Influence of reconsolidation techniques and strain rate on the stiffness of undisturbed clays from triaxial tests

This paper concerns the stiffness assessment of undisturbed clays from tria xial tests. The paper summarizes the research activity undertaken at the au thors' universities over the last five years by means of triaxial cells equ ipped with local gages for axial and radial strain measurements and with pi ezoceramic bender elements for the measurement of the propagation velocity of differently polarized 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 conditio ns. In particular the paper deals with four different topics: (1) evaluatio n of sample disturbance by means of different methods, (2) assessment of th e reconsolidation techniques that minimize the sample disturbance effects, (3) influence of strain rate on the stiffness of undisturbed clays, (4) sti ffness anisotropy of undisturbed clays at small strains.