Cyclic and dynamic behaviour of a Canadian sensitive clay

Clays with higher undisturbed undrained shear strengths than remoulded strengths are considered sensitive. While the stress-strain behaviour of these clays under monotonic loading condition was widely investigated, few data are available of their behaviour under cyclic and dynamic loading conditions. This paper presents the preliminary results of an experimental program on undisturbed samples of a sensitive clay retrieved at Saint Luc de Vincennes (Quebec). In particular, the paper shows the comparison among the modulus reduction curve, G/G0 - γ and the damping ratio variation with shear strain, D - γ measured using different devices, trying to highlight the main factors influencing the observed behaviour, including sample disturbance and storing method. The tests were carried out using one torsional shear and two different cyclic simple shear devices capable of investigating from small to large shear strains. The tests were carried out by three different laboratories at the Université de Sherbrooke, Canada, the University of Naples Federico II and the Sapienza University of Rome, Italy. Oedometric tests also performed by the three different research teams indicate that the clay samples were carefully shipped and stored, and the soil specimens were accurately prepared. Some differences were observed in the G/G0(γ) and D(γ) curves obtained by different tests, some of them ascribed to the intrinsic anisotropy of the investigated clay.