Asymptotic behaviour of a granular soil in strain path testing

Abstract

This Paper investigates the asymptotic behaviour of a granular soil in strain path testing for triaxial samples and cuboidal mntiaxial samples using constant strain increment ratio paths. Techniques for the precise control of strain increment ratio of samples were developed. Strain path control started from isotropic and anisotropic stress states. Asymptotic behaviour associated with the SOM (swept-out memory) concept was observed. For test data from tests with strain path control starting from a pre-failure stress state, a unique relationship between the asymptotic stress ratio and strain increment ratio can be established. Different asymptotic behaviour was observed when strain path control started after the failure stress state had been achieved. The concept of a limit surface is also shown by asymptotic behaviour. KEYWORDS:constitutive relations; laboratory tests; sands.L'article Ctudie le comportement asymptotiqne d'un sol granulaire lors d'essais de chemin de diformation r&ali&s sur des Bchantillons triaxiaux ou cubiques multiaxiaux, pour des incrkments de dkformation constants. Une technique a iti! develop p&e afin de contrdler prkciskment I'inckment de dkformation de I'khantillon, c'est i dire son chemin de dkformation. Le contrale du chemin de d&formation dtbute sur nn k-tat de contrainte qui peut @tre soit isotrope, soit anisotrope. Un comportemeot asymptotique, associi! au concept SOM (swept-out memory) a CtL! observk. Pour les donnkes provenant des essais i chemin de dkformation contrCdi! at P Ctat de contrainte de p&rupture, une seule relation peut Etre mise en kvidence entre la contrainte asymptotiqne et l'incriment de dkformation, Differents comportements asymptotiques ont par centre Ctk observb lorsque le contr8le du chemin de dkformation commence apr&s mise en place de 1'Ctat de contrainte menant $ la rupture. Le concept de surface limite est Cgalement dkmontri par ce comportement asymptotique.

An improved version of barodesy for clay

“…13 Predictions of proportional paths with the R -function [21] in which c 1 and c 2 are calibrated on the basis u c . The results are in good agreement with the relation by Chu and Lo [3]. u c is chosen to 25 in this plot 13 The equation …”

“…The R-function (Eqs. 3-5) includes c 1 and c 2 , captures critical states and Jáky's relation K 0 ¼ 1 À sin u c for oedometric compression and produces similar results to Chu and Lo's relation [3]. Results are presented in Appendix 1.…”

“…The stretching tensor D is the symmetric part of the velocity gradient. 3 The mean effective stress is p :¼ À 1 3 tr T, and e vol ¼ tre is the volumetric strain. In this article, d :¼ tr D 0 ¼ _ e vol =j _ ej is used as a dilatancy measure.…”

“…In c, barodesy for clay [20] (2012) is compared with the version presented here (2016), and u c is chosen as 22:6 2 The term objectivity points to the fact that material behaviour is frame-indifferent, i.e., the behaviour is independent of the observers' motion. 3 In general, stretching D is only approximately equivalent to the strain rate _ e. For rectilinear extensions, D equals _ e, with _ e being the logarithmic strain tensor. 4 However, for sand versions of barodesy (e.g., Kolymbas [10]), the exponent is smaller \1.…”

“…The constitutive model for soil called barodesy, proposed by Kolymbas [9][10][11][12], is based on the asymptotic behaviour of granulates expressed by the two rules proposed by Goldscheider [6], which have been experimentally confirmed for sand and clay [3,6,26,27]: (1) starting at the stress-free state, T ¼ 0, proportional strain paths 1 lead to proportional stress paths (see footnote 1); and (2) starting at T 6 ¼ 0, proportional strain paths lead asymptotically to the corresponding proportional stress paths starting at T ¼ 0. This means that proportional stress paths function as attractors.…”