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Toshihiro Noda - One of the best experts on this subject based on the ideXlab platform.
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Determination of Parameter in SYS Cam-Clay Model of Ultra-Soft Clay
Applied Mechanics and Materials, 2015Co-Authors: Bin Bin Xu, Toshihiro NodaAbstract:Parameter analyses in the constitutive Model determine the precision of numerical results. Cam-Clay Model is the first elasto-plastic Model in the world and widely used in the practical engineering. SYS Cam-Clay Model is proposed based on Cam-Clay Model by incorporating the concept of overconsolidation, soil structure and anisotropy. There are two groups of parameters in this Model, elasto-plastic parameters that are exactly same as those in Cam-Clay Model and evolutional parameters that decide the variation of overconsolidation, soil structure and anisotropy. The detailed process to determine the parameters is introduced step by step.
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Sensitivity Analysis of Parameters in SYS Cam-Clay Model
Advanced Materials Research, 2014Co-Authors: Toshihiro Noda, Kentaro NakaiAbstract:The SYS Cam-Clay Model, which is extended based on the Cam-Clay Model and the critical state theory, is able to describe the heavily overconsolidated and structure soils. However compared with Cam-Clay Model with five elasto-plastic parameters there are six additional evolutional parameters in SYS Cam-Clay Model and the sensitivity analysis of the new added parameters should be carried out. Through the calculation of constitutive response assuming the uniform deformation field, the sensitivities of degradation index of structure, degradation index of overconsolidation ratio and rotational hardening index are investigated respectively. It can be seen that the peak strength and the “rewinding behavior” in the effective stress path are influenced greatly while there is no coupling effect of these parameters mutually. The initial overconsolidation ratio and degree of structure also have an effect on the mechanical behavior and the initial specific volume.
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soil water coupled finite deformation analysis based on a rate type equation of motion incorporating the sys cam clay Model
Soils and Foundations, 2008Co-Authors: Toshihiro Noda, Akira Asaoka, Masaki NakanoAbstract:This paper presents a new method of soil-water coupled finite deformation analysis of saturated soils that considers inertial forces. This method allows changes in the geometric shape of the soil to be taken into account and is capable of dealing with all types of external forces irrespective of whether they are static or dynamic. To be more specific, the paper describes the following points, which differ from the conventional methods: 1) the governing equations for saturated soil including the rate-type equation of motion containing a jerk term of the soil skeleton conforming to u-p formulation and updated Lagrangian, 2) derivation of a weak form of the rate-type equation of motion and discretization of the finite elements, and 3) use of the implicit time integration method for application of the conventional linear acceleration method (which assumes linear variation of acceleration) to the jerk term. By mounting the elasto-plastic constitutive equation (SYS Cam-Clay Model), which can cover a wide range of soils and soil conditions, onto the above method of analysis, examples of simulation of dynamic/static triaxial laboratory testing of saturated soil specimens are described. The soil specimens were assumed to be medium dense sand under conditions of small-amplitude cyclic loading, partial drainage, and constant cell pressure. The simulation yielded the following results: (1) In the case of low frequencies, compaction occurs during loading and compression progresses over the entire specimen. (2) In the case of high frequencies, during loading and in the period in which wave propagation continues within the specimen after the end of loading, compaction occurs at the drained end of the specimen, whereas liquefaction occurs in its interior. After this stage, massive compression takes place within the specimen, leading to consolidation (consolidation after liquefaction).
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Simulation of shear and one-dimensional compression behavior of naturally deposited clays by super/subloading yield surface Cam-Clay Model
Soils and Foundations, 2005Co-Authors: Masaki Nakano, Toshihiro Noda, Kentaro Nakai, Akira AsaokaAbstract:Naturally deposited clays exhibit complicated mechanical behavior that differs from that of remolded clays. For example, clay in a normally consolidated state commonly exhibits softening in undrained shear tests or rewinding in a heavily overconsolidated state. The Super/subloading Yield Surface Cam-Clay Model (Asaoka et al., 1998, 2000, 2002) was proposed in an attempt to clarify the complicated mechanical behavior in naturally deposited clays. In this constitutive Model, the concepts of structure, overconsolidation, anisotropy, and their evolution laws, are introduced into the modified Cam-Clay Model. In the present study, undrained triaxial compression tests and oedometer tests were carried out on two types of naturally deposited undisturbed clay, Pleistocene clay and Holocene clay, and the behavior was then simulated using the Super/subloading Yield Surface Cam-Clay Model. The findings of the present study are as follows: 1) For the two types of undisturbed clay, the Super/subloading Yield Surface Cam-Clay Model can simulate undrained triaxial compression behavior ranging from the normally consolidated state to the overconsolidated state, corresponding to various isotropic pressures using a single set of material constants. 2) In addition, the Model can simulate one-dimensional compression behavior using the same material constants as those used for the simulation of the undrained triaxial compression behavior. 3) Through the simulation, the mechanical behavior of Pleistocene clay and Holocene clay, which have different loading histories and have undergone different aging effects, can be described by the different evolution parameters, as well as the elasto-plastic parameters.
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superloading yield surface concept for highly structured soil behavior
Soils and Foundations, 2000Co-Authors: Akira Asaoka, Masaki Nakano, Toshihiro NodaAbstract:ABSTRACT 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 consolidated 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 over consolidated state and structured state without any change of stresses, are beyond the scope of this study.
Akira Asaoka - One of the best experts on this subject based on the ideXlab platform.
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soil water coupled finite deformation analysis based on a rate type equation of motion incorporating the sys cam clay Model
Soils and Foundations, 2008Co-Authors: Toshihiro Noda, Akira Asaoka, Masaki NakanoAbstract:This paper presents a new method of soil-water coupled finite deformation analysis of saturated soils that considers inertial forces. This method allows changes in the geometric shape of the soil to be taken into account and is capable of dealing with all types of external forces irrespective of whether they are static or dynamic. To be more specific, the paper describes the following points, which differ from the conventional methods: 1) the governing equations for saturated soil including the rate-type equation of motion containing a jerk term of the soil skeleton conforming to u-p formulation and updated Lagrangian, 2) derivation of a weak form of the rate-type equation of motion and discretization of the finite elements, and 3) use of the implicit time integration method for application of the conventional linear acceleration method (which assumes linear variation of acceleration) to the jerk term. By mounting the elasto-plastic constitutive equation (SYS Cam-Clay Model), which can cover a wide range of soils and soil conditions, onto the above method of analysis, examples of simulation of dynamic/static triaxial laboratory testing of saturated soil specimens are described. The soil specimens were assumed to be medium dense sand under conditions of small-amplitude cyclic loading, partial drainage, and constant cell pressure. The simulation yielded the following results: (1) In the case of low frequencies, compaction occurs during loading and compression progresses over the entire specimen. (2) In the case of high frequencies, during loading and in the period in which wave propagation continues within the specimen after the end of loading, compaction occurs at the drained end of the specimen, whereas liquefaction occurs in its interior. After this stage, massive compression takes place within the specimen, leading to consolidation (consolidation after liquefaction).
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Simulation of shear and one-dimensional compression behavior of naturally deposited clays by super/subloading yield surface Cam-Clay Model
Soils and Foundations, 2005Co-Authors: Masaki Nakano, Toshihiro Noda, Kentaro Nakai, Akira AsaokaAbstract:Naturally deposited clays exhibit complicated mechanical behavior that differs from that of remolded clays. For example, clay in a normally consolidated state commonly exhibits softening in undrained shear tests or rewinding in a heavily overconsolidated state. The Super/subloading Yield Surface Cam-Clay Model (Asaoka et al., 1998, 2000, 2002) was proposed in an attempt to clarify the complicated mechanical behavior in naturally deposited clays. In this constitutive Model, the concepts of structure, overconsolidation, anisotropy, and their evolution laws, are introduced into the modified Cam-Clay Model. In the present study, undrained triaxial compression tests and oedometer tests were carried out on two types of naturally deposited undisturbed clay, Pleistocene clay and Holocene clay, and the behavior was then simulated using the Super/subloading Yield Surface Cam-Clay Model. The findings of the present study are as follows: 1) For the two types of undisturbed clay, the Super/subloading Yield Surface Cam-Clay Model can simulate undrained triaxial compression behavior ranging from the normally consolidated state to the overconsolidated state, corresponding to various isotropic pressures using a single set of material constants. 2) In addition, the Model can simulate one-dimensional compression behavior using the same material constants as those used for the simulation of the undrained triaxial compression behavior. 3) Through the simulation, the mechanical behavior of Pleistocene clay and Holocene clay, which have different loading histories and have undergone different aging effects, can be described by the different evolution parameters, as well as the elasto-plastic parameters.
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superloading yield surface concept for highly structured soil behavior
Soils and Foundations, 2000Co-Authors: Akira Asaoka, Masaki Nakano, Toshihiro NodaAbstract:ABSTRACT 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 consolidated 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 over consolidated state and structured state without any change of stresses, are beyond the scope of this study.
Masaki Nakano - One of the best experts on this subject based on the ideXlab platform.
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soil water coupled finite deformation analysis based on a rate type equation of motion incorporating the sys cam clay Model
Soils and Foundations, 2008Co-Authors: Toshihiro Noda, Akira Asaoka, Masaki NakanoAbstract:This paper presents a new method of soil-water coupled finite deformation analysis of saturated soils that considers inertial forces. This method allows changes in the geometric shape of the soil to be taken into account and is capable of dealing with all types of external forces irrespective of whether they are static or dynamic. To be more specific, the paper describes the following points, which differ from the conventional methods: 1) the governing equations for saturated soil including the rate-type equation of motion containing a jerk term of the soil skeleton conforming to u-p formulation and updated Lagrangian, 2) derivation of a weak form of the rate-type equation of motion and discretization of the finite elements, and 3) use of the implicit time integration method for application of the conventional linear acceleration method (which assumes linear variation of acceleration) to the jerk term. By mounting the elasto-plastic constitutive equation (SYS Cam-Clay Model), which can cover a wide range of soils and soil conditions, onto the above method of analysis, examples of simulation of dynamic/static triaxial laboratory testing of saturated soil specimens are described. The soil specimens were assumed to be medium dense sand under conditions of small-amplitude cyclic loading, partial drainage, and constant cell pressure. The simulation yielded the following results: (1) In the case of low frequencies, compaction occurs during loading and compression progresses over the entire specimen. (2) In the case of high frequencies, during loading and in the period in which wave propagation continues within the specimen after the end of loading, compaction occurs at the drained end of the specimen, whereas liquefaction occurs in its interior. After this stage, massive compression takes place within the specimen, leading to consolidation (consolidation after liquefaction).
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Simulation of shear and one-dimensional compression behavior of naturally deposited clays by super/subloading yield surface Cam-Clay Model
Soils and Foundations, 2005Co-Authors: Masaki Nakano, Toshihiro Noda, Kentaro Nakai, Akira AsaokaAbstract:Naturally deposited clays exhibit complicated mechanical behavior that differs from that of remolded clays. For example, clay in a normally consolidated state commonly exhibits softening in undrained shear tests or rewinding in a heavily overconsolidated state. The Super/subloading Yield Surface Cam-Clay Model (Asaoka et al., 1998, 2000, 2002) was proposed in an attempt to clarify the complicated mechanical behavior in naturally deposited clays. In this constitutive Model, the concepts of structure, overconsolidation, anisotropy, and their evolution laws, are introduced into the modified Cam-Clay Model. In the present study, undrained triaxial compression tests and oedometer tests were carried out on two types of naturally deposited undisturbed clay, Pleistocene clay and Holocene clay, and the behavior was then simulated using the Super/subloading Yield Surface Cam-Clay Model. The findings of the present study are as follows: 1) For the two types of undisturbed clay, the Super/subloading Yield Surface Cam-Clay Model can simulate undrained triaxial compression behavior ranging from the normally consolidated state to the overconsolidated state, corresponding to various isotropic pressures using a single set of material constants. 2) In addition, the Model can simulate one-dimensional compression behavior using the same material constants as those used for the simulation of the undrained triaxial compression behavior. 3) Through the simulation, the mechanical behavior of Pleistocene clay and Holocene clay, which have different loading histories and have undergone different aging effects, can be described by the different evolution parameters, as well as the elasto-plastic parameters.
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superloading yield surface concept for highly structured soil behavior
Soils and Foundations, 2000Co-Authors: Akira Asaoka, Masaki Nakano, Toshihiro NodaAbstract:ABSTRACT 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 consolidated 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 over consolidated state and structured state without any change of stresses, are beyond the scope of this study.
Kentaro Nakai - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity Analysis of Parameters in SYS Cam-Clay Model
Advanced Materials Research, 2014Co-Authors: Toshihiro Noda, Kentaro NakaiAbstract:The SYS Cam-Clay Model, which is extended based on the Cam-Clay Model and the critical state theory, is able to describe the heavily overconsolidated and structure soils. However compared with Cam-Clay Model with five elasto-plastic parameters there are six additional evolutional parameters in SYS Cam-Clay Model and the sensitivity analysis of the new added parameters should be carried out. Through the calculation of constitutive response assuming the uniform deformation field, the sensitivities of degradation index of structure, degradation index of overconsolidation ratio and rotational hardening index are investigated respectively. It can be seen that the peak strength and the “rewinding behavior” in the effective stress path are influenced greatly while there is no coupling effect of these parameters mutually. The initial overconsolidation ratio and degree of structure also have an effect on the mechanical behavior and the initial specific volume.
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Simulation of shear and one-dimensional compression behavior of naturally deposited clays by super/subloading yield surface Cam-Clay Model
Soils and Foundations, 2005Co-Authors: Masaki Nakano, Toshihiro Noda, Kentaro Nakai, Akira AsaokaAbstract:Naturally deposited clays exhibit complicated mechanical behavior that differs from that of remolded clays. For example, clay in a normally consolidated state commonly exhibits softening in undrained shear tests or rewinding in a heavily overconsolidated state. The Super/subloading Yield Surface Cam-Clay Model (Asaoka et al., 1998, 2000, 2002) was proposed in an attempt to clarify the complicated mechanical behavior in naturally deposited clays. In this constitutive Model, the concepts of structure, overconsolidation, anisotropy, and their evolution laws, are introduced into the modified Cam-Clay Model. In the present study, undrained triaxial compression tests and oedometer tests were carried out on two types of naturally deposited undisturbed clay, Pleistocene clay and Holocene clay, and the behavior was then simulated using the Super/subloading Yield Surface Cam-Clay Model. The findings of the present study are as follows: 1) For the two types of undisturbed clay, the Super/subloading Yield Surface Cam-Clay Model can simulate undrained triaxial compression behavior ranging from the normally consolidated state to the overconsolidated state, corresponding to various isotropic pressures using a single set of material constants. 2) In addition, the Model can simulate one-dimensional compression behavior using the same material constants as those used for the simulation of the undrained triaxial compression behavior. 3) Through the simulation, the mechanical behavior of Pleistocene clay and Holocene clay, which have different loading histories and have undergone different aging effects, can be described by the different evolution parameters, as well as the elasto-plastic parameters.
Yu-jun Cui - One of the best experts on this subject based on the ideXlab platform.
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A two-surface plasticity Model for cyclic behavior of saturated clay
Acta Geotechnica, 2019Co-Authors: Ren-peng Chen, Shu Zhu, Peng-yun Hong, Wei Cheng, Yu-jun CuiAbstract:This paper presents a two-surface plasticity Model for describing some important features of saturated clay under cyclic loading conditions, such as closed hysteresis loops, cyclic shakedown and degradation, and different stress–strain relations for two-way loading. The Model, namely ACC-2-C, is based on the elastoplastic Model ACC-2 (an adapted Modified Cam Clay Model with two yield surfaces) developed by Hong et al. (Acta Geotech 11(4):871–885, 2015). The small-strain nonlinearity concept is adopted to achieve the nonlinear characteristics of clay during unloading–loading stage. The new hardening law related to accumulated deviatoric plastic strain is proposed for the inner surface to describe the cyclic shakedown and degradation. Following the advantages of the ACC-2 Model, the constitutive equations are simply formulated based on the consistency condition for the inner yield surface. The Model is conveniently implemented in a finite element code using a stress integration scheme similar to the Modified Cam Clay Model. The simulation results are highly consistent with experimental data from drained and undrained isotropic cyclic triaxial tests in normally consolidated saturated clay under both one-way and two-way loadings.
