A controlling method of the settlement-induced bearing capacity of squeezed branch piles

The load-bearing capacity of squeezed branch piles(SBPs) can significantly increase under small incremental settlement deformations. By simultaneously controlling the pile top load and settlement to meet control requirements，the full potential of the SBP’s bearing capacity can be realized. This study introduced a load transfer equation for SBPs without critical displacement，incorporating the displacement parameter corresponding to 0.5 times the ultimate bearing capacity. A failure model for the soil around the bulb was established based on Meyerhof’s bearing capacity theory，determining the effective length of the shaft resistance in the straight section. A pile-soil failure model for SBPs with different bulb spacing was developed，identifying the optimal bulb spacing. An improved load transfer analysis method，considering both pile top design boundary conditions and pile tip control boundary conditions，enables synergistic control of both bearing capacity and settlement，achieving dual control targets. Field static load tests combined with numerical simulations verified the pile-soil failure model of SBPs and determined parameters for the load transfer equation. The theoretical framework optimized the pile length and layout of bulbs or branches under field conditions. Case verification showed that，while meeting design requirements，the optimized scheme reduces pile length by 14.3 meters，with a reduction of 3 branches and 1 bulb. The error between the theoretical ultimate bearing capacity and the numerical model calculation is 2.9%. © 2024 Academia Sinica. All rights reserved.