Optimal pile spacing considering soil arching effect for composite pile-supported foundation pit

Abstract

The study aims to investigate the optimal spacing of piles in composite pile-supported excavations. By considering the characteristics of the composite pile support structure and the distribution of soil sliding forces behind the piles, this study formulated a simplified soil arch model in the shape of a semi-elliptical line. Utilizing static equilibrium conditions and the limit equilibrium theory, the study successfully developed a computational model for the soil arch in composite pile-supported excavations and derived the corresponding formula for calculating pile spacing. The accuracy and reliability of this method were validated through practical engineering cases. A systematic analysis of key factors, including cohesion, internal friction angle, and soil pressure, was conducted to reveal their influence on pile spacing. The results indicate an increasing trend in pile spacing with higher cohesion, a nonlinear increase with an elevated internal friction angle, and a decrease in pile spacing with greater soil pressure. The proposed formula for pile spacing is applicable not only to composite pile-supported excavations but also for calculating pile spacing in scenarios with identical-sized pile support, highlighting its broad generality and applicability. The research offers a dependable theoretical foundation for the secure and economically efficient design of composite pile support structures in engineering practice.