Papers - KYOKOWA Hiroyuki
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Effect of lattice-frame reinforced geosynthetics on seismic stability improvement of embankment on loose sand deposit Reviewed
M. Okamoto, T. Obara, Y. Nakajima, T. Yoshida, Y. Kitamoto, H. Kyokawa, Y. Sawada, K. Fujisaki
15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability 2324 - 2329 2015
Publishing type：Research paper (international conference proceedings)
The authors have developed a specific geosynthetic for reduction of differential settlement, composed of woven textile sheet and lattice frame of mortar injected fabric hoses, providing high bending rigidity. To examine the reinforcement effect of this geosynthetic system, called the lattice-frame reinforced (LFR) sheet, a series of dynamic centrifugal model tests and finite element analyses were carried out. The results showed that the LFR sheet was capable of reducing differential settlement due to seismic liquefaction and effective to reduce horizontal deformation of liquefiable layer as well as the case in which the improved zone was totally set under the embankment.
DOI： 10.3208/jgssp.IGS-28
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Why do constitutive models using (p and q) have problems? Reviewed
T. Nakai, H. M. Shahin, M. Hinokio, H. Kyokawa
Geomechanics from Micro to Macro - Proceedings of the TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, IS-Cambridge 2014 2 683 - 688 2015
Publishing type：Research paper (international conference proceedings)
Most constitutive models have been formulated using the stress invariants (p and q) since the Cam clay model was developed. It is known that such models cannot describe uniquely the deformation and strength of soils under three different principal stresses. Then, the concept of tij has been proposed to describe uniquely the stress-strain behaviors in general three-dimensional (3D) stress conditions. In this paper, some inevitable problems of the ordinary models are firstly clarified. After then, the meaning of the tij concept and the method to apply tij concept to elastoplastic models are presented, since the details of the tij concept were described in the previous papers. This concept was found out from the idea that the frictional law essentially governs soil behavior. Using this concept, any kinds of one-dimensional models and/or three-dimensional models formulated by using (p and q) can be easily extended to general three-dimensional models. © 2015 Taylor & Francis Group.
DOI： 10.1201/b17395-122
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Simple modeling of time-dependent behavior for structured soils Reviewed
Teruo Nakai, Hossain Md Shahin, Hiroyuki Kyokawa
Springer Series in Geomechanics and Geoengineering none 331 - 337 2015
Publishing type：Research paper (international conference proceedings)
© Springer International Publishing Switzerland 2015. A simple model to describe time-dependent behavior of various soils in 1D stress conditions is presented in this paper. The model is formulated not using the usual viscoplastic theories such as over-stress type and non-stationary flow surface type but utilizing the subloading surface concept by Hashiguchi (1980), and paying attention to the experimental results that the normally consolidation line (NCL) on the e-ln σ plane shift depending on the strain rate. The present model can describe various time-dependent behaviors not only of normally consolidated soil but also of over consolidated and naturally deposited soils in the same manner without violating the objectivities. The 1D model can easily be extended to the 3D using the tij concept (Nakai and Mihara 1984).
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Simple modeling of time-dependent behavior for normally consolidated soil and structured soils Reviewed
T. Nakai, H. M. Shahin, H. Kyokawa
49th US Rock Mechanics / Geomechanics Symposium 2015 2 878 - 885 2015
Publishing type：Research paper (international conference proceedings)
Copyright 2015 ARMA, American Rock Mechanics Association. Simple models to describe time-dependent behavior of geomaterials in ID and 3D stress conditions are presented. After explaining previous viscoplastic models and the problems these models contain, a new time-dependent model is presented which is formulated not using usual viscoplastic theories but utilizing the subloading surface concept by Hashiguchi [1]. Based on experimental results, it has been shown that the normal consolidation line (NCL) and the critical state line (CSL) on the e - Inσ plane can shift vertically depending on the strain rate. The model can describe time-dependent behaviors of both normally consolidated unstructured as well as structured soils in the same manner. To describe the behavior of structured soil, a state variable, ρ, which represents the influence of density, and another state variable, ω, which represents the bonding effect, are introduced. After the formulation is explained in one-dimension to highlight the fundamental concepts of the model, it is extended to three-dimensions using the tij concept [2].
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Simple Expression of the Ultimate Lateral Resistance of Piles on Sand based on Active Pile Length Reviewed
AGLIPAY Mary Roxanne, KONAGAI Kazuo, KIYOTA Takashi, KYOKAWA Hiroyuki
Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE)) 71 ( 4 ) I_329 - I_336 2015
Language：Japanese Publisher：Japan Society of Civil Engineers
Simulation of the in-situ behavior of pile foundation is necessary in the seismic design and assessment for target structural integrity and performance during earthquakes. Generally, the pile behavior is governed by its deformation. For commonly used flexible piles, this deformation is observed to be significantly greater near the ground surface and becomes negligible with increasing depth. This region of significant deformation is defined as the active pile length, <i>L<sub>a</sub></i>. To simply investigate the behavior response of pile embedded in a homogeneous sandy soil, a plane strain condition using the 2D finite element method in nonlinear analysis was done. The subloading <i>t<sub>ij</sub></i> model is used to model the elasto-plastic behavior of the soil and the pile is modeled as a 2D continuum-based beam element. Based on the rigorous solution, piles reach the ultimate state of its side soil under large lateral deformations. In this case, a soil wedge can be observed being pushed up along this active pile length. Therefore, a simplified method using the active pile length as a key parameter to describe the ultimate lateral resistance of piles embedded in sand is presented for more practical approach in the seismic design and assessment of piles.
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Numerical simulation of thermo-hydro-mechanically coupled processes during ground freezing and thawing Reviewed
H. Kyokawa, Y. W. Bekele
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 379 - 384 2015
Publishing type：Research paper (international conference proceedings)
Fully coupled Thermo-Hydro-Mechanical (THM) processes in the freezing and thawing phenomena of ground are studied numerically. Theoretical formulations for modeling the THM process of frozen soil are presented in this study. Fully saturated frozen soil composed of soil, water and ice is modeled as a homogeneous three-phase mixture (theory of multiphase mixture) and the governing equations of frozen ground are accordingly derived by combining the individual governing equations constituting phases with consideration of interaction between phases, especially water and ice phases. Those governing equations are solved by the finite element method with simple supplementary equations representing mechanical/hydraulic/thermal characteristics of frozen soil. From a parametric study on freezing process of one-dimensional soil column test, it is shown that the freezing volume change is affected by the hydraulic condition since the freezing consolidation occurs due to the changing of water pressure and effective stress at unfrozen area. © 2015 Taylor & Francis Group, London.
DOI： 10.1201/b17435-63
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On thermo-hydro-mechanically (THM) coupled finite element modeling of ground freezing and thawing Reviewed
Y. W. Bekele, H. Kyokawa
Numerical Methods in Geotechnical Engineering - Proceedings of the 8th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2014 2 959 - 964 2014
Publishing type：Research paper (international conference proceedings)
Fully coupled thermo-hydro-mechanical (THM) processes in the freezing and thawing phenomena of ground are studied numerically. Theoretical and numerical formulations for modeling the THM process is proposed. Porous media theory is used for deriving the governing equations in the theoretical formulation. A saturated frozen soil is assumed and this three-phase porous medium is modeled as a homogeneous continuum. The main governing equations derived in the theoretical formulation are the linear momentum balance equation, the energy balance equation and the mass balance equation for the pores. Supplementary equations in the theoretical formulation include thermodynamic equilibrium for pore pressures, a soil-water characteristic curve for the degree of water saturation, Darcy's law for water flow and Fourier's law for thermal conduction. The finite element method is used for the spatial discretization of the governing partial differential equations and the finite difference method for temporal discretization. The matrix equations are derived to accomodate both linear and nonlinear material behaviors for the constitutive equations of the soil skeleton. © 2014 Taylor & Francis Group, London.
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Rational expression of time-dependent behavior from normally consolidated soil to naturally deposited soil Reviewed
T. Nakai, H. M. Shahin, H. Kyokawa
18th International Conference on Soil Mechanics and Geotechnical Engineering: Challenges and Innovations in Geotechnics, ICSMGE 2013 1 255 - 258 2013
Publishing type：Research paper (international conference proceedings)
Fundamental concepts of the ordinary elasto-viscoplastic modelings, which are the non-statonary flow surface model and the over-stress type model, are explained in one-dimensional (1D) compression of normally consolidated soil for easy understading. Then, a new approach to describe various time-dependent behaviors of soils is presented extending the advanced elastoplasitic theory based on the subloading surface concept without employing usual elasto-viscoplastic theories. Throughout the simulations of various time-dependent behaviors of normally consolidated clay, the features of these three types of time-denpendent models are clarified. In addtoin, 1D anlyses using the proposed model are carried out not only for normally consolidated clay but also for over-consolidated clay and strauctured clay such as nuturally deposited clay. The analytical results simulate well the features of time-dependent behavior of various clays including the delayed settlement of sturctured clay.
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Significance of t<inf>ij</inf> concept in constitutive modeling of geomatrials Reviewed
T. Nakai, H. M. Shahin, M. Hinokio, H. Kyokawa
Computational Geomechanics, COMGEO III - Proceedings of the 3nd International Symposium on Computational Geomechanics 108 - 122 2013
Publishing type：Research paper (international conference proceedings)
© 2013 Computational Geomechanics, COMGEO III - Proceedings of the 3nd International Symposium on Computational Geomechanics. All rights reserved. Simple and unified method to describe stress-strain behavior in general three-dimensional stress condition, which has been called the tij concept, was presented by Nakai & Mihara (1984). Since this concept is based on the idea that the frictional law essentially governs soil behavior, its meaning is very clear. Using this concept, any kind of one-dimensional model and/or three-dimensional model formulated by using (p and q) can be easily extended to general three-dimensional conditions. Method for formulating the constitutive model using the tij concept and the meaning of the tij operator are reviewed. The validity of this concept is also checked by simulation of various types of shear tests in general three-dimensional conditions.
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Liquefaction-induced damage on the reclaimed area in Urayasu city and the result of SWS test Reviewed
YOKOYAMA Yutaka, KYOKAWA Hiroyuki, KONDO Yasuto, KIYOTA Takashi
SEISAN KENKYU 64 ( 6 ) 853 - 857 2012
Language：Japanese Publisher：Institute of Industrial Science The University of Tokyo
The 2011 off the Pacific coast of Tohoku Earthquake induced liquefaction causing damage to residences and buried lifelines in the entire filled ground in Urayasu city, Chiba prefecture. Since immediately after the earthquake, authors have conducted SWS test at several monthly intervals at the site in the particularly serious damaged area. The result of SWS tests suggests that the fill sandy soil having a high fine content was liquefied, and the penetration resistance of its layer which had remarkably decreased due to liquefaction recovered two month after the earthquake. Moreover, the possibility of re-liquefaction is discussed based on the value of liquefaction resistance in this report. [This abstract is not included in the PDF]
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Survey report on Liquefaction-induced damage in Urayasu city caused by The 2011 of the Pacific coast of Tohoku Earthquake Reviewed
KYOKAWA Hiroyuki, KIYOTA Takashi, KONDO Yasuto, KONAGAI Kazuo
Japanese Geotechnical Journal 7 ( 1 ) 265 - 273 2012
Language：Japanese Publisher：The Japanese Geotechnical Society
On March 11<sup>th</sup>, 2011, the Pacific coast of Tohoku Earthquake hit east Japan. The earthquake-induced liquefaction caused severe damage to residences and buried lifelines in Tokyo bay area. This report summarizes result from field investigation including SWS test in Urayasu city, Chiba prefecture. Grading analysis was also conducted on in situ samples and boiled sands which were retrieved at liquefaction sites. From these investigations, this report shows the liquefaction characteristic causing the wide range of serious subsidence in reclaimed area in Urayasu city. Comparing with the result of investigations in Christchurch city, New Zealand which has suffered the damage of re-liquefactions by the 2010-2011 Canterbury Earthquake, the possibility of re-liquefaction in Urayasu is discussed in this report.
DOI： 10.3208/jgs.7.265
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Description of time-dependent behavior of soils using subloading surface concept Reviewed
Nakai Teruo, Shahin Hossain Md., Kikumoto Mamoru, Kyokawa Hiroyuki
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan 61 ( 0 ) 108 - 108 2012
Language：Japanese Publisher：National Committee for IUTAM
As an application of the simple and advanced method for modeling of soil features developed in our laboratory, one-dimensional and three-dimensional inviscid models are extended to ones which can describe various time-dependent behaviors of soils not using the existing viscoplastic theories but introducing and revising the subloading surface concept by Hashiguchi. The performance of the proposed models are confirmed through the simulations of various time-dependent behaviors on normally and over consolidated clays and naturally deposited clay
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SURFACE RUPTURE OF THE NORMAL SEISMIC FAULTS AND SLOPE FAILURES APPEARED IN APRIL 11<sup>th</sup>, 2011 FUKUSHIMA-PREFECTURE HAMADOORI EARTHQUAKE Reviewed
KAZMI Zaheer Abbas, KONAGAI Kazuo, KYOKAWA Hiroyuki, TETIK Cigdem
Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE)) 68 ( 4 ) I_1285 - I_1292 2012
Language：English Publisher：Japan Society of Civil Engineers
On April 11<sup>th</sup>, 2011, Iwaki region of Fukushima prefecture was jolted by Fukushima-Prefecture Hamadoori Earthquake. Surface ruptures were observed along causative Idosawa and Yunotake normal faults. In addition to numerous small slope failures, a coherent landslide and building structures of Tabito Junior High School, bisected by Idosawa Fault, were found along the causative faults. A precise digital elevation model of the coherent landslide was obtained through the ground and air-born LiDAR surveys. The measurements of perimeters of the gymnasium building and the swimming pool of Tabito Junior High School have shown that ground undergoes a slow and steady/continual deformation.
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ROAD BRIDGES IN MINAMI-SANRIKU WASHED AWAY IN THE MARCH 11<sup>th</sup> 2011 GREAT EAST JAPAN EARTHQUAKE AND TSUNAMI Reviewed
AGLIPAY Mary Roxanne I., KONAGAI Kazuo, KYOKAWA Hiroyuki, KESHAB Sharma
Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE)) 68 ( 4 ) I_1307 - I_1314 2012
Language：English Publisher：Japan Society of Civil Engineers
On March 11<sup>th</sup>, 2011, Minami-Sanriku, located in the northeastern coast of Japan was severely inundated by the tsunami that followed the Great East Japan Earthquake on March 11, 2011. Road bridges near the coastlines in this area have been extensively damaged with their decks being overturned or carried over long distances. An attempt was made to deduce as rational scenarios as possible before remaining debris was cleaned up. Though the reasons for the washout of bridges can be many and complex, it is to be noted that bridge decks have hollows for the optimum light-weight solution, which fact eventually allowed the bridge decks to be carried over remarkable distances. Poor connection details and cavities, hollows between deck beams, are considered to have facilitated overturning due to uplift forces.
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A simple and unified one-dimensional model to describe various characteristics of soils Reviewed
Teruo Nakai, Hossain M.D. Shahin, Mamoru Kikumoto, Hiroyuki Kyokawa, Feng Zhang, Marcio M. Farias
Soils and Foundations 51 ( 6 ) 1129 - 1148 2011.12
Language：English Publishing type：Research paper (scientific journal) Publisher：The Japanese Geotechnical Society
A simple and unified constitutive model for soils, considering various effects such as the influences of density, bonding, time dependent behavior and others, is presented in this paper. The elastoplastic behavior of over consolidated non-structured soils under a one-dimensional stress condition is firstly presented by introducing a state variable that represents the influence of density (stage I). To describe the one-dimensional stress-strain behavior of structured soils, attention is focused on density and bonding as the main factors that affect the response of this type of soil, because it can be considered that soil a skeleton structure which is in a looser state than that of a normally consolidated soil is formed by bonding effects (stage II). Furthermore, a simple method is presented which allows for other soil characteristics to be considered, such as time and temperature dependency, and the effect of suction in unsaturated soils. Experimental observations show that the normally consolidated line (NCL) in the void ratio-stress relation (e.g., e-ln s curve) shifts depending on the change of strain rate, temperature, suction and others (stage III). The validation of the model at stages I and II is demonstrated by simulating one-dimensional consolidation tests for normally consolidated, over consolidated and natural clays. The applicability of the model at stage III is verified not only by the simulations of time-dependent behavior of clays in one-dimensional element tests but also by the soil-water coupled finite element analysis of oedometer tests as a boundary value problem. The extension from one-dimensional models to three-dimensional models is easily achieved by defining the yield function using stress invariants instead of one-dimensional stress 'σ' and by assuming an appropriate flow rule in stress space. The details of the modeling in general three-dimensional stress conditions will be described in another paper (Nakai et al., 2011).
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A simple and unified three-dimensional model to describe various characteristics of soils Reviewed
Teruo Nakai, Hossain M.D. Shahin, Mamoru Kikumoto, Hiroyuki Kyokawa, Feng Zhang, Marcio M. Farias
Soils and Foundations 51 ( 6 ) 1149 - 1168 2011.12
Language：English Publishing type：Research paper (scientific journal) Publisher：The Japanese Geotechnical Society
A simple and unified model to describe some features of soil behavior in one dimensional condition is presented in another related paper (Nakai et al., 2011). In the present paper, this one-dimensional model is extended to describe not only the soil features explained in the related paper three-dimensionally (3D), but also to explain other soil features found in multi-dimensional conditions, such as shear behavior considering the influence of intermediate principal stress on the deformation and strength of soils, and the positive and negative soil dilatancy. Firstly, the first step in extending any kind of one-dimensional model to a three-dimensional one is explained in detail: the significance of tij concept and its stress invariants (tN and tS) is explained and compared with the idea of ordinary stress invariants (p and q) used in the Cam clay model. Then, the advanced elastoplastic relations (stages I to III) in the one-dimensional condition presented in the related paper are re-formulated as three-dimensional models-e.g., a model for over consolidated soil, a model for structured soil and a model which considers time-dependent behavior. The three-dimensional models for over consolidated soil (stage I) and structured soil (stage II) are formulated so as to coincide with the subloading tij model developed by Nakai and Hinokio (2004) and by Nakai (2007), respectively. The validity of the models in stage I and stage II is checked by simulations of various shear tests for sands with different void ratios and for over consolidated and natural clays under drained and undrained conditions. The model in stage III is verified by simulations of shear tests with different strain rates, and by simulating creep tests and others, not only for normally consolidated clay but also for non-structured and structured over consolidated clays under drained and undrained conditions.
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Survey report on damage of landfill in Miyagi Prefecture caused by the 2011 Tohoku earthquake Reviewed
KIYOTA Takashi, KYOKAWA Hiroyuki
SEISAN KENKYU 63 ( 6 ) 709 - 715 2011
Language：Japanese Publisher：Institute of Industrial Science The University of Tokyo
The Tohoku earthquake hit the east Japan on March 11<sup>th</sup>, 2011. Many coastal areas along Pacific Ocean were destroyed by tsunami, while a large number of geo-disasters was caused by the earthquake over a large extent of area in the eastern Japan. In Miyagi prefecture, there are many artificial earth fills for housing estate that suffered from serious earthquake-induced damage. During the construction of these areas, cut-and-fill work was carried out, and most of the significant earthquake-induced damage could be found in a fill part. This report summarizes damage aspects of landfills that have so far been found by the author’s field investigations. [This abstract is not included in the PDF]<br>
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Simple modelling of stress-strain behaviour of unsaturated soils Reviewed
M. Kikumoto, H. Kyokawa, T. Nakai
14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering 2011
Publishing type：Research paper (international conference proceedings)
A simple constitutive model taking account of the necessary features of unsaturated soils is proposed by extending an elastoplastic model for saturated soils. The proposed model is formulated using the Bishop's effective stress and the critical state friction angle is thus assumed to be constant. In the model, the decrease (or increase) in the degree of saturation is linked with upward (or downward) movement of normally consolidation line in the plane of mean effective stress and void ratio, by which the typical volumetric behaviours of unsaturated soils are properly described. A simple method for extending a classical water characteristics curve assuming a unique relationship between suction and degree of saturation to incorporate the effects of hydraulic hysteresis and density is also proposed. In this paper, mechanisms of hydraulic collapse and compaction of soils are discussed through a series of simulations by the proposed model.
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New approach for modeling time-dependent behavior of geomaterials Reviewed
T. Nakai, H. M. Shahin, M. Kikumoto, H. Kyokawa, F. Zhang, M. M. Farias
Computational Geomechanics, COMGEO II - Proceedings of the 2nd International Symposium on Computational Geomechanics 49 - 62 2011
Publishing type：Research paper (international conference proceedings)
A simple method to describe time-dependent behavior for various kinds of soils is presented. The model is formulated not using usual viscoplastic theories but utilizing the subloading surface concept by Hashiguchi (1980) and paying attention to the experimental results, which show that the normal consolidation line (NCL) and the critical state line (CSL) on the e - lnσ plane shift depending on the strain rate. The formulation is first explained in one-dimensional conditions in order to understand the method easily. After that, using the tij concept proposed by Nakai and Mihara (1984), the one-dimensional model is extended to a three-dimensional one. The validity of the present model is verified using various kinds of simulations of time-dependent behavior in both conditions - e.g., onedimensional compression tests under different strain rate, oedometer tests including secondary consolidation, creep and stress relaxation tests, constant strain rate triaxial tests and others.
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Modeling of one-dimensional consolidation behavior for clays Reviewed
T. Nakai, H. M. Shahin, H. Kyokawa, Y. Miyahara
14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering 2011
Publishing type：Research paper (international conference proceedings)
A simple method to describe stress-strain behavior of structured soils under normally and over consolidated states in one-dimensional stress condition is presented by introducing a state variable (ρ) to represent the influence of density and another state valuable (ω) which represents the imaginary increase of density by boding effect. Then, another state variable (ψ) is introduced to describe the time dependent behavior, the temperature dependent behavior, the effect of saturation and others. Here, the state valuable (ψ) has a function which shifts the normally consolidation line (NCL) due to the strain rate, temperature, saturation and others. Although the models are formulated in one-dimensional condition in this paper, it is possible to extend them to three-dimensional ones using t ij concept, easily.
