Investigation of Squeezed Branch Pile Capacity Under Combined Horizontal–Uplift Loading

This paper investigates the bearing behavior of squeezed branch piles and straight-shaft piles under uplift and combined horizontal–uplift loading in silty clay strata. Utilizing a combined approach of laboratory model tests and numerical simulation, the influence of key parameters, such as the depth of the first branch and branch spacing, on the bearing capacity was systematically analyzed. The results demonstrate that under combined loading, the bearing capacity of squeezed branch piles is significantly superior to that of straight-shaft piles, with double-branch piles outperforming single-branch piles. The bearing capacity increases with the depth of the first branch and the branch spacing, reaching its optimum when the first branch is buried at a depth of 6 d (where d is the straight-shaft pile diameter). This study also reveals a unique mechanical response under combined loading: the load–displacement curves exhibit a “smoothed” characteristic, rendering the traditional inflection point method unsuitable for determining the ultimate bearing capacity. Furthermore, a significant coupled weakening effect exists between horizontal and uplift forces. However, increasing the depth of the first branch (to 6 d) and the branch spacing can effectively mitigate this effect, enhancing the pile’s stability under complex loading conditions. This research provides a crucial basis for the optimized design and application of squeezed branch piles in complex loading environments.