Influence of Pile Arrangement and Bearing Stratum Thickness on Vertical Performance of Steel Pipe Sheet Pile Foundations

Publication Title
Influence of Pile Arrangement and Bearing Stratum Thickness on Vertical Performance of Steel Pipe Sheet Pile Foundations

Abstract

Steel pipe sheet pile (SPSP) foundations are composite structural systems commonly used in port and river structures in Japan, consisting of closely spaced steel pipe piles connected by mechanical joints. While their lateral resistance mechanisms have been extensively studied, the vertical bearing behaviorparticularly under group pile effectsremains insufficiently understood. This study investigates the vertical bearing capacity of SPSP foundations through a series of centrifuge model tests conducted under a 50g field at the Disaster Prevention Research Institute (DPRI), Kyoto University. The piles were modeled as non-displacement piles, and installation-induced stress changes were not considered. The experiments focused on the influence of pile configuration (single, three- and five-pile series, and five-pile cross groups) and bearing layer thickness below the pile base (10D, 3D, and 1D, where D is the pile diameter). The dense bearing layers and overlying soft strata were prepared using silica sand with controlled relative densities. The results showed a distinct group pile effect: as the number of piles increased, the unit bearing capacity per pile decreased. In particular, the five-pile cross group exhibited the most significant reduction, attributed to restricted settlement and reduced mobilization of tip resistance in the confined layout. Moreover, thinner bearing layers led to a pronounced decrease in capacity for group pile foundations, with shaft friction becoming the dominant resistance mechanism. These findings suggest that particular attention should be paid to the selection and evaluation of the bearing layer in SPSP foundation design, especially under dense pile group configurations.

Authors
Yasuo Sawamura; Kota Higuchi; Ryuichi Kato; Yasumasa Soga; T. Kanazawa; Naoki Deguchi

Published In

11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)

Theme

Session 6: Onshore and offshore foundation systems