Small strain behaviour of soils in controlled suction conditions

This paper discusses the influence of suction on small strain stiffness (G0) of soils. It is mainly based on experimental measurements performed at the Department of Geotechnical Engineering of the University of Naples Federico II (Italy) with an innovative Resonant Column-Torsional Shear device (RCTS_NS) working under suction controlled conditions. The observed trend of G0 with matric suction and mean net stress are discussed, and an interpretation criterion based on the simultaneous presence of bulk- and menisci-water inside the pore space is given. A review of the limited amount of literature data on small strain stiffness measured in suction controlled conditions is then presented and used to validate the proposed interpretation frame. Finally, the same data and those collected with the RCTS_NS are then used to analyse the effects of soil grading on the initial stiffness versus suction relationship.