A non‐coaxial constitutive model for sand deformation under rotation of principal stress axes

Lashkari, Ali; Latifi, Malihe

doi:10.1002/nag.659

Cited by 67 publications

(30 citation statements)

References 46 publications

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“…Based on laboratory observations, a number of advanced constitutive models have been developed, e.g., bounding surface hypoplasticity model (Li and Dafalias 2004;Lashkari and Latifi 2008;Yang and Yu 2012), yield vertex model (Tsutsumi and Hashiguchi 2005), double shearing model (Zhu 2006 a, b), yield vertex and double shearing model (Yu 2008). A state parameter has been introduced in the models to quantify the effect of material anisotropy, and often for simplicity, it is assumed that material anisotropy remains unchanged during the process of loading even though induced anisotropy has been noticed as early as in 1940Õs (Casagrande and Carrillo 1944).…”

Section: ! Introductionmentioning

confidence: 99%

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Yang

et al. 2015

Geomechanics and Geoengineering

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Abstract:! This paper presents an experimental investigation revisiting the anisotropic stress-strainstrength behaviour of geomaterials in drained monotonic shear using Hollow Cylinder Apparatus. The test program has been designed to cover the effect of material anisotropy, preshearing, material density and intermediate principal stress on the behaviour of Leighton Buzzard sand. Experiments have also been performed on glass beads to understand the effect of particle shape. This paper explains phenomenological observations based on recently acquired understanding in micromechanics, with attention focused on strength anisotropy and deformation non-coaxiality, i.e., non-coincidence between the principal stress direction and the principal strain rate direction. The test results demonstrate that the effects of initial anisotropy produced during sample preparation is significant. The stress-strain-strength behaviour of the specimen shows strong dependence on the principal stress direction. Pre-loading history, material density and particle shape are also found to be influential. In particular, it was found that non-coaxiality is more significant in preloaded specimens. The observations on the strength anisotropy and deformation non-coaxiality were successfully explained based on the Stress-

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Section: ! Introductionmentioning

confidence: 99%

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Yang

et al. 2015

Geomechanics and Geoengineering

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“…Initial (i.e., inherent) anisotropy can influence the stress-strain behavior, dilatancy, and direction of principal strain rates when granular media are subjected to rotation of principal stress axes (e.g., [24,45,49,54,100]). In the current form, the proposed model only takes into account the effects of stress-induced anisotropy on the sands behavior.…”

Section: Discussionmentioning

confidence: 99%

Prediction of flow liquefaction instability of clean and silty sands

Lashkari

2015

Acta Geotech.

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Adding a small amount of non-plastic silt to clean sands may lead to dramatic loss of shear strength and a noteworthy tendency toward contraction when the mechanical behavior of the mixture is compared with that of the clean host sand. Thus, simulation of the behavior of silty sands with varying fines content is still a challenging subject in geomechanics. A unified constitutive model for clean and silty sands is presented in this paper. To eliminate the factitious decrease of void ratio associated with inactive silt particles in various silty sand mixtures, the concept of equivalent void ratio is used in the model formulation instead of the global void ratio. In addition, the instantaneous soil state is expressed in terms of intergranular state parameter taking into account the combined influence of intergranular void ratio, mean principal effective stress and fines content. Then, dilatancy and plastic hardening modulus are directly linked to the intergranular state parameter. To improve the model capacity in simulation of cyclic tests, new features are added to the plastic hardening modulus. It is shown that the proposed model can reasonably reproduce the mechanical behavior as well as the onset of flow liquefaction instability of clean and silty sands using a unique set of parameters. List of symbolsA Dilatancy parameter (Eq. 22) B Model parameter (Eq. 31) b Fines participation factor (Eq. 2) c (=M e /M c ) Model parameter c h Plastic hardening parameter (Eq. 23) D pp , D pq , D qp , D qq See Eqs. (45)-(49) d Dilatancy function (Eq. 22) e Global void ratio e* Equivalent intergranular void ratio (Eq. 2) e 0

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“…Of the most notable is the vertex-structure (tangential) plasticity model proposed by Rudnicki and Rice [7]. Compared with other non-coaxial theories, such as kinematic hardening boundary surface model [11,12] or subloading surface model [13], the vertex plasticity model was developed in the context of standard elaso-plastic theory. Hence, this class of models can facilitate their use in numerical analysis.…”

Section: Non-coaxial Modelmentioning

confidence: 99%

“…It was also shown that non-coaxiality has great effects on stress dilatancy and cause less dissipation energy [9,10]. As the rotation of principal stress axes, non-coaxiality also has a significant influence on the feature of stress-strain and tends to cause larger unrecoverable strain by softening shear modulus [11][12][13]. More recently, spectral analysis by Qian et al [14] related non-coaxiality to two distinct mechanisms, i.e., anisotropy of material and non-proportionality of loading.…”

Section: Introductionmentioning

confidence: 96%

Macro-micromechanical approaches for non-coaxiality of coarse grained soils

Qian

Huang

Sun

2011

Sci. China Technol. Sci.

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For coarse grained soils, their principal stress directions may change when the water level of embankment dam varies instantaneously. In this loading case, the principal directions of stress and strain rate will become non-coaxial. In an effort to model non-coaxial behavior, a modified three-dimensional non-coaxial model is developed in the context of vertex yield (tangent plasticity) theory. Discrete Element Method (PFC) incorporating user-defined interparticle contact models is also employed to gain an insight into microscopic mechanism of non-coaxiality. The analysis focuses on non-coaxial behaviors under simple shear condition. It has been shown that the proposed non-coaxial model gives good predictions for non-coaxiality with reference to microscopic observations while the classical coaxial model fails to simulate the non-coaxial behaviors. In general, non-coaxiality as a result of the rotation of principal stress, is large at a small shear strain, and inclined to become negligible with increasing shear strain. For coarse grained soils, their non-coaxiality tends to largely depend on the initial normal pressure, where a larger degree of non-coaxiality can be observed at a higher pressure. coarse grained soils, non-coaxiality, particle flow code, simple shear Citation:Qian J G, Huang M S, Sun H Z. Macro-micromechanical approaches for non-coaxiality of coarse grained soils.

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A non‐coaxial constitutive model for sand deformation under rotation of principal stress axes

Cited by 67 publications

References 46 publications

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Prediction of flow liquefaction instability of clean and silty sands

Macro-micromechanical approaches for non-coaxiality of coarse grained soils

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