In this study, the elastic modulus of cemented sand and gravel (CSG) dam and its dependence on confining pressure were clarified by performing triaxial compression tests and pressuremeter tests. The results of these material tests were verified by a reproduction analysis of the dynamic behavior of the Apporo Dam during an actual earthquake. By analyzing 30 seismic records of the dam, the dynamic characteristics of the dam were clarified. New findings were obtained regarding the dynamic characteristics of this new type of dam that originated in Japan. In addition, after checking the internal and external stabilities of the Apporo Dam with the results of the reproduction analysis, it was confirmed that the trapezoidal CSG dam has excellent seismic resistance.

 In this paper, we study Euler’s theory of column buckling based on continuum mechanics. The key point is the use of a recursive-form function for displacement at a finite deformation state. It is shown that the governing equation of Euler’s theory can be derived from a functional of a linearly elastic continuum by using the recursive-form displacement, and analytical solutions are obtained by solving the resulting nonlinear differential equation. The load coincides with that predicted by the original theory, but the mode is slightly different due to the effect of finite deformation. Discussions are made on the results obtained for the column buckling equation considering finite deformation.

 Inland flooding can occur frequently due to localized torrential rainfall magnified by climate change. However, quantitative monitoring measurement has not yet been well-established for evaluating the damage and drainage management of inland flooding. There is also no existing threshold for evacuation, on the basis of such complicated and qualitative information. In this study, for the purpose of understanding the risk distribution of inland flooding, we have improved the numerical analysis method (DIEX-Flood) to enable it to perform high-speed calculations in order to interpolate and extrapolate the “point” water- level observation data in the sewage pipe to the “line” data with high accuracy. The improved model was verified by using water-level observation data of a sewer pipe. The results indicate that the proposed method can forecast the streamwise distribution of the water level with high accuracy by using data assimilation. With data assimilation, casting is corrected with less influence from rainfall prediction errors and other potential errors.

 Bangladesh is one of the most disaster-prone countries in the world, with great negative consequences being associated with various natural and human-induced hazards. Therefore, the evaluation of long-term variation in recorded meteorological and hydrological time-series data is necessary for infrastructure development in the future. In this study, we collected 32-year monthly precipitation data at 36 locations in Bangladesh, 116-year monthly precipitation data at seven areas in India and 30-year data of the daily water level at four locations in the Ganges Brahmaputra Meghna and Haor in Bangladesh. We conducted a trend analysis using these data as well as a correlation and causality analysis in order to find the relation to global-scale phenomena such as Southern Oscillation Index (SOI) and Dipole Mode Index (DMI). We used the Mann-Kendall test and Seasonal Mann-Kendall test for long-term trend test of precipitation and river water level; the wavelet and cross-wavelet coherence analysis for correlation; and VAR-LiNGAM for causality between the precipitation and SOI, the precipitation and DMI. The Mann-Kendall test and Seasonal Mann-Kendall test showed a significant decrease in precipitation in the central part of Bangladesh. Meanwhile, no significant decrease is shown in the northern part and no trend of precipitation is shown in other parts. The slope of the 32-year trend is found to be bigger compared to the 116-year data of India. The daily water level of three major rivers show a significant decrease in the recent 30 years. Especially, the slope of the trend in Brahmaputra is bigger than those of the other parts of Bangladesh. For the relation to global-scale phenomena, the cross-wavelet coherence analysis shows that the correlation of DMI to monthly precipitation is stronger than that of SOI. The VAR-LiNGAM analysis shows the causality from DMI to precipitation in the Bengal area with five to six months lag.

 Selective supply of fine sediments to a gravel-bed river that contains varying grain sizes leads to riverbed fluctuations. This is due to filling of the fine sediments between gravels and the sheltering effect on the flow of immobile materials. When implementing sediment replenishment from dams to the downstream river, it is important to evaluate the impact on bed variations including biological habitats. A model representing such sediment transport is essential for this purpose. This study presents an extended bed variation model that considers the sheltering effect of exposed riverbed materials and changes in porosity to represent riverbed variations with fluctuations in the exchange layer. The model was applied to a sediment supply field experiment conducted in the Yahagi River to confirm its practicality.

 This study focuses on a dielectric model for wet soils that relates the complex permittivity and water content of bulk wet soils to obtain soil moisture retrievals from satellite observations. Contrary to the earlier examinations that have been made for the Soil Moisture and Ocean Salinity (SMOS) mission of the European Satellite Agency (ESA) at 1.4 GHz (L-band microwave range), this study targets 6.9 GHz (C-band) of the Advanced Microwave Scanning Radiometer 2 (AMSR2) of the Japan Aerospace Exploration Agency (JAXA), considering the frequency dependency of the dielectric behavior of wet soils.

 The Dobson model is the most widely used dielectric model and is currently used in JAXA’s standard algorithm. ESA also used the Dobson model, but it switched to using the Mironov model in 2012 for its operational algorithm. In addition to these two models, the Wang-Schmugge model and our proposed model were numerically analyzed to clarify the effect on soil moisture retrievals by replacing the dielectric model from Dobson with another model at 6.9 GHz.

 Large differences were observed between the Dobson and Mironov models, especially for the soil types that contain large quantities of sand or clay. The Wang-Schmugge model showed similar estimates to those of the Mironov model but with a large difference in the estimated amount and permittivity of bound soil water. The estimated wet-soil permittivity by our proposed model was smaller than those of other models in many cases, slightly for temperate soils and significantly for tropical soils. Both the amount and permittivity of bound water in the proposed model were smaller than those of the Mironov and Wang-Schmugge models. The quantification of the amount and permittivity of bound water was shown to be the key in the dielectric model, and further validation with soil samples, especially with tropical samples, is necessary.

 Field observation of chlorophyll fluorescence and laboratory experiments were conducted on the oxygen consumption rate of the causative red-tide dinoflagellate Akashiwo sanguinea to estimate the nighttime oxygen consumption rate by algal respiration in the field. The estimated oxygen consumption rate based on these data was compared to the oxygen consumption rate of suspended solids and sediments in previous studies. Diurnal vertical migration of dinoflagellates and their nighttime respiration in the bottom layer contributed significantly to hypoxia and oxygen consumption through suspensions and sediments. Furthermore, based on the continuous observation results, the diurnal vertical migration of A. sanguinea was remarkably reduced during the period of development of hypoxia with oxygen saturation below 20%. This suggests that the hypoxia levels affect the patterns of A. sanguinea migration.

 This paper aims to formulate the upstream water level of the flow over finite-length weirs with rectangular cross-section in the flow direction in order to obtain basic information for flood management planning of rivers with weir(s). Experimental data by Govinda Rao and Muralidhar, which gave the discharge coefficient related to the flow pattern over the crest, were selected as base data. Equations for the upstream water level were obtained as the functions of the critical depth, h_c, with application ranges almost correspondent to those of the formula by Govinda Rao and Muralidhar. The obtained formula gave proper evaluation for the upstream water level of Bazin’s experimental data obtained for a wide range of hydraulic condition.

 Evaporation from natural lakes and artificial reservoirs represents loss of water resources; unfortunately, existing estimations are based on simplified methods. Evaporation is a phenomenon related not only to inlake thermodynamics but also to water surface area change driven by riverine in- and outflows. Thus, this study aims to reestimate evaporation on a global scale with a coupled model framework of hydro- and thermodynamics in rivers and lakes, of which estimate is consistent with previous ones. It was found that evaporation per area from reservoirs is more significant than that from natural lakes due to the difference in spatial distribution, and reservoir construction increases evaporative loss due to the warming up of water surface, in addition to an increase in surface area. The estimation of storage in each water body also showed that most of the residence time is caused by lakes. These results suggest that it is crucial to consider the thermodynamics of lakes and their interactions with rivers to estimate water resources and their quality.

 The role of shallow coastal ecosystems in mitigating climate change is drawing the attention of researchers, policymakers, and citizens. However, to date there has been no nationwide estimate of atmospheric carbon dioxide (CO₂) uptake and carbon storage by shallow coastal ecosystems in Japan. In this study, in accordance with Intergovernmental Panel on Climate Change guidelines, we defined the uptake/emission rate of atmospheric CO₂ by an ecosystem as the rate of change in its carbon stock. We then estimated the potential CO₂ sink of shallow coastal ecosystems throughout Japan. We estimated the present nationwide potential carbon sink to be 1.32 million tons of CO₂/year, with an upper limit of 4.04 million tons of CO₂/year. Based on this estimate, it may help to include shallow coastal ecosystems as a new CO₂ sink under Japanese law and to incorporate them into existing marine environmental policies and frameworks.

 This study aims to develop a system that improves operational efficiency by centrally managing the information obtained at each stage of the design, construction, and maintenance of mountain tunnels. In this study, the items required for mountain tunnels are examined in reference to building information modeling (BIM) that has been developed in the field of architecture. The basic information includes topography, geology, and support design information at the planning stage; observation, measurement, and analysis results during construction; and information on concrete lining deformation at the post-completion maintenance stage. In addition, the BIM/construction information modeling and management (CIM) practical application system is developed and applied to the site by considering the prediction of geological conditions in front of the tunnel face and the prediction of fault fracture zones and water inflow to ensure that the construction is carried out safely and as planned. Moreover, drawing the BIM/CIM in 3D is expected to promote information sharing and speed up decision making between clients and contractors, consequently leading to construction deadline conformance, construction cost reduction, and ensuring a safe and secure construction.

 The estimation of tunnel deformation from the change in the profile is expected to improve the efficiency of inspection. This paper considers the applicability of a tunnel deformation estimation from a point cloud adopting elliptic Fourier analysis. Tunnel deformation is estimated from the difference in the Fourier series representations of the outline before and after deformation. The deformation of a Shinkansen tunnel calculated in the numerical analysis is estimated to evaluate the method’s accuracy. The numerical results show that the estimation of the normal displacement is highly reliable, with the estimation error being roughly proportional to the measurement error. The estimated displacement fluctuates around the true value. In contrast, the reliability of the estimation of the tangential displacement tends to be low because this displacement does not contribute to the change in the outline. The estimation error increases rapidly with the measurement error, and the estimated displacement tends to be independent of the true value. The proposed estimation method is applicable even when the outline is not closed.

 Distracted driving is a leading cause of global traffic accidents. The attitude towards distracted driving directly affects distracted driving behavior. For road safety, it is necessary to find out what factors affect the driver's attitude towards distracted driving. In this study, a questionnaire was designed to collect necessary data including attitudes towards many types of distracted driving behaviors, quality of life (QOL), driving pattern, personal attributes, and accident-related experiences of private car owners. A structural equation model (SEM) was established to estimate the correlation between the attitude towards distracted driving and the observed variables. The results show that driving pattern, QOL, personal attributes are related to the attitude towards distracted driving; QOL and driving pattern are correlated, and the attitude toward distracted driving is related to the accident experience. The result is beneficial for us to understand distracted driving and to improve road safety.

 Proxy responses in social surveys produce several biases and reduce survey quality. In this study, we used the rounding error in reported trip departure/arrival times to measure quality deterioration due to proxy responses in a travel survey. In self-reported travel surveys, the trip departure/arrival times are often reported as rounded values, such as those ending in 00, 10, 15, 30, and 45 min. We hypothesized that, compared to self-response, proxy response often contains more rounded departure/arrival times. Data from the 2017 US National Household Travel Survey were used to analyze the demographic characteristics and effects of proxy responses. A descriptive analysis revealed that males in their 20s–50s tended to be proxy respondents, whereas males in their 50s or older tended to be proxy completers. Proxy-reported discretionary trips were often misreported, and proxy responses often contained rounded departure/arrival times. To control the effects of demographic variables, we finally estimated a binary logit model to describe the relationships among the self- and proxy response choices, demographic attributes of the respondents, and rounding in the reported times The results revealed a statistically significant association between proxy response and rounded reported time, supporting our hypothesis.

 The falling weight deflectometer (FWD) test, an effective and quantitative method, has been used to evaluate the soundness of road bridge slabs. In FWD tests using an impact load acting on asphalt concrete paved on the slabs, the measured deflection includes deformation of the asphalt concrete and is influenced by its stiffness. For periodic inspections and soundness evaluation, it is essential to eliminate the influence of temperature-dependent asphalt concrete from the measured deflection. The authors have analytically investigated a method for correcting such influence, including average temperature estimation inside asphalt concrete. However, the correction method proposed remains experimentally unverified. In this study, simulated RC slabs were constructed to verify the influence of the asphalt concrete and the accuracy of the correction method. The results verify the accuracy of the correction method in the winter season. However, the accuracy tends to decrease in the summer season, particularly for thick asphalt concrete with high average inside temperature.

 Timber piles for ground improvement have many potential applications, and increasing carbon storage by expanding their usage is expected to contribute to net-zero greenhouse gas emissions by 2050. For this contribution to be reported by the Government of Japan, the rate of mass loss of underground wood must be estimated quantitatively; however, the rate of mass loss is currently unknown. In this paper, a study was performed of Japanese cedar cylindrical piles that were excavated after being buried with their heads at the ground surface for about 10 years in the Inashiki plateau, Japan. The rate of mass loss was analyzed, assuming that no wood decay occurred at depths below the lower limit of the groundwater level. The part of the piles in the range of groundwater fluctuation did not have recognizable mass loss. However, at depths above the upper limit of the groundwater level, the half-life of the mass loss of the parts of the piles where the outer peripheral shape remained was about 50 years, and that of the parts with cross-sectional loss was less than about 10 years.

 Nanosilica (NS) is available in various types or sizes and has been the focus of many research attempts on bitumen. However, most of the publications have failed to acknowledge or implement the effects of the NS type itself. The tendency for clustering in NS particles induces large lumps rather the fine particles, which impacts all the bitumen properties. Likewise, the dimension of clusters should be minimised by the appropriate selection of NS size and mixing conditions. Cryogenic SEM is a versatile tool to track the size of clusters, so it was employed here to visualise the changes in intact bituminous samples. This study introduced three NS types, 20–30 nm, 60–70 nm, and 20–30 nm with couplant, to the class C320 bitumen at dry and wet mixing conditions. Captured images were processed by ImageJ software to examine the status of clusters for various mixtures. Frequency sweep DSR tests and column chromatography were also undertaken to determine the likely relationships of bitumen properties at the nano to macro levels. It is found that, the NS type directly affects the average size of clusters, consequently, the rutting and fatigue performances of the binder. In addition, 60nm NS demonstrated the smallest size of clusters with better performances than other NS types.

 Building/Construction Information Modeling/Management (BIM/CIM) is a key process in enhancing the productivity of all processes of civil infrastructure projects such as plan, investigation, survey, design, construction, O&M, and rehabilitation. In this study, three types of 3-D laser scanning methods, aerial laser scanning (ALS) system, mobile mapping system (MMS), and terrestrial laser scanning (TLS) system, were applied for the topographic survey to introduce BIM/CIM for a highway project. In this paper, the accuracy of three types of laser scanning methods were validated and the creation of 3-D terrain TIN model was also discussed for highway projects. Through the case study, one of the biggest challenges to applying CIM for highway projects was clarified. Since infrastructure construction projects, especially highway projects, have a much wider area than building construction projects, the data size of highway projects becomes much bigger building projects. This study shows the way to create reasonable digital terrain model (DTM) for 3-D highway design in order to introduce CIM from topographic surveys for road/highway projects.