Mechanical behaviour of a natural soft clay

The results of an experimental study on the mechanical behaviour of the natural soft clay found at Pisa are discussed. Triaxial and true triaxial stress path-controlled tests were carried out, in which the soil was subjected to a variety of drained stress paths, each starting from the in situ stresses. The stress-strain behaviour was observed to be substantially non-linear from the very beginning of the loading process. The observed results ale interpreted using concepts of hardening plasticity, The influence of the damage produced in the clay microstructure during loading is evaluated through a normalization technique. A comparison between the behaviour of the natural and the reconstituted clay is also presented. The results of the true triaxial tests show strength anisotropy, In both the triaxial and the true triaxial tests, the observed stiffness was found to depend strongly on the direction of the stress path.