A novel procedure to determine shear dynamic modulus and damping ratio for partial saturated compacted fine-grained soils

This paper presents a new procedure for the characterisation of the dynamic mechanical properties of unsaturated fine-grained soils (i.e., dynamic shear modulus and phase angle). The procedure uses a rheometer, which is a conventional device for the characterisation of viscous and viscoelastic materials but with limited used in the area of geotechnical engineering. Tests were carried out on cylindrical samples following a dynamic loading scheme under strain-controlled conditions. This research is divided into two phases. The first phase aims at validating the proposed experimental methodology. Thus, one sample of kaolin was tested using the proposed methodology, and the results were compared against those obtained from the conventional Resonant Column test. During the second phase, samples of kaolin were compacted at the optimum Proctor Standard; conditioned at different degrees of saturation, and tested using the proposed procedure to show its applicability on partially saturated soils. The dynamic shear modulus and phase angle of these samples were measured using a strain level ranging from 6×10^-6 to 1×10^-3 with different suction conditions and without confinement pressure. The results suggest that the newly developed procedure could be more versatile and accurate than available standardized tests.