Movement mechanism of tsunami boulders was analyzed by three-dimensional numerical simulations of coupled fluid-solid motions. Flume experiments were firstly performed where dam-break flows moved tsunami boulders. Then, the numerical simulations were performed on the experimental results. The numerical simulation results reproduced well the relation between dam depths and movement distances of tsunami boulders measured in the plural experiments and time variation of water levels around a tsunami boulder. A control volume around the tsunami boulder that is fixed to the moving boulder was determined, and the temporal variation of the fluid force and momentum exchange at the border of the control volume were revealed from the numerical simulation results. Moreover, investigation on fluid and contact forces revealed the characteristic mechanism where tsunami boulders move so that streamwise fluid forces balance to the friction forces exerted from the channel bottom that is roughly governed by the buoyancy of the tsunami boulder.

 Adaptive Mesh Refinement (AMR) and Distributed Memory Parallel (DMP) techniques accompany complexities in storing and updating the information of neighboring cells especially in the case of unstructured grids. In this study, we have proposed the grid system named as “Systematic Grid” to remedy this problem based on the object-oriented design. This grid system employs a hierarchical structure of objects composed of Domain, Block, Element and Connector objects. These objects are designed as units of parallelization, mesh refinement, variable management and data exchange, respectively. The Domain object is the collection of the Block objects and the Element objects with an arbitrary shape and resolution are uniformly embedded in the Block object. Therefore, there always exists a simple grid structure inside the Block object. The connections between these objects are controlled by the Connector objects which absorb the difference in resolution for data communication. We constructed a hydrodynamic models based on the Systematic Grid with the Discontinuous Galerkin (DG) method and applied to advection and wave problems. As a consequence, we obtained reasonable accuracy and efficiency for these problems with the present model.

 A risk evaluation method for erosion type levee breach based on understanding the existing river conditions was proposed. The method was developed for 97.5 to 106.5 km of the Chikuma River, which suffered a left bank levee breach during the Typhoon No. 19 flood in 2019. The risk evaluation was conducted using the information available prior to the 2019 flood, and the levee breach area, which was located on the opposite bank of the attacking point of river flow before the flood, was detected as high risk area. The practical issues found in the process of developing the method were systematically organized in a series of flows leading to the evaluation results, and the constraints for solving each issue, the target level required for technological development, and the necessity of acquiring river channel and structure data that affect the risk evaluation in practice have been concretely presented.

 The results of irregular wave studies are usually organized in the form of mean wave heights or significant wave heights. Thus, both the large waves that dominate the hydraulic phenomena and the smaller waves that do not dominate the hydraulic phenomena are lumped together in the statistics. Therefore, it is sometimes difficult to predict the effects of large waves that cause disasters based on their average values. For regular waves, this study clarifies the hydraulic phenomena around an artificial reef through large scale experiments and numerical calculations by CADMAS-SURF. The mean quantity is obtained as an expected value by assuming the Rayleigh distribution for the wave height appearance distribution of irregular waves. This is then correlated with the case using irregular waves. The hydraulic phenomena caused by several waves during large waves of irregular waves can be understood through results of regular waves.

 A theoretical formula of permeability tensor based on crack tensor has been proposed as an effective stress-dependent hydraulic conductivity tensor for jointed rock masses modeled as three sets of orthogonal joints. In this study, a stress-dependent equation was developed for application to general joint structures obtained from field joint surveys. It was used to investigate changes in the anisotropy of the hydraulic conductivity tensor with respect to depth. The anisotropy of the hydraulic conductivity tensor was expressed by the parameter FA using the invariants of the hydraulic conductivity tensor, and the rotation of the principal direction is also shown. The results were as follows:

 • If the stress field is isotropic and the pseudo-elasticity index H of the joint is constant, the anisotropy of the hydraulic conductivity tensor is determined by the anisotropy of the joint structure and is maintained with respect to depth. In this case, the average hydraulic conductivity is uniquely depth-dependent, regardless of the anisotropy of the crack structure.

 • Under non-isotropic stress, the depth change in FA and rotation of the anisotropic principal axis are noticeable in shallow areas and move to deeper areas depending on the H of the joint. Therefore, the estimation of H is important.

 • Without considering the mutual interference between the joint structure and ground stress, it is not possible to infer the directional dependence of the hydraulic conductivity tensor.

 This study interviewed 12 experts from overseas cities with the aim of learning from examples in overseas countries about the impact of electric kickboard sharing on the public, and to assist in the consideration of policies for the full-scale introduction of the system in Japan. As a result, several experts indicated that a night-time ban on electric kickboards is effective as a measure to prevent drunk driving, that sidewalk riding is undesirable for pedestrian safety and stress, and that they had issues with traffic education on electric kickboards but were looking for specific educational entities and methods. Other issues of particular interest indicated that “Restrictions should be set on the entry of operators”, “It is uncertain whether this mobility is really a sustainable vehicle” and “Helmet use is strongly recommended based on patient data regarding accidents”, which should be newly or continuously discussed in the future.

 One lesson learned from the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant is that initiatives should be introduced to proactively disclose information related to nuclear safety design that contributes to the public interest and expert knowledge and that discussions with society should be respected. In this study, experts and engineers involved in the JSCE Committee on Nuclear Civil Engineering conducted a survey using the Delphi method for consensus building to clarify their role within society and the type of risk communications for which they should aim. Experts and engineers want information dissemination and dialogue with society about “how risk assessment is incorporated into design” (such that the design considers uncertainties related to natural hazards such as earthquakes). This recognition of the need suggests that communication with society is still lacking, despite a substantial shift in attitude from “explaining about safety” to “facing the risks and talking about the necessity of safety.” This study revealed that support is needed to shift the “interaction” model. The results of this study can be used for risk communication during normal times as a shared goal of nuclear safety design.

 Due to the aging of infrastructure, the population decline, and the severe financial situation, the choice and concentration are advocated from the viewpoint of efficiency of public investment. In the choice and concentration, cost-benefit evaluation by the three benefits has become established. However, many local communities appeal to the Government about the benefit from regional characteristics and needs. We analyze how the Government evaluate benefits and decide policies in fact. We raise the issue of the choice and concentration, the direction of study about evaluation and the importance of considering not only efficiency but also the essential value of roads.

 The opening ceremonies of new bridges named “watarizome” has been conducted for centuries based on Shinto-style in Japan. Three generations of couples consisting grand-parents, parents and young couple are invited to the ceremony and walk on the bridge together as the first users in order to give hope for longevity of the structure. This paper describes about the transition and details of the ceremony base on existing documents. I expect that the set of information in this paper which was non-existent will contribute to the tradition of this unique civil engineering ceremony for the future.

 In this report, we conducted a questionnaire survey of the Takatamatsubara Tsunami Memorial Park to understand the use of the park in its third year of operation, considering its design characteristics. The results of the survey showed that visitors' perceptions of the park were categorized into five types of entities: "Focus on learning about disaster prevention", "Recalling Takatamatsubara landscape", "Mourning and praying for the sea", "Enjoying multifunctional activities", and "Symbolic prayer for recovery". Furthermore, these were discussed in terms of social demographics, purpose of visit, and relationship with facilities which left impressions, and information for future maintenance, management, and operation was presented.

 In the past, some cases of incomplete grout filling have been reported in post-tensioned PC bridges. In this study, we conducted accelerated corrosion experiments and static loading tests on specimens simulating grout void near the PC steel bending-up zone. The results revealed that the decrease in tension force due to corrosion was attributed not only to the reduced cross sectional area of the PC steel but also to the reduction in stiffness of the structural concrete caused by corrosion-induced cracking. Furthermore, regarding the specimens with inadequate grout filling designed to have a shear strength lower than the bending strength, it was observed that when the PC steel is not corroded, bending failure occurs, whereas when the PC steel is corroded, shear failure is identified. Finally, a reproducible model of the experiment was constructed using 3D nonlinear finite element method.

 In the event of a major earthquake directly beneath the capital, widespread damage to critical infrastructure such as sewage systems, water supply, and gas networks is anticipated, raising concerns about the concurrent competition for emergency restoration among these infrastructures. This study aims to quantify the effectiveness of emergency restoration in sewer network, employing the concept of the resilience triangle, for effectively and rationally advance emergency restoration. Specifically, targeting areas prone to liquefaction, scenarios were established to prioritize the emergency restoration of sewage systems, as well as scenarios where sewage system restoration is a lower priority. The study verified differences in resilience between the two scenarios and examined the improvement effects of each scenario. Additionally, an attempt was made to quantitatively demonstrate the impact of seismic reinforcement projects from a resilience perspective. The novel methodology presented in this research allows for practical applications of emergency restoration procedures and the selection of project locations for seismic reinforcement projects in sewage systems.