Contact Tensor in Constitutive Model for Granular Materials

“…F ij characterises the inherent fabric anisotropy, but its effect must be related to the loading direction. Motivated by the suggestion of Tobita & Yanagisawa (1988), a modified stress,T T ij , is defined bŷ…”

Section: Incorporation Of Inherent Anisotropy Effectsmentioning

confidence: 99%

“…Serious effort has been undertaken to link microstructural observations on the soil fabric to the soil plasticity (e.g. Matsuoka & Nakai, 1982;Nakai & Matsuoka, 1983;Oda & Nakayama, 1988, 1989Tobita & Yanagisawa, 1988;Tobita 1989;Oda, 1999). The aim was to rationally introduce anisotropic soil responses into the well-established framework of continuum mechanics.…”

Section: Introductionmentioning

confidence: 99%

A constitutive framework for anisotropic sand including non-proportional loading

Dafalias

2004

Géotechnique

133

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An existing platform model for inherently anisotropic sands is extended to account for deformations induced by non-proportional loadings. The platform model is within the framework of critical-state soil mechanics, and the inherent anisotropy is accounted for by rendering the critical-state line in the e-p plane and the deviatoric plastic modulus functions of a scalar-valued anisotropic parameter, A. The latter is defined in terms of joint isotropic invariants of a symmetric fabric tensor and a properly defined loading direction tensor. Proportional and some non-proportional loading responses, including stress reversals, can be successfully simulated by the platform model, but the response under loading involving significant principal stress rotations requires the introduction of an additional loading mechanism. This new mechanism is associated with components of the stress ratio rate and plastic strain rate, which are orthogonal to a loading direction coaxial with the stress ratio. The novelty in this respect is associated with the dependence of the dilatancy and plastic modulus of this new mechanism on a second anisotropic parameter, A, to account for the fabric anisotropy effect along the lines of the platform model. The resulting comprehensive model successfully simulates experimental data reflecting the complex combined effects of fabric anisotropy and non-proportional loading histories.

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“…The constitutive models based on modified stresses had successfully captured the material anisotropic property where the modified stresses were obtained by modifying the nominal stress with a fabric tensor (Oda and Nakayama 1989;Tobita 1989). It was also suggested that the isotropic yield condition in terms of the modified stresses could lead to an anisotropic yielding and hardening nature of the granular materials with less mathematical complexities as only the isotropic material constants were needed (Tobita and Yanagisawa 1988). This method has been extensively adopted by researchers to study the anisotropic yield or failure criteria for geomaterials (Gao et al 2010;Kong et al 2013;Shaverdi et al 2013).…”

Section: Modified Stress For Characterization Of Inherent Anisotropymentioning

confidence: 99%

“…A modified stress tensor is introduced to combine the stress tensor and the fabric tensor as follows (Oda 1993;Tobita and Yanagisawa 1988;Yang et al 2008 …”

Section: Modified Stress For Characterization Of Inherent Anisotropymentioning

confidence: 99%

A generalized Drucker–Prager viscoplastic yield surface model for asphalt concrete

et al. 2014

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A Generalized Drucker-Prager (GD-P) viscoplastic yield surface model was developed and validated for asphalt concrete. The GD-P model was formulated based on fabric tensor modified stresses to consider the material inherent anisotropy. A smooth and convex octahedral yield surface function was developed in the GD-P model to characterize the full range of the internal friction angles from 0 to 90 degrees. In contrast, the existing Extended Drucker-Prager (ED-P) was demonstrated to be applicable only for a material that has an internal friction angle less than 22 degrees.Laboratory tests were performed to evaluate the anisotropic effect and to validate the GD-P model. Results indicated that 1) the yield stresses of an isotropic yield surface model are greater in compression and less in extension than that of an anisotropic model, which can result in an under-prediction of the viscoplastic deformation; and 2) the yield stresses predicted by the GD-P model matched well with the experimental results of the octahedral shear strength tests at different normal and confining stresses. By contrast, the ED-P model over-predicted the octahedral yield stresses, which can lead to an under-prediction of the permanent deformation. In summary, the rutting depth of an asphalt pavement would be underestimated without considering anisotropy and convexity of the yield surface for asphalt concrete. The proposed GD-P model was demonstrated to be capable of overcoming these limitations of the existing yield surface models for the asphalt concrete.

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Contact Tensor in Constitutive Model for Granular Materials

Cited by 22 publications

References 6 publications

Quantifying and modelling fabric anisotropy of granular soils

Quantifying and modelling fabric anisotropy of granular soils

A constitutive framework for anisotropic sand including non-proportional loading

A generalized Drucker–Prager viscoplastic yield surface model for asphalt concrete

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