Model Test Study on Bearing Performance of Squeezed Branch Pile Under Combined Loads

This study investigates the mechanical performance of squeezed branch piles under combined loads (horizontal combined with uplift/compression) in silty clay through model tests. Based on a systematic comparison of the mechanical responses among straight-shaft piles, single-plate piles, and double-plate piles, the load-dependent behavior of branched piles is revealed, and optimized design principles are proposed. The results demonstrate that under horizontal combined loads, squeezed branch piles effectively mobilize soil-arching effects via the bearing plates, leading to significant enhancements in both horizontal and vertical-bearing capacities compared to straight-shaft piles. Double-plate piles exhibit superior overall deformation resistance due to composite confinement; however, an adverse superposition effect at a plate spacing of 2 d may result in a marginally lower capacity. The horizontal capacity of single-plate piles increases with embedment depth, with the axial force peaking at a critical depth of 4 d (embedment depth of first plate). The upper plate plays a dominant role in resisting deformation, consistently carrying 75–105% higher axial force than the lower plate. This research provides important theoretical support and practical references for the design of pile foundations subjected to complex loading conditions.