Finite Element Simulation Analysis of the Influence of Pile Spacing on the Uplift Bearing Performance of Concrete Expanding-Plate Pile Groups

Concrete expanding-plate piles (CEP piles) represent a novel type of variable cross-section concrete cast-in-place pile, wherein one or more bearing plates are added to the pile body to enhance its load-bearing capacity. Compared to traditional uniform-diameter uplift piles, the bearing plates of CEP uplift piles provide additional resistance against uplift, substantially increasing the pile's uplift bearing capacity. CEP piles exhibit a wide range of application potential in structures such as high-rise buildings, cable-stayed bridges, and offshore platforms. However, due to changes in the load-bearing mechanism, the pile-soil interaction of CEP piles significantly differs from that of straight-shaft piles. Theories applicable to the group effect of straight-shaft piles cannot be directly applied to CEP piles, which has led to imperfections in the theoretical framework for designing CEP piles in practical engineering applications, hindering their broader adoption. Therefore, this paper employs a finite element simulation analysis to study the failure modes of three groups of symmetrically arranged CEP pile groups. The effects of pile spacing on the uplift bearing capacity of CEP pile groups are investigated, leading to a revision of the formula for calculating the uplift bearing capacity of CEP pile groups. This study enhances the theoretical understanding of the load-bearing behavior of CEP pile groups, providing a theoretical basis for their practical engineering applications.