This study compares two damage estimation methods to establish a technique for quickly and accurately estimating damage from the Nankai Trough earthquake scenarios. In the first method, we estimated damage by regression using the total stock and the predicted seismic intensity scale distribution. This approach comes from the previous study. The second method used the maximum interstitial deformation angle per building to estimate damage by physics-based simulation. We applied an urban building and geotechnical model of Kobe City, for which we automatically created BIM using DPP. Subsequently, we summarized the significance of estimating damage from the Nankai Trough earthquake scenarios and addressed concerns regarding the privacy of the base registry. Future efforts aim to estimate localized damage across various stock items for the Nankai Trough earthquake scenarios, focusing on privacy considerations.

In the construction industry, 3D models are often used to share information among stakeholders. It is expected that the 3D model can be used for numerical analysis to perform detailed and advanced simulations. However, the models that can be constructed with commercially available 3D modeling software cannot be used for numerical analysis or can only be used with specific analysis tools. In addition, because commercial products are sold in packaged form, the use of the models is extremely limited. In 2021, Takeyama et al. developed a method for constructing a Grid Ground Model, which is a general purpose mediation model with general ground information, including boring data and soil test results. By building a common data structure once, flexible data manipulation can be performed. Based on this technology, this study developed a model building function that can be used for more advanced applications, including analysis using finite element analysis (FEA), by providing a high level of generality in the use of internal parameters and the geometry processing process. Using the developed technology, a detailed numerical analysis model was constructed through simple operations. This technology is useful for disaster damage estimation and advanced design or maintenance of construction works. In addition, the models can be highly integrated with a wide variety of software, contributing to a significant reduction in the number of man-hours required for work and to the advancement of the use of 3D models in the future.

Bentonite-based materials are candidate buffer materials for the geological disposal of radioactive waste in many countries. Once the disposal facility is closed and the groundwater level recovers, the buffer will gradually become saturated by the infiltration of groundwater. The swelling properties of saturated bentonite affect the distribution of dry density and the stress state within the buffer. Therefore, to evaluate the long-term safety of the buffer, a model must be developed that can continuously express the mechanical behavior of bentonite from the construction and operation of the repository for disposal (the unsaturated state) to the resaturation phase (saturated state). In this study, the existing elastoplastic constitutive model for saturated expansive soils was extended to predict the mechanical response in the unsaturated state. In formulating this model, the effective degree of saturation and the plastic volumetric strain were employed as the hardening parameters to express the changes in stiffness and swelling properties due to desaturation or saturation. In addition, a method was proposed for estimating the material parameters added to the expanded constitutive model. This study demonstrated the validity of the proposed constitutive model and the parameter estimation method by comparing the results of simulations with those of laboratory tests.

本研究では,記述形式の異なる様々なデータを自動で変換・統合する技術(DPP)を用いて設計実務で使用する地震・津波シミュレーション技術の合理化を図った.具体的には,国土交通データプラットフォームで入手できるボーリングデータや数値標高モデルを用いて汎用地盤モデルGridModelを作成し,自動で節点や境界条件を設定して3次元有限要素モデルに変換し,FLIP等の地震応答解析ソフトの入力ファイルとして出力する.また,「内閣府 南海トラフの巨大地震モデル検討会」データから自動でT-STOC用の入力ファイルを作成するプログラムを開発した.さらに,これらの入力データ自動作成プログラムを連携させ,地震応答解析による地表面の沈下等の結果を津波シミュレーションで考慮する方法を試行した.

Rainfall is considered one of the main causes of slope failures. Recently, the occurrences of heavy downpours due to the effects of climate change have been observed all over the world, and slope failures induced by rainfall have frequently occurred accordingly. The condition of the slope during rainfall changes from moment to moment according to the infiltration of rainwater. Therefore, numerical analysis considering the interaction between ground mechanical behavior and groundwater flow is indispensable to consistently evaluate the transition from stable state to failure. This paper presents the numerical analyses of slope failures induced by rainfall using the MPM-SPH coupling method, which is suitable for large deformations and soil-water interaction problems in geotechnical engineering. First, the MPM-SPH coupling formulation for unsaturated soil is briefly described. Numerical analyses of slope failures induced by rainfall are then shown. Parametric studies about the coefficient of saturated permeability are performed to examine the effects of the hydraulic characteristics. The results indicate that the scale of slope failure and the shape of collapse are largely influenced by the hydraulic characteristics of the slope.

: This study deals with the problem of axial and radial swelling of a cylindrical bentonite specimen with a gap at the top or side. Unsaturated soil water coupled finite element analyses are carried out to analyze how the bentonite specimen changes during the process of swelling due to water absorption from the surface facing the gap. The behavior of the bentonite after the finite gap is filled by the swollen bentonite until the equilibrium state is also analytically evaluated. The analysis results show that the distribution of void ratio and swelling pressure in the specimen remains non-uniform in both axial and radial swelling, even if the bentonite specimen reaches a saturated and equilibrium state. In the case of axial swelling, the radial and hoop stresses remain equal at all positions in the specimen, whereas in the case of radial swelling, an anisotropic stress state, in which even the radial and hoop stresses are different, is observed immediately after the start of water absorption, resulting in the formation of complex stress distribution in the radial direction.

: The risk assessment of liquefaction damage is crucial for recovery from large-scale earthquakes, which are predicted to occur in recent years. In this study, the liquefaction risk is evaluated over a wide area through effective stress analysis, considering the interaction between the soil particles and pore water. The target area of the analysis was the 23 wards of Tokyo, including the zero-meter zone, and a 3D ground model was constructed from the borehole data. A vertical columnar ground model is established at 463 locations from the 3D ground model using the material parameter determination flow. The liquefaction risk of a wide area is evaluated by performing seismic response analysis using two types of earthquake motions for each analysis point, thus showing the difference in the risk and degree of liquefaction by location. In the future, various dynamic analyses must be conducted with sufficient resolution and compared with the actual damages.

Recently, the occurrence of large earthquakes has become a concern in Japan, prompting the need for a numerical method that can accurately predict real phenomena, such as the elastoplastic soil-water coupled finite element method. Because the elastoplastic constitutive model requires many material parameters, various soil tests and specialized knowledge are needed to determine these material parameters. In this study, a new method was proposed to determine the material parameters from the limited ground information obtained by borehole inspections and the method was validated by comparing the numerical results with monitored seismic behavior. One-dimensional seismic analyses were conducted using the material parameters estimated from borehole data near the target sites. It was confirmed that the amplitude and predominant period obtained by numerical simulation were consistent with the monitored data. As a result, it was found that the dynamic numerical result was more consistent with the monitored data when the compression index was set to be larger than that in the static analysis.

Earthquake induced liquefaction is one of the main geo-disasters threating urban regions, which not only causes direct damages to buildings, but also delays both real-time disaster relief actions and reconstruction activities. It is thus important to assess liquefaction hazard of urban regions effectively and efficiently for disaster prevention and mitigation. Conventional assessment approaches rely on engineering indices such as the factor of safety (FS) against liquefaction, which cannot take into account directly the uncertainties of soils. In contrast, a physics simulation-based approach, by solving soil dynamics problems coupled with excess pore water pressure (EPWP) it is possible to model the uncertainties directly via Monte Carlo simulations. In this study, we demonstrate the capability of such an approach for assessing an urban region with over 10 000 sites. The permeability parameters are assumed to follow a base-10-lognormal distribution among 100 model analyses for each site. A dynamic simulation is conducted for each model analysis to obtain the EPWP results. Based on over 1 million EPWP analysis models, we obtained a probabilistic liquefaction assessment. Empowered by high performance computing, we present for the first time a probabilistic liquefaction hazard assessment for urban regions based on dynamics analysis, which consider soil uncertainties.

The material point method (MPM) has recently been used to perform soil–water interaction analysis for fully saturated soil in geotechnical engineering. In MPM, to treat fully saturated soil, two types of discretization methods have been mainly used: the single point formulation and the double point formulation. The former discretizes the soil–water mixture with a single set of particles, whereas the latter discretizes the soil phase and the water phase separately by using different sets of particles. In both the discretization methods, the flux boundary condition is imposed on the background mesh nodes, and the prescribed pore water pressure boundary condition is directly applied to the particles. This is the reason behind the complexity involved in the setting of boundary conditions for the coupled MPM. To reduce this complexity, this paper presents a discretization technique that combines MPM with smoothed particle hydrodynamics (SPH). SPH is used for the discretization of the generalized Darcy’s law to impose the flux boundary condition directly on the particles. The proposed formulation is validated through the soil–water interaction benchmark problems: the consolidation problems of Terzaghi and Mandel–Cryer. The numerical results are in good agreement with the analytical solutions, which validates the proposed method.

There have been attempts to improve the operational efficiency of construction projects and plan response countermeasures for estimated damage following disasters through the utilization of accumulated electronic data, which constructs a digital twin that can reproduce a physical space in cyberspace and feedback the cyberspace simulation results to physical space. However, the application of such simulations is limited, unless numerical models can be automatically constructed from the data. In this study, we develop a program that utilizes a data processing platform to read, transform, and integrate data to create mediated data with a common data structure. This mediated data can be used to construct analytical models for various numerical analyses. Using the program developed, a grid model of 3-D ground surface as the mediated data was constructed based on borehole data obtained through a ground survey. Each grid point has basic material parameters of soil, and these parameters are estimated from borehole data and other investigation reports. Each grid point has general geotechnical parameters and can be easily converted to a 3-D finite-element model. When the borehole data is added or changed, the analytical model can be updated with almost no cost, whereas it would be very costly to create the model manually.

The pagoda of Wat Krasai, built in the 17th century on the outskirts of the Ayutthaya district in the Kingdom of Thailand, tilts approximately 2 degrees to the north and may continue to tilt further. The cause of this tilt is thought to be the uneven settlement of the foundation ground, but no supporting evidence has been presented. Three cohesive soil layers that may cause uneven settlement have been confirmed in the foundation ground around the pagoda, but soil tests are inadequate, leading to uncertainty in proving the cause of inclination. Hence, the cause of inclination was investigated in this study by calculating the inclination that can occur within the realistic ranges of the soil properties through numerical analysis using the finite element method. A method of correcting plane strain analysis, which has a low computational cost, with a three-dimensional effect coefficient, was utilized to assess over 500 cases considering ground material uncertainties, and the probability distribution of the possible inclinations was calculated. This method is useful as it considers fluctuations in the ground material parameters to address land settlement, which is largely influenced by the three-dimensional effects. This approach will also be applicable to future predictions aimed at pagoda preservation.

Although the soil, water and air coupling theory has been deductively derived from the three-phase mixture theory, assumptions and interpretations inherent in soil mechanics are also conveniently introduced in this theory. Mechanical properties of unsaturated soils are phenomenologically integrated into the constitutive equation for a deformation problem, with effective stress expressed as a combination of partial stresses acting on each phase of the mixture. The governing equations of two seepage problems describing the movements of pore water and pore air are formulated by a priori introduction of Darcy’s law. Consequently, the coupling theory consists of a deformation problem and two seepage problems, in which the soil-water retention characteristics play the role of a mediator connecting these problems. If the theoretical structure is clarified in this way, an extension of this theory is easily made. In this paper, the extension of the theory to each of four examples and their performance is demonstrated. The features of settlement caused by absorption of soil water due to vegetation; dissolution, advection and diffusion of substances in groundwater; desaturation and state change due to vaporisation of dissolved gas from pore water; and the liquefaction potential of unsaturated soil are presented.

Through quantitative measurement of the accuracy and the convergence of error, code verification can objectively assess the quality of a simulation code. A lack of analytical benchmark solution for nonlinear problems makes it difficult to verify soil dynamics simulations in geotechnical engineering. To overcome such difficulty, this study makes use of a novel code verification technique, the method of numerically manufactured solutions (MNMS). By utilizing MNMS, the accuracy of a simulation code for nonlinear soil dynamics problems was measured. The orders of the convergence rate of the errors, with respect to the spatial and to the temporal discretization, were found to be in good agreement with the theoretical orders of the numerical methods. By demonstrating the applicability of MNMS for verifying nonlinear soil dynamics simulations, it is hoped that the concept and the necessity of code verifications can be appreciated for simulations of geotechnical engineering problems.

Conventional methods for liquefaction assessment using engineering indices such as Factor of safety against Liquefaction (FL) tend to overestimate liquefaction hazards. The soil dynamics analysis-based assessment with automatic modeling is more rational and robust. Soil properties are known for large uncertainties. Rather than deterministic soil models, statistical models for soil parameters should be considered. With automatic modeling, a large number of statistic models can be generated without difficulty. The problem becomes how to assess liquefaction hazard with statistic models in an efficient way. Using high performance computing, we develop an efficient liquefaction assessment method for statistical modeling of soils. A high parallel efficiency can be achieved and a large number of statical models of the order of 104 can be simulated within a reasonable time span. The method developed in this paper can be used as an efficient tool for unravelling critical parameters of soil liquefaction.

In the wide area of the eastern part of Tokyo, the ground level is less than mean sea level. This area is more vulnerable to disasters than other areas. If large flood damage such as storm surge should occur in this area, the disaster would be a long-term catastrophe. On the coast of Tokyo Bay, countermeasures have been taken by tide embankments and floodgates. However, considering the damage scale when it occurs, an analysis in this area is very important. In this area, ground settlement occurred and groundwater head dropped because groundwater excessively withdrew by the industrial purpose during the period of economic growth. Currently, the groundwater head recovers and the ground settlement has been subsided. However, due to the groundwater head fluctuation, pore water pressure distribution had been different from hydrostatic pressure distribution. Therefore, in the analysis in this area, it is necessary to consider past groundwater head fluctuation. In this research, the ground settlement and the distribution of pore water pressure are simulated from groundwater level fluctuation over the past 100 years. Then, we conducted the seismic analysis by input the distribution of effective stress calculating from the simulated ground water pressure. The sites analyzed in this research are Tokyo Sea Life Park at the mouth of Arakawa River.