Lingayen Bay of a slender shape located 150 km north of Manila faces the South China Sea, and it satisfies the condition of High-angle waves because of its slender shape, causing the predominance of longshore sand transport. Villages are located along the coastline, and groins have been constructed along the shoreline to protect these villages against erosion. However, the spatial imbalance of longshore sand transport was triggered by the construction of these groins, resulting in erosion downcoast of each groin. In this study, the shoreline changes in the vicinity of the groins were investigated using satellite images as well as field observation on February 23, 2018, taking a concave shoreline between the Balili and Aringay Rivers in Lingayen Bay as an example. On the basis of these data, future measures were discussed.

 Futtsu cuspate foreland, which separates Tokyo Bay and Uraga Strait and extends westward, connected to Dai-ichi-kaiho Island in 1982. However, beach has been eroded in recent years, resulting in large shoreline recession. In this study, field observations were carried out at the tip of this cuspate foreland on July 16, 2017 and November 23, 2018 to investigate the present conditions of the foreland, as well as the shoreline change analysis using past aerial photographs. When the volume change of the beach was calculated from the change in the foreshore area between 2004 and 2018, and was multiplied by the characteristic height of beach changes of 3.1 m, eastward longshore sand transport on the north coast of the cuspate foreland was evaluated to be 1,160 m³/yr, assuming that sand supply from the south side was entirely disrupted. Sandy beach has been disappearing owing to the imbalance in longshore sand transport at Futtsu cuspate foreland.

 Point Higashihenna-zaki extends at the southeast end of Miyako Island. At the south end of this point, rocky cliffs have collapsed by wave action. To investigate the mechanism, oblique aerial aphotographs of the rocky cliffs were taken using a drone on October 2017 as well as the investigation of the crack formed on the surface of the headland. Regarding the main external force to force the collapse of the rocky cliff, wave gages were installed at three points near the reef edge offshore of the headland between October 18 and November 19, 2017. On the basis of these field data, the cause of the collapse of the rocky cliffs was investigated. The main causes were considered to be due to wave abrasion and weathering of raised coral reef composed of limestone.

 Nagame-no-hama barrier island is located at the north end of Kami-koshiki Island in Kagoshima Prefecture and faces the East China Sea. This barrier island has 4.2 km length and is mainly composed of gravel, which was supplied from the sea cliffs at the north end of the island by storm waves in winter. The Tanoshiri Rock protrudes at the northwest end of this barrier island, and southeastward longshore sand transport seems to be blocked by this rock. This is contradictory to the extension of a long barrier island on the southeast side of this rock, and this suggests that there is some mechanism for longshore sand transport to pass through this rock. However, it was unknown. In this study, this mechanism was investigated by field observations, the analysis of aerial photographs as well as the numerical simulation using the BG model.

 Field observation was carried out on November 26, 2018 near Point Zampa facing the South China Sea in Okinawa to investigate the deposition of the coral sand (debris) along the shoreline. On the basis of the measured grain sizes of coral sand and the berm height, the movement of sand placed along the reef edge due to waves was predicted using the BG model considering the change in grain size. Near Point Zampa, the most predominant wave direction is from NNW and the secondly direction of waves from SW. Due to these wave incidences, sand can be driven to the shoreline from the north reef edge, forming the present sandy beach along the shoreline.

 When a wave-sheltering structure is constructed in a wave field where waves are incident from two directions, the wave action from one direction disappears in the wave-shelter zone, and otherwise balanced sandy beach will deform significantly. Such beach changes can take place on coral reef coast such as that in Okinawa, and the impact of the construction reaches the nearby coast. One of the examples can be seen after the construction of Irab Bridge connecting Miyako and Irabu Islands. The same changes occurred in Kin Bay in Okinawa after the construction of a causeway. In this study, the effect of the construction of a causeway was investigated using aerial photographs and field observations.

 The formation of a blowout was predicted using a cellular automaton method, while changing the width and direction of a path crossing the coastal sand dune, and the appropriate direction of a path by which the formation of a blowout can be prevented was investigated. The example of a path to reach the shoreline on Sunayama Beach on Miyako Island was investigated, in which a narrow path covered with dense subtropical vegetation on both sides of the path was effective in preventing windblown sand. As another example of the path where a blowout was formed, the Node coast with much windblown sand causing a blowout to the hinterland was considered. Taking these examples into account, numerical simulations of the formation of a blowout was carried out.

 Extraordinary high waves associated with Typhoon No. 1721 hit the Shimizu coast in Suruga Bay on October 2017, resulting in severe damage of No. 2 breakwater out of four breakwaters placed along the shoreline. Severe erosion also occurred along with wave overtopping over the seawall and the deposition of gravel to the backward of the seawall. Concrete blocks composed of No. 1 breakwater upcoast of the L-shape groin which was under construction at that time were widely scattered. In this study, the wave condition during Typhoon No. 1721, and topographic changes before and after the typhoon waves were investigated. Furthermore, the Narrow Multi-beam survey was carried out to study the damage of the breakwaters.

 The relationship between countermeasures against beach erosion and tsunami was investigated, taking the area around the artificial headland No. 12 on Horikawa Beach located in the north part of the Kujukuri coast as an example. On this beach, southwestward longshore sand transport prevails and HLs have been constructed from upcoast, resulting in the expansion of the eroded area. Also, sand dune with 6 m height has been preserved as a measure against tsunami on this beach, but such sand dune has been eroded while losing its effect. This situation has been investigated by the comparison of aerial photographs and field observation. Urgent measure against beach erosion should be taken so as for the effect of sand dune against tsunami to be maintained.

 Beach nourishment using 2.0×10⁵ m³ of gravel has been planned at Katayamazu area of the Ishikawa coast to recover a sandy beach of 20 m width. In this beach nourishment, gravel, which is stably deposited near the shoreline was employed, and 4.7×10⁴ m³ of gravel has been supplied to the coast by 2017. To accomplish the beach nourishment, it is required to evaluate the effect of beach nourishment using coarse material. In this study, measured beach changes after the beach nourishment were reproduced using a contour-line-change model considering the change in grain size of bed material. Beach changes were also predicted when waves are obliquely incident to the shoreline at a large angle to investigate a possibility of sand discharge turning around the tip of the river mouth jetty.

 In Tottori Prefecture, sand dredging is a challenge in sandy beaches in the vicinity of the quay or mooring basins with shallow water depth where larger-scale dredgers cannot operate. Therefore, an alternative compact sand extraction system is required.

 In this study, a new sand recycling system was developed using a compact jet pump sand extraction device combined with a relay pump for longer distances. This system is more compatible with the dredging sand volume of approximately 1000-3000 m³ per year, which is characteristic of the small fishery ports in Tottori. The effects of the new system were examined through a field test.

 In this study, the numerical simulations of tidal current and sediment transport in the Kanmon Waterway were performed by using a numerical model FVCOM (Finite Volume Coastal Ocean Model (Chen et al. 2003)), in order to discuss the influence of the sea level departure on the sand waves. The numerical simulatin results suggested that the spatial difference of sea level departure in Kanmon strait slightly changes the tidal current around Tanoura area, and consequently affects the development of sand waves.

 In the experiment investigating the sand movement, the topographic changes by the successive wave for a certain time were measured and the change process and volume were analyzed. However, there are few experiments grasping the topographic changes with the sand movement in detail. It is difficult to say that the sand movement process to the topographic change is understood adequately. In this study, simultaneous measurement of topographic change and sand movement was carried out by colored sand tracking to investigate the detailed sand movement process in the initial stage of the topographic change. As a result, the sand movement per wave action was confirmed using colored sand coverage ratio. By analyzing the mixing situation of colored sand under the bottom surface, the sand movement was confirmed at the locations where the colored sand movement was not measured by the coverage ratio. These experimental results showed the sand movement range and its path which were difficult to catch by only the measurement of topographic change.

 In assessing wave conditions influencing on topographic change, it is useful to estimate beach topography and wave conditions from coastal images. The purpose of this study is to investigate the relationship between wave conditions and coastal images taken with a network camera installed at Shichiri-Mihama Ida beach using deep learning. The coastal images were labeled with significant wave heights and periods at Owase, tidal levels at Kumano, and various values obtained from these parameters. As a result, it was revealed that the wave run-up showed high relevance to the coastal images.

 A beach change analysis method for three-dimensional (3D) coastal current fields was developed and applied to the calculation of beach deformation around the artificial reef system. We compared this computational output with the observed erosion-deposition maps which was derived from the two depth survey data before and after the event of half year period including winter monsoon winds and a typhoon. During the target period, 10 representative storms are selected and their steady-state solutions of wave field and 3D coastal current field were computed. The storm durations were determined with the concept of equivalent total energy flux. Using these wave and currents fields, the erosion-deposition analysis was conducted and the spatial distributions of the computed coastal deformation for all storms were summed to compare with the observed erosion-deposition map. By this method, it was shown that the erosion-deposition tendency can be reproduced with a certain degree of accuracy even in long-term beach change analysis of the 3D coastal current field in which heavy computational burden is obliged.

 Sea level rise and wave characteristics change under climate change have been reported, and the impact assessments due to theses change have been carried out by several researchers. In general the beach profile change on climate change is simulated using Bruun rule only considering sea level rise. However the wave characteristics change is important in considering beach profile change. In this study, impact assessments of shoreline change on climate change are investigated using high resolution reanalysis (JRA-55-Wave) and wave climate projection data sets. First, the one line model was calibrated for confirm to reproduce the past shoreline change on Tottori Sand Dune Coast. Next, the future change of shoreline change due to wave characteristics change was investigated. It was found that the future change of shoreline change due to the wave characteristics change is about 10% of the past shoreline change.

 The rip current is a main cause of drowning accidents in Japan. To prevent drowning accidents, lifesavers detect the rip current, and give a caution to beach users. However, rip current accidents are not prevented completely because of not only difficulty of finding rip currents, but also the lack number of lifesavers compared with total number of beach users. Therefore, it is highly important to estimate in advance the occurrence of rip current accidents. In this study, we studied outbreak factors of rip current accidents at Onjuku beach using the statistical analysis. As a result, the rip current accident happened in following conditions; Fine whether, a large number of beach users, the sea condition is not so good for a sea bathing, the wave height is from 1.5 to 2 m, the wave period is from 10 to 11 s, and the wave direction is between S and SE according to data from the Japan Meteorological Agency.

 Almost all drowning accidents were caused by the rip current in Japan. In order to prevent rip current accidents, lifesavers inform beach users by an announcement, and flags and signboards. However, rip current accidents have not decreased because beach users can’t perceive the place of occurrence and don’t understand the risk. Former studies have suggested that given sufficient visual information, it is possible for beach users to identify the rip current. The aim of this study is to investigate the relationship between visualized rip current and the risk management awareness at Onjuku beach among beach users. As a result of statistical analysis, it was suggested by this survey that the information of the visualized rip current can prevent drowning accidents because beach users could perceive and avoid the rip current.

 Undertow is a significant offshore-ward current that is induced by a shoreward water mass flux under wave breaking and Eulerian drift in non-wave-breaking conditions. The undertow generates offshore sediment transport and also affects swimming safety. To increase the understanding of the undertow, field observations were conducted on a barred beach, Hasaki coast, Japan, for 21 days from May 13 to June 2, 2016. A Horizontal Acoustic Doppler Current Profiler was used to measure cross-shore currents, i.e., undertow, and water levels in the surf zone. Observed data was analyzed to investigate the characteristics of the spatial and wave-energetic distributions of the undertow exceedance probability (hereafter as P_E). When the wave energy flux level was high, the undertow became larger, and its P_E increased. By contrast, the P_E during a low wave energy level decreased with larger water depths, and its lowest value was in the trough region. Applying a Weibull distribution to P_E curves can develop a statistical model of the undertow, and it can be considered that the Weibull parameters are affected by the combination of normalized values of the wave energy flux, relative surf zone location, and normalized water depth. The two parameters of Weibull distribution was able to estimate using the normalized parameter, and the model well predicted the P_E. Furthermore, to demonstrate the effect of tidal ranges on the undertow, the P_E distributions for each wave energy level and location were distinguished by the water level, i.e. tidal elevation, as high-tide or low-tide durations. The undertow P_E was greater for low-tide data than those for high-tide and the full data at a low wave energy level.

 The Bakkai Fishing Port, which was constructed facing the Rishiri Channel, is characterized by the strong influence of both nearshore and winddriven currents due to a location on a small cape in a strong wind area, and shoaling of Harbor has been a problem for many years. In this study, current and sediment transport characteristics at the entrance of the Bakkai Fishing Port were examined based on a detailed field survey and numerical analysis. As a result, current characteristics including the circulation at the port entrance depending on the wave/wind directions were clarified. The inflow characteristics of littoral drift into the port during high waves, as well as suspended sediment concentration, were also clarified.It has become possible to reproduce relatively short-term(about three months) change of bottom topography by this calculation to which the wind-driven current was added and taking into account the time series variations of waves and winds during high waves.

 In Sanbyakken area bounded by the Nakatsu and Kakise Rivers flowing into the Nakatsu tidal flat, a sandbar of 600 m length extends with a salt marsh in the hinterland. Recently, large topographic changes have occurred around this sandbar. In particular, the river mouth closure is worried at the Kakise River mouth located at the south end of the sandbar because of deposition of southward longshore sand transport. In this study, the shoreline changes of the sandbar were investigated using aerial photographs taken since 2012 to investigate the method for the mouth to be stabilized, and the present condition of the sandbar was studied using a drone and beach survey. Furthermore, detail profiles near the sharp break in the slope near the lowtide shoreline was measured.

 A new method by the concept of entropy has been used to classify sediment color distribution. We objectively characterized the distribution profile and clarified the relationship between the geology and sediment characteristics. Sediment colors were defined by L*a*b* instead of RGB, and of the following four indexes, lightness, hue, saturation and chromaticity, lightness was the optimal index. In order to determine the optimal number of groups, a C-H criterion, Rs statistic and the skewness of the third moment on sediment color distribution were used. The sediment colors could be divided into 7 groups. Kagoshima Pref. has geology of the Shirasu plateaus, but the sediment color could be grouped by white minerals such as quartz and feldspar contained in granite and pyrophorite and colored minerals such magnetite contained in mafic volcanic rock, and therefore, they can be related to geology. In addition, it could be possible to make sediment transport path clear by focusing on a specific mineral such as olives.

 On the coastal part of Awaji Island, there was a storm surge caused by typhoon 21 in 2018. In addition, there are concerns about the damage of the coastal zone due to the occurrence of the Nankai Earthquake. If such a large-scale earthquake occurs, the existing coastal structure may collapse due to liquefaction of the sandy beach.

 In this study, we aims to grasp the spatial features of the coastal beach on Awaji Island by analyzing the image to understand the characteristics of the particle size and shape of the coastal sandy beach of Awaji Island and considering the liquefaction characteristics by shaking table experiment.

 From the results of this study, as a spatial feature of the coastal sandy beach of Awaji Island, sand with large particle size is distributed on Osaka bay side, but the shape is rounded as a whole. Also, there was a tendency to liquefy as it approached a true circle. Especially, sand on the Kii Channel side is easier to liquefy than sand in other areas.

 Sediment compatibility refers to the sediments ability to perform well compared to that of the native sand. It is often based on the granulometric similarity of the sand originally present in the beach and the sand that is used in the beach nourishment.Various methods are used to obtain this compatibility and the method used in the study is the median (D₅₀) grain size distribution. Two beaches (one native and the other nourished) located in Luzon, specifically in Ternate, Cavite, Philippines were investigated according to the characteristics of sand grain size. Specifically, the study aims to; (1) compare the median grain size (D₅₀) distribution of both nourished and native sand, (2) generate spatial distribution with respect to beach profile, and (3) identify the effects of sediment compatibility. Results of the sieve analysis range revealed that median grain size (D₅₀) of the nourished beach sand (0.5mm - 1.2mm) is greater than that of the native beach sand (0.19mm - 0.47mm). Based on the concept of sediment compatibility, the material used for nourishment in Puerto Azul area is not compatible as the nourished beach has significantly larger D₅₀ values. Both the dry and wet areas of the beach produced the largest values of D₅₀ ranging from 0.65mm to 1.2mm for the nourished beach and 0.21mm to 0.48mm for the native beach. The swash area produced the finest grain size among all the areas with D₅₀ ranging from 0.5mm to 1mm in the nourished beach and 0.19mm to 0.43mm in the native beach. The average slope of the nourished beach (15.5:100) is almost twice the average slope of the native beach (8:100), which supports the grain size characteristic of the study area that larger grain size develops a steeper slope compared to smaller grain size. The transport of the nourished sediments may be due to the incompatibility as well as the difference in specific gravity with the native sand.

 The Great East Japan Tsunami destroyed the coastal embankments because of local scouring behind embankment induced by tsunami overflow. Generally, tsunami attacks coastal area two or more times, and secondary tsunami wave is sometimes larger than first wave. The mitigation to the secondary wave of tsunami is important. However, the effects of coastal forests and local scouring behind coastal embankment on secondary tsunami wave have not been clarified. The objective of this study is to investigate the effects of coastal forests and local scouring on tsunami wave. From experimental results, the maximum water level increased on local scouring for effect of damming-up by tsunami flow mitigation of local scouring. On the other hand, the force acting on tree increased for effect of increase of water level. The numerical method was validated as compared with the experimental results. The KK-scheme has good reproducibility compared with the general up-wind scheme. Then, the numerical simulation of real scale based on non-linear long wave equations was carried out using the KK-scheme. There is not so much difference of the maximum water level by the existence of local scouring. The arrival time of tsunami has difference by the existence of local scouring.

 The effectiveness of gabions against tsunami-induced scour at the landward toe of a coastal dike was investigated from hydraulic experiments. Experimental results showed that the installation of gabions moved a scour hole landward and reduced its maximum depth. This effect was reconfirmed from the hydraulic experiments in addition to existing numerical analyses not considering the leakage of sand and the displacement of gabions. Furthermore, it was found that a scour hole grew rapidly due to sand leakage after the gabions were displaced largely. This suggested that connected gabions could be more effective to reduce the displacement of the gabions and the gaps between the gabions.

 It is important to develop a quantitative evaluation and design method considering the ductility of breakwater structures tsunami external loads of tsunamis; this must be investigated from both coastal engineering and geo-engineering perspectives. For this reason, tsunami-induced failure mechanics of a breakwater structure must be clarified. The study indicates the importance of the yield surface of the bearing capacity of the seabed under the breakwater structure in the quantification of its ductility. The relationships among the vertical, horizontal, and moment loads acting on the breakwater, which lead to bearing failure, were comprehensively investigated based on the results of a finite element analysis. The bearing capacity failure of the breakwater could be predicted quantitatively and comprehensively by introducing the concept of the yield surface, even as the failure mode changes depending on the complex and various load conditions of the tsunami.

 Tsunami debris objects are a cause of expanding disaster and/or obstructing emergency response activities. Their motion has been experimentally investigated, and practical calculation models have been also developed for estimating it. This study focuses on a group of debris objects in which individual objects can collide with each other. At first, motion of the group was experimentally analyzed. The experiment showed that the center of mass of the group of debris objects was similarly moved in the direction of tsunami inundation flow even in different conditions of the size of debris objects and the initial setting of debris position. Dispersion of individual debris objects obviously took place in the direction of tsunami inundation flow, comparing to that of the cross direction. The significant dispersion was caused when the flow hit the debris group. A tsunami numerical simulation model of T-STOC could calculate motion of the center of mass of the group in error by less than plus and minus 100 percent. For further improvement of calculation models to estimate motion of debris objects, interaction between the objects and tsunami flow should be included in the calculation.

 In 2011 Tohoku Pacific Ocean Earthquake, many oil storage tanks located in the coastal area drifted, and fire caused by spilled oil is a problem. Many of the oil storage tanks damaged by the tsunami are small-scale tanks that are less than 1,000kl, and these countermeasures for tsunami drifting are urgent. Therefore, the authors suggest fixed between the tank base and the RC slab using CFRP sheet that is excellent in durability, workability and tensile strength. In this paper, to confirm the influence on this measure at earthquake, shaking table test using 20kl tank was carried out. In addition, the effect of countermeasures against drifting during tsunami wave action was examined by nonlinear finite element analysis.

 To prevent the overturning of caissons due to overflow tsunamis, the effectiveness of configuration change in the caissons was investigated from hydraulic experiments and numerical analyses. From experimental and numerical results, it was found that the resilience of a trapezoidal caisson was higher than that of a rectangular caisson and an L-shaped caisson because the configuration of the trapezoidal caisson prevented the separation of the overflow and the formation of a vortex reducing an increase in wave pressure acting on the landward surface of the caisson.

 We interviewed fishery operators at Tarocho Fisheries Cooperative Association and Yoshihama Fisheries Cooperative Association in Iwate prefecture who did not suffer damage such as overturning from the 2011 Earthquake off the Pacific Coast of Tohoku owing to standing out to sea. After clarifying the actual evacuation sea area, we conducted simulation of the tsunami caused by the Earthquake off the Pacific Coast of Tohoku to analyze the relation between current velocity distribution in the actual sea area and fishing boat speed.

 The analytical results suggest that the sea area where the maximum tsunami current velocity is less than 1/2.5 of the boat speed can be set as an evacuation sea area. It is necessary to expand the scope of survey and make close study of the relation because the shape and size of fishing boats were different, the tsunami periods and wave height varied each other and the number of fishing boats subject to the survey was small. At all events, we inferred the sea area where the maximum tsunami current velocity was about 2.0 – 3.0/s can be set as a fishing boat evacuation area.

 Proper evacuation is important for tsunamis. The authors in their previous work had shown that the number of casualties were reduced by selecting the evacuation route focusing on maximizing the length of time before one encounter the tsunami after its occurrence, compared to the shortest route that has been conventionally employed for tsunami evacuation model. However, this effect has been verified only in areas with complex topography. This study, we verify the generality of this model and analyze the recommended route. As a result, it become clear that this model can reduce the number of casualties even in areas with simple topography. It is found that evacuating to the shortest distance from the refuge or escaping from the inundation area is effective in the area where the run-up speed of tsunami is much higher than the evacuation speed. In other words, seaward evacuation, which is not recommended for ordinary evacuation, is possibly accepted. On the other hand, it is found that evacuation to the land side, which is the ordinary direction to escape from the tsunami, is effective in areas where the tsunami speed is small.

 Many kinds of floating sea structures are set up in the inner bays of ria coasts. When a tsunami strikes, it is especially difficult for fishers and anglers to escape from those points back to land. We propose a tsunami evacuation planning method that considers the distribution of floating sea structures. Firstly, through analysis by aerial photographs, we ascertain the kinds of the floating sea structures and their locations. Secondly, we determine the evacuation time from a floating sea structure to the land by GIS. Finally, we classify them based on the evacuation time and tsunami arrival time. Our proposed method was applied to Minamiise Town, Mie, Japan, and showed that there are some high risk structures, especially fishing rafts. We point out the need to set a special landing point for those structures.

 The Natori River mouth and sandy coast have encountered a large-scale morphological change since The Great East Japan Earthquake and Tsunami in 2011. The left sandy beach of river mouth along with the Idoura Lagoon was almost disappeared and the sandspit was flushed entirely by the tsunami. The subsequent recovery of the sandy beach and lagoon showed totally different morphology as compared with that used to be before the tsunami, including intrusion of large amount of sediment into the mouth. This morphology change caused reduction of river mouth width, raised serious concerns of water level rise during flood time and change of ecological environment in the tidal area. To examine the recovery process of the river mouth till now, this study, by using aerial photos, made a thorough analysis of the morphology variation of the Natori River mouth. It emphasized that although a 70m retreat of shoreline is seen, the recovered shape of the left sandy coast has been analogous to the pre-tsunami situation. Additionally, deposition between jetty and embankment was also observed due to wave overtopping.

 Since rust layer at the surface of corroded steel is removed due to sea ice action in ice-infested sea, this phenomenon of corrosive wear subsequently leads to promotion of wear due to increase of corrosion. Damage to training levees made of steel-sheet-pile-type seawalls on the Sea of Okhotsk occurred earlier than expected, since larger wear rate of steel structure had not been considered in their design.In the paper, degradation mechanism of steel structure is investigated through indoor tests focused on sea ice impact. The effect of main factors on wear thickness is examined as parameters such as sea ice temperature, impulse and momentum of sea ice, impact ice load, sand inclusion and so on. It is shown that wear thickness can be estimated by impact ice load (pressure) at the real contact area between sea ice and rust layer.

 To reveal the damage mechanisms (abrasive wear) of steel material caused by the friction of sea ice containing sand particles in ice-infested waters where active sea ice movement is seen, field experiments to understand processes whereby sand particles can be captured by sea ice along with a sliding wear test were performed. As one of the processes, it was presumed that sand particles heated by solar radiation on ice surface gradually penetrated along with freezing/thawing cycles of the ice surface, snowfall and sea spray. From the wear test, it was found that the steady ware rate, defined as wear amount per unit length, increased linearly with decrease in ice temperature and in sliding speed. The steady wear rate when both corrosive and abrasive wears occur at the same time was presumed to become larger than that by summing each corrosive and abrasive wear simply, which indicated the synergistic effect.

 The abrasion process of a slit type seawall constructed on a rocky coast was investigated by field observation data. The movement characteristics of 100 kg round stones due to wave action were disclosed by hydraulic experiments with a model scale of 1/20. The abrasion damage mainly appeared near the still water level, which was corresponding to the position with the highest collision rate. It was also shown that the collision rate was higher for longer wave period conditions. The relationship between the wave height and the collision speed was shown for three wave period conditions based on the result of video analysis on the stone movement pattern due to wave action. The characteristics of flow patterns and overtopping waves were investigated up to the design wave condition by hydraulic experiments with a model scale of 1/40. The abrasion rate of the slit type seawall was estimated to be 10 mm / year by the existing experimental formula using observed wave data at the nearest NOWPHAS station. The estimated abrasion rate was nearly the same as the observed value. Furthermore, the repairing method was proposed for the damaged slit type seawall based on the results of the wave overtopping test.

 This paper shows the durability tests results on rubber fender for mooring facilities in ports. These tests were employed by rubber fender manufactures based on PIANC guideline on 2002. Test results are analyzed on temperature condition, residual strain of fender and energy absorption after durability test. Regulation value on ratio of energy absorption and residual strains after durability tests are proposed.

 We have already clarified the residual structural performance of corroded beam by loading test of specimen. However, the validity of simulating real corroded beam by electrical corrosion method and reliability of using scale-down specimen are still need to be discussed. In this study, load tests for real corroded beam and electrical corroded specimen on same scale are first conducted to verify the effect of different corrosion methods. The effect of scale factor is also verified afterwards by comparing the actual scale specimen and the scale-down one. As a result, electrical corroded specimen tends to have higher rigidity modulus over real corroded beam, and scale-down specimen shows the possibility of higher rigidity modulus during post-yield region even with higher deterioration degree towards actual scale specimen due to show strain-hardening effect easily.

 The case of upgrading the structural performance of an existing breakwater is increasing to extend the service life and enhance the resistance against extreme forces. Therefore, the needs for reinforcing the existing caisson is increasing. The method of solidification of filling materials may be one solution. However, the effect of the solidification on reinforcement of the caisson has not been well-understood. The purpose of this study is to investigate the effect of solidification of filling materials on the load-bearing performance of the caisson through experiments.

 The static loading test was carried out with four types of the caisson model specimen. One of the results showed that the load-bearing capacity of the RC wall was significantly increased by solidification of filling materials. Moreover, the deformation of RC wall of the specimen was decreased with increasing the compressive strength of the solidified material as well as the thickness of it. From these results, the solidification of filling materials may contribute to a decrease in the deformation as well as an increase in load-bearing capacity of the RC wall of the caisson model.

 In this study, focusing on the biodegradation of surplus excavation soil, the authors conducted unconfined compression tests and investigated the influence of biodegradation on the shear strength of mixed soil with iron and steel slag. The results show that with biodegradation and ground granulated blast furnace slag, the addition of foaming agent and blow-off inhibitor did not influence the shear strength of soil. However, with fine content of steelmaking slag, the strength of specimens with biodegradation was lower than other specimens. On the other hand, without biodegradation but with ground granulated blast furnace slag, the strength of specimens without biodegradation was lower than other specimens. Moreover, the addition of foaming agent and blow-off inhibitor did not influence the deformation characteristics of soil.

 Cement-treated soils have been developed in the field geotechnical engineering, and cement-mixing has been widely utilized as a recycling technique.Authors have developed a technique called the cement-mixing and mechanical dehydration method (CMD) as one of recycling techniques for soft clay slurry and investigated the strength properties and the dehydration properties of CMD soil block.This study investigates long-term strength of CMD soil block in terms of the difference of the manufacture season and curing condition. The results obtained from this study are summarized below.

 (1) The water content of CMD soil block decreases about 15 % decrease with increasing curing days irrespective of the season of manufacture season.

 (2) Unconfined compressive strength of CMD soil block produced in summer seasons does not change from 10 MN/m². Unconfined compressive strength of those produced in winter season increases about 9 MN/m² with increasing curing days.

 (3) CMD soil block with low water-cement ratio shows high unconfined compressive strength. There is the following relationship. q_u=14.566×(W/C)^-1.5316 summer season, q_u=6.8697×(W/C)^-1.0089 for winter season.

 Recently, demand for deepening of existing quay has been increasing. A new method by grouting was developed which enables deepening of existing gravity-type quay wall without realignment by consolidating part of rubble mound. It is necessary for actual execution to interpret appropriate strength properties determined by site conditions when setting or implementing a design strength of improved clods, and determination of the quality of improved clods as well. Then several strength tests were conducted and confirmed its adaptability. In addition durability against repeated load by tidal fluctuation and earthquake was verified.

 Integrated coal gasification combined cycle (IGCC) is gathering attention because IGCC has high net thermal efficiency and superior environmental performance. In the power generation process of IGCC, coal gasification molten slag (IGCC slag) is generated as byproduct and the disposal cost of IGCC slag is high. Therefore, effective use of IGCC slag is required. In this research, it is focused on that coal fired power plants are located near the sea. If IGCC slag can be used for marine structures, transportation cost can be reduced and large amounts of IGCC slag can be consumed because volume of marine structures is relatively large.

 First, the chloride penetration resistance of concrete using IGCC slag was investigated by experiment. It was found that chloride penetration resistance is improved by using IGCC slag because concrete becomes denser with increase in the replacement ratio of IGCC slag. Next, the economical and environmental efficiency by using IGCC slag for marine structures is investigated by Data Envelopment Analysis. It is found that economical and environmental efficiency is improved by using IGCC slag and the effectiveness of using IGCC slag for marine structures was shown.

 The deterioration of reinforced concrete structures may lead to their destruction. Therefore, it is required to accurately predict the deterioration due to salt damage for maintenance and management. In particular, for the cold and snowy coastal areas suffering from the harsh environment, it is important to evaluate and verify methods using conventional salinity diffusion prediction parameters. For this study, frost damage and sea-ice wear were selected as deterioration phenomena that should be considered together with salt damage for the cold and snowy Hokkaido coast. Moreover, it was confirmed before the study that the calculation of three salinity diffusion prediction parameters is appropriate in general, and it was surmised that a combination indicators with due consideration of the durability in Hokkaido is related to differences from the Mainland of Japan. Furthermore, it is reported that, at a practical level, it is possible to predict the deterioration with almost no issues using the salinity diffusion prediction parameters calculated according to a conventional procedure not depending on the offshore area.

 In Japan, wave-dissipating blocks with legs (with and without rebar) are often used for breakwaters. On the other hand, although there are few cases in foreign countries at present, there is also a possibility that the cases where similar wave dissipating blocks are used will increase in the future. When considering the applications for foreign countries, not only the mechanical properties of concrete used in blocks, but also information on the durability of concrete as shown below is required; 1) resistance to deterioration of concrete under marine environment, 2) Penetration resistance of chloride ion due to rebar corrosion. On the other hand, there is little quantitative information on durability of blocks in Japan.

 In order to understand the durability of the concrete used for the wave-dissipating block, the actual condition was surveyed on the block in Japan that has passed for a long time in marine environments. In addition, when designing and constructing harbor concrete structures in foreign countries, points to be considered when examining the durability of concrete are also organized.

 Reinforced concrete structures located in the coastal area are affected by rebar corrosion caused by salt attack. Evaluation of residual performance is important to maintain and manage these structures. Although the structural performance and durability performance of the structure strongly depend on the presence or absence of corrosion of the rebar and the amount of corrosion reduction. Since the inspection required for deterioration diagnosis is visual inspection is standard, if it is possible to estimate the amount of corrosion of rebar directly under the cracked part by the opening width of the corrosion crack presented on the concrete surface, it contributes to advanced maintenance and management It is considered to be a thing.

 In this research, we experimentally grasp the change of deformation field of RC member cross section at the progress of rebar corrosion in RC by digital image correlation method. Furthermore, the analysis of corrosion expansion of rebar by damage model based on fracture mechanics developed in recent years, and the reproducibility of the deformation field of concrete by the analysis is examined.

 When cement treated soil contacts with seawater, white color sediments may be observed at surface of the treated soil. The white sediments have a function to suppress deterioration due to seawater. In this study, in order to clarify the conditions of formation of the sediments, an immersion test simulated marine environment using two types of cement treated soil specimens with different stabilizer was conducted. It was observed that, the sediments were generated when cement treated soil had pH greater than about 12.5 irrespective of stabilizer types. Furthermore, based on the obtained results, an alkaline aid was added at the time of preparation of cement treated soil to promote the formation of sediments. It was confirmed that the formation of sediments was promoted, and deterioration suppression effect was given to cement treated soil.

 We investigated quantitative amount and characteristic of distribute of SUSPENDED SOLIDS (SS) from mixture of dredged soil and steelmaking slag in brine with solid state and throwing method in laboratory and field experiments. We focused on fluidity (slump) about the soil and the throwing method imagined barge direct (throwing on face) and grab down (throwing in brine). In laboratory, we examined relation of ideal slump value (1-7 cm) with SS. In field, we examined characteristic of SS amount of the soil produced accordance with result of laboratory in brine every throwing method. From the above, the amount of SS from the soil can be controlled by ideal slump value and throwing method in brine.

 When we construct backfill using dredged soil improved with converter slag, we need to management the slope of accumulated mound in the sea. Therefore, we conduct laboratory test and field test to determine the relationship between fluidity and slope of accumulated mound with dredged soil improved with converter slag. From the result of the test, we found that the slope can be managed by the slump value and shear strength as the fluidity index. In addition, the slope stability was shown to be able to be expressed by shear strength, saturated density and height.