研究者詳細 - 野田　利弘

論文 - 野田　利弘

分割表示 206 件中 181 - 200 件目／全件表示 >>

"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. 頁： 113-118 2000年9月

「構造」を持った過圧密土の弾塑性挙動査読有り

浅岡顕，中野正樹，野田利弘

土木学会応用力学論文集 3 巻頁： 335-342 2000年8月

Delayed compression/consolidation of naturally clay due to degradation of soil structure 査読有り

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

Soils and Foundations 40 巻 ( 3 ) 頁： 75-85 2000年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Soils and Foundations 40 巻 ( 2 ) 頁： 99-110 2000年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Soils and Foundations 40 巻 ( 1 ) 頁： 85-97 2000年2月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

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，地盤工学会頁： 5-8. 1999年5月

Progressive Failure of Heavily Overconsolidated Clays

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

Soils and Foundations 39 巻 ( 2 ) 頁： 105-117 1999年4月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

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査読有り

野田利弘，高稲敏浩，浅岡顕

土木学会論文集 617/Ⅲ-46 巻頁： 125-138 1999年3月

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

Soils and Foundations 38 巻 ( 4 ) 頁： 173-181 1998年12月

Superloading yield surface concept for the saturated structured soils 招待有り

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

Proc. 4th European Conf. on Numerical Methods in Geotechnical Engineering, Udine, Italy. 頁： 233-242 1998年10月

間隙水の移動を伴った過圧密土の遅れ破壊の解析

浅岡顕，野田利弘，高稲敏浩

応用力学論文集(土木学会) 1 巻頁： 449-460 1998年8月

Consolidation deformation behavior of lightly and heavily overconsolidated clay foundation

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

Soils and Foundations 38 巻 ( 2 ) 頁： 75-91 1998年6月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

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.

Undrained creep rupture of normally consolidated clay triggered by the "mode switching" during pore water migration

Asaoka, A. and Noda, T.

Proc. of. Intl. Symp. on Deformation and Progressive Failure in Geomechanics 1 巻頁： 21-26 1997年10月

Progressive failure of heavily overconsolidated clay under constant load application, an experiment and its application

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

Proc. of. Intl. Symp. on Deformation and Progressive Failure in Geomechanics 1 巻頁： 69-74 1997年10月

Effects of changes in geometry on the linear elastic consolidation deformation

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

Soils and Foundations 35 巻 ( 1 ) 頁： 29-40 1997年9月

Slaking behavior of saturated mudstones

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

Proc. of. 14th Intl. Conf. on Soil Mechanics and Foundation Engineering, Hamburg 1 巻頁： 25-28 1997年9月

Soil-water coupled behavior of heavily overconsolidated clay near/at critical state line

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

Soils and Foundations 35 巻 ( 1 ) 頁： 13-28 1997年3月

Annealable Behaviour of Saturated Clay, An Experiment and Simulation 査読有り

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

Soils and Foundations 35 巻 ( 4 ) 頁： 9-20 1995年12月

Effects of Pore Water Migration on the Ultimate Behaviour of Soils

Asaoka, A and Noda, T.

Proc. of the 5th International Symposium on Plasticity and Its Current Application 1 巻頁： 407-410 1995年7月

Imperfection-sensitive Bifurcation of Cam-clay under Plane Strain Compression with Undrained Boundaries

Asaoka, A. and Noda, T.

Soils and Foundations, Journal of JSSFME 35 巻 ( 1 ) 頁： 83-100 1995年3月

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