Anisotropic Behaviour of Sand in the Small Strain Domain. Experimental Measurements and Modelling
This paper deals with the initial and loading path induced anisotropy for a sub angular granular material, Hostun sand. The “quasi” elastic properties observed in the small strain domain (<10−5 m/m) are considered. A “static and dynamic” triaxial device is used for the experimental campaign. First, the five parameters of the transverse isotropic elastic compliance tensor are experimentally obtained. The experimental investigations consist in applying small axial cyclic loadings (strain amplitude cycle εsa≅ 10−5 m/m) and four types of dynamic wave propagations, generated by piezoelectric sensors (compressive and shear waves in axial and radial directions). The followed isotropic and deviatoric stress path underlines the effects of respectively inherent and induced anisotropy. A rheological hypoelastic model, called DBGS model, which takes into account the stress induced anisotropy, is firstly described. This model is not sufficient to properly describe experimental results at isotropic stress state as well as thus obtained during deviatoric stress path for medium and large strain. Then, an extension of the model is proposed, called DBGSP model, where strain induced anisotropy is taken into account. The concept of virtual strain induced anisotropy is introduced in this rheological hypoelastic model developed at ENTPE, and the ability of the model to foresee experimental behaviour is checked.
Keywordsgranular media sand small strain hypoelasticity anisotropy wave propagations local measurements triaxial device
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