Small strain behaviour of a silty sand in controlled-suction RCTS tests

An experimental study has been carried out using a new resonant column – torsional shear cell to investigate the small strain behavior of an unsaturated compacted silty sand. The device, recently developed at the Dipartimento di Ingegneria Geotecnica di Napoli (Italy), is fitted for controlled-suction testing using the axis-translation technique. Both optimum and wet of optimum compacted specimens have been tested to analyze the effects of suction and fabric on soil behavior. Shear stiffness measurements have been taken during constant-suction tests. Collected data indicate an S-shaped initial shear stiffness versus suction variation, which can be explained considering the progressive change from a bulk-water regulated soil response to a menisci-water regulated soil response. A model is proposed to account for the observed trend. Results highlight significant effects of suction and fabric on soil behavior.