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A laboratory study of anisotropic geomaterials incorporating recent micromechanical understanding

Yang, L.-T.; Li, X.; Yu, Hai-Sui; Wanatowski, D.

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L.-T. Yang

X. Li

Hai-Sui Yu

D. Wanatowski


This paper presents an experimental investigation revisiting the anisotropic stress–strain–strength behaviour of geomaterials in drained monotonic shear using hollow cylinder apparatus. The test programme 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 are significant. The stress–strain–strength behaviour of the specimen shows strong dependence on the principal stress direction. Preloading history, material density and particle shape are also found to be influential. In particular, it was found that non-coaxiality is more significant in presheared specimens. The observations on the strength anisotropy and deformation non-coaxiality were explained based on the stress–force–fabric relationship. It was observed that intermediate principal stress parameter b(b = (σ2 − σ3)/(σ1 − σ3)) has a significant effect on the non-coaxiality of sand. The lower the b-value, the higher the degree of non-coaxiality is induced. Visual inspection of shear band formed at the end of HCA testing has also been presented. The inclinations of the shear bands at different loading directions can be predicted well by taking account of the relative direction of the mobilized planes to the bedding plane.

Journal Article Type Article
Acceptance Date Nov 12, 2015
Online Publication Date Dec 24, 2015
Publication Date Oct 31, 2016
Deposit Date Oct 25, 2017
Publicly Available Date Oct 25, 2017
Journal Acta Geotechnica
Print ISSN 1861-1125
Electronic ISSN 1861-1133
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 11
Issue 5
Keywords Anisotropy; Discrete elements; Laboratory tests; Numerical models; Plasticity; Sand (soil type)
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