Directory of Researchers
| TAKEYAMA Tomohide |  |
| Graduate School of Engineering / Department of Civil Engineering | |
| Professor | |
| Civil Engineering / Architecutre and planning / Building Engineering |
Researcher Profile and Settings
Affiliation
＜Faculty / Graduate School / Others＞
Graduate School of Engineering / Department of Civil Engineering＜Related Faculty / Graduate School / Others＞
Faculty of Engineering / Department of Civil Engineering
Teaching
- Graduate School of Engineering / Department of Civil Engineering, 2021, Advanced Applied Geomechanics
- Graduate School of Engineering / Department of Civil Engineering, 2021, Advanced Science and Technology A
- Graduate School of Engineering / Department of Civil Engineering, 2021, Computational Geotechnical Engineering
- Faculty of Engineering / Department of Civil Engineering, 2021, Introduction to Civil Engineering
- Faculty of Engineering / Department of Civil Engineering, 2021, Practice in Civil Engineering and Safety Guidance Ⅰ
- Faculty of Engineering / Department of Civil Engineering, 2021, Soil Mechanics I
- Faculty of Engineering / Department of Civil Engineering, 2021, Practice in Civil Engineering and Safety Guidance Ⅱ
- Faculty of Engineering / Department of Civil Engineering, 2021, Numerical Simulation Exercise
- Faculty of Engineering, 2021, Advanced Liberal Arts Seminar in Faculty of Engineering (Civil Engineering)
Research Activities
Research Areas
- Social infrastructure (civil Engineering, architecture, disaster prevention) / Geotechnical engineering
Awards
Published Papers
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.
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, Dec. 2021, IEEE-ASME TRANSACTIONS ON MECHATRONICS, 26 (6), 2881 - 2887, English[Refereed]
Scientific journal
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.
CHINA UNIV GEOSCIENCES, WUHAN, Oct. 2021, JOURNAL OF EARTH SCIENCE, 32 (5), 1129 - 1138, English[Refereed]
Scientific journal
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.
GEOMATE INT SOC, Oct. 2021, INTERNATIONAL JOURNAL OF GEOMATE, 21 (86), 48 - 54, English[Refereed]
Scientific journal
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.
GEOMATE INT SOC, Sep. 2021, INTERNATIONAL JOURNAL OF GEOMATE, 21 (85), 1 - 9, English[Refereed]
Scientific journal
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.
GEOMATE INT SOC, Jun. 2021, INTERNATIONAL JOURNAL OF GEOMATE, 20 (82), 161 - 169, English[Refereed]
Scientific journal
- 2021, Proceedings of Kansai Geo-Symposium, 9温度勾配による不飽和ベントナイト中の水分移動シミュレーション
[Refereed]
- Springer International Publishing, 2021, Challenges and Innovations in Geomechanics, 794 - 801
[Refereed]
In book
© 2019 Elsevier Ltd 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.
Jan. 2020, Computers and Geotechnics, 117[Refereed]
Scientific journal
- 2020, 神戸大学年安全研究センター研究報告, 24, 53 - 65最適化手法を用いた土/水連成問題に対する分離型解法の収束性に関する研究
- 2020, 神戸大学年安全研究センター研究報告, 24, 44 - 52室内試験に基づく繰り返し挙動を表現できる 構成モデルのパラメータ同定方法
- 2020, Kansai Geo-Symposium論文集, 8, 160 - 165都市全体を対象とした液状化後の地盤沈下現象に関する解析的研究
[Refereed]
- Thomas Telford Ltd., 01 Sep. 2019, Geotechnical Research, 6 (3), 156 - 176, English
[Refereed]
Scientific journal
© 2019 Elsevier B.V. Effective and efficient liquefaction hazard assessment is critical in making disaster mitigation plans for urban regions. In this paper, we present a numerical-simulation (NS)-based method for assessing urban-wide liquefaction hazard. The method includes an automatic modelling for individual sites and an application of high-performance computing (HPC) for efficient assessment. The feasibility of the method is demonstrated by conducting simulations for more than 10,000 individual sites in an urban region. The urban-wide assessment results depend on a pressure threshold of liquefaction occurrence and the dependence increases as the ground motion increases. A comparison with a conventional method using engineering indices (EI) shows a tendency of the EI-based method to predict a considerably greater number of liquefied sites than the proposed method. With the continuing improvement on numerical simulations and on computer efficiency, NS-based assessments can be regarded as promising alternatives to conventional EI-based methods for urban-wide liquefaction assessment.
14 Aug. 2019, Engineering Geology, 258 (14), English[Refereed]
Scientific journal
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.
Tech Reviews Ltd, 15 May 2019, Journal of Civil Engineering and Construction, 8 (2), 41 - 47, English[Refereed]
Scientific journal
- Feb. 2019, Journal of Engineering and Construction, 8 (1), 13 - 18, English
[Refereed]
Scientific journal
- 2019, International Journal of Computational Methods, 16 (5), English
[Refereed]
Scientific journal
- 2018, Proceedings of the 7th International Conference on Unsaturated Soils, EnglishNumerical analysis of vacuum consolidation considering dissolved gasses
[Refereed]
International conference proceedings
Currently, finite element codes for small-strain have been widely applied in geotechnical engineering problems. However, the limitations of these codes are recognized, especially when the strain is large. To overthrow such limitations, finite-strain finite element code for porous media is needed. Therefore, this study aims to implement the finite element code for coupled solid-fluid at finite strain for static and dynamic problems. Firstly, the governing equation for porous media at finite-strain was introduced. Then, the mixed formulation of both phases with respect to the reference coordinates by deriving the governing equations with respect to the reference or current coordinates and by considering the solid and fluid as separate, was given. At present, the code is developed only for elastic regime as its preliminary step. In this study, the proposed code has been verified with the static and dynamic problem. And, the result of the finite-strain finite element code is then compared with the result of the analytical solution and small-strain finite element code within the small-strain regime. Thereafter, the proposed code was used to estimate the response of the earthen dam when subjected to a dynamic load. Finally, the results, discussion, and comparison between small- and finite-strain finite element analyses were presented.
GEOMATE International Society, 2018, International Journal of GEOMATE, 15 (51), 1 - 8, English[Refereed]
Scientific journal
- Mar. 2017, 都市安全研究センター研究報告, (21), 27 - 35, Japanese地盤動的解析のための試験結果のばらつきを考慮したパラメータ範囲の検討
Research institution
- Mar. 2017, 都市安全研究センター研究報告, (21), 49 - 62, JapaneseB 値に与える影響因子とB 値測定手法がせん断挙動に及ぼす影響
Research institution
When the deep mixing columns were used to support embankment slope, the columns may fail under either the internal or the external failure pattern, dependent on the strength of columns, soil condition, and loading condition. A shallow layer, produced by shallow mixing method, was proposed to fix and reinforce these isolated columns. In this study, the centrifuge model tests were carried out to simulate the embankment construction on the soft ground, improved by the columns and the shallow layer. The effect of the shallow layer and column strength on increasing the embankment stability can be addressed from the model tests. The failure of isolated columns was compared to that of columns with the reinforcement of shallow layer in terms of internal stability. In addition, by using the test data simple calculations based on limit equilibrium were also carried out to access the failure patterns of column in both internal and external stabilities.
American Society of Civil Engineers (ASCE), 2017, Geotechnical Special Publication, (289), 471 - 480, English[Refereed]
International conference proceedings
- 2017, 都市安全研究センター研究報告, (21), 49 - 62, JapaneseＢ値に与える影響因子とＢ値測定手法がせん断挙動に及ぼす影響
Research institution
- 2017, 都市安全研究センター研究報告, (21), 27 - 35, Japanese地盤動的解析のための試験結果のばらつきを考慮したパラメータ範囲の検討
Research institution
- 2017, Proc. of 19th International Conference on Soil Mechanics and Geotechnical Engineering, 2607 - 2610, EnglishStudy on failure mechanisms of the deep mixing columns reinforced by a shallow mixing layer
[Refereed]
International conference proceedings
Soil liquefaction induced by earthquakes poses a great threat to urban areas, not only by causing direct damages to infrastructures but also by delaying rescue and relief actions. Established engineering assessment methods using indices such as factor of safety against liquefaction (FL) tend to overestimate liquefaction hazards. While the standard usage of soil dynamic analysis for liquefaction assessment is limited to a single site with detailed site information. In this paper, we propose a framework based on soil dynamics for assessing liquefaction hazard for urban areas which contain numerous sites with borehole logs only. The framework is featured by generating analysis models and by estimating material parameters automatically from available borehole information. The governing equations for soil dynamics are solved by a finite element code. Liquefaction hazard is assessed according to the solutions of excess pore water pressure for given seismic waves. As demonstrations, we show simulation results of simple shear tests and of seismic response for a target site under loadings of artificial and of actual seismic waves. The automatic model construction and parameter estimation enable this framework being applied effectively for urban-area-wide liquefaction assessment, as an alternative for the current practices based on engineering indices.
WORLD SCIENTIFIC PUBL CO PTE LTD, Aug. 2016, INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS, 13 (4), English[Refereed]
Scientific journal
- 2016, 土木学会論文集B3（海洋開発）, 72 (2), 408 - 413, Japanese
[Refereed]
Scientific journal
- 2016, International Journal of Geosynthetics and Ground Engineering, English
[Refereed]
Scientific journal
- 2016, Proc. of the 7th International Conference on Computational Methods, EnglishHigh performance computing for liquefaction hazard assessment with statistical soil models
[Refereed]
International conference proceedings
- 2016, Proc. of the 12th World Congress on Computational Mechanics, EnglishHigh performance Computing for Assessing Hazard of Earthquake induced Liquefaction in Urban Regions
[Refereed]
International conference proceedings
- 2016, Journal of JSCE, 4 (1), 92 - 105, English
[Refereed]
Scientific journal
- 2016, Proc. of the 19th Southeast Asian Geotechnical Conference & 2nd AGSSEA Conference, EnglishCentrifuge model tests on deep mixing columns reinforced by a stabilized shallow mixing beneath an embankment
[Refereed]
International conference proceedings
- Microscopic image of meta-stability of clays
The authors carried out a series of triaxial "undrained" tests on undisturbed samples taken from 4 sites and found that development of pore water pressure especially at the early stage of the tests is more appreciable in the slower tests than faster tests. The test data for the slower tests suggest the existence of a sharp corner (vertex with a singular point) on the yield locus of a normally consolidated clay at the stress point representing the effective stress state of virgin consolidation. The existence of metastable space in the strain increment space is found to be closely related to the existence of the sharp corner (singular point) and/or smooth but sharply curved corner of the yield surface. Based on the above mentioned experimental and theoreticalworks, discussed in this paper is the metastable behavior expected to be seen in the metastable space. © 2015 Taylor & Francis Group.
2015, Geomechanics from Micro to Macro - Proceedings of the TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, IS-Cambridge 2014, 2, 727 - 732[Refereed]
International conference proceedings
- Simulations of physical models of undercut slope lying on inclined bedding plane
An 80m high wall slope at Mae Moh mine, Lampang, Thailand, sits on a low friction interface between an underburden clay stone and a thin clay layer. Stability of the sizable slope will be questionable when being undercut and mined. To study the behaviors of the undercut slope lying on an inclined bedding plane, a number of physical models are studied. For the physical models, a 1.3m × 0.06m × 0.8m (W × H × D) undercut slope model was constructed by using humid sand on low friction Teflon sheet as a smooth interface. In the physical model test, the base part of the model was started to excavate from two central slices of 50mm wide and expanded until a failure occurred. The test results were compared with the numerical analyses by the Smoothed Particle Hydrodynamics (SPH) method. The simulation can express the failure observed in the physical model tests. © 2015 Taylor & Francis Group, London.
2015, Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 1481 - 1486[Refereed]
International conference proceedings
- Japan Society of Civil Engineers, 2015, Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 71 (2), I_419 - I_427, Japanese
[Refereed]
Scientific journal
- 2015, The Official Journal of the International Association of Lowland Technology, 17 (3), 139 - 146, EnglishThe influence of soil disturbance on material properties and micro-structure of cement-treated soil
[Refereed]
Scientific journal
- 2015, Proc. of the 7th Regional Symposium on Infrastructure Development, EnglishThe influence of soil disturbance on cement-treated soil strength
[Refereed]
International conference proceedings
- 2015, Proc. of the International Conference on Soft Ground Engineering, EnglishExperimental and Analytical Study of the Effect of Partial Decrement in Permeability of PVDs on Consolidation
[Refereed]
International conference proceedings
- 2015, Proc. of Deep Mixing 2015, EnglishDeep Mixing Column Group Reinforcement by a Shallow Mixing Layer Beneath an Embankment
[Refereed]
International conference proceedings
- 2015, Proc. of the International Conference on Soft Ground Engineering, EnglishCentrifuge Model Tests on the External Failure of DM Columns Fixed by Shallow Stabilization
[Refereed]
International conference proceedings
- 2015, Proc. of the the International Conference on Computational Methods, EnglishA soil dynamics based liquefaction potential assessment framework for urban sites
[Refereed]
International conference proceedings
- 2015, International Journal of Material Science and Engineering, 2 (1), 20 - 25, EnglishA finite element method to describe the cyclic behavior of saturated soil
[Refereed]
Scientific journal
Soil cement mixing by deep mixing technique is used as a soft soil improvement method. Deep mixing columns are widely used to support embankment constructed on a soft ground area. In order to applying this improvement method, the failure pattern of group column type improvement should be analyzed. Researches on the failure pattern of columns are done by some authors when the columns individually fail. Due to individual failure of columns under loading, a layer of shallow mixing layer is proposed to reinforce individual columns working as a group in order to increase the stability as well as loading capacity of columned improved area. This research focuses on the failure pattern of group of columns which are fixed by the shallow mixing layer under embankment. By comparing to failure mechanism of individual columns, the effect of shallow mixing layer on failure pattern of deep mixing columns is also discussed. Finite element method is used for this analysis with Plaxis code under plain strain condition. The effect of thickness of shallow mixing layer on reducing horizontal displacement of embankment isvarious with different values of strength and stiffness of cement mixing area which is discussed in this research.
Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, 2015, 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability, 2 (63), 2144 - 2148, English[Refereed]
International conference proceedings
In Akita region along the northwest coast of Japan, about fifty tons of salt per kilometre of the highway is used to prevent the snow on the road surface from freezing every year. Reported in this paper is the estimate of the salt contamination in paddy fields adjacent to Akita Expressway. The speed of the travelling diffusion front of the possible saline ground water was estimated as low as 2 mm/year. In the paper, we also review the current operation of Akita Expressway in terms of snow removal and freeze prevention during the winter season.
Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, 2015, 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability, 2 (50), 1745 - 1748, English[Refereed]
International conference proceedings
The East Japan Earthquake and Tsunami caused serious damages in the coastal area of eastern Japan. Many houses and cars on the road were swept away by the tsunami. Also, industrial facilities such as chemical plants in the coastal area were completely destroyed. Damage from saline seawater was not limited only to the rice field areas, and there were also serious anxieties regarding the possibility of ground contamination as a result of harmful heavy metals that leaked from destroyed chemical plants. In light of this scenario, we carried out a quantitative survey to examine these areas. This paper reports on the results of our survey. It was found that high salt concentrations were detected on the ground surface but predictions state that these concentrations can be diluted with rainfall. It was also revealed that serious ground contamination due to the harmful heavy metals was not detected.
2014, Theoretical and Applied Mechanics Japan, 62, 141 - 148, English[Refereed]
Scientific journal
In the present soil–water coupled finite element method (FEM) analysis, a program known as deformation analysis considering stress anisotropy and reorientation (DACSAR Iizuka and Ohta, Soil Found 27(3): 71–87, 1987), the spatial discretization procedure for representing the water head at the center of each finite element was adopted. However, it is known that the outflow of pore water from the element boundary happens to be incorrectly calculated depending on the mesh arrangement and the inclination of the boundary. To address this problem, this chapter proposes a more rigorous spatial discretization procedure for pore water flow. Namely, the hybrid-type penalty method (HPM) is introduced to spatially discretize the pore water flow in soil–water coupled finite element formulation, and the DACSAR program is modified using the proposed technique.
Springer Netherlands, 2013, Geotechnical, Geological and Earthquake Engineering, 25, 163 - 179, English[Refereed]
In book
After the Great East Japan Earthquake occurred on 11 March 2011, many earthquake-induced damages of levees and reclaimed lands were reported. According to the investigation to the failure characteristic of levees summarized by Tohoku Regional Development Bureau of MLIT, damages caused by liquefaction of foundation ground would involve basal settlement and saturated condition of loosening construction materials inside levees submerged under water. This study aims to highlight that initial stress states influenced by passive arch action across a basal deflection plays a dominant role in mechanisms of weakening resistance against liquefaction and will contribute to embankments stability evaluation against earthquake.
National Committee for IUTAM, 2013, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 62 (0), 114 - 114, Japanese© Springer Science+Business Media Dordrecht 2013. In this chapter, the stress–strain relationship on the singular point of the yield surface of the original Cam clay model and the Sekiguchi-Ohta’s model is derived in order to compute the volume change correctly. Metastable space, the range of increment of strain in which effective stress does not get away from the singular point of yield surface, was theoretically derived. In metastable space, the increment of volumetric strain is larger than the increment of deviatoric strain.
2013, Geotechnical, Geological and Earthquake Engineering, 25, 229 - 239[Refereed]
In book
This paper reports the investigation of ground contamination resulting from Tsunami due to the Great East Japan Earthquake. We visited sites at suburbs of Sendai and Ishinomaki and took soil samples at the sites to analyse heavy metal contamination. Herein, the sites st suburbs of Sendai were chosen as a typical area where any industrial facilities did not exit and the sites at Ishinomaki as a typical area where many industrial facilities were destroyed due to the Tsunami. As conclusion, heavy metal contamination were not found resulting from destroyed industrial facilities but contaminated soils that had been settled under the sea were brought by Tsunami and covers the sites at Ishinomaki.
National Committee for IUTAM, 2013, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 62 (0), 110 - 110, Japanese- 01 Aug. 2012, 土木学会年次学術講演会講演概要集(CD-ROM), 67th, ROMBUNNO.VII-066, Japanese東日本大震災における津波由来土壌汚染調査
It is difficult to estimate the current stress state of existing embankments because of their inherent sloping geometric shapes. Therefore an elastic analysis is always carried out in advance and the calculated stress state, assumed as the current stress, is used as an input parameter in the deformation analysis of an embankment. However, the stress state of a banking material can be quite complicated since banking materials are elasto-plastic and unsaturated in most cases, and, their behavior strongly depends on the stress history. In this study, the banking process is simulated with an elasto-plastic constitutive model for unsaturated soil. Specifically, the effects of banking speed and initial suction within the banking material are considered. It is found that the post-banking stress state depends on the distribution of the initial suction due to soil-water retention characteristics. © 2011 Taylor & Francis Group, London.
01 Dec. 2011, Unsaturated Soils - Proceedings of the 5th International Conference on Unsaturated Soils, 2, 1337 - 1342A sand valley is a conjugate problem of sand heap. A typical geometry of planar valley under constant unit weight lying at the angle of repose is illustrated by two adjacent infinite sand heaps. The rigid body of infinite depth of cohesionless material is considered in two-dimensional quasi-static equilibrium. This study reveals the solutions according to a particular description of stress paths where the principal stress orientation provides additional equation to the two equilibrium equations for analyzing three unknowns of stress variables. Closed-form stress solutions for loose sand valley formed at the angle of repose in the planar two-dimension were derived based on the fixed principal axis hypothesis using the Lamé-Maxwell equations of equilibrium. Paths of principal stresses describe self-weight transfer mechanism under the static equilibrium.
National Committee for IUTAM, 2011, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 60 (0), 221 - 221, Japanese- A finite element simulator for mechanical behavior of unsaturated earth structures exposed to evaporation and moisturization
To predict the long-term elasto-plastic behavior of unsaturated earth structures, a constitutive model, which can express the following typical mechanical behavior of unsaturated soil, is needed. This includes shrinkage and increase of stiffness upon drying (i.e. suction increase), collapse with reduction of stiffness upon wetting (i.e. suction decrease), and the influences of suction history related to the hysteresis of soil-water retention characteristics. In this study, a new constitutive model is proposed for unsaturated soil where the effective degree of saturation is used as a parameter relating to stiffness. The model shows good agreement with experimental results. In addition, a soil/water coupled finite element simulation code (simulator), as applied to this model, is introduced. The appropriateness of the simulator is demonstrated for the case of a virtual fill.
CRC PRESS-TAYLOR & FRANCIS GROUP, 2010, UNSATURATED SOILS: THEORETICAL AND NUMERICAL ADVANCES IN UNSATURATED SOIL MECHANICS, 711 - +, English[Refereed]
International conference proceedings
- 2010, 応用力学論文集(CD-ROM), 13, 423 - 430, Japanese築堤シミュレーションにおける設定条件が盛土内応力分布に及ぼす影響
[Refereed]
- Sep. 2009, 応用力学論文集, Vol.12,pp.187-194, JapaneseHPMを用いた土/水連成有限要素解析における水頭の空間離散化
[Refereed]
Scientific journal
This paper describes a trial of geotechnical asset management for highway embankments placed on very soft clayey grounds at Ebet-su, Hokkaido in Japan. The highway was constructed 30 years ago and is still settling year by year requiring a considerable cost of maintenance. The paper consists of (i) characterization of the ground conditions at the sites, (ii) the class B predictions of the mechanical behaviour of embankments during construction works employing a soil/water coupled finite element code, (iii) predictions of long-term settlement of the embankments based on the information obtained at the stage (ii), (iv) estimates of maintenance cost of the embankments based on the computed long-term settlement and (v) verification of the proposed method of geotechnical asset management by comparing the maintenance cost estimated based on the above stated method and the maintenance cost actually needed in the past 30 years. © 2009 IOS Press.
2009, Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering, 3, 2139 - 2142, English[Refereed]
International conference proceedings
- 神戸大学, 2009, Report of Research Center for Urban Safety and Security Kobe University, 13 (13), 1 - 9, Japanese
- Saga University, 2009, The Official Journal of the International Association of Lowland Technology, 11 (2), 41 - 46, EnglishSoil\/water coupled analysis for construction management of highway embankments on soft clay
[Refereed]
Scientific journal
Discontinuity at the vertex of the Sekiguchi-Ohta model causes numerical troubles when associated flow rule is applied because the singularity encountered in the derivatives of yield function. Based on Koiter's associated (low rule, the numerical implementation to accommodate the vertex singularity had been generalized. The set of applied strains had been formulated and defined as the domain of metastability. This study is focused on validity of the domain of metastability by a regularized method. Infinitesimal vicinity adjacent to the vertex is considered to regularize all of plastic flow in outwards normal direction to the yield surface. It was confirmed that the metastable domain of the Sekiguchi-Ohta model is bounded by an elliptical cone in principal strain space.
2009, Theoretical and Applied Mechanics Japan, 57, 89 - 94Scientific journal
- Numerical modelling for life cycle planning of highway embankments on soft foundations
This paper presents the applicability of soil/water coupled finite element modelling (S/W FEM) as a tool for supporting life cycle planning of highway embankments on soft foundations. To begin with, as a case study, the S/W FEM of a 30 years old existing highway embankment is conducted and its prediction of long-term settlement and deformation is verified. The constitutive model mainly employed in this modelling is an elasto-viscoplastic model developed by Sekiguchi and Ohta (1977). Secondly, the life cycle planning of highway embankments based on the FE simulation of long-term performance is trialled. The geotechnical performance-related indicators (GPRIs) relevant to geotechnical indicators (GIs) of highway embankments are investigated for life cycle planning. The case study with numerical modelling and life cycle planning of highway embankments described in this paper may be found to be applicable and efficient for use in geotechnical asset management practices.
CRC PRESS-TAYLOR & FRANCIS GROUP, 2008, ADVANCES IN TRANSPORTATION GEOTECHNICS, 389 - +, English[Refereed]
International conference proceedings
- Dec. 2007, Proc 13th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, CD-ROM, EnglishAnalysis of embankment by nonlinear contractancy description
[Refereed]
International conference proceedings
- May 2007, Proceeding of the 16th Southeast Asian Geotechnical Conference, pp.289-296 (0), 325 - 331, EnglishCoefficient of earth pressure at-rest derived from the Sekiguchi-Ohta model
[Refereed]
International conference proceedings
- 2007, First Sri Lankan Geotechnical Society International Conference on Soil and Rock Engineering(CD-ROM)Comparison of original and modified cam clay models extended for K0-consolidated clays
- 2007, First Sri Lankan Geotechnical Society International Conference on Soil and Rock Engineering(CD-ROM)Soil/water coupled F.E. Simulation of field performance of 5 embankments placed on homogeneous clay
The mechanical behaviour of 5 pre-loading highway embankments placed on very uniform soft Ariake Clay is analysed by employing the soil/water coupled finite element programme DACSAR coded by Iizuka and Ohta incorporating an elasto-viscoplastic constitutive model proposed by Sekiguchi and Ohta. A series of computer simulation confirms that a set of input data closer to the reality results in the better performance of the computer simulation especially in calculating the lateral movement of subsoil beneath the toe of the embankments. Copyright ASCE 2006.
2006, Geotechnical Special Publication, (156), 440 - 453, English[Refereed]
International conference proceedings
- 2005, 21世紀COEプログラム「都市地震工学の発展と体系化」, 96 (No.), 35 - 46地盤動態解析の基礎理論
盛土構造物の土/水連成弾・粘塑性有限要素プログラムによる動態解析は,過去何年かの実績によって高い再現性が確認されている.そこで,本研究では軟弱地盤上に盛土構造物を建設する際に講じる対策工法を評価する手段として有限要素プログラムを利用することを目的とし,秋田県,大沢郷に建設された道路盛土を対象に解析を行った.軟弱地盤対策工に関する仮想的なケーススタディの解析結果を用いて軟弱地盤対策工の評価を行った.
The Japanese Geotechnical Society, 2004, Proceedings of the Japan National Conference on Geotechnical Engineering, 39, 1325 - 1326性能発注では,設計・施工段階における将来の性能保証やライフサイクルコストの評価が要求される。本研究は、既に長期間供用されている軟弱地盤上の道路盛土を対象とし、追加地盤調査と挙動解析をペアで実施することにより、過去の挙動履歴をどの程度評価できるか検討したものである。盛土の法肩と平地部で実施した地盤調査データと土/水連成弾・粘塑性有限要素法による挙動解析結果は,施工期間の挙動計測や地盤調査結果による過去の実績を表現できており,当該解析手法の性能設計への適用性や既存盛土の改修工事設計等に有用であることを確認した。
The Japanese Geotechnical Society, 2004, Proceedings of the Japan National Conference on Geotechnical Engineering, 39, 1327 - 1328- Sep. 2003, Proc. International Workshop on Geotechnics of Soft Soils, pp.49-62, English15 years continuous settlement of a highway embankment on very soft clay
[Refereed]
International conference proceedings
有明粘土が堆積する長崎自動車道武雄インターチェンジ付近の平地部において、幅と高さの比が異なるベーンせん断試験やサンプリング試料による鉛直・水平両方向の圧密及び一面せん断試験、三軸CUバー試験等を実施した。本研究では、これらの力学試験結果や物理試験による塑性指数から推定あるいは決定される静止土圧係数や限界状態定数について比較検討することにより、各種算定式の信頼性について精査を行う。また、実際の盛土に対する土/水連成弾塑性FEM解析を実施し、静止土圧係数や強度定数の算定法の違いが結果に及ぼす影響について検討した。
The Japanese Geotechnical Society, 2003, Proceedings of the Japan National Conference on Geotechnical Engineering, 38, 299 - 300A lack of analytical benchmark solution makes it difficult to verify soil dynamics simulations of nonlinear geotechnical problems. This study makes use of a novel code verification technique, the method of numerically manufactured solutions (MNMS), to overcome such difficulty. Using MNMS, the accuracy of a nonlinear soil dynamics simulation code based on finite element method (FEM) is verified. The orders of the convergence rate of the relative errors with respect to the discretization size are found to be in good agreement with the theoretical values prescribed by the numerical methods.
National Committee for IUTAM, 2019, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 65, 233 - 233, Japanese
MISC
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- 第39回地盤工学研究発表会, 2004長期供用後の地盤調査と挙動解析による軟弱地盤上の道路盛土の性能評価
- 第38回地盤工学研究発表会, 2003有明粘土地盤における静止土圧係数および限界状態定数推定法の精査
- 第38回地盤工学研究発表会, 2003有明粘土地盤における静止土圧係数および限界状態定数推定法の精査
- 第37回地盤工学研究発表会, 2002軟弱地盤上の盛土構造物の挙動解析‐施工過程の詳細な再現‐
- 第37回地盤工学研究発表会, 2002軟弱地盤上の盛土構造物の挙動解析‐長期的な性能‐
Association Memberships
Research Projects
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Kobe University, Apr. 2020 - Mar. 2023, Principal investigator東京東部低地における液状化等による防潮施設の被害予測
- 学術研究助成基金助成金／基盤研究(C), Apr. 2018 - Mar. 2021, Coinvestigator
Competitive research funding
- 学術研究助成基金助成金／若手研究(B), Apr. 2017 - Mar. 2019, Principal investigator
Competitive research funding
- 鉄道総合技術研究所, 共同研究, 2017 - 2019, Principal investigator損傷過程を考慮可能な盛土の解析手法に関する研究
- 学術研究助成基金助成金／挑戦的萌芽研究, Apr. 2016 - Mar. 2018, Coinvestigator
Competitive research funding
- 株式会社 大林組, 共同研究, 2016 - 2019, Principal investigator地盤の浸透破壊の予測技術の高度化
- 前田建設 株式会社, 共同研究, 2016 - 2017, Principal investigator地盤工学に関わる周辺環境の影響と問題発生メカニズムの工学的検討
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Kyoto University, Apr. 2015 - Mar. 2018, CoinvestigatorExperimental and theoretical diagnosis of arch collapse with liquefaction in embankment constructed on soft ground subjected to seismic loading
In this study, dynamic centrifuge model tests of an embankment placing on rigid base and soft base modelled by urethane were conducted to investigate the liquefaction resistance in association with the change of the stress distribution inside embankments due to basal subsidence. Experimental results reveal that lateral spreading deformation causes reduction in horizontal earth pressure along the bottom of highly-compacted embankments due to concave settlement of the base. Moreover, arch action was formed underneath the core of embankment as reduction in vertical earth pressure was observed due to the basal subsidence and loosening of inner zone after submersion in Metalose supplied inside the embankment. Comparisons between embankments built on the urethane ground and those built on rigid ground imply that basal subsidence decreases liquefaction resistance in embankments during an earthquake.
- 株式会社 大林組, 受託研究, 2015 - 2015, Principal investigatorソイルセメント柱列壁の実大載荷試験のシミュレーション
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Tokyo Institute of Technology, Apr. 2013 - Mar. 2016, CoinvestigatorOn the impact of deterioration of soils due to seepage-induced internal erosion on seismic performance of existing embankment
Internal erosion has a certain impact on seismic performance of existing embankment. To evaluate conditions of the embankment before earthquake, deterioration process of soil/geotechnical structure due to seepage flow is needed to be understood. In this research, suffusion is focused on among the various modes of the internal erosion. Physical model tests and numerical simulations are conducted to examine the seepage-induced suffusion process in the embankment. Optical quantification of suffusion in plane strain physical model is successfully made using digital microscope. A plane strain erosion apparatus equipped with microscope observation is developed, which allows detailed observation of the deterioration process and investigation of the mechanical consequences of soils subjected to internal erosion.
- 科学研究費補助金／基盤研究(B), Apr. 2012 - Mar. 2016, Coinvestigator
Competitive research funding
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B), Grant-in-Aid for Young Scientists (B), Tokyo Institute of Technology, 2011 - 2012, Coinvestigator not use grantsMonitoring technique development for stress distribution in groundslopes based on the Lame-Maxwell equations of equilibrium
This research aims to investigate the basic concept of load transfer mechanisms by focusing on physical model tests and theoretical analysis of the stress field. In order to perform a quantitative evaluation by stress analysis based on the Lame-Maxwell equations of equilibrium, theoretical solutions of stress distribution in sand heap, sand valley, earth retaining wall and slope were developed and verified by physical models. Finally, the use of the cylindrical air gypsum plaster on the slopes as a monitoring method of principal stress direction stress was examined by observing the direction of the crack.
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Kobe University, 2009 - 2011, CoinvestigatorSalt damage/Ground deformation Mechanism and its repair method using porous ceramic particles made from paper sludge
It is well known that salt rock layer is widely deposited under the Eurasian basement. Underground water contains weakly salt where the salt rock layer is occasionally deposited near the ground surface. Such a typical example can be seen in the northeast area of Thailand. Agricultural productivity decreases due to the salt damage of that the salty ground water level gradually rises resulting in appearance of salt crystals on the ground surface associated with annual repeat of rainy and dry seasons. This research project is intended to develop a numerical computation technique to reveal the mechanism of salt damage which will lead desertification. On the other hand, paper sludge discharged from paper manufacture causes a serious environmental problem. Such sludge can be changed to porous stable ceramic materials by burning it at 1300 degrees. This research project also aims at utilizing such materials to protect and repair the salt damage.
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research, Grant-in-Aid for Challenging Exploratory Research, Tokyo Institute of Technology, 2009 - 2010, Coinvestigator干潟に生息する二枚貝の生態行動の土質力学的解明とその数値モデル化
本研究は、干潟に生息する二枚貝に着目しその生態行動を一連の土質力学的問題として分解して、二枚貝の生態行動を数値モデル化することを目的とし、初年度では干潟でアサリとシオフキを対象として二枚貝の潜砂挙動の観察を行い、地盤上に水平に横たわる二枚貝は「足を突っ込む」「体を立てる」「体を引き込む」という3つの段階を経て地盤内に潜るということを明らかにした。 上記の成果を元に,本年度は二枚貝が生息可能な地盤条件を推定可能な理論モデルの構築を行った。理論モデルは、干潟材料を摩擦性の剛塑性体と仮定し、基礎の極限支持力解の3種を援用するものである。「足を突っ込む」行為は、円錐物体の貫入問題としてモデル化されうる。すなわち二枚貝の足を基礎とみなし、基礎の極限支持力と足の伸長力による設置厚を比較することで、地盤の破壊、すなわち貫入が可能であると判定するものである。ここで二枚貝の足幅を殻長の1/4、足の円錐頂角を30度、足の伸長力を殻長に比例するとの仮定ものとで理論計算を行うと、殻長20cmの二枚貝は、干潟の相対密度が60%程度までは足を突っ込めるが相対密度80%では不可能になることが導け、生息可能な干潟の地盤力学的パラメータとの関連が明らかとなった。次に「体を立てる」行為は、剛体の力学モデルによる転倒判定と拡張された浅い基礎の支持力問題として解釈が可能である。転倒しない場合は、二枚貝の体を基礎とみなし、基礎の極限支持力と、自重および足の収縮力との合力による接地圧の比較から地盤破壊が判定される。その結果、殻長とともに水位が大きく影響していることが導ける。 このように、理論支持力モデルによって、干潟の密度、水位条件によって二枚貝の生息範囲が限定されることが明らかとなった。さらに二枚貝は相対密度の高い締まった地盤では、自らの体を傾斜させることで低下する基礎の極限支持力を巧みに利用していることも、支持力モデルから説明可能であることが明らかとなった。
- 厚生労働科学研究費補助金, 2008 - 2010, Coinvestigator土砂崩壊防止のための対策工に関する研究
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A), Grant-in-Aid for Scientific Research (A), Tokyo Institute of Technology, 2008 - 2010, CoinvestigatorFundamental study on seismic stability of tunnels in weakly cemented soil and its countermeasures
Tunnels in weakly cemented or no-cemented soils are susceptible to damages by ground motions or displacements caused by earthquake. In order to investigate complicated seismic soil-structure interaction of such tunnels, various model testing techniques has been developed, such as an active type shear box and a fault simulators. Three specific conditions were considered in this study, namely, 1) shallow tunnels which are subjected to shear deformation of grounds, 2) Tunnels in weak ground which is subjected to large earth pressure, and 3) tunnels in an alluvium subjected to fault displacement. From the model test results and numerical simulation, typical deformation and failure mechanism of these tunnels are scrutinized and effective countermeasures against them are discussed.