Simplified Analysis Method of Seismic and Static Stability for Embankments Supported with Concrete Piles in Soft Ground

A simplified analytical method is provided for the overall seismic and static stability of embankments supported with concrete piles in soft soil according to the pseudo-static approach. Mobilized shear forces on the piles intersected by the slip surface are involved in the proposed method. This method was originally established on four aspects: the circular slip surface assumption, pile bending–tension failure mechanism, simplified Bishop’s assumption, and elastic-beam-on-foundation model. The proposed method innovatively obtained the overall safety factor and critical slip surface of the piled-embankment system as well as the bending moment and shear force profiles of the piles. Moreover, it reproduced the progressive failure process of the system with the piles fracturing gradually. This method was verified by centrifugal tests and numerical simulations, and their safety factor relative errors were within 5%. Examples showed the safety factor decreased nonlinearly by 33% as the horizontal seismic coefficient increased from 0 to 0.2. The piles fractured progressively toward the interior of the system after the first one failed at the embankment toe. As the pile spacing in the two directions respectively increased from 3 to 5 times the pile diameter, the shear force of the critical pile at the slip surface increased slightly. Reinforcements in the embankment cushion may deepen the pile failure positions. This work provides a significant design reference for piled embankments under seismic conditions, including aspects such as overall stability, internal forces, and the progressive fracture of piles.