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 has been mainly applied in coastal areas such as ports and airports, and accordingly ground upheaval often becomes a problem. In this study, the performance of the new CPG (U/D (up and down) method) was compared with that of the conventional CPG (BU (bottom up) method, and the upheaval control, liquefaction countermeasure effect and the shape of the mortar improvement bodies were verified by using actual construction machinery on the ground mixed with fine particles. Consequently, the average value of the upheaval quantity at a total of 12 locations on the fine-grained ground was 7.5 mm for conventional BU method and 2.4 mm for the U/D method, therefore, the U/D method reduced the upheaval quantity by 68%. In terms of the liquefaction countermeasure effect, the increase in the SPT-N value by the U/D method was approximately 1.9 times that by the BU method. Furthermore, the mortar improvement bodies measured and analyzed using a 3D scanner were 1.23 times larger on average and 1.41 times larger in median than those of the conventional BU method.

 Long-term shoreline changes of Banzu tidal flat in Tokyo Bay were investigated using aerial photographs and satellite images. Longitudinal profiles across the foreshore and tidal flat along several transects were measured together with the sampling of seabed materials. On the basis of these data, recent topographic changes of the Banzu tidal flat were investigated. Then, regarding the tidal motion as a type of waves, the equilibrium slope concept under waves was applied to the formation of the tidal flat with a gentle slope as well as the foreshore of the marginal coast of the tidal flat. Due to the field observation and previous studies, topographic changes of tidal flat are caused by the suspension of the bottom sediment under tide, whereas that of the foreshore is caused by waves.Amodel for predicting the topographic changes was developed, taking both effects into account. In this model, the exchange of bed material between the tidal flat and the foreshore can take place.

 The separation of beach rock due to waves was investigated using satellite images and field observations, adopting the Bise coast located at the tip of Motobu Peninsula on Okinawa Island as a study site. On this coast, the debris of beach rock was transported both shoreward and southward by longshore sand transport after the separation of beach rock near the shoreline. Based on the field observation, a model for predicting three-dimensional beach changes was developed by applying the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept) and considering the separation and movement of debris of beach rock. The movement and deposition of beach rock debris on the foreshore was successfully predicted under the assumption that the debris has a large equilibrium slope as that on gravel beach. The predicted distribution of debris along the shoreline was in good agreement with the measured result.

 In the eastern part of the Odawara coast (Miyuki-no-hama coast) located west of the Sakawa River mouth, both shoreline changes in response to the variation of the Sakawa River delta and the shoreline recession due to decrease in northeastward longshore sand transport occurs. In the vicinity of the Sanno River mouth, beach width is narrow, and a submarine canyon develops offshore the shoreline with a steep slope. Because of this, severe wave overtopping occurred during Typhoon No. 19 hit this area on October 12, 2019. In this study, beach changes were investigated using aerial photographs and satellite images including the overall river delta as well as sampling test of seabed material. Based on these field data, a measure to recover the shoreline was considered by beach nourishment using coarse material.

 A model for predicting topographic changes around a river mouth subject to obliquely incident waves was developed using the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept) in place of the contour-line change model proposed by Iwase et al. A field observation was carried out at a small river flowing into Lake Hinuma on the northeast side of Oyazawa-bana sand spit to verify the applicability of the model. Using this model, the mechanism of the development of the terrace offshore of the river mouth subject to the obliquely incident waves was investigated as well as the study of the effect of the training jetty to the topography around the river mouth.

 A sandy beach named Yoshihama area with 850 m length is located northeast of the Yugawara coast in Kanagawa Prefecture. This beach has been used for a bathing beach. In recent years, rapid shoreline recession occurred at the southwest part of this beach and the foundation of the seawall of the Manazuru coastal road running through this area was exposed to waves due to erosion. The shoreline changes in this area were investigated using aerial photographs and satellite images taken until 2022. Due to the analysis, it was found that although the rapid shoreline recession occurred by storm waves associated with T1919 hit this area on October 12, 2019, the sandy beach was recovered under the calm waves after the typhoon. In this study, beach changes of the area were reproduced using the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept). The measured beach changes were successfully explained by the numerical results.

 In the port planning of Hitachi-naka Port, it is determined that the east breakwater of the port is to be extended by 2032 southward for 350 m length relative to the present condition, resulting in the total length from 5,650 m to 6,000 m. After the elongation, the direction of waves incident from the opening between the tip of the east breakwater and Isozaki fishing port breakwater rotates clockwise, resulting in the increase in incident wave angle relative to the direction normal to the shoreline. This enhances the intensity of northward longshore sand transport. Taking these changes into account, beach changes of Ajigaura Beach were predicted using the BG model. It was concluded that the recovery of a sandy beach is possible at Ajigaura Beach when an impermeable breakwater is newly constructed south of the present south breakwater together with the beach nourishment using 30,000 m³ of sand, even if the east breakwater is elongated. Moreover, the removal of the north breakwater is effective to reduce the closedness of Ajigaura Beach.

 The authors have proposed a structure in which a larger cylindrical underwater seismic control plate is partially submerged in water around the monopile foundation of an offshore wind turbine to reduce the cross-sectional force of the MP (hereinafter referred to as "MP") by the interaction between the seismic control plate and water when the MP and the seismic control plate vibrate horizontally when subjected to external forces. Although it has been confirmed from shaking table tests using an underwater seismic table that the cross-sectional force acting on the MP is reduced, a quantitative evaluation method for the resistance due to water, which is considered to be one of the seismic control mechanisms, remains an issue. In this study, the external force due to water was expressed by the Morrison equation, and the damping term of the equation of motion was modeled simply by using damper elements to reproduce the results of shaking table tests using a beam-spring model. The results of the analysis confirmed that the modeling method using the Morrison equation was generally able to reproduce the experimental results.

 Ground improved by compaction method to prevent liquefaction of sandy soil may not reach the required N-value after improvement due to the spatial variability of the soil to be improved or other reasons. In some cases, such as airport facilities with large improvement areas and complex soil types, it is difficult to evaluate the entire improvement block as a whole because the N value differs for each boring after improvement. Therefore, in this paper, the distribution of 𝐹𝐿 is represented by random field theory for a partially compacted improved ground that does not reach the required N value. Then, bearing capacity and deformation analyses considering spatial variability of the improved ground were conducted by Monte Carlo simulation using the finite element method. Based on the results, we proposed a method for verifying the bearing capacity and runway surface deformation (gradient) under aircraft transportation, which are required for airports after the event of a large-scale earthquake. As a result of the bearing capacity and deformation verification for Airport A, it was judged that the required bearing capacity and deformation performance after the earthquake were satisfied. In the future, we would like to propose a simplified method to determine the bearing capacity and deformation based on the performance-based specifications for the target ports and airports by adding case studies in which the FL distribution is varied.

 This study has developed a wave hindcasting system that can accurately determine wave conditions in near real-time (within an hour), which is essential for disaster response, offshore construction work, and other maritime operations. The system uses two wave models, WAVEWATCH III (WW3) for the external domain and Simulating WAves Nearshore (SWAN) for the seas around Japan (inner domain). Wind-forcing is provided by an atmospheric analysis GPV that offers accurate 10 m wind with a horizontal resolution of 2 km available every 30 minutes. To ensure predictive accuracy, the real-time wave hindcast system results were compared with observed wave data at various locations, and the statistical results showed that the predictions were equally or slightly precise compared to the those using the hourly analyzed atmospheric GPV.

 In this study, in order to clarify the influence of topographic changes caused by tsunami on the transport and accumulation of debris, we developed a numerical model considering both the topographic changes and debris transport, and conducted numerical studies on debris transport phenomena in a port and around a coastal area during tsunami attack. The simulations of debris transport in the harbor with movable bed showed that the debris remaining rate in the harbor may be low under the condition that the debris does not touch the ground. In addition, the simulations of debris transport on a uniform slope with movable bed showed that the effect of topographic changes on the debris remaining rate on land is relatively small. However, with topographic changes, debris may accumulate deeper into the land area than without the change. These results indicate that the necessity of considering topographic changes in predicting the transport and accumulation of debris in ports and coastal areas where the seabed is composed of fine sand.

 In order to protect port facilities and hinterlands from flooding caused by tsunamis and storm surges, a movable seawall system installed on the seabed that can close the harbor entrance without obstructing the landscape is attracting attention. These movable gates are required to withstand massive earthquakes and subsequent tsunamis without collapsing and losing their protective function. The authors proposed a new type of "movable lifting gate," which is installed below the seabed of the harbor entrance. In this paper, a method for verifying the tsunami protection effect and structural stability against the tsunami loading under a liquified ground condition is proposed to assure the safety of entire system, assuming various design conditions of an industrial complex port to be affected by the Nankai Trough earthquake. A series of analysis considering seismic, liquefaction, and tsunami loads confirmed that the "movable lifting gate" is safe against expected external forces of earthquakes and tsunamis.

 Shear loading tests were conducted on the junction pipes of steel pipe sheet pile foundations, using the interlocking conditions as a parameter. The junction type used was of the P-P type, using steel pipes with lattice pattern projections on the inner surface. The interlocking conditions included five types: standardly neutral condition, two types of compression conditions where the junction pipes compete and two types of tensile conditions where the junction pipes separate from each other.

 The test results showed that the shear characteristics (stiffness and shear force) were varied depending on the interlocking condition of the junction. The shear characteristics of the interlocking condition where the pipes only move tangentially, were generally comparable to those of the neutral condition. In addition, based on the experimental results, it was found that the inter-locking condition involving rotation of one side of the junction pipe showed different shear characteristics (some shear characteristics increased, and some decreased) compared to the neutral condition.

 In harbours for offshore wind turbines, self-propelled SEP vessels anchor at the quay and land the spudcan at the end of the leg on the seabed, with extremely high loads of 50 to 250 MN. This may cause harmful residual displacement of the quay wall after the landing of the leg, and measures to increase the bearing capacity by replacing the surface ground with crushed stone have been considered. However, the bearing capacity evaluation using the general formula derived from the Terzaghi equation is difficult due to the non-uniformity of the crushed stone-replaced ground. In this study, vertical loading model tests were first implemented in a centrifugal force field on ground containing a crushed stone layer to determine the bearing capacity characteristics. Then, to estimate the bearing capacity obtained from the model tests, an attempt was made to evaluate the bearing capacity using the circular slip analysis. The results showed that the circular slip analysis with the adjusted coefficient improved the accuracy of bearing capacity estimation.

 In order to gain a detailed understanding of the distribution of seaweed beds, which have attracted attention as a CO₂ sink, we performed measurements using airborne laser bathymetry (ALB), a green laser survey technique, at the Port of Wajima. Although the area of seaweed beds is often used to calculate CO₂ uptake, we investigated a method to calculate the volume of the seaweed as an indicator of biomass from point cloud data obtained by ALB. The conventional filter method for ALB data has difficulty discriminating underwater noise from seaweed beds; however, the point cloud reflection intensity of the data acquired by ALB can be used to discriminate between them. Using seaweed bed data and seafloor data determined by reflection intensity, the area, average height, volume, and average coverage of the seaweeds beds within the measurement area could be calculated, thus demonstrating the effectiveness of green laser survey as a method for identifying seaweed beds.

 Recently, monopile type foundation is popularly used for fixed foundation for offshore wind facilities and has tended to make the penetration length as short as possible, based on the JIP project "PISA" in Europe. In the PISA project onshore field tests are conducted and developed the enhanced 1D beam-spring models compared with 3D FEM analysis. In this project, monotonic loading tests were conducted on sandy and clay soils, and field loading tests are recommended, but field tests are not easy to conduct in terms of materials and measurement scale, such as using steel piles with a diameter of 1-2 m to simulate the prototype monopile.

 Therefore, the model tests such as centrifuge tests may be applied. However, there are no examples of generalized scaling law for static behavior, while there are some studies on the dynamic response of structures, including soils, using generalized scaling law that combines the 1G field scaling law and the centrifugal field scaling law. In this paper the application of the generalized scaling law to monotonic loading tests using centrifuge loading tests is focused, where the scale of experiments is relatively small, to analyze the behavior of piles depending on the penetration length and to reproduce it using a beam spring model. As a result, the static response of the prototype with 3/β was reproduced by the application of generalized scaling law and as to 1/β and 2/β, more modified calculation method should be considered.

 Using FVCOM, we developed a high-resolution numerical model for predicting sea conditions in Shibushi Bay based on DR_Ep and MSM forecast data. The output results of water temperature, salinity, and current velocity distribution from the SB model have high resolution and it is suggested that the model is very effective for searching fishing grounds. Furthermore, by comparing the calculated results with the observed results, it was shown that the SB model has good reproducibility for water temperature at the mouth of the bay and salinity at the back of the bay.

 In our research, we developed a carbon-fixed artificial stone by adding and fixing carbon materials to Calcia artificial stone, a low CO₂ emission material. This stone showed strength equivalent to riprap, and increased strength when replaced with CO₂ fixed steel slag. Marine algae growth tests with Undaria pinnatifida suggested its potential application to algae reef blocks. When introduced into seaweed bed construction, the total emissions after construction and shared use amounted to -20t-CO₂, indicating from the calculations that it results in carbon negativity.

 In this study, we surveyed the damage to port facilities, tsunami height, and seafloor uplift in the northwestern coastal area of the Noto Peninsula in order to clarify the actual damage caused by the Noto Peninsula earthquake in 2024.

 At Akasaki fish port, tsunami traces on the fishing port facilities were confirmed, and the inundation depth and trace height were estimated to be about 2.35 m and 4.2 m, respectively. In Kuroshima and Wajima ports, we confirmed the uplift of the seafloor. In the Kuroshima fishing port, the vertical distance of the seafloor uplift at the port mouth was about 3.7 m, and the entire port was on land. The survey results, satellite images, and laser survey geographic information indicate that the uplift of the ground on the western side of the Noto Peninsula is a factor that mitigates tsunami damage. On the other hand, the uplifted ground had little effect on the wave speed and height of the tsunami.

 Rocks and stones are widely used to prevent scour around monopiles of offshore wind turbines. In order to reduce the construction period by bulk construction, it is possible to consider using large-sized, water-permeable, high-strength geotextile with continuous chains as a scour protection measure instead of rocks and stones. In this study we treated the sheet laid on the seabed as a rigid body, and performed numerical experiments using CADMAS-SURF/3D V1.5 to investigate the uplift force exerted on the sheet by waves. For the impermeable sheet, a significant uplift force is generated when there is even a small gap between the sheet and seabed surface. A permeable sheet will experience less uplift force than an impermeable sheet, and a significant reduction in uplift force can be achieved by further minimising the gap between the sheet and seabed surface. For this reason, chains or similar materials that can easily follow deformation are suitable as the weight on the seat. The mass of the chains required for the permeable sheet is sufficient about at 1/20th of that for the impermeable sheet, indicating a significant advantage of the permeable sheet.

 In recent years, the use of mechanically compacting flowable concrete in civil engineering structures is expected to be promoted from the viewpoint of productivity improvement. In addition, as the trend toward decarbonization accelerates, the application of mechanically compacting flowable concrete can reduce construction time and thus reduce CO₂ emissions associated with the operation of construction equipment. This paper investigates the effect of mechanically compacting flowable concrete on productivity and the reduction of CO₂ emissions from construction machinery. The results suggest that the use of mechanically compacting flowable concrete improves productivity by increasing the efficiency of workability. The results also indicated that CO₂ emissions from construction machinery can be reduced because the shorter working time due to improved workability leads to less operating time of construction machinery.

 In recent years, data-driven approaches such as machine learning and deep learning have attracted attention in coastal engineering and oceanography for their potential to address computational cost and accuracy limitations. However, ensuring reliability based on physical laws remains challenging. In response, machine learning models incorporating physical laws have been developed. This study examines the applicability and learning methods of one such technique, Physics-Informed Neural Networks (PINNs), as an alternative model for numerical solutions to wave propagation. The study confirmed that PINNs estimates based on linear long-wave theory on a uniform gradient slope align with theoretical values and that the estimation time is fast. Additionally, increasing the number of collocation points during learning contributes to improved estimation accuracy, though it also increases learning time. The study provides an indicator of the appropriate number of collocation points per wavelength, considering learning costs and model performance.

 In order to clarify the influence of rubble mound configurations at the head of vertical breakwater on harbor tranquility, we have adopted the following two typical cases; one is comprised of depth contour lines with right angled corners (angular-type mound) and another one with rounded corners (rounded-type mound). The extended Green's function method to variable water depths was applied to compute the wave height distributions in the model harbor with a detached breakwater of composite type for both regular and irregular waves. Here, the two typical configurations of rubble mound at the breakwater head were examined to know the effectiveness for harbor tranquility. As a preliminary study to the above, we have also carried out the examinations on wave deformations by shoals of two different types, such as a circular shoal and a square shoal. As a result of examinations, it is clarified that the angular-type mound may cause much higher waves at the harbor pier on shore side. It is also seen that a square shoal may converges much more wave energy at the back of the shoal.

 In order to decarbonize port construction, CO₂ emissions during construction of port structures are calculated and trends are analyzed. Then, based on the results, measures to reduce CO₂ emissions are being studied. On the other hand, from the perspective of life cycle assessment, it is necessary to consider reduction measures for CO₂ emissions generated during the entire life cycle of structures, and it is also important to understand CO₂ emissions from demolition and removal of structures during and after their use.

 In this paper, embodied carbon was estimated and evaluated using an actual seawall as a case study to understand the amount of CO₂ emissions generated during the life cycle of a port structure. The CO₂ emission reduction effect of reusing stones, soil, and sand generated from the demolition of the first-lifecycle seawalls as construction materials for the second-lifecycle seawall was also estimated, assuming that a new facility with the same cross section is constructed after the demolition and removal of the seawall.

 In order to appropriately evaluate the strength of steelmaking slag mixed marine clay with natural moisture content, we conducted a laboratory mixing test using hand mixer and forced twin-screw mixer. As a result, Since marine clay with natural moisture content has low fluidity, forced twin-screw mixer was found to be appropriate. Furthermore, with the aim of proposing a laboratory mixing test method that can be carried out with small samples, we investigated the following combinations: (1) use of Hobart mixer, (2) removal of modifiers with a particle size of 10 mm or more, and (3) use of specimens with a diameter of 50 mm. As a result, using a Hobart mixer with modified stirring blades, it was possible to mix to the same quality as a forced twin-screw mixer. In addition, since the effect of removing 10 mm or more of modifying material on the 28-day strength is enough small, and there was a good strength correlation between the 100 mm diameter specimen and the 50 mm diameter specimen. From these results, it was found that the strength could be evaluated with a small amount of sample by appropriately correcting the specimen dimensions.

 The tidal flat is subjected to tidal intrusion of seawater with spatially and temporally different characteristics. The bottom water that flows up to the tidal flats contains a variety of suspended and dissolved organic matter, which may have a significant impact on the tidal flat environment. The oxidation-reduction potential (ORP) indicates the potential for redox reactions between dissolved ions and suspended solids electrodes in seawater. It thus provides an indicator for estimating the impact of redox substances on the tidal flat environment. In contrast, ORP sensors using sensitive membranes are not suitable for continuous measurement in the field environment where organisms inhabit. This paper aims to develop an ORP sensor to measure the effect of upwelling water on the tidal flat environment and to understand the electrode reaction characteristics to enable the development of a device that can measure changes in the tidal flat environment in response to upwelling water.

 In this study, a series of laboratory experiments were conducted to investigate the drainage properties of the polymer mixed soils. The results showed that, although the drainage tendency differs depending on the type of soil and polymer used in the experiments, short-term drainage performance improves under certain conditions. It was also found that this short-term drainage performance can be evaluated by using the activity of the original soil. Furthermore, consolidation test results showed that coefficient of consolidation and coefficient of permeability of the polymer mixed soils were lower than those of the subject soil. This was inconsistent with the short-term drainage performance improves observed in the simple drainage test. The short-term drainage considered to be the discharge of excess water that was not taken up during floc formation.

 Centrifuge model tests were conducted to clarify the basic characteristics of resistance to caisson overturning of a reinforcing embankment composed of wave-dissipating blocks. The behavior of the reinforcing embankment during caisson overturning was observed by static loading tests, and the resisting moment was measured. It was found that the resisting moment tended to increase as the inclination angle increased, but as the inclination angle increased, the reinforcing embankment were deformed and the initial resisting force against repeated external forces decreased. However, for a small tilt angle of 0.5 degrees, the deformation of the embankment is small, and the resistance force is maintained against the repetitive external force. As for the effect of the shape of the embankments on the resisting moment, the shape effect is relatively small if the number of total blocks is the same. However, it is effective to make the height of the embankments higher than the thickness of two layers.

 In response to the problems of submerged breakwater installed as a countermeasure against coastal erosion, such as rising water levels behind submerged breakwater and scouring by offshore currents, we proposed a flat plate type submerged breakwater that is a structural form only at the top of the submerged breakwater, and through hydraulic model experiments and numerical experiments, the high wave damping effect and the water level rise suppression effect behind the structure were demonstrated.

 As a result, it was confirmed that a flat plate type submerged breakwater with a height similar to the top length of the submerged breakwater can be expected to have a wave dissipation effect similar to that of a submerged breakwater. Furthermore, it was clarified that the water level rise can be suppressed and the offshore flow velocity can be reduced by removing a lower part of the submerged breakwater as tunnel. Although it is possible to reduce the rise in water level with a removal of lower part, from the viewpoint of preventing scouring, it was confirmed that the flat plate type submerged breakwater was particularly effective because the off-shore flow velocity decreases as the increase of removal area.

 Existing hydraulic experiments on wave pressure and force acting on a vertical wall induced by a bore-like tsunami containing kaolin as a bottom sediment were simulated using a numerical model FS3M, that can consider the apparent density and viscosity of fluid containing the sediment. Through a comparison with experimental data, the predictive capability of the model was demonstrated in terms of water level, quasi-static pressure on the vertical wall, and force on the vertical wall induced by quasistatic pressure, except for surge-front pressure. Furthermore, it was found that the maximum wave force on the vertical wall caused by quasi-static pressure can be larger at low concentrations and is always smaller at high concentrations compared to that for clear water multiplied by the apparent specific weight of the water containing the kaolin. If a suspended sediment concentration of 7% is assumed in tsunamis, the result above supports the ASCE 7 standards and the FEMA P646 guidelines.

 The effectiveness of flume-type anti-oscillation tanks against the motion of a floating caisson close to rubble mound and existing caissons during installation work was investigated from hydraulic experiments using regular and unidirectional irregular waves. The experiments on regular waves showed that the non-dimensional amplitude of the heave of the floating caisson decreased with an increase in the free water filled in the anti-oscillation tanks when the incident wave period was close to the natural period of the heave. The non-dimensional amplitude of the pitch was decreased by the presence of the free water in the anti-oscillation tanks regardless of the incident wave period. The non-dimensional amplitude of the roll was less affected by the free water in short wave conditions, while it could be increased by the presence of the free water in long wave conditions. Similar tendencies were observed in the experiments for unidirectional irregular waves. These results suggested the effectiveness of anti-oscillation tanks against the heave and pitch of a floating caisson during installation work.

 Microplastics (MPs) were detected in sand and mud samples collected from a variety of locations, at a total of 14 survey points, along the coast of Tokyo Bay. The relationship between the MPs contained in the digestive system and individual differences in the bivalve snail Mercenaria mercenaria inhabiting the Yatsu tidal flat in the innermost part of Tokyo Bay, and the amount of false excrement and MPs content from the feeding experiments with the addition of MPs. The number of MPs was counted and the water purification ability and impact on the ecosystem were studied. As a result, a positive correlation was found between the shell length and mass weight of Mercenaria mercenaria, and regarding the relationship between weight and MP content, the MP content began to spread irregularly when the weight exceeded 50 g and tended to decrease when the weight exceeded 150 g. In addition, although the added MPs were detected in the excreted simulated feces, it was not detected in the body, which affected the amount of filtered water as a biological function.

 One type of seawalls is the gravity type, which is often complex due to existing foundations and buried sheet piles. In this case, the seepage in the foundation ground when the tsunami arrives is complex. In addition to being an unsaturated seepage problem, it is assumed that air is trapped and pneumatic pressure is generated, complicating the problem. In this study, centrifuge model tests were carried out on a seawall during a large overtopping tsunami, focusing on ground seepage. The results showed that even before the crushed stone layer below the seawall block was filled with water, the pneumatic pressure inside the stone layer increased, which could lead to a lifting pressure. The possibility of piping failure from the sand layer to the stone layer and the countermeasures against it were also demonstrated. It was also shown that overflow scouring of the ground behind the seawall caused ground failure and movement of the seawall block.

 Calcia improved soil is a material that is a mixture of dredged soil and steelmaking slag, and is used as a reclamation material, a construction material for shallow areas, etc. Since steelmaking slag is a by-product, the CO₂ emissions of calcia improved soil are low. As a method for further decarbonization, it is possible to use calcia improved soil in which CO₂ is fixed in steelmaking slag or calcia improved soil in which carbon-containing substances are mixed.

 As a result of mixing tests, the strength of calcia improved soil using steelmaking slag that fixed CO₂ increased when the CaCO₃ content was 6 to 8%, and the strength increased with calcia improved soil that mixed calcium carbonate and biochar. In addition, CO₂ emissions were negative for calcia improved soil using CO₂-fixing slag and calcia improved soil mixed with biochar.

 It is expected to promote ecological activity by increasing sand diameter particles with increasing complexity on tidal flats created using GCA. In this study, we investigated the effects of GCA on the ecological regeneration of reductive tidal flats (tidal flats constructed with GCA) where organic sludge from sewage systems (oil and grease, etc.) is continuously deposited, and analyzed the properties of the organic composition of the mud sediment, to clarify the effects (increase in sand diameter particles with increasing complexity). The results showed a relationship between biological activity and an increase in the size of sand particles with the increase in organic matter complexity. The organic matter content, elemental composition, grain size analysis and acid degradation tests were analyzed for each combustion temperature range of the sediment mud based on the loss by combustion method (IL₃₀₀ method).

 In the Tottori Sand Dune Beach, where beach nourishment and sand bypassing have been implemented as part of a coastal conservation plan, the installation of artificial reef breakwaters was completed in 2017. The survey data conducted since 2004 were analyzed by adding data from 2009. The empirical orthogonal function (EOF) was used for the shoreline analysis, and the CSHOR model for the on-offshore cross beach profile. The shoreline remained almost stable after the installation of artificial reef breakwaters was completed, and difference in wave number on the west side and the east side were observed in cusp and other uneven terrain. It was confirmed that the critical water depth of sediment movement calculated with the top 5% of wave heights observed at Tottori Port is corresponding appropriately to the site. Despite efforts using the CSHORE model, the study did not yield reasonable results, and it is necessary to consider two dimensional model and validate parameters for more accurate analysis.

 Inclined capillary barriers (CB) are an efficient slope disaster prevention technology to control rainfall infiltration, which using an upper finer soil layer and a lower coarser soil layer to com-pose layered grounds. Therefore, CB has the function to block rainwater infiltration and to act as a drainage function in grounds. Moreover, it has been found that crushed shell particles can be used instead of general coarser soil layers in CB.The purpose of this paper is to evaluate the rainfall infiltration control function of shellshaped CB, which have been attracting attention as a countermeasure for improving the stability of embankments and embankments during short duration heavy rainfall, which has been increasing in recent years. Crushed shells, which are a component of shell type CB, have a flat particle shape, and their anisotropic permeability and pore connectivity coefficient, one of the unsaturated infiltration characteristics, have not been clarified. In this study, two parameters that can reproduce the measured results were numerically and experimentally identified through laboratory experiments and saturated-unsaturated seepage flow analysis.

 The purpose of this study is to obtain basic knowledge for a design that considers the reinforcing effect of Counter-Weight Block (hereinafter referred to as "CWB") reinforcement embankment against the overturning of a breakwater. We investigated the effect of different cross-section figures and structures of CWB reinforcement embankment on the reinforcing effect against overturning using centrifuge model tests. The results indicated that a staircase cross-section figure is desirable for the CWB reinforcement embankment. However, when the caisson wall and the CWB reinforcement embankment are in close contact, a gap will form between the caisson wall and the CWB reinforcement embankment after the first overturning action. Consequently, the resisting moment at the initial stage of the second and subsequent overturning actions becomes minimal. It was shown that the use of filling stones between the caisson wall and the CWB reinforcement embankment in advance contributes to improving the reinforcing effect against repeated overturning actions. However, the challenge with large-scale overturning is that the crown height of the filling stones gradually decreases, and the reinforcing effect becomes smaller.

 Jacket-type earth retaining walls are consist of jackets and steel pipe sheet piles. AU-shaped structure have proposed which have additional steel pipe sheet piles in a direction perpendicular to the direction of extension of the wall to increase the flexural rigidity of the entire structure. In this study, the horizontal resistance behavior of high flexural rigidity pile and effect of reinforcing wall’s rigidity partially are considered by model loading experiments. As a result, high rigidity model piles tend to fall over and pull against the ground with increasing load. It is proved that the U-shaped structure with partial high flexural rigidity resists more than I-shaped one with the same flexural rigidity with less steel materials.

 In tropical and subtropical countries, there is a strong trend to using mangrove forests as a disaster prevention function, and from a technological support perspective, it is important to survey mangrove forests and verify their disaster prevention effects. However, traditional surveys targeting mangrove forests commonly use leveling surveys, making it difficult to track changes in mangrove forests and surrounding morphology with large time-spatial scale.

 In this study, we conducted a photogrammetry using RTK-UAV targeting mangrove forests and surrounding morphology in the Nagura Bay of Ishigaki City. As a result, we verified that various parameters of mangrove morphology good accuracy local measurements, and we also conducted an analysis of factors influencing sediment accumulation trends on the offshore and onshore sides of mangrove forests.

 It is desirable to position efforts to decarbonize port construction in the formation of a "carbon neutral port" (CNP). In order to efficiently reduce CO₂ emissions during construction of port structures, a simple estimation of CO₂ emissions at the design stage would be useful for evaluating specific low-carbon measures and their effects.

 In this study, CO₂ emissions during construction were first calculated for six PC piers, and a trend analysis was conducted. In addition, a simple estimation method of CO₂ emissions from the superstructure of PC piers was studied for use in the design phase. As a result of the trend analysis, most of the CO₂ emissions were derived from materials, and a correlation was observed between the CO₂ emissions and the total mass of the steel pipe piles. The proposed simplified estimation method was able to estimate the CO₂ emissions from the construction of the superstructure with an accuracy of 65 to 87 %.

 Sea grass algae, which are a source of CO₂ absorption, are attracting attention for their effective-ness in reducing global warming as "blue carbon". However, the Seto Inland Sea has long experienced a decline in its algal beds due to a variety of factors, and its biological resources have also been on the decline. In recent years, technological development for the creation of seaweed beds has been actively carried out in many parts of Japan, and the creation of artificial seaweed beds is desired.

 This study confirmed the superiority of artificial reefs with a flow control function over existing technologies by quantitatively evaluating them through hydraulic experiments and evaluating their functions after they have been sunk. The objective was to develop a new seaweed bed creation technology by verifying the effect of artificial reefs on the population of organisms, carbon fixation and CO₂ reduction.

 As wind turbines become larger, monopiles(MPs), which are the main type of foundation for offshore wind farms, tend to become larger, especially in Japan, due to the increase in seismic load, which poses a challenge to their construction by SEP vessels. A structure to reduce the seismic sectional force of the MP foundation is proposed, in which a cylindrical underwater seismic control panel("seismic control panel") covering the MP is partially submerged in the water. However, compared to the existing MP, the location where the seismic isolation plate is installed may increase wave action due to the increased outer diameter, making it necessary to study the effect of waves. In this study, the wave resistance of MP foundations with seismic control panel was examined by comparing the bending strain at the base of MP foundations based on hydraulic model experiments and dynamic analysis.As a result, it was confirmed that the MP with seismic control panel has no adverse effect on wave resistance except for the effect of increased outer diameter, which is usually assumed in the foundation design.

 In this study, accuracy of evaluation methods of site amplification factors [SAF] without in-situ earthquake observations was verified based on 27 sites all over Japan. There are 3 methods without in-situ earthquake observations for port and harbor facilities. One is the method based on microtremor measurements [Method1], the second is the improved method of the Method1, which is applied in a case that peak amplitude of microtremor horizontal to vertical spectral ratio [HVSR] of two sites ((1) site where the facility is being constructed, (2) site of nearby strong motion station) are more than about twice as much or more [Method1’], and the third is the method based on empirical relation between SAF at a port and nearby strong motion station [Method2]. On the other hand, there is the evaluation method of SAF based on in-situ earthquake observations [Method0] as an especially reliable method. We verified the 3 methods (Method1, Method1’, Method2) using the sum of squared errors from Method0 [SSE], SSE weighted by SAF evaluated by the method0 [Weighted SSE], distance between the peak frequencies of the two SAF [Δf] and distance between the peak heights of the two SAF [ΔPeak_SAF]. Furthermore, we verified the impact on structural design of port and harbor facilities using velocity power spectrum intensity [PSI] as an indicator. As a result, Method1 performed the best based on the comparison based on SSE, Δf andΔPeak_SAF. However, it was revealed that there are some cases that the SAF evaluated by the Method1 deviate from the SAF evaluated by the Method0. Therefore, we described probable factors of the deviations and some notes for structural design in this paper.

 The authors have proposed a seismic control structure in which a larger cylindrical underwater seismic control panel is partially submerged around the monopile foundation of an offshore wind turbine. This structure is expected to reduce the seismic cross-sectional force generated in the monopile by the interaction with water during vibration, and its effectiveness has been confirmed by underwater shaking table tests. However, the mechanism of seismic control has not been fully clarified. In this study, we focused on the liquid motion of water between the underwater seismic control panel and the monopile as one of the seismic control mechanisms, and conducted shaking table tests around the seismic control plate to investigate the vibration characteristics due to the liquid motion. From the results, it was clarified that the fluid force due to the liquid motion contributes to the seismic resistance and this force can be modeled by a mass point, a spring and a damper in the numerical analysis.

 Recently, in order to improve productivity at construction sites, there are increasing expectations for precasting for port structures such as piers. The authors have proposed a new pile cap connection method using loop joints when the precast method is used for the upper concrete of a pile type pier. In this study, in order to reduce the construction range of cast-in-place concrete and reduce offshore work, we conducted an experiment to examine the practicality of a loop joint that has a loop diameter that is the minimum bending radius of the reinforcing bar and does not have a straight lap joint. From the results of tensile test using small test specimens and cyclic loading tests using inverted T-shaped test specimens simulating pile cap joints, was confirmed that the precast joints to which this construction method was applied can ensure sufficient strength and deformation performance against the expected loads by placing many horizontal reinforcing bars inside the loop joints and increasing the amount of loop reinforcing bars.

 In recent years, for the loading of offshore wind power generation equipment, quay wall structures that construct block or lattice-shaped walls through deep mixing methods have been widely adopted as the structure of base ports. Quay walls that load large offshore wind turbines are expected to withstand significant loads, necessitating a unified method for evaluating the allowable load capacity. However, for the ground improved by deep mixing method, not only the method for evaluating ground bearing capacity but also the clarification of its failure modes has been insufficiently organized. This study aims to establish a method for evaluating the ground bearing capacity assuming a semi-infinite state of the improved ground. By conducting vertical load experiments in a centrifugal force field, it elucidates the differences in failure modes based on the compressibility of the improved ground's parent material and proposes a method for evaluating ground bearing capacity from the unconfined compression strength of the improved ground.

 Toward the application of numerical analysis in evaluating local scouring around offshore wind turbine foundations, a three-dimensional coupled fluid-structure-sediment-seabed interaction model (FS3M) was applied to hydraulic experiments on local scouring around a monopile and suction buckets in Yamano and Furuhata (2022). From a comparison with experimental data, the predictive capability of the model was demonstrated in terms of the nondimensional maximum scour depth, the location of the maximum scour depth, and the location of deposition for the monopile and the suction bucket with diagonal members without openings. The predictive capability was also demonstrated in terms of the location of the maximum scour depth and the location of accumulation for the suction bucket without diagonal members and the suction bucket with diagonal members with openings. However, it was found that there were still issues to be solved in other aspects. This suggested that it is essential to improve numerical accuracy by calibrating physical parameters related to sediment transport.

 In recent years, container terminals (CTs) have been required to improve their productivity to cope with the global increase of cargo transportation demand and labor shortages, and to decarbonize for achieving the carbon-neutral society. CTs using Automated Storage and Retrieval System (ASRS) have the advantages of increasing the number of container storage tiers, eliminating the need for rehandling of containers, and leveling off work load of cargo handling in the CT through decentralized storage, but few studies have analyzed its cargo handling efficiency in detail. In this study, the existing CTs using ASRS were classified and their characteristics were analyzed, and then the storage capacity, cargo handling speed and CO₂ emissions were quantitatively evaluated by numerical simulation. From the results, the number of tiers that realize both high storage capacity and cargo handling speed, and the CO₂ emissions by each cargo handling machine and operation in certain conditions were clarified. Based on the above, a direction for upgrading cargo handling, such as a further increase in storage capacity and a reduction in CO₂ emissions, at the CTs using ASRS were proposed.

 In recent years, a shift to a recycling-oriented society has been called for, and the promotion of the recycling of waste resources is an urgent task. One of the waste resources is scallop shells, a by-product of fisheries, but they are classified as industrial waste, and their utilization has not progressed due to disposal costs. In this respect, its utilization as a construction material is expected, but the use of lightweight scallop shells (crushed scallop shells) as a substitute for sand is limited, and its utilization is far from sufficient. On the other hand, crushed scallop shells are expected to be applied to pore water pressure dissipation method during earthquakes because of their high permeability by adjusting the particle size, etc. In this study, a laboratory shaking table was used for the experiment.

 In this study, we investigated the particle emergence of crushed shells in a columnar drain against excess pore water pressure during earthquakes by laboratory shaking table experiments. As a result, it was found that the crushed shells are effective in dissipating pore water pressure, and that particles do not float in the drain during shaking and that the drain maintains its function.