| 1. |
- Yin, Z. Y., et al.
(författare)
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An anisotropic elastic-viscoplastic model for soft clays
- 2010
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Ingår i: International Journal of Solids and Structures. ; 47:5, s. 665-677
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Tidskriftsartikel (refereegranskat)abstract
- Experimental evidences have shown deficiencies of the existing overstress and creep models for viscous behaviour of natural soft clay. The purpose of this paper is to develop a modelling method for viscous behaviour of soft clays without these deficiencies. A new anisotropic elastic-viscoplastic model is extended from overstress theory of Perzyna. A scaling function based on the experimental results of constant strain-rate oedometer tests is adopted, which allows viscoplastic strain-rate occurring whether the stress state is inside or outside of the yielding surface. The inherent and induced anisotropy is modelled using the formulations of yield surface with kinematic hardening and rotation (S-CLAY1). The parameter determination is straightforward and no additional experimental test is needed, compared to the Modified Cam Clay model. Parameters determined from two types of tests (i.e., the constant strain-rate oedometer test and the 24 h standard oedometer test) are examined. Experimental verifications are carried out using the constant strain-rate and creep tests on St. Herblain clay. All comparisons between predicted and measured results demonstrate that the proposed model can successfully reproduce the anisotropic and viscous behaviours of natural soft clays under different loading conditions.
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| 2. |
- Yin, Z. Y., et al.
(författare)
-
Evaluation of the influence of elasto-viscoplastic scaling functions on modelling time-dependent behaviour of natural clays
- 2010
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Ingår i: Soils and Foundations. ; 50:2, s. 203-214
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study the influence of the scaling functions in Perzyna's type elasto-viscoplastic models for predicting time-dependent behaviour of natural clays. The constitutive models were developed based on the overstress theory with different scaling functions and on the elastoplastic model S-CLAY1S which accounts for induced anisotropy and gradual degradation of apparent soil bonds. Laboratory tests were simulated on natural clays under one-dimensional and triaxial conditions to evaluate the scaling function influence in the modelling of the strain-rate effect on soil strength and creep effect. The influence of scaling functions on modelling the time-dependent behaviour under pressuremeter condition was also numerically examined. This test is treated as an example of a boundary value problem, which also allows us to see if this in situ testing is capable of deriving the parameters controlling the time-dependent behaviour.
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| 3. |
- Yin, Z. Y., et al.
(författare)
-
Micromechanical analysis of kinematic hardening in natural clay
- 2009
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Ingår i: International Journal of Plasticity. - : Elsevier BV. - 0749-6419. ; 25:8, s. 1413-1435
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a micromechanical analysis of the macroscopic behaviour of natural clay. A microstructural stress-strain model for clayey material has been developed which considers clay as a collection of clusters. The deformation of a representative volume of the material is generated by mobilizing and compressing all the clusters along their contact planes. Numerical simulations of multistage drained triaxial stress paths on Otaniemi clay have been performed and compared the numerical results to the experimental ones in order to validate the modelling approach. Then, the numerical results obtained at the microscopic level were analysed in order to explain the induced anisotropy observed in the clay behaviour at the macroscopic level. The evolution of the state variables at each contact plane during loading can explain the changes in shape and position in the stress space of the yield surface at the macroscopic level, as well as the rotation of the axes of anisotropy of the material.
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