Investigation of the Axial-Bearing Mechanism of Single and Group Squeezed Branch Piles in Soft Soil Combining Field Measurements and Numerical Modeling

Squeezed branch (SB) piles, featuring branches along the pile shaft, have been increasingly applied to reinforce soft foundations. However, the load-bearing behavior and interaction mechanism of SB pile groups in soft soils remain insufficiently understood, leading to potential overdesigned solutions. This study aimed to close the knowledge gap by investigating the axial bearing characteristics of both single and group SB piles in soft soils through field tests and numerical simulations. A full-scale load test on an instrumented SB single pile was conducted to assess its bearing capacity. A validated three-dimensional numerical model was then used to analyze the load–settlement response, group efficiency, and load transfer mechanism of SB piles. The results indicate that the branches bear approximately 60%–70% of the total load. The load behavior of the branch is influenced by factors such as branch diameter (D) and bearing stratum, resulting in a reduced pile tip load of 19.4% in the SB pile group, compared to 51.2% in straight piles. Increasing the diameter ratio improves the ultimate bearing capacity by 82%–194% compared to straight piles. The group efficiency is strongly influenced by the number of piles and pile spacing, with eight times pile shaft diameter (d) identified as the optimal pile spacing for SB piles in soft soil. Furthermore, the lower branch mobilizes a larger soil volume to distribute compressive load. Interbranch spacing influences bearing capacity by altering the properties of the soil beneath the branches.