double joints sealed by water-swelling sealant. Additionally filling the clayey geo-material into the chamber sandwiched between the joints works so well as backup measures, the impervious performance is improved further. Though water leakage from the joints before filling the material has bare possibility, imperviousness reliability should be improved furthermore. In order to hedge the risk of water leakage, prototype widened box-shaped steel sheet pile is developed to reduce the joints and post-construction repairing method is conducted experimentally. As results, these methods described earlier would be useful to reduce the risk of water leakage.

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