Modeling of a soft clay gentle slope with sand layer in centrifuge under seismic loading: PIV and strain rate analysis

Dynamic soil parameters such as the shear modulus suffer degradation while damping in soil increases under dynamic loading. These can be determined from various tests such as element tests, field tests and centrifuge experiments. Most of the studies about dynamic soil characterization have focused on evaluating these parameters assuming horizontal ground conditions without considering the effect of static shear stresses induced by ground inclination. This paper presents a dynamic centrifuge test conducted on a layered gentle slope comprising clay and sand, to obtain experimental data in terms of shear modulus and damping for various shear strains. Particle Image Velocimetry (PIV) was employed to measure the displacements and to calculate accelerations due to seismic loading at various depths throughout the slope model. The results suggest that the static shear stress caused by the profile inclination causes a more pronounced degradation of the shear modulus when compared to flat ground conditions. Moreover, the damping during the centrifuge test exhibited larger values than expected, following a similar behavior observed in other experimental programs. The strain rate analysis revealed the mobilization of shear stresses higher than the monotonic shear strength for the clay layers during the seismic shaking.