关键词: 管桩, 开挖残余效应, 沉桩阻力, 承载性状, 单桩竖向承载力

Abstract: The squeezing effect of the pipe pile at the bottom of the foundation is reduced by the excavation, which changes the axial capacity characteristic of the single pipe pile at the bottom of the excavation. Based on Vesic cavity expansion theory, considering the residual effect of the change of pressure at the bottom of the excavation, an estimation method for the jacking resistance is presented in this paper. Furthermore, based on the jacking resistance of pipe piles, an empirical formula for the axial ultimate capacity of the single pile is given. Moreover, the reliability of the empirical formula and the axial bearing influence factors of the pipe pile are studied in this paper. By comparing the estimation values of the resistance on the pile tip, the earth pressure on the pile side and the jacking resistance of the pipe pile with the measured values, the results show that the measured values of the resistance on the pile tip, the earth pressure on pile side and the jacking resistance of the pipe pile fit well with the calculated results, which verify the feasibility of the empirical formula. Based on Qu/Pu ratios by fitting method, the deviations between measured and estimation values are only 4.17% and 5.64% respectively, which also verify the feasibility of the empirical formula to the jacking resistance of a single pile. Moreover, it is found that the ratios of L/d and L/H have a significant effect on the earth pressure on the pipe pile, the jacking resistance, and the axial capacity of the single pipe pile. The smaller the ratios of L/d and L/H are, the greater the radial pressure of the pile, the more significant effect on the jacking resistance and the axial capacity of the single pile. The above conclusions can provide a theoretical basis for the design of the pipe pile at the bottom of the foundation excavation.

Key words: Pipe Pile, Residual Effect by Excavation, Jacking Resistance, Bearing Characteristic, Single Pile Axial Capacity