Simple shear testing of sensitive very soft offshore clay for wide strain range

Stiffness and damping properties of sensitive very soft clay sediments of the Italian Adriatic continental shelf are determined by means of two staged (a 12-stages and a 2-stages test respectively) cyclic simple shear tests. The apparatus used in this research is capable of investigating the stress-strain behaviour of the soil in a wide range of shear strains, from about 0.0004% to 1%. Test results were expressed in terms of small-strain shear modulus G0 and of normalized equivalent shear modulus (Geq/G0) and damping ratio (D) versus cyclic shear strain amplitude (gc). These parameters were analyzed in the framework of existing literature by comparison with empirical correlations developed for onshore materials of different plasticity and, limited to G0, also for soft soils. The dependence of G0, Geq/G0-gc and D-gc on factors such as void ratio, stress history and loading cycles is analyzed and discussed.