Response of pile groups with X and circular cross-sections subject to lateral spreading: 3D numerical simulations

Abstract

Abstract Recent 1-g shake table experiments have shown that the relatively new X-shaped cast-in-place piles can improve the seismic response of slopes susceptible to lateral-spreading as compared to conventional bored piles when mitigated using the pile-pinning method. This paper presents three-dimensional (3D) nonlinear dynamic numerical simulations of groups of piles with X-shaped cross-sections subjected to lateral spreading to broaden the understanding of their effectiveness in mitigating slope displacements. The unit cell method is used with the stress-ratio controlled and critical state-compatible Dafalias-Manzari model to capture appropriate cyclic behavior of the liquefiable soil surrounding the piles subjected to seismic ground motions. The numerical simulations facilitate the evaluation of various parameters controlling soil-pile interaction and the structural pile response, including the effect of pile spacing, pile fixity, pile orientation, slope angle, and geometrical effects of the pile cross-section with emphasis on the X-shaped section. The results demonstrate that X-shaped pile groups can significantly reduce lateral slope displacements compared to the unimproved or circular pile-improved ground, and that the spacing, pile orientation and pile fixity play a critical role in the deformation response. These findings provide insight to the design of pile-improved ground as well as the structural design of piling adjacent to or within liquefiable slopes.