Seismic Factor of Safety for 3D Reinforced Soil Slope with Piles under Unsaturated Condition

This study investigates the seismic stability of reinforced slope under a three-dimensional (3D) rotational horn-like failure mechanism, using the pseudo-dynamic approach and provides a new procedure to estimate factor of safety (FS) for slope. Such a procedure is able to figure out the influences of the seismic force, the soil property and the reinforcement by piles. Pseudo-dynamic approach is used to describe the seismic force in the time-to-spatial fields in unsaturated soils where matric suction works. Compared to the pseudo-static approach, the current approach considers the effects of time and spatial through the horizontal and vertical shear waves. For the pile driving, different insertion depths can yield various results, whether two work conditions of considering the pile resistance or not are discussed. FS of this study undergoes a decrement as the increase of the pile resistance and seismic force, indicating that the insertion depth affects FS where FS decreases in the early period of pile driving, after that increases and keeps constant in the late of pile driving, showing evident unimodal characteristics during the pile driving. The new expressions for slope reinforced by piles are presented for practical use in unsaturated soil engineering.