Strain localization of Mohr-Coulomb soils with non-associated plasticity based on micropolar continuum theory

Tang, Jianbin; Chen, Xi; Cui, Liusheng; Liu, Zongqi

doi:10.1016/j.jrmge.2023.02.029

Cited by 5 publications

(3 citation statements)

References 34 publications

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“…In recent years, the framework of FEM-SOCP based on the micropolar continuum (referred to as mpcFEM-SOCP from here on) has been successfully applied to various geotechnical problems involving strain localization (e.g., Refs. [32][33][34].…”

Section: Introductionmentioning

confidence: 99%

“…Nonetheless, many existing elastoplastic formulations of FEM-SOCP (or mpcFEM-SOCP) have been developed based on the explicit variable (EV) scheme (e.g., Refs. [30][31][32]34), while the implicit variable (IV) scheme of FEM-SOCP possesses some advantages such as high efficiency and good numerical accuracy. For instance, Hjiaj et al 36 proposed the implicit form of the evolution rule of the MCC model, so that the hardening variable can be incorporated into the optimization problem and handled similar to the stress.…”

Section: Introductionmentioning

confidence: 99%

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Geotechnical analysis involving strain localization of overconsolidated soils based on unified hardening model with hardening variable updated by a composite scheme

Tang,

Chen,

Cui

et al. 2024

Num Anal Meth Geomechanics

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Strain localization simulation of overconsolidated soils with high overconsolidation ratio (OCR) has been a long‐standing challenge. Some critical state soil models, including the modified Cam‐clay (MCC) model, have been widely applied, but they may not predict the shear dilatancy of overconsolidated soils well in some cases. Hence, the unified hardening (UH) model, which may be viewed as a generalized version of the MCC model, is implemented. It has been recognized, nonetheless, that without resorting to the regularization mechanism, the standard finite element method (FEM) or the second‐order cone programming optimized finite element method (FEM‐SOCP) often experiences instability or interruption of calculating the hardening‐softening responses of overconsolidated soils. To resolve the aforementioned difficulty, the UH model is developed and implemented in the framework of FEM‐SOCP based on the micropolar continuum (mpcFEM‐SOCP) to predict strain localizations of overconsolidated soils. Furthermore, to obviate non‐convexity of mpcFEM‐SOCP induced by material softening, an effective composite update scheme of hardening variable pc, which refers to the implicit variable (IV) scheme for the hardening stage and then refers to the explicit variable (EV) scheme for the softening stage, is proposed. Based on one biaxial compression problem and one rigid strip footing problem, numerical analyses disclose that by applying mpcFEM‐SOCP in conjunction with the composite update scheme of pc, the UH model of micropolar continuum can effectively predict the strain localization behavior of overconsolidated soil during its failure stage, and the stable hardening‐softening responses of overconsolidated soils can be readily attained.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Geotechnical analysis involving strain localization of overconsolidated soils based on unified hardening model with hardening variable updated by a composite scheme

Tang,

Chen,

Cui

et al. 2024

Num Anal Meth Geomechanics

Self Cite

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“…The compressive strength and shear strength are recognized as fundamental mechanical properties by the geotechnical community [38]. According to the Mohr-Coulomb strength theory, which is widely used in civil engineering [39][40][41][42][43][44], the shear strength envelope of saturated samples from unconsolidated undrained tests (UU tests) theoretically should be horizontal (i.e., ϕ u = 0). However, as discussed, the loess is typically in a state of unsaturated condition.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Shear Strength of Unsaturated Loess Samples from Conventional Triaxial Shear Tests Applying Rubber Membrane Correction

He,

Zhou,

Vanapalli

et al. 2024

Sustainability

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The shear strength parameters of loess samples are determined from conventional triaxial shear test results and used in the rational design of sustainable geotechnical infrastructures. However, the rubber membrane that is used in the triaxial shear apparatus for applying the all-around pressure to the test specimen has a significant influence on the measured shear strength parameters. In this paper, remolded and undisturbed unsaturated loess samples from northwest China are used in a comprehensive testing program to determine the shear strength from triaxial tests and understand the influence of a rubber membrane. The results show that the measured undrained cohesion from unconsolidated undrained triaxial tests on unsaturated soil specimens with and without a rubber membrane are significantly different. In this study, differences in the shear strength with and without a rubber membrane are assessed from shear strength index values that can be determined from undrained cohesion and the internal friction angle derived from conventional triaxial tests. Experimental results suggest that predominant changes arise mainly in the undrained cohesion values. The change rate of shear strength indices values of undisturbed loess shows a strong correlation with its water content; however, it is weak for remolded loess. The correlation coefficient between error and measured values of all shear strength indices is more than 0.8. Empirical correction relationships for triaxial shear tests with a rubber membrane for three different types of loess were established from the investigations. The simple approach used in this study can be used as a reference to apply corrections to the measured undrained cohesion values of unsaturated loess samples from northwest China.

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A large deformation gradient theory for glassy polymers by means of micromorphic regularization

Hamdoun,

Mahnken

2024

Arch Appl Mech

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Cold forming of polycarbonate films results in the formation of shear bands in the necking zone. The numerical results obtained from standard viscoplastic material models exhibit mesh size dependency, requiring mathematical regularization. For this purpose, we present in this work a large deformation gradient theory for a viscoplastic isotropic material model published before. We extend our model to a micromorphic model by introducing a new micromorphic variable as an additional degree of freedom along with its first gradient. This variable represents a microequivalent plastic strain. The relation between the macroequivalent plastic strain and the micromorphic variable is accomplished by a micromorphic coupling modulus. This coupling forces proximity between the macro- and microvariables, leading to the targeted regularization effect. The micromorphic model is implemented as a three-dimensional initial boundary value problem in an in-house finite element tool. The analysis is performed for both uniaxial and biaxial specimens. The provided numerical examples show the ability of our model to regularize shear bands within the specimens and address the issue of localization.

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Strain localization of Mohr-Coulomb soils with non-associated plasticity based on micropolar continuum theory

Cited by 5 publications

References 34 publications

Geotechnical analysis involving strain localization of overconsolidated soils based on unified hardening model with hardening variable updated by a composite scheme

Geotechnical analysis involving strain localization of overconsolidated soils based on unified hardening model with hardening variable updated by a composite scheme

Determination of the Shear Strength of Unsaturated Loess Samples from Conventional Triaxial Shear Tests Applying Rubber Membrane Correction

A large deformation gradient theory for glassy polymers by means of micromorphic regularization

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