The solute transport behaviors in porous materials must be predicted to evaluate the performance of the sandy ground improvement and concrete structure repair by the injection of a chemical solution. This paper presents a simple analytical model for predicting the time variations in the solution concentration distribution by advection, mechanical dispersion and diffusion phenomena caused by the solution injection in porous materials. The governing equation for solute transport is derived by assuming that the solution infiltration by injection and solute diffusion in porous materials can be separately expressed as advection, mechanical dispersion and diffusion phenomena. Additionally, the advection term in the governing equation is defined by considering the effect of variation of the driving force for solution infiltration due to the pressure loss in pores of the porous materials. An analytical solution is derived by solving the governing equation, which is a nonlinear advection-diffusion equation. The analytical results suggested that the time variations in the solution concentration distribution depended on the advection phenomenon by the solution injection in the initial stage of the solute transport process, and that the solute was transported over a long period owing to the mechanical dispersion phenomenon.

 Concrete structures in coastal areas are designed in consideration of collisions with tsunami debris. The lack of knowledge on evaluating the integrity of small boats (FRP boats) that may drift in collisions has been a challenge in tsunami resistant design, and two-dimensional static analysis is usually used in the design of seawalls. We proposed a method to evaluate the three-dimensional dynamic response of FRP boats by setting the axial stiffness based on the load-displacement relationship of FRP boats and inputting the collision load by a spring. The results of the response evaluation of the structure obtained by this method were compared with the results of the conventional response evaluation, and the influence of the difference in analysis methods was confirmed.

 During the torrential rainfall in July 2020, Hitoyoshi City was severely damaged by the combination of internal flooding and external flooding. In this study, we developed real-time inundation model for evacuation and community planning (RIMEC) in Hitoyoshi city using the results of the high-precision internal flooding analysis (2D-IMEC) as teacher data. By applying RIMEC to multiple heavy rainfall events in the past, we found the new evacuation criterion considering internal flooding, and showed its application to the real-time prediction of internal flooding.

 Furthermore, we showed that it is possible to share the risk of flooding and the concept of damage mitigation with local stakeholders by creating the basin water balance map based on the analysis results of 2D-IMEC and RIMEC, which clearly shows the changes in the flooding situation and its amount.

 This study first clarifies the definitions of the wave runup reduction factor used in this paper, the roughness factor in the EurOtop manual used in the USA and Europe, and the coefficient of equivalent crown height used in Japan, and then shows how the mean wave overtopping discharge changes as the reduction factor changes. After referring to Goda’s diagrams of wave overtopping discharge of vertical seawalls and wave-dissipating block covered seawalls and to the runup reduction factor estimated from recently carried experiments for runup reduction of both seawalls, the runup reduction factor was modeled as a function of installed water depth of seawalls. The experimental results of EurOtop’s block-covered breakwater are well predicted by IFORM using the proper runup reduction factor, and recent experimental data of seawall covered with wave-dissipating blocks are also well predicted by IFORM with safety evaluation for small non-dimensional wave overtopping discharge less than 10^-4

 A calculation model was developed to calculate ground reaction coefficient at the ground surface in the event of pipe failure to obtain knowledge useful for improving the efficiency of inspections. Comparison with the model and full-scale experiments simulating a failed pipe confirmed that the model can evaluate the ground reaction coefficient on the safe side. Comparison with geotechnical investigations of damaged pipes in the field suggests that, after loosening is generated by damage to the pipes, loosening may develop, resulting in a progressive decrease in the ground reaction coefficient. Also, a simplified evaluation method for the evaluation of degree of influence on track displacement due to pipe failure was developed based on the calculation model, and the result was summarized in the form of a chart with the axes of diameter and depth. The chart can be utilized to identify pipes that should be inspected intensively.

 According to the Ministry of Land, Infrastructure, Transport and Tourism, the external diseconomies caused by the increasing number of mismanaged vacant houses in Japan range from disaster prevention and crime prevention to sanitation and scenery. Therefore, it is useful to make practical use of the increasing number of vacant houses to create sustainable, casual places for social interaction. In this study, we conducted a questionnaire and interview survey of (1) local residents, (2) event participants, and (3) event planners at an event using vacant houses in Misato Town, Kumamoto Prefecture, to examine the effects of exchange in the community. The purpose of this study was to clarify the conditions and effects of promoting interactions within the community based on the actual conditions of interactions using vacant houses. The results of the study revealed that the relationships formed during the exchange events led to the following changes in awareness: (1) "a more apparent interest in the community" among neighborhood residents, (2) "discovery of local attractions" among event participants, and (3) "willingness to continue holding events" among event planners.

 To increase the number of regional experience seekers in region that are inaccessible by land routes, expanding the use of aircraft is necessary. In this study, we focused on the population that uses aircraft, and clarified the characteristics of the destinations and the types of activities taken part in, as well as what is necessary for encouraging a broader and deeper involvement in the region. We found that the most popular destinations were located in areas with trunklines or relatively large local airports. We also found that creating a system that provide incentives such as mileage may be useful in increasing the number of regional experience seekers. Finally, we found that the usability of transportation, financial burdens on visiting the region, limited time availability are the barriers for being a regional experience seekers.

 This study develops a demand-driven transport network formation model that explains the emergence of the Hub-and-Spoke (HS) structure. To this end, we revisit and reformulate Mori (2012) model to provide a game-theoretic framework for understanding how passengers’ choices shape the transport network. We then show that this model can be viewed as a potential game, allowing us to characterize its equilibria using the potential function. Furthermore, we demonstrate that the potential maximization problem can be transformed into the Minimum Concave-cost Network Flow Problem (MCNFP). Based on this, we introduce a global optimization algorithm for solving MCNFP to derive the stochastically stable equilibrium. Through numerical experiments, we show that transport networks with an HS structure emerge as the stochastically stable equilibrium of the game.

 Concrete work often encounters challenges such as cold joints and poor filling in hot weather conditions. These issues primarily arise due to the increased loss of fluidity and shortened setting time caused by elevated concrete temperatures. In light of these concerns, this study proposes a new chemical admixture incorporating fluidity retainers and setting retarders to address the abovementioned issues associated with hot weather concreting. This study shows three significant contributions: 1) the admixture formulation consisting of poly-carboxylic acid, oxy-carboxylic acid, and sugar effectively mitigates slump loss and prolongs setting time in high temperatures; 2) concrete incorporating the proposed admixture significantly enhances workability retention and extends setting time, enabling a comparable performance level at 20°C to be achieved even at temperatures exceeding 35°C; 3) the admixture does not adversely affect concrete strength and durability. Subsequently, in a practical implementation of the admixture on an actual construction project under hot weather conditions, it was observed that concrete incorporating the admixture exhibited performance levels equivalent to these achieved at 20°C.

 The effect of a highly concentrated NaCl solution used as mixing water on the performance of concrete was experimentally investigated. The experimental results showed that when the NaCl concentration in the mixing water was 20% or higher, the adiabatic temperature rise and heat generation rate were smaller than those of tap water, and drying shrinkage was also suppressed as a result of the suppression of drying. The compressive strength of the material was found to be about the same in outdoor air curing as in sealed curing, although the 28-day strength was reduced by about 20%. Numerical results indicate that the use of NaCl solution of more than 20% as mixing water is effective in preventing initial cracking due to drying and thermal stress. The results also suggest that the use of aqueous NaCl solution is effective in preventing steel corrosion due to the significant increase in concrete saturation and the decrease in dissolved oxygen content caused by the presence of solute.

 This study aims to investigate the corrosion inhibition effect of cathodic protection with the pre-injection of an electrolyte solution and crack injection repair as a pretreatment on reinforced concrete with corrosion-induced cracks. A current supply experiment for 244 days was conducted with mortar specimens with corrosion-induced cracks generated by dry-wet cycling. The collected data through the experiment includes the repair condition of the speci-mens, the growth of the corrosion-induced cracks, the amount of cathodic polarization and polarization characteristic of the rebar, and the corrosion mass loss of the rebars. The average corrosion mass loss of the specimens pretreated with the pre-injection of a 10 % calcium nitrite solution and the subsequent injection of ultrafine particle cement was suppressed by 65% compared to the specimens without pretreatments and cathodic protection. This corrosion inhi-bition effect was mainly attributed to the passivation of the corroded rebar by nitrite ions and the improvement of the electrical conductivity between the rebar and surrounding concrete by the electrolyte solution.

 This paper reports the results of various experiments conducted to clarify the mechanism of pinholes and blistering in the waterproof layers of road bridge concrete decks. In the experiments, pinholes and blisters in the waterproofing layer were reproduced using concrete slabs with different concrete pore structure and moisture contents, and multiple experiments were conducted. As a result, it was clarified that pinholes occur when the air inside voids located at a very shallow position in the concrete surface expand due to the heat of the waterproofing material, causing the air to be released to the surface through the pores. Regarding blistering, it was clarified that it occurs when moisture inside the concrete moves to the surface during the process of evaporation to the exterior due to rising atmospheric temperature, where it turns into water vapor and expands in volume. Furthermore, it was shown that pinholes and blistering tend to occur more easily in concrete with many pores than in dense-surfaced concrete, and that these phenomena can be suppressed by constructing a denser surface layer.

 Incineration, which breaks molecular bonds for decomposition, is one promising countermeasure to prevent the environmental contamination of per- and Polyfluoroalkyl Substances (PFAS). However, since the incineration process generates hydrogen fluoride (HF) as a by-product, conventional methods cannot deal with considerable PFAS. This study conducted a pilot scale test to evaluate the decomposition performance of PFAS contained in the aqueous film-forming foam (AFFF) using incineration. Per Fluoro Octane Sulfonic acid (PFOS) of 33 mg/kg or Per Fluoro Octanoic Acid (PFOA) of 370 mg/kg, which was contained in the AFFF, can be decomposed to >99.99979% or 99.99996%, respectively. The gas pipe damage and dioxin generation can be prevented by maintaining the drainage gas temperature to more than 500°C at the heat exchanger and approximately 100°C at the chimney.