M. Biglari - International Institute of Earthquake Eng. and Seismology (IIEES), Tehran, Iran
M. Jafari - International Institute of Earthquake Eng. and Seismology (IIEES), Tehran, Iran.
A. Shafiee - International Institute of Earthquake Eng. and Seismology (IIEES), Tehran, Iran
C. Mancuso - Dipartimento di Ingegneria Idraulica, Geotecnica ed Ambientale at the University of Naples federico II, Naples, Italy.

An experimental study has been carried out to investigate the effects of isotropic compression,wetting and drying on the initial shear stiffness, G0, of an unsaturated silty clay, tested both in normally consolidated and over-consolidated conditions. A fixed-free Resonant Column- Torsional Shear device, working in suction controlled conditions has been used. Specimens have been compacted at the same void index by wet tamping. G0 has been measured almost continuously along complex stress paths. The behaviour observed on wetting paths clearly indicates that G0 significantly depends on volumetric state. On normally consolidated samples for which wetting is accompanied by collapse, reduction in suction has not remarkable effect on G0. Conversely, in the case of over-consolidated samples G0 significantly reduces as suction decreases.

unsaturated kaolin, small strain behaviour, volumetric behaviour, isotropic compression, wetting-drying