Anisotropy of small strain stiffness of undisturbed and reconstituted clays

This paper concerns the assessment of the elastic shear modulus G(o) of reconstituted and undisturbed clays by means of seismic measurements performed during triaxial compression tests. The experiments were performed by means of a triaxial cell 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 tests were performed on reconstituted specimens of Fujinomori (Japan) clay and on intact specimens of two Italian clays (Pisa and Augusta). Seismic tests were performed during saturation process, consolidation and shearing. These measurements allowed to determine the small strain shear modulus in the vertical and horizontal plane (G(vh),G(hh)). In particular the paper deals with the following topics: i) assessment of the stiffness anisotropy at small strains, ii) assessment of the decay of G(o) during shearing in order to define the sensitivity of this parameter to sample disturbance.