Centrifuge modelling of cone penetration tests in unsaturated clayey sand under various hydraulic conditions

In-flight cone penetration tests (CPTs) have been conducted extensively to characterize centrifuge models of dry and saturated soils, but only a limited number of studies have focused on unsaturated soils. This paper presents centrifuge modeling of CPTs conducted on unsaturated clayey sand models prepared at various hydraulic conditions including as-compacted, wetting (rainfall) and drying (evaporation). The objectives of this study were to evaluate effects of stress level induced by centrifuge acceleration and to investigate the impact of hydraulic processes on the cone tip resistance (q_c). Results shows that variations of q_c with depth obtained from different centrifugal acceleration are in very good agreement and similarity of q_c and water content distribution in centrifuge models is validated. In addition, it was found that matric suction has greater impact on the q_c than total vertical stress. The CPTs performed on clayey sand show that the cone tip resistance increases as the degree of saturation decreases under different hydraulic conditions. A correlation between the cone tip resistance and degree of saturation is applicable to both wetting and drying processes. The CPT results and in-flight water content measurements provide a good indication of strength and stiffness change in unsaturated soil subject to changes in hydraulic conditions.