7 years have passed since CIM was proposed in 2012 by MLIT in Japan, but its utilization for port construction is still insufficient. Under these circumstances, we carried out the first CIM utilization work (designated by the customer) for the port construction of the MLIT.We showed specific examples of CIM utilization and discovered the advantages and problems encountered which are divided into the following items:1.Solutions to the problems encountered can be solve by CIM, 2.Explanation using data visualization improves understanding between concerned parties, 3.The application of CIM to the construction management, 4.The application of CIM during final inspection, 5.Electronic inspection using CIM. We also examined the future prospects of CIM.

 Installing floodgates and movable breakwaters ―such as flap gates and self-elevating seawalls at the opening of a port― are attracting attention as effective countermeasures against tsunamis and storm surges. However, a previous study revealed that inflow of seawater takes place through small gaps in the movable gates. Additionally, it is necessary to consider intrusion from the other parts, as these floodgates are used in combination with existing structures such as breakwaters and coastal dykes. In particular, a breakwater consists of a rubble mound, and thus there is a concern that tsunamis and storm surges will enter the port through the voids between stones when different water levels occur on each side of the breakwater. Because this risk has yet to be adequately recognized by engineers, an inflow rate assessment method has not been established to date. In this study, a method for evaluation of the inflow discharge through a breakwater mound by conducting a hydraulic experiment and numerical analysis is proposed. As a result, it was identified that seawater inevitably enters a port through the porous rubble mound when tsunamis and storm surges occur. In particular, it was found that a long-period wave tends to be less attenuated even if the opening is perfectly enclosed by floodgates.

 It is a problem that the rubble mound is damaged if high waves such as typhoons attack during construction of the rubble mound seawall. It is thought that the velocity above the crest is important for the stability assessment of the rubble mound. In this study, the applicability of OpenFOAM was examined in order to evaluate the velocity above the rubble mound crest. The rubble mound is reproduced as a porous body. The hydraulic model test and the numerical analysis results were compared, and good reproducibility was obtained from the initial waveform by reproducing the motion of the wave generator in the experiment. Moreover, it has become clear that it is important to set the porosity of the rubble mound. Sufficient accuracy was obtained for the flow velocity that is essential for the stability assessment of rubble mound. And, the water level inside the rubble mound was also reproduced. Furthermore, in order to evaluate the damage process of the rubble mound, it became clear that the examination by the irregular wave is necessary instead of the regular wave.

 In this study, we compared three-dimensional numerical models with the experimental result of tsunami with large-scale eddy. The employed general-purpose models were OpenFOAM, CADMAS-SURF/3D (CS3D), and T-STOC, which have been often used in coastal and ocean engineering. First, we examined the validation of OpenFOAM changing the difference scheme of advective term which effects calculation accuracy. We confirmed that higher-order difference scheme is important for calculation stability and accuracy, and introduced the second-order upwind difference scheme into CS3D and T-STOC. The three models was recognized to reproduce the hydraulic experiment on tsunami eddy appropriately

 In the 2011 off the Pacific coast of Tohoku earthquake tsunami, many oil storage tanks suffered great damage in the oil complex located in the coastal area. Of these, "small-scale tanks" less than 1,000 kL are reported to be about 90 %, and it is extremely important to take safety countermeasures at the time of the tsunami targeting these.

 Therefore, the authors have proposed countermeasures to prevent sliding and drifting with carbon fiber sheets (CFRP) that are excellent in durability (corrosion resistance), workability, and tensile strength, as a measure against tsunami to small-scale tank bodies. One is to restrain the tank base and the RC foundation by CFRP, and the other is to install an eye plate in the middle of the tank side plate via the CFRP and extend the wire to the ground anchor etc. In this study, hydraulic model experiments and CFD analysis for tsunami exerting force were performed on the proposed countermeasures.

 In this study, we constructed a long-term joint probability distribution model of wind and waves using the observation data in offshore Kitakyushu city, for fatigue assessment of offshore wind turbine. However, it was found that the previous model underestimated the wind speed averaged wave period. Thus, the model was improved according to the wave characteristics in Japan Sea area. We proposed a model combining the developed wind-waves empirical model and the swell propagation model. It was confirmed that the improved model suppressed the excessive development of waves and reproduced the local wave characteristics well. In constructing the model, we proposed a new wave index, wave development coefficient, which quantified the development of wind waves.

 Evaluation of Severe Sea State conditions (SSS) of offshore wind turbines during power generating in the Hibiki-Nada sea-area was investigated in order to set reasonable design of the support structure. First, wind-wave condition was simulated for the past 30 high wave events in order to obtain simultaneous distribution of wind speed and wave heights. Next, using the Inverse First-Order Reliability method (IFORM), the environmental contour defining 50-year return period combinations of mean wind speed and significant wave height was evaluated. The results show that the estimated SSS wave height at the rated wind speed is lower than the 50-year wave height. Furthermore, it was found that more rational and economical design can be realized through further reduction of the design wave height, considering that power generation is not resumed immediately if the wind speed exceeds the cut-out value.

 Among renewable energies, wave generation is less popular, because the energy concentration is lower than another natural energies. The wave energy resources is evaluated in this study for es-timation of possibility of the wave generation. Some wave parameters in mechanical and marine engineering which contain wave direction are evaluated because wave direction should be im-portant for efficiency of generation devices. First, the wave potential along Japanese shoreline is calculated from Nationwide Ocean Wave information network for Ports and Harbours (NOWPHAS), and Kashima area is selected as the suitable location for wave generation, because the wave energy potential is higher than others and stable seasonally. Next, wave potential maps are computed with the ocean model, SWAN. The potential is Choshi is hight in the map, and this result indicate the possibility of wave generation there. The parameter “Directionally resolved wave power” which takes wave direction into account, is 29 % less than Omni-directional wave power at Choshi due to the limitation of the direction.

 Numerical simulations of velocity and energy potential of tidal currents in consideration of density stratification were carried out at Oshima Strait, Nagashima Strait, and Kuronoseto Strait around Kagoshima. The monthly mean values of velocity and energy potential were trend to be larger in winter than in summer. The decrease in tidal current velocity in summer may be due to the tidal energy being consumed to weaken density stratification. The annual mean value of extractable energy was 1.0 MWh in Oshima Strait, 4.1 MWh in Nagashima Strait and 12.8 MWh in Kuronoseto Strait.

 The Ariake Sea, which is frequently hit by typhoons, is highly vulnerable to storm surges, therefore accurate estimation of storm surge and high wave is highly desired under future climate of global warming. In order to do that, understanding of typhoon characteristics in the future climate is required. Hence, we evaluated future changes of the typhoon characteristics near the Ariake Sea using a large ensemble climate prediction dataset (d4PDF). In this study, the moving direction and degree of bending in typhoon tracks, which greatly affect storm surges, as well as typhoon intensity and frequency were statistically evaluated. As a result, it has become clear that, in the future climate, the intensity of typhoons passing over the west sea of the Ariake Sea become greater and the risk of storm surge will be higher. Furthermore, the dispersion of the moving direction of typhoons increases, and the number of typhoon turning to the right based on the moving direction increases in the future climate.

 Sagami Bay is an open and deep sea facing the Pacific Ocean. The storm surge here has a very small wind set up, and the water level mainly rises due to the suction effect. In particular, because of its steep topography on the western coast, wave maintain its height even in the shallow coastal area and break in the narrow surf zone causing the beating Wave Setup. The analysis of the storm surge including the high waves and Wave Setup (Wave Setup storm surge) in the Sagami Bay was conducted for Typhoon No. 12 that struck in July 2018(T.1812).As a result, on the western coast of Sagami Bay, high waves directly invade the coastal area due to local surf zone breaking, causing fluctuating Wave Setup with the maximum height of 2.7 m above the mean sea level. It was shown that the area where the high surge and waves are generated is tightly related to the coastal current system, and the generation area is geographically fixed. At these places, the risk of wave overtopping disaster is extremely high.

 The reproducibility of stochastic tropical cyclone model in Ishigaki-jima Island has been examined and showed the good performance. The reproduced typhoon intensity and the storm surge for 5000 years have been estimated from results of the combined stochastic and empirical estimation models. In this area, the tropical cyclones translate toward the north and north-east is severe to the storm surge. However, the substantial risk of the storm surge caused by the tropical cyclone translate toward the north-west is relatively higher.

 Typhoon Linda in 1997 is considered to be the worst tropical cyclone ever to make landfall in the Mekong Delta, Southern Vietnam. Linda caused catastrophic social impact with over 3,000 fatalities and US$385 million in property loss. The fatalities were mostly fishermen and sailors who were caught at sea in Linda’s path and unable to escape. There is little information about Linda because of the lack of a detailed post-disaster investigation. In this study, we conducted an interview survey with local residents of Con Dao Island, where Linda passed nearby, to reveal how this historical disaster event remains in their memory. A numerical simulation using the coupled typhoon, storm surge, and wind-wave model was also performed to investigate the spatial extent of the storm surge and high waves during Linda’s passage. The results showed that the storm tide was not necessarily extreme, but reached 1.5 m in the delta. In comparison, waves off the Mekong Delta were estimated to be 8 m high, which appears sufficient to capsize many wooden fishing boats.

 “ICT dredging” in harbor field is one of “i-Construction” measures promoted by the Ministry of Land, Infrastructure, Transport and Tourism and dredging construction fully using ICT, such as the multibeam echo sounder bathymetric survey. The quality has improved by using the multibeam echo sounder bathymetric survey because it can survey all sea area, the unmeasured area is smaller than the singlebeam echo sounder bathymetric survey, and the soil volume can be calculated more accurately than “average cross section method”, which was used before. On the other hand, the multibeam echo sounder bathymetric survey surveying currently in operation can not be said to have achieved productivity in terms of time and cost for operating the data instead of the singlebeam echo sounder bathymetric survey. Based on these, the standards for the multibeam echo sounder bathymetric survey developed in fiscal 2017 was revised in fiscal 2018, but similar problems still remain. In this study, we prose to improve productivity by optimizing the standard of the acquisition point density for the multibeam echo sounder bathymetric survey.

 The Ministry of Land, Infrastructure, Transport and Tourism promotes "i-Construction" to improve productivity and “ICT Dredging” using three-dimensional point cloud data for a series of construction processes has been introduced in harbor field. On the start of “ICT Dredging” in fiscal 2017, standards are set which based on trial constructions and various issues. “Manual of volume calculation using three-dimensional data in harbor dredge” is one of them, which stipulates the method of calculating dredged soil volume using three-dimensional point cloud data. In the trial of “ICT Dredging”, it was concerned that difference in soil volume by complex field conditions. But the method of calculating dredged soil volume using three-dimensional point cloud data has some parts where complicated field conditions are not reflected.

 In this study, we considered the method of calculating dredged soil volume under complicated field conditions by using three-dimensional point cloud date as KAIZEN of standards of “ICT Dredging”.

 In the present situation, inspections by eye are widely used to diagnose fishing port facilities. However, regarding submersible parts of breakwaters and mooring facilities, it is pointed out that the results of visual checks by divers are inconstant and subjective. Also, submersible surveys are required to be improved from perspectives of taking considerable time and efforts as well as considering safety concerns. In this research, an inspection method using narrow multi-beam sonar was examined to assure objectivity of submerged facility inspections and alleviate diving works. Its applicability was examined by on-site tests based on the judgement standard of deterioration for fishing port facilities. As a result, high applicability of this method was confirmed to evaluate relatively large-scale and detrimental damages such as transfer, scattering and damages of wave dissipating blocks, deficits of concrete structures, and lack of electric protections. Its effectiveness as a screening of submersible surveys was confirmed through using this method as a simple diagnosis prior to detailed inspections.

 In the midst of the increasing Port Structures that have crossed the in-service period of 50 years from construction, there is also deterioration in the number of divers carrying out the underwater investigation. Hence it is indispensible to develop a technique capable of carrying out wider area investigation in a shorter time, as an alternative of the current method of regular inspection of port structures by divers. Using realtime Underwater Sonar, the possible alternative methods has been checked for the inspection items mentioned in the Guidelines on Inspection and Diagnosis methods of Port structures.

 In this paper, a tool that compares the present realtime sonar data with the past data is developed. Its adaptability to the inspection items as mentioned in the guidelines and its efficiency on the time taken for inspection has been investigated. While the past research concludes that the adaptability to the inspection items was low, the feasibility of using underwater point cloud data in convolutional neural network for port maintenance is also reported.

 A floating drone so-called “SWANS” which can be photographed underwater and measured water depth was developed. This device was applied to coral reef monitoring. SWANS has ability to perform underwater monitoring quickly, easily and safety without diving. It can operate stably at a significant wave height of 21cm or less, while taking off, landing and moving on the sea surface. It was applied for monitoring of coral reefs in Kerama Islands, Okinawa Prefecture. The line transect survey and detail analysis of coral coverage were conducted. Moreover, data of photographs and water depth which collected by SWANS, were contributed to SfM analysis and created a 3D topographic maps and ortho image.

 Airborne Laser Bathymetry （ALB） is an aircraft sounding technique that transmits green laser through water. As a technology that seamlessly obtains airborne underwater data, its application and utilization in river and shore management are many, whereas its applicability in port projects is few. Therefore, in our current research, the applicability of ALB is examined at three ports that have different transparency conditions of 3m to 15m.

 As a result, there are some troubles found in data acquisition under caisson wall area and in high turbid environment. However, this technique can be expected to be used in port and harbor projects, from the confirmation of continuous data acquisition even up to 20m depth.

 On National Route No. 232 along Rumoi coast in Hokkaido, the wave overtopping leads damaged along coast by the strong west wind. The ridgeline and shallow water survey are conducted at the damaged area as a countermeasure. This area is very challenging for surveyor because there are shallow reef zoon around 300m offshore and extensively developed bar around surf zone. Therefore, Airborne LiDAR Bathymetry(ALB) method was utilized for the survey. In this survey, ALB was able to detect maximum depth of 10m and the topography was well detected such as bar at water depth 3m and rocks above water distributed shallow area. In comparison with the prior survey method, the ALB are effective for shallow water survey: position accuracy was achieved within 15cm, and field and analysis work time are 2.3 times efficient, cost effective when the survey track lines are over 2.1km, aerial photos can be collected simultaneously.

 In usual, it is dangerous to measure a settlement of wave-dissipating blocks immediately after a disaster. The surveys are implemented, sometimes, with standing directly on the blocks by the surveyors. Therefore, the measurements based on UAV particularly with a RTK-GNSS system, which are provided reasonably in recent, are expected to achieve a safer, more reasonable and accurate survey. In this study, the UAV-based surveys are implemented with targeting port structures by some different systems for comparison. The first is a conventional photogrammetric survey based on a UAV. The second is the conventional survey by UAV with GCP. The third is a survey based on a UAV with an installed RTK-GNSS system, which does not require the additional GCP survey on the target structure. The last is a survey based on a UAV with PPK-GNSS system, which is a relative new method. The last system also does not require the GCP survey. The experiment shows an effectiveness of the RTK and PPK GNSS-UAV systems getting small errors no more than a few cm.

 In order to investigate topographic change in gravel beaches using a UAV-SfM/MVS survey, it is important to re-construct a high-accurate three-dimensional model. The aim of this study was to clarify an optimum analysis method for the UAV/SfM-MVS survey at gravel beaches and the characteristics of topographic change in the Shichirimihama Ida coast was investigated from the three-dimensional model. As a result, it was found that a reproducibility of the three-dimensional model was influenced by a parameter in the “Align photo” analysis. Moreover, it was revealed that deposition was caused by low and long period waves in the Shichirimihama Ida coast.

 As an initial survey method after earthquake disasters for mooring facilities, utilization of unmanned aerial vehicles (UAV) was examined. Although it is possible to evaluate the displacement by analyzing the captured image taken by UAV, it is important to set control points to ensure accuracy. In large-scale earthquakes, the residual displacement of the quay wall to the sea must affect the large area of the back ground, and the control points whose coordinates have been measured before the earthquake should also be moving. Therefore, it is necessary to newly set the control points and measure the coordinates after the earthquake for the accurate evaluation, but it is difficult if we cannot enter the facility by tsunami warning. In this study, the limited use of control points after the earthquake was assumed in the image processing. The influence of arrangement of control points on the measurement accuracy of residual displacement in mooring facilities was evaluated in such a situation.

 From the viewpoint of landscape and beach utilization, the crown height of seawalls should be as low as possible. Various types of low crown height seawall have been proposed. When there is a limit to expansion of seawalls to the front sea area, vertical block masonry seawalls are sometime applied. However, the shapes of wave-dissipating blocks vary, and comparisons of their overtopping characteristics have not been conducted. The purpose of this study is to clarify the effect of reducing wave overtopping on two types of block masonry seawalls comparing to vertical seawall. Results indicated that the wave-dissipating block masonry seawall with the diamond-shaped opening with the lid crown parapet can reduce wave overtopping under any conditions. In addition, calmness of the front sea area can be improved due to low wave reflection rate, and wave runup can be smaller than vertical seawall.

 In this study, a simple method for the wave-overtopping prevention was proposed. The method utilizes a cylindrical body (assumed length of 5-10m) for the vertical seawalls, the both ends of the cylindrical body are moored using rope to the front face of the seawalls. The mooring allows that the cylindrical body moves following the wave motion in front of the seawall. This method has several merits, for example, low cost, ease of construction and maintenance, and so on. First, model experiments were conducted to confirm the performance of the method. Next, numerical simulations were performed to estimate the reduction of wave-overtopping rate by this method. The numerical model was "DualSPHysics" which is based on the Smoothed Particle Hydrodynamics (SPH) model. The cylindrical body, however, was fixed at several different positions in the simulations because the numerical model cannot simulate the motion of mooring objects. From the experimental results and the numerical simulations, it was confirmed that the proposed method can efficiently reduce the wave-overtopping quantity, and the SPH model can be a useful tool to investigate the performance of the proposed method in detail.

 Sea salt spray consists of small particle of seawater, generated by interaction of wave, wind and coastal structures. Sea salt spray, which is transported by wind sticks to the surface of structures, harms long-term durability of the structures. In this study, field observation of sea salt spray from sea surface were carried out in the coast where the wave-dissipating concrete blocks were installed. From the results, it was shown that the amount of the sea salt spray from sea surface is related to the wave-dissipating concrete blocks installed in the coast. The increased amount of spray is estimated by classifying a locations of the wave-dissipating concrete blocks.

 Countermeasures against deterioration of port facilities in Japan are urgently required. It is necessary to catch signs of deterioration and to take preventive measures before the facilities are deteriorated. Therefore, a low cost, simple and highly reliable inspection system for predicting deterioration is needed. Since mooring facilities in ports are greatly affected by salt, in the case of concrete structures, it is effective to collect information on the chloride ion concentration on the surface of the structure in order to accurately grasp the sign of this deterioration. In this research, we report the contents of verifying the performance of equipment by developing non-destructive, non-contact, compact, portable and high-performance equipment based on near infrared spectroscopy. Moreover, it confirmed that two-dimensional imaging in the chloride ion concentration of the specimen cross section could be performed in a short time and with high accuracy. We also conducted outdoor measurements and confirmed that two-dimensional imaging of chloride ion concentration is possible almost accurately.

 It is required to have information on the soil conditions of fine fraction content and SPT-N value for estimating the liquefaction potential of ground, or for conducing soil improvement such as the chemical grouting method.

 In this study, machine learning techniques as the random forest method, the support vector machine and the neural network are applied analyzing boring-operation data obtained in the past soil improvement works at Tokyo International Airport. It is found out that the soil conditions of fine fraction content and SPT-N value can be accurately predicted by the multi-task learning model based on the neural network.

 From the viewpoint of CIM and initial defect in marine ground improvement, a way to obtain more detailed construction management information in addition to the conventional construction management information is required. In the present study, in order to examine the relationship shear wave velocity and shear strength of ground improvement soil as an approach to development of new quality management method of ground improvement based on Shallow seismic reflection profiles, made the ground improved specimens, conducted bender element test and the element test. In addition, we compared the shear strength estimated by various design equation based on N-value to shear strength of experiments, examined the applicability of design equation based on N-value. As a result, it was confirmed that shear wave velocity and shear strength have positive correlation. The shear strength estimated by various design equation based on N-value have large variation by design equation based on N-value was implied.

 A large number of scallop shell which is a by-product of fishery are stock piled around fishing ports such as Hokkaido because the method of disposal and utilization has not been established. In recent years, attempts have been made to effectively use crushed scallop shell particles (hereinafter referred to as crushed shell particles) as a construction material such as a mixture material in caisson filling materials, quay-wall back filling material in fishing ports. It has not been sloved the scallop shell are stock piled around fishing ports. This study elucidated the shear strength characteristics of the crushed shell particles considering particle size by laboratory experiment and clarified analytically the countermeasure effect considering the shear strength characteristics of the crushed shell particles appling to the ground improvement material. As a result, the crushed shell particles are a highly effective material as a ground improvement material. It is thought the utilization of crushed shells has a possible to contribute greatly to the promotion and construction of recycling society.

 One of the measures to prevent salt accumulation in semi-arid areas is the Capillary Barrier ground (hereinafter, CB ground) which is a soil layer structure composing of a sand layer over the gravel layer. Dry sand in semi-arid areas is difficult to hold the layer boundary surface long term because it is easy to be mixed in the gap between gravel particles due to the vibration at the time of construction. The CB ground was clarified that the dry sand was mixed into the gap of the crushed shell particles layer at the same time while retaining the function by using crushed shell particles as an alternative material for gravel materials. However, The CB ground was composed of crushed shell layer containing fine scallop shell particles has possible to decrease the function of increasing moisture because the water characteristic curves are different depending on the size of the shells. This study elucidated the CB ground composing of crushed shell particles layer containing fine particles has effect of the long-term capillary from observation in the laboratory experiment and was performed numerical analysis to clarify the water behavior in the specimen.

 A new sounding method, named Vibro Sampling and Cone Penetration Test (VS-CPT) was proposed as an economical and effective geotechnical investigation method for shallow ground about 20 meters below seafloor.

 A series of experiments of penetration tests in a model sand bed were conducted to study a proper shape of the probe that reduce penetration resistance and assure sample retrieval. The results demonstrated that vibration is effective for penetration and sand sample can be obtained if the aperture ratio was 0.5 or more. Furthermore, a prototype test device (Mark 1) with an aperture ratio of 0.67 was designed and manufactured for penetration depth of 2 meters.

 As a part of elucidation of the dynamic characteristics of fine particles considered to be an important factor in maintenance for tidal flat, we carried out a hydraulic model experiment focusing on the change of topography consisting of sand-clay mixed sediments by wave conditions and clay content. The characteristics of the topography and the influence of the spatial distribution of clay on the sediment characteristics of the mixed sediment were investigated. As a result, in the case of sediment consisted of clay and sand, the effect of the cohesion of clay was effective in delaying the topographic change. Mixed sediment was eroded by the movement of sand after clay particle is washed out. Moved sand covered mixed sediment and reduced the erosion.

 Assuming that the removed soil containing radioactive cesium generated by the decontamination after the FDNPP accident is finally disposed of in an offshore disposal facility, we examined the permeability, cesium adsorption characteristics, compressibility and consolidation characteristics, regarding the mix design of the sealing geomaterial used for the bottom shielding of the facility. The incremental loading consolidation test examined the permeability, compressibility and consolidation characteristics, and the consolidation and seepage test examined the cesium adsorption characteristics. Bentonite, sand and zeolite were added to marine clay, and by examining each characteristic when they added individually, we showed the possibility to predict each characteristic in case of adding multiple materials.

 PS (Paper Sludge) ashes are discharged from paper mills and becomes popular in not only absorbing technology but also environmental purification. In this study, the strength of the dredged mud improved by PS ash stabilizing materials are investigated for the purpose of utilizing it for marine neighboring facilities. As PS ash improved materials have high φ' and c' and can secure predetermined degree of compaction within wide range of water contents. Utilization is enabled around ocean facilities even though the dredging mud was unsuitable for ground reclaimed and the backfill for marine facilities.

 From the experiences gained from the field tests some supplementary methods assisting permeation of cement solutions through silty sand deposits were pursued based on laboratory permeation tests, and one method was found promising. This method employs the injection of water, following infiltration of relatively dense cement solutions which would be terminated by cement particles trapped within microscaled silty sand skeletons. However, it is not enough about the storage of result which perseverance of liquefaction. Unfortunately it is difficult to use this material for real construction site now. Then, in this study, the authors group measured dynamic properties by dynamic shear test using tri-axial test machine and bender element test machine. Bender element is test method can measure shear moduli when strain level is about around 10^-4 % and it can set into triaxial test machine easily. And authors changed volume of injecting cement and estimated effect of concentration of cement amounts dynamic properties of grouted sand contained fines. In addition, the authors tried to propose the shear modulus evaluation formula using the test results. As a result, it was possible to calculate an evaluation formula, though limited.

 In the vacuum consolidation method, it is difficult to determine the vacuum operation period as to be satisfied with the design specification.

 The design and construction management of vacuum consolidation method in a certain coastal area in Vietnam were performed. In this paper, the design of vacuum consolidation using ground model obtained from soil investigation, monitoring results and modification of design were described. And the determination method of vacuum operation period using the monitoring results was discussed.

 To propose the simple determination method for consolidation parameters of clays for the reclamation analysis, the results of Multi-Sedimentation Tests (MST) in Japan were collected, and the high correlation between liquid limits of clay and indexes of compressibility and rate of consolidation obtained from the MST’s were confirmed. Using these high corrections, the determination method of consolidation parameters was proposed. The effectiveness of proposed method was confirmed from the back-analysis for the construction record of Kita-Kyushu airport.

 A simple method to deal with unsaturated soil for the volume-of-fluid (VOF) method was proposed and incorporated into a VOF-based numerical model, FS3M. Furthermore, the FS3M was improved to compute unsaturated seepage flow more accurately. From comparison with experimental data, the predictive capability of the improved FS3M was demonstrated for unsaturated seepage in a dike and overflow-induced erosion of an unsaturated dike. This suggested the usefulness of the improved FS3M in assessing such phenomena related to unsaturated soil.

 Authors are developing a countermeasure to prevent the destruction of sand boil induced by liquefaction by using shallow vertical drain (PVD). Along with the 1G model test in previous study, a seepage analysis and centrifuge model tests are conducted to establish a design method considering real application in this study. With the PVD spacing of 1.2 m and length of 3 m, the transmission of liquefaction to ground surface is prevented while allowing liquefaction to occur in deeper portion. Consequently, sand boil and its destruction are also prevented by the use of PVD. In comparison to the current application of PVD on preventing liquefaction, a much-lower construction cost is expected with the less use of PVD.

 Liquefaction prediction is based on liquefaction strength presumed from the N-value. In the case of soil with fine contents, the N-value is revised depending on the content rate(Fc) and the plasticity index(Ip). But the impact of the sand’s uniformity coefficient and fine content’s plasticity against accuracy of liquefaction prediction is not adequately investigated. Based on the above, this research experimentally studied the effect of the sand’s uniformity coefficient and fine content’s plasticity on the correlation between the N-value and liquefaction strength of mixed sandy soil. This research showed the possibility for the risk of liquefaction being underestimated in case where the sand’s uniformity coefficient is low while it tends to be assessed on the safe side if the sand’s uniformity coefficient is high.

 The Bengkalis Island, Indonesia which lies in front of Malacca Straight has been experiencing severe coastal erosion process since 1955. At the present, Bengkalis Regional Government has started the mangrove plantation to prevent the coastal erosion. This paper has studied the ability of mangrove in reducing hydrodynamic impact due to physical characteristics of the tree. Xbeach1D model was employed to simulate the wave attenuation in the mangrove trees. Computation result demonstrated that the red mangrove (Rhizophora mangle) had better reduction rate of wave heights and suitable for plantation.

 In this paper, the authors conducted numerical analyses of wave propagation in order to clarify the influence of the developmental condition of a sand spit on intrusion characteristics of waves into an estuary. In the numerical analyses, the opening position of river mouth, the flow depth around the opening, and the opening width were changed systematically, and the NOWT-PARI which is based on a Boussinesq equation was applied. Consequently, our analysis results showed a possibility that the wave intrusion into the deep part of the estuary is reduced because the waves entering from the opening propagates to the opposite side of the opening depending on the hydraulic conditions. Moreover, the analysis results pointed out that the cause which the waves entering from the opening deflected in the opposite direction might be the influence by the large-scale vortex formed in the estuary due to the inflow from the opening.

 Koga beach is located in the north of Kyushu. This beach is a pocket beach and this has the groins at the both ends of the beach, furthermore there is a submerged breakwater at the offshore of the beach. In this beach, an accident of 4 people drowned occurred in August 2017. When the accident occurred, 2 children played at the water’s edge of the beach, however the big waves suddenly reached the beach and the children carried away to the offshore. In this research, we tried to grasp the reason why the accident occurred. Firstly, we conducted the field survey one month after the accident, and we got the geographic information of the beach and the geographic feature of the domain. After the survey, we made the geographical grid data for the numerical simulation. Secondary, Koga beach is located at the base of a peninsula, therefore, when the prevalent wave from NNE direction incidents to this domain, the wave in this domain diffracts and attenuates. In contrast, when the wave from NNW direction incidents to this domain, the wave does not attenuate. When the accident occurred, the wave always incident from NNE direction, however the wave direction changed NNW direction in an instant. Therefore, we simulated the wave height profiles in this domain. In this case, we simulated two cases, that is, NNE and NNW wave direction cases, and compared the wave height between at the offshore and at the beach. As the results, when the wave direction was NNE, the wave attenuated around Koga beach. Finally, we simulated the wave dynamics in the pocket beach, and we grasped how the wave moved in the pocket beach. As the result, the wave velocity became over 3 m/s around the accident occurred point.

 In order to mitigate meandering damage of a detached breakwater in a harbor region, wave height distributions and resultant wave loads about an isolated and finite length breakwater located offshore side of a straight land boundary have been studied from the theoretical point of view. Especially influence of reflected waves from the straight land boundary on wave loads acting on the breakwater is extensively examined for various detached distances between the breakwater and land boundary. In the examinations, characteristics of wave heights and wave forces on both sides of the breakwater have been clarified to obtain the spatial distribution of resultant wave forces along the breakwater line.

 On submerged breakwaters, fringing reefs and atolls which have large steps, it is difficult to conduct a stable calculation of wave transformation by using a Boussinesq model which is derived with a mild slope approximation. In this study, a “step boundary technique” is newly developed to give an appropriate flux to the boundary between calculation regions which are separated on a large step by compulsion.

 While the improved model with this technique can calculate partial wave reflection and transmission on a step, the wave height distributions due to wave breaking and dispersion on a submerged breakwater, which were measured in a previous model experiment in a flume, are reproduced with good accuracy.

 In the previous study, we have developed an approximate method to analyze wave interactions with multiple permeable breakwaters in a harbor. In this study, to confirm the applicability of this approximate method, wave interaction problems among floating breakwater arrays and landside seawalls in a harbor have been examined extensively. The comparison test between previous experimental results on a floating breakwater array and calculation results was carried out to find out the necessary interaction order of transmitted waves among the multiple breakwaters.

 Currently, the estimation of wind-waves on coastal waters is commonly done in practice on structured mesh. However, when complex geometries arise (for instance, irregular coastlines, islands and breakwaters) multistage nesting with smaller grid spacing which entails high computational cost is required on structured mesh and even then it is sometimes difficult to get accurate bottom topographical approximation of only required areas. In contrast, since unstructured mesh can perform detailed geometrical approximation only at necessary places, it is expected to reduce the computational cost while securing the accuracy of the bottom topographical approximation.

 Hence, the objective of this study is to analyse wind waves with SWAN (Simulating WAves Nearshore) model, which is commonly used in practice for nearshore wave analysis, on structured mesh and unstructured mesh and, thereby to find out an effective approach to use SWAN model in future practice. The behaviour of SWAN model on structured mesh (ST-SWAN) and on unstructured mesh (UNST-SWAN) was analysed and advantages of UNST-SWAN over ST-SWAN were discussed. Wind-waves were estimated during the arrival of Typhoon with ST-SWAN and UNST-SWAN. Wind-wave characteristics obtained from both ST-SWAN and UNST-SWAN were basically consistent. Considering the advantages of UNST-SWAN, an effective approach to apply SWAN model in future practice by combining both structured and unstructured mesh where necessary was proposed during this study.

 Typhoon generated wave behavior in Osaka Bay under recent three major typhoons (T1820, T1821, and T1824) is simulated and discussed in the study. Simulation was conducted using third generation wave model WAVEWATCH III, and results showed that the impact areas for each typhoon can be explained by looking in to the sea wave properties enter into the bay area. Wave energy is represented with significant wave height related to each categorized components of wave frequency, and their contribution to the damages and critical conditions caused by each typhoon are discussed. Analysis shows that the longer period swell enters into the bay area for T1821 than that of for T1820. In contrary, effect of wind waves for T1820 is larger in North and West side of the bay while T1821 affect more in the Eastward side. In addition, wind data from two sources [Local Forecast Model (LFM) and Meso Scale Model (MSM)] by Japanese Meteorological Agency (JMA) were used in the study and the simulation effectiveness in related to wind source is also discussed in the study. However, results with newer and finer LFM wind data showed better agreement with observations in comparison to weaker MSM wind data.

 This study analytically shows that two time series(x_i, y_i)-related 5 statistical quantities such as mean values (x, y), variances(S_x², S_y²), covariance C or slope value of a correlation straight line passing through the origin a₀ can be derived from another 5 statistical quantities such as slope value a and intercept value b of a correlation straight line, bias ν, correlation coefficient ρ and root-mean-square error σ without using the original time series data and vice versa. The validity is confirmed by almost perfect agreement between the above-mentioned statistical quantities estimated using the observation-based and the MSM(Meso Scale Model)-based wind speed data samples over 1 year at 9 ocean buoy stations deployed around offshore areas of Korea. On the contrary, substitution into the derived relationships of either of two sets of the 5 statistical quantities such as a, b, ν, ρ, σ provided by Heo et al.¹⁾ does not yield either the observation-related mean value x or the variance S_x² to be essentially coincident with each other in the two cases. This may be a problem to be solved in the concerned paper.