Influence of Reconsolidation Techniques and Strain Rate on the Stiffness of Undirsturbed Clays from Triaxial Tests

This paper concerns the stiffness assessment of undisturbed clays from triaxial tests. The paper summarises the research activity undertaken at the authors' Universities over the last five years by means of triaxial cells equipped with local gauges for axial and radial strain measurements and with piezoceramic bender elements for the measurement of the propagation velocity of differently polarised shear waves. The main purpose of this research was to define reliable test procedures in order to determine the stiffness of geomaterials to be used for settlement analysis under working load conditions. In particular the paper deals with four different topics: i) evaluation of sample disturbance by means of different methods, ii) assessment of the reconsolidation techniques which minimise the sample disturbance effects, iii) influence of strain rate on the stiffness of undisturbed clays iv) stiffness anisotropy of undisturbed clays at small strains.