Faculty Profiles - NODA, Toshihiro

Papers - NODA, Toshihiro

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*An elasto-plastic description of two distinct volume change mechanisms of soils Reviewed

Asaoka, A., Noda, T., Yamada, E., Kaneda, K. and Nakano, M.

Soils and Foundations Vol. 42 ( 5 ) page： 47-57 2002.10

Language：English Publishing type：Research paper (scientific journal)

In critical state soil mechanics, the volume change behavior of soils has typically been analyzed based upon conventional "e-logp' relationships". However, compaction/densification of loose sand, for example, can sometimes occur even without any significant increase of mean effective stresses. This study presents a model which considers the fact that volume change can occur due to decay/collapse of the structure of soils. Taking into consideration the differences between clay and sand, this study models super-subloading surfaces together with rotational hardening using the modified Cam-clay model. The effects of decay of the soil structure, loss of overconsolidation and evolution of anisotropy are mutually discussed concerning their relationship with ongoing plastic deformation. Fundamental constitutive model responses are illustrated in the present study particularly for "compaction" of sand. Repeated application of low-level shear stress upon loose sand yields a huge amount of volume compression, which is due to the rapid collapse of the initial soil structure. Repetition of the loading also results in a rapid increase of the overconsolidation ratio. Drained and undrained shear behavior of the sand naturally changes remarkably along this densification/compaction procedure, which is also consistently predicted using a single set of soil parameters. Elasto-plastic behavior of the same sand at various densities is thus totally described in the present study in a single the-oretical framework based on soil parameters independent of density.

DOI： 10.3208/sandf.42.5_47

Effects of sampling on delayed compression of naturally deposited clay

Noda, T., Nakano, M., Kaneda, K., Asaoka, A. and Yamada S.

Proc. of 1st International Workshop on New Frontiers in Computational Geomechanics (IWS-CALGARY 2002) page： 83-90 2002.9

浅い基礎の設計理論と実際～パイルド・ラフト基礎を中心にして～ Open Access

三村衛，野田利弘，山田英司，高稲敏浩，小高猛司，島津多賀夫

土と基礎，地盤工学会 Vol. 50 ( 8 ) page： 15-17 2002.8

水～土連成計算を用いた砂杭拡径による砂地盤の締固めメカニズムの一考察 Reviewed Open Access

野田利弘，高稲敏浩，高木健次，野津光夫

土木学会論文集 Vol. Ⅵ-46 ( 679 ) page： 111-122 2001.6

Decay of structure and loss of overconsolidation

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

Proc. Int. Workshop on Deformation of Earth Materials, TC34 of ISSFMGE, Sendai. page： 109-118 2001.5

泥岩粒の粘土化が原因となる飽和した泥岩砕石集合体の時間依存的力学挙動 Reviewed Open Access

中野正樹，野田利弘，高木健次，浅岡顕

地盤工学論文報告集 Vol. 41 ( 2 ) page： 143-151 2001.4

An elasto-plastic description of the difference between sand and clay Invited

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

Proc. 10th Int. Conf. IACMAG (Int. Association for Computer Methods and Advances in Geomechanics), Tucson, Arizona, U.S.A. Vol. 1 page： 263-270 2001.4

パイルド・ラフト基礎が設置された地盤の水～土連成弾塑性変形解析 Reviewed Open Access

山田英司，高稲敏浩，水野和憲，大野雅幸，野田利弘

土木学会論文集 Vol. 659/Ⅲ-52 page： 113-128 2000.9

"Sensitivity Ratio" and "Sampling Disturbance" of natural soils in terms of degradation of soil structure

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

Proc. Int. Sym. on Coastal Geotechnical Engineering in Practice (IS-YOKOHAMA 2000), Yokohama. page： 113-118 2000.9

「構造」を持った過圧密土の弾塑性挙動 Reviewed Open Access

浅岡顕，中野正樹，野田利弘

土木学会応用力学論文集 Vol. 3 page： 335-342 2000.8

Delayed compression/consolidation of naturally clay due to degradation of soil structure Reviewed

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

Soils and Foundations Vol. 40 ( 3 ) page： 75-85 2000.6

Language：English Publishing type：Research paper (scientific journal)

The superloading yield surface concept applied to the original Cam-clay model is examined for the application to the one-dimensional consolidation problems of highly structured soils. When the proposed elasto-plastic constitutive model is taken to be the case for a structured soil, the one-dimensional consolidation computation clarifies the following : (1) Delayed consolidation should occur even under one-dimensional compression condition with a considerably low stress ratio when softening of the soil occurs with volume compression. The delayed consolidation is the consolidation process that has sometimes been referred to as "secondary compression". (2) The structure is always degrading as plastic deformation proceeds even within the period of "secondary compression". (3) The decay of overconsolidation to normal consolidation also proceeds with plastic deformation. In this sense, the degradation of structure can not be independent of the decay of overconsolidation. However, since the decay of overconsolidation is much faster than the degradation of structure in clay, then softening becomes possible with volume compression even under a considerably low stress ratio. Recovery of structure with time due to chemical bonding effects etc. in soil particles is beyond the scope of this study.

Superloading yield surface concept for highly structured soil behavior Reviewed

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

Soils and Foundations Vol. 40 ( 2 ) page： 99-110 2000.4

Language：English Publishing type：Research paper (scientific journal)

The superloading yield surface concept is newly introduced to the original Cam-clay model in order to describe some aspects of the mechanical behavior of highly structured soils, in which destructured soils are assumed to follow the original Cam-clay model. Following are typically those aspects: (a) structured soils are always "bulky" compared with destructured soils, and if they are in the normally consolidatcd state they always take their state variables outside the "Roscoe surface" of the Cam-clay model (b) when void ratios are the same, structured soils exhibit strengths higher than those of destructured soils; (c) for the same stresses, the void ratios of structured soils are greater than remolded soils. The structured state of a soil is simply defined as the size ratio of the original Cam-clay yield surface and the superloading yield surface that should lie above the Cam-clay yield surface. On the basis of "unconventional plasticity" theory the superloading yield surface concept, together with Hashiguchi's subloading yield surface concept, describes the degradation processes from both an overconsolidated state to a normally consolidated state and a structured state to a destructured state. These degradation processes continue gradually with ongoing plastic deformation. Since plastic deformation is irreversible, the decay of soil structure is also irreversible: The degraded state can not come back to the original state again through elasto-plastic mechanical operation alone. Chemical and/or thermal effects with "aging", that are said to newly generate both overconsolidated state and structured state without any change of stresses, are beyond the scope of this study.

Delayed failure in soft clay foundations Reviewed

Noda, T., Fernando, G.S.K. and Asaoka, A.

Soils and Foundations Vol. 40 ( 1 ) page： 85-97 2000.2

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

Even in normally consolidated or lightly overconsolidated clay foundations failures can occur some days/weeks after the load application is completed. Such an event can sometimes be attributed to creep-like failure. In this paper, the time dependent failure of a homogeneous normally consolidated soft clay foundation has been investigated using soil-water coupled elasto-plastic finite deformation analysis. The inviscid subloading surface Cam-clay model, which can express smooth transition from overconsolidated states to normally consolidated states during reloading, was used for the soil. With drained boundaries a clay foundation can experience failure, instead of consolidation, with the elapse of time after the end of load application. The foundation stays apparently stable for some time until it experiences a sudden failure. The occurrence of such a delayed failure in an elasto-plastic soil foundation is triggered off by the predominant pore water migration over the drainage from the soil mass due to softening that results in the increase of excess pore water pressure under this constant load. With time, the region in the foundation under higher excess pore pressure expands outward progressively from the centerline until failure. The pore pressure increase under constant load is similar to observed cases that registered increase in piezometric heads. When the magnitude of load at the end of construction is comparatively low, i. e. comparatively below the stationary load, only the consolidation process proceeds.

飽和粘土の遅れ破壊現象の水～土連成解析

野田利弘，中野正樹

土と基礎，地盤工学会 page： 5-8. 1999.5

Progressive Failure of Heavily Overconsolidated Clays

Asaoka, A., Nakano, M., Noda, T., Takaine, T., Kaneda, K. and Constantinescu Dan T.

Soils and Foundations Vol. 39 ( 2 ) page： 105-117 1999.4

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

In this study, in order to comprehend the progressive failure of an overconsolidated clay, triaxial compression tests under constant load application for the overconsolidated Kawasaki clay are carried out. These tests show, after a certain period of time, axial strain rate fluctuations with marked peaks until the specimen reaches outright failure. The experimental procedure is then numerically simulated using the soil-water coupled finite element technique. While the numerical simulation for the triaxial compression test under axi-symmetric conditions did not exhibit the same behavior as in the triaxial test (shear band formation and fluctuation of axial strain rate in the axial strain rate vs. axial strain plot), under plane-strain conditions it properly described the fluctuation of axial strain rate as observed in the experiments. Such fluctuations in the axial strain rate are closely related to the progression of the localized shear zones within the specimen. This behavior is attibuted to the "non-local" characteristics of saturated clays. Since the pore water supply to the localized shear zone can not always be sufficient due to Darcy's law which limits the gradient of global seepage head in the soil, the specimen exhibits varying strain rates. Tertiary mudstone pebbles can be idealized as heavily overconsolidated clay. The progressive failure of a heavily overconsolidated clay suggests that the behavior of crushed Tertiary mudstone is due to slaking at the contact points between the pebbles.

水～土連成計算による土留めに作用する力の時間依存性挙動の解析 Reviewed Open Access

野田利弘，高稲敏浩，浅岡顕

土木学会論文集 Vol. 617/Ⅲ-46 page： 125-138 1999.3

Displacement/Traction Boundary Conditions Represented by Constraint Conditions on Velocity Field of Soil

Soils and Foundations Vol. 38 ( 4 ) page： 173-181 1998.12

Superloading yield surface concept for the saturated structured soils Invited

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

Proc. 4th European Conf. on Numerical Methods in Geotechnical Engineering, Udine, Italy. page： 233-242 1998.10

Delayed Failure of Overconsolidated Soils due to Pore Water Migration

Vol. 1 page： 449-460 1998.8

Consolidation deformation behavior of lightly and heavily overconsolidated clay foundation

Asaoka, A., Noda, T. and Fernando, G. S. K.

Soils and Foundations Vol. 38 ( 2 ) page： 75-91 1998.6

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

Non-linear consolidation deformation behavior of saturated clays under embankment loading (plane strain) has been investigated using numerical analysis. The governing equations are based on the finite deformation theory which considers both geometric non-linearity and material non-linearity and the finite element method is used for the solution procedure. The subloading surface Cam-clay model for finite deformation is employed for the non-linear material behavior of lightly/heavily overconsolidated clays. The clay foundation response to embankment construction under both the non-linearities is discussed within the Critical State Soil Mechanics framework. For overconsolidated soils, both the hardening and softening behavior above the critical state line (p'-q stress space) occur with plastic volume expansion. The area under the embankment slope reaches the normally consolidated state first during load application. In a lightly overconsolidated clay foundation, this area undergoes strong strain localization which can lead to physical failure of the structure. The embankment toe area of a heavily overconsolidated clay foundation exhibits a softening behavior with net volume dilatation at the end of the consolidation. The drained loading of a heavily overconsolidated clay foundation tends to give higher load bearing capacity than for undrained loading as in the case of lightly overconsolidated soils.

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