Three‐dimensional anisotropic plasticity model for sand subjected to principal stress value change and axes rotation

Non‐coaxial response refers to the deviation between the directions of the principal stress and plastic strain increment. In this paper, an extended hypoplastic model is proposed based on the anisotropic critical state theory, to describe the non‐coaxial and anisotropic response of sand subjected to both monotonic loading and rotation of principal stress axis. A fabric tensor that characterizes the internal structure of sand is introduced into a hypoplastic model, to reflect the effect of fabric anisotropy on the dilatancy and strength of sand. A Lode‐angle‐dependent hypoplastic potential surface is employed, rendering the flow direction no longer co‐directional with the stress tensor in the deviatoric plane. The fabric tensor is further incorporated into the flow direction, enabling the model to generate a non‐coaxial response. Upon shearing, the fabric evolves toward the loading direction following a properly defined evolution law, and the model response becomes purely coaxial at the critical state when the fabric becomes co‐directional with the loading direction. The tangential loading effect is further introduced to simulate the stiffness degradation of sand during undrained rotational shearing. The model is demonstrated to be capable of simulating the prismatic yet complex anisotropic behavior of sand under both proportional and non‐proportional loading conditions.

Section: Simulation Of Elemental Testsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Non‐coaxial hypoplastic model for sand with evolving fabric anisotropy including non‐proportional loading

Liao

Yang

2021

“…Currently, most of the existing studies focus on the individual effect of either the FC or PSR. There are a few considerations of the combined effect 27,46–50 . However, most of these studies mainly focus on the induced anisotropy behavior under the pure PSR loading conditions (principal stress rotation with fixed principal stress magnitudes).…”

Section: Introductionmentioning

confidence: 99%

“…There are a few considerations of the combined effect. 27,[46][47][48][49][50] However, most of these studies mainly focus on the induced anisotropy behavior under the pure PSR loading conditions (principal stress rotation with fixed principal stress magnitudes). There is a lack of experimental verification for their constitutive models in different undrained cyclic loading conditions including the liquefaction.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of cyclic shear tests considering the fabric change and principal stress rotation effects

Wang

Yang

et al. 2022

Cyclic loadings could induce complicated soil responses, including the fabric change and principal stress rotation, both of which would reduce the effective confining pressure and accelerate the build‐up of excess pore water pressures, thus leading to sand liquefaction in undrained conditions. The principal stress rotation, even without the change of principal stress magnitudes, would further generate the accumulative plastic shear strains. However, most of the existing studies focus on their individual effect and the combined effect was seldom considered. In this paper, a numerical approach including an elastoplastic sand constitutive model is proposed to consider the combined effect of the fabric change and principal stress rotation. In this model, the fabric change is considered with the anisotropic critical state theory and the principal stress rotation is considered by splitting the plastic strain increment into the monotonic part and rotational part. By simulating a series of cyclic shear tests, results from the numerical solutions are found showing good agreements with the existing experimental results and the importance of considering the combined effect is demonstrated. The approach can be used to predict the stress‐strain response of sand and guide the design of foundations especially in undrained cyclic loading conditions, for example, earthquake loadings conditions.

“…Constitutive modeling with anisotropic plasticity for geomaterials has been and is still a very active research area. We refer to several recent research works: anisotropic viscoplastic Cam-clay model for shale by Borja et al, 62 adaptive constitutive modeling with rotational hardening by Dejaloud and Rezania, 63 anisotropic model considering fabric evolution with the aid of DEM numerical tests by Wang et al, 64 and anisotropic model applicable to change in principal stresses and their axes rotation by Xue et al 65 These studies are; however, limited to the small strain framework.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic subloading surface Cam‐clay plasticity model with rotational hardening: Deformation gradient‐based formulation for finite strain

Yamakawa

Hashiguchi

Sasaki

et al. 2021

This study is aimed at developing an anisotropic elastoplastic constitutive model for geomaterials at finite strain and its stress calculation algorithm based on the fully implicit return-mapping scheme. The Cam-clay plasticity model is adopted as a specific prototype model of geomaterials. As a pertinent representation of deformation-induced anisotropy in geomaterials, nonlinear rotational hardening is incorporated into the model in a theoretically reasonable manner by introducing the dual multiplicative decompositions of the deformation gradient tensor. In addition to the usual decomposition into elastic and plastic parts, the plastic part is decomposed further into a part contributing to the rotational hardening and a remainder part. The former part leads to a back stress ratio tensor related to the rotational hardening via a hyperelastic-type hardening rule. The constitutive theory is thereby formulated on proper intermediate configurations entirely in terms of deformation-like tensorial variables possessing invariance property, without resort to any objective rates of stress or stress-like variables. Combining the Cam-clay plasticity with the concept of subloading surface, a class of unconventional plasticity, enables the model to be capable of reproducing complex hardening/softening accompanied by volumetric contractive/dilative responses.Basic characteristics and predictive capability of the proposed model, as well as the accuracy of the developed numerical scheme, are verified through several numerical examples including monotonic and cyclic loadings. K E Y W O R D Sanisotropy, cam-clay plasticity, finite strain, return-mapping algorithm, rotational hardening, subloading surface conceptThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.