Influence of sample slenderness and boundary conditions in triaxial test – a review

In the past decades an extensive work was done in order to improve the performance and increase the reliability of triaxial testing. Among the several changes made in order to solve the inaccuracies of the traditional test configuration, two of them are discussed in this paper: the sample slenderness (in other words, the H/D ratio) and the introduction of smooth end platens instead of the rough ones. By using H/D=1 and not the usual H/D=2 ratio, the formation of a single line-rapture and the bulge shape seem prevented. The smooth ends decrease the restrain at the top and bottom of the sample. From a theoretical point of view the effects of these changes are clear, but experimentally, the results coming from various studies are contradictory. The purpose of this paper is to elucidate the previous findings on the topic, including both laboratory and FEM modelling test programs.