Faculty Profiles - NODA, Toshihiro

Papers - NODA, Toshihiro

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Effects of embankment rigidity on behavior of naturally deposited soils during/after earthquakes

Noda, T., Asaoka, A, Nakano, M. Nakai, K. and Takeuchi, H.

Proc. of International Workshop on Earthquake Hazards and Mitigations page： 249-256 2007.12

Language：English

The effects of the rigidity of earth structures such as embankments on the deformation behavior of sand-clay laminated soil (top layer of sand, under-layer of clay) and embankment coupled systems during and after earthquakes were investigated. The investigation was carried out through static and/or dynamic soil-water coupled finite deformation analysis using the SYS Cam-clay model as the constitutive equation of soils. The results showed that the large-scale deformation behavior of the top sand layer during and after seismic activity is different from that of the clay under-layer depending on the rigidity of the embankment. If the embankment is made up of soft soil, the occurrence of liquefaction of the top sand layer during an earthquake is accompanied by large-scale deformation of the embankment itself, but the clay under-layer remains almost unaffected even after the earthquake. In contrast, if the embankment is rigid, while the sand layer is again subjected to liquefaction during the earthquake, the embankment load is transferred to the lower clay layer, leading to large-scale ground (clay layer) settlement after the earthquake has passed.

Elasto-plastic description of various soils having distinct skeleton structure Invited

Noda, T.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) Vol. Post conference volume page： 364-373 2007.12

Language：English

Naturally deposited clay and loose sand are generally said to have a highly developed soil skeleton structure. Of the three skeletal determinants (structure, overconsolidation, anisotropoy), this paper focuses particularly on structure and argues that alongside structural degradation there is also an opposite process of upgradation. This upgradation process is then introduced as a new extension into the authors' existing SYS Cam-clay model, which incorporates the soil skeleton mechanisms into the original Cam-clay model as a base. Using this extended model, observations are made on the role of the upgradation process in leading to a ductility behavior in the naturally deposited clay and to a cyclic mobility behavior in the sand.

Structural upgradation in clay and sand accompanying plastic swelling Reviewed

Noda, T., Asaoka, A., Nakai, K. and Tashiro, M.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) page： 23-26 2007.12

Language：English

Liquefaction-induced consolidation settlement of soil after earthquake Reviewed

Asaoka, A., Sawada, Y., Noda, T. and Nakai, K.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) page： 602-605 2007.12

Language：English

A calculated case history concerning a soil of alternate layers of sand and clay is presented through a soil-water coupled computation employing the SYS Cam-clay model. Delayed consolidation settlement at this site has definitely been occurring as a result of embankment loading, and is in fact still continuing. In the computation, the delayed compression is due to a progressive breakdown in the clay skeleton structure. If there were to be an earthquake in the course of this delayed consolidation, even the medium-dense upper layer of sand would be certain to liquefy, resulting in considerable undrained shearing deformation in the clay layers beneath. Following the earthquake, the sand layer would consolidate within a few hours, but the underlying clay layers would remain subject to an additional consolidation settlement due to the earthquake for several tens of years.

Seismic/post-seismic response of a natural soil in delayed settlement

Asaoka, A. and Noda, T.

page： 73-86 2007.11

Language：English

This paper is a natural extension of the former paper (Asaoka and Noda, 2007), published by the same authors in the international workshop on Constitutive Modelling held in Hong Kong. The behavior of a naturally deposited soil in a delayed consolidation phase during/after and earthquake is presented as a soil-water coupled calculation example. Emphasis is laid throughout on the importance of an analytic technique that copes consistently with all soils, clay or sand, in all states, consolidated or liquefied/compacted, and is sufficiently all-round to cover both static and dynamic problems. The soil in the example consists of an 8m top-layer of sand and a 13m under-layer of alluvial clay, and has undergone more than 20 years of continuous consolidation settlement since being loaded with a highway embankment. Settlement loss exceeds 3m, and no end to the process is yet in sight. After showing that delayed compression of this kind is due to a progressive breakdown in the clay skeleton structure, this paper makes clear what will happen at this site if the top-layer of sand is liquefied by being struck by an earthquake and sustained consolidation/shear deformation then continues in the clay under-layer for several tens of years.

Explanation of cyclic mobility of soils: approach by stress-induced anisotropy Reviewed

Zhang, F., Ye, B., Noda, T., Nakano, M. and Nakai, K.

Soils and Foundations Vol. 47 ( 4 ) page： 635-648 2007.8

*Some bearing capacity characteristics of a structured naturally deposited clay soil Reviewed

Noda, T., Asaoka A. and Yamada S.

Soils and Foundations Vol. 47 ( 2 ) page： 285-301 2007.2

*All soils all states all round geo-analysis integration

Asaoka A. and Noda, T.

International Workshop on Constitutive Modelling - Development, Implementation, Evaluation, and Application page： 11-27 2007.1

Some distinct characteristics of natural clay that yields large residual consolidation settlement

Nakano, M., Tashiro, M., Noda, T. and Inagaki, M.

Proc. of 3rd Int. Workshop on New Frontiers in Computational Geomechanics (IWS-XIAN 2006) page： 73-78 2006.10

High ductility of structured clay and cyclic mobility of sand

Nakai, K., Noda, T., Nakano, M., Tashiro, M. and Asaoka, A.

Proc. of 3rd Int. Workshop on New Frontiers in Computational Geomechanics (IWS-XIAN 2006) page： 183-186 2006.10

飽和粘土地盤の圧密変形に及ぼす幾何学的非線形性の効果 Reviewed

竹内秀克，高稲敏浩，野田利弘

応用力学論文集，土木学会 Vol. 9 page： 539-550 2006.9

A super/subloading yield surface approach to compaction/liquefaction of sand and secondary consolidation of clay

Asaoka, A., Nakano, M. and Noda, T.

Proc. of the 2nd China-Japan Geotechnical Symposium page： 24-33 2005.10

Progressive consolidation settlement of naturally deposited clayey soil under embankment loading Reviewed

Noda, T., Asaoka A., Nakano, M., Yamada, E. and Tashiro, M.

Soils and Foundations Vol. 45 ( 5 ) page： 39-52 2005.10

Long-term consolidation settlement with progressive failure of soil skeleton structure

Asaoka, A. Noda, T. and Tashiro, M.

Proc. 2nd Int. Workshop on New Frontiers in Computational Geotechnics (IWS-Fortaleza) page： 83-88 2005.9

沈下低減と荷重分担に着目したパイルドラフト敷設地盤の変形解析 Reviewed

野田利弘，田代むつみ，高稲敏浩，浅岡顕

土木学会論文集 Vol. 799 ( Ⅲ-72 ) page： 37-49 2005.9

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

パイルドラフトを弾性体，自然堆積地盤を水～土2相系の弾塑性体として，3次元有限変形解析を実施し，基礎形式（杭長・杭配置）・ラフト剛性等が，沈下量低減と杭の荷重分担率に及ぼす影響を調べた．杭が長い場合ほど高拘束で低圧縮性の地盤深部に荷重が伝達され，また杭が外側に均等配置された場合ほど地盤から受ける杭の摩擦抵抗が大きくなるため沈下抑制に効果的であるが，杭の荷重分担率が大きくなる,などを示した．

Progressive consolidation of highly structured clay under embankment loading Reviewed

Asaoka A., Noda T., Yamada E. and Tashiro M.

Proc. the 16th Int. Conference on Soil Mechanics and Geotechnical Engineering page： 1831-1835 2005.9

Language：English

A long-term continuous consolidation settlement often observed in a natural soft clay foundation is numerically simulated using "super/subloading elasto-plastic constitutive model." The settlement behavior was found to exhibit accelerated rate of settlement several times during consolidation with a rise of excess pore water pressure under a constant applied load after the completion of the embankment. The likely causes of this lie in the progressive decay of soil skeleton structure of the clay which causes "compression accompanied by softening."

Soil-water coupled elasto-plastic analysis on bearing capacity of naturally deposited clay soil Reviewed

Noda, T. and Yamada S.

Proc. the 16th Int. Conference on Soil Mechanics and Geotechnical Engineering page： 933-937 2005.9

Authorship：Lead author Language：English

To investigate a problem of bearing capacity of a natural clay, a soil-water coupled finite deformation analysis is performed with the elasto-plastic constitutive model that describes the effect of the decay of soil skeleton structure due to plastic deformation. From the computational results the findings are as follows: (1) In a structured clay soil, a load peak phenomenon appears, accompanied by a local circular slip field. (2) In a clay soil possessing anisotropy, this area of failure is more confined, and the peak is lower.

A soil-water coupled analysis on compaction of sandy ground

Noda, T., Yamada, E., Yamada, S. and Asaoka, A.

Geomechanics: Testing, Modeling, and Simulation, Geotechnical Special Publication No. 143 page： 269-285 2005.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The mechanism and characteristics of a static compaction pile method for sandy ground that is used as a measure against liquefaction, in which non-vibratory cavity expansion is gradually carried out from the bottom up, are numerically investigated using a soil-water coupled computation. The compaction procedure of the sandy ground is simulated employing a Super/subloading Yield Surface Cam-Clay model as an elasto-plastic constitutive model for sand. By introducing the concepts of soil structure, overconsolidation and stress-induced anisotropy and their evolutions, this model allows the description of a wide variety of sand behaviors using a single set of material parameters that are independent on density.
From the computational results, it is found that loose sandy ground is easily compacted/densificated because, in terms of sand elements, the soil structure of the sand is rapidly collapsed until the expansion takes place around the sand element and at the loading stages at which the casing pipe is driven in. Moreover, the shear characteristics of the ground are further improved because the overconsolidation ratio of the sand is increased cumulatively when the expansion is performed above the sand element and at the unloading stages at which the casing is pulled out.

Mechanical behaviour of structured clay and simulation

Shibuya, S. Li, D. Noda, T. and Nakano, M.

Geomechanics: Testing, Modeling, and Simulation, Geotechnical Special Publication No. 143 page： 286-306 2005.6

Elasto-plastic behavior of naturally deposited clay during/after sampling Reviewed

Noda, T., Yamada S. and Asaoka A.

Soils and Foundations Vol. 45 ( 1 ) page： 51-64 2005.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Changes in soil structure and overconsolidation in highly structured natural deposited clay as a result of sampling and setting in laboratory tests, together with their effects on the subsequent mechanical behavior, are numerically investigated in terms of unconventional elasto-plastic mechanics. To describe the mechanical behavior, a Super/subloading Yield Surface Cam-Clay model is employed. This model allows a description of the decay of soil structure, loss/increase of overconsolidation and evolution of anisotropy with ongoing plastic deformation from the process of the soil sampling through the unloading with swelling up to the subsequent tests.
The clay sample, after being collected, mounted on the test apparatus, and subjected to isotropic unloading and/or one-dimensional unloading with swelling down to the first stage vertical loading level, displays a response to some degree different from that of the soil at the original sampling site, in the following respects. An overconsolidated sample subjected to isotropic unloading with swelling will display rewinding behavior in a subsequent undrained tri-axial compression test, and “secondary consolidation"/“delayed compression" in a one-dimensional consolidation test. In contrast, a sample subjected to one-dimensional unloading with swelling will not become heavily overconsolidated but will remain in a state of either slight overconsolidation or normal consolidation accompanied by destructuration, and will display unloading at the beginning of a subsequent one-dimensional compression test. The most important thing to note from the testing viewpoint is that one-dimensional unloading with swelling gives better results than isotropic unloading, in the sense that the subsequent compression test is better able to predict the in-situ “consolidation yield stress".
Artificially disturbed clay subjected to repeated undrained shearing after sampling suffers a significant loss of structure. This results in a drop in

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Papers - NODA, Toshihiro