Induced anisotropy in a sand

Abstract

Controlled changes of principal stress directions have been applied to dense sand samples undergoing plane strain. The new apparatus and development problems are described before results are presented for a series of tests in which a single sudden rotation of principal stress directions was applied to each sample of dense sand. The magnitudes of these single rota- tions varied from 0° to 90°, individual rotations differing by 5° or 10°. The influence of inherent anisotropy was eliminated by depositing the samples in the direction of the subsequently applied intermediate principal stress (δe2, =O). The results demonstrate that induced anisotropy can have a large effect on magnitudes of strain increments and cause a small and quickly reducing deviation of the principal axes of stress and strain increment. There is a strong indication that for plastic strain no-extension directions define axes of induced anisotropy. Des changements contrôlés de directions de contrainte principale ont été appliqués à des échantillons de sable dense subissant une déformation plane. Les nouveaux appareils et leur constructions sont décrits avant de présenter les résultats d'une série d'essais dans lesquels une seule rotation soudaine de directions de contrainte principale fut appliquée à chaque échantillon de sable dense. L'importance de ces simples rotations variait de 0° à 90°, les rotations individuelles différant de 5° ou 10°. L'influence de I'anisotropie propre fut ˜ĺiminée en déposant les échantillons dans la direction de la contrainte principale intermtdiaire (δe2 = 0) qui allait &citc;tre. Les résultats démontrent que l'anisotropie induite peut avoir un effet considérable sur I'importance de l'accroissement de contrainte et provoquer une petite divergence rapidement réduite des axes principaux d'accroissement de contrainte et de dtformation. 11 y a une forte prtsomption que pour la déformation plastique les directions de non-extension définissent les axes d'anisotropie induite.

Shear banding modelling in cross-anisotropic rocks

“…This type of material is said to be transversely isotropic or cross-anisotropic (Amadei, 1983). A second possible type of anisotropy is an 80 induced anisotropy that results of the loading and deformation following the material deposition (Arthur et al, 1977a;Abelev & Lade, 2004). During material loading, applied stresses may in fact engender a modification of the solid particles spatial arrangement which can lead to anisotropic material behaviour (Oda et al, 1985).…”

Macro deformation and micro structure of 3D granular assemblies subjected to rotation of principal stress axes

“…Ishihara and Li [3] devised the torsional shear apparatus and demonstrated the sensitivity of material behaviour to strain-controlled cyclic torsional shear on initial K 0 and lateral confinement. Arthur et al [4] applied controlled changes of principal stress axes with the Directional Shear Cell and studied sample behaviour to shearing after a pre-loading to a high stress ratio and a rotation of principal stress axes. Extensive experimental observations on sand responses to principal stress rotation have been published since the 1980s' [5][6][7][8][9][10] using the hollow cylindrical device which offers independent control of the magnitudes and directions of principal stresses.…”

Quasi-Elastic Deformation Properties of Toyoura Sand in Cyclic Triaxial and Torsional Loadings

“…The anisotropy of soil can be divided into the inherent anisotropy (Oda, 1972a, b;Arthur and Menzies, 1972) and induced anisotropy (Arthur et al, 1977;Wong and Arthur, 1985). Note that the term "induced anisotropy" will be referred herein as stress-induced anisotropy (Bellotti et al , 1996).…”