边载作用下隔离桩隔离效果的影响因素研究

Factors influencing isolation effects of isolation piles under side loading

以港珠澳大桥海底沉管隧道基础沉降控制研究为科研背景,为研究岛头边载作用下隔离桩隔离效果的影响因素,进行了8组室内模型试验,分别研究了隔离桩桩长、桩径、桩间距及隔离桩距减沉桩距离S1等因素对隔离效果的影响。试验结果表明:减沉桩桩身最大轴力、弯矩随隔离桩桩长的增加而减小,并且当隔离桩桩长达到所需的嵌固深度时,对弯矩的隔离效果非常显著;隔离桩桩径的增加或桩间距的减小不仅提高隔离桩对竖向变形的隔断能力,同时也使得隔离桩之间土拱效应增强,减沉桩桩身最大轴力、弯矩随着隔离桩桩径的增加而减小,随隔离桩桩间距的减小而减小,同时,当隔离桩桩间距达到8D时,对轴力与弯矩的隔离效果可以忽略不计;减沉桩桩身最大轴力随S1的减小而减小,而S1的变化对弯矩的隔离效果影响不显著;研究成果可为隔离桩的应用提供较好的参考。

Based on the settlement control of the immersed tube tunnel in Hong Kong-Zhuhai-Macao Bridge, eight groups of labortary model tests on length and diameter of piles, pile spacing and distance S1 between isolation piles and settlement reducing piles are performed to study the isolation effects of isolation piles under large side loading in the island edge. The results show that the maximum axial force and bending moment of settlement-reducing piles decrease with the increasing length of isolation piles, meanwhile a sufficient length of isolation piles plays a significant role in diminishing the bending moment. The increasing diameter of isolation piles or the decreasing spacing of isolated piles can enhance the obstructing ability of vertical deformation and strengthen the soil arching effect. The maximum axial force and bending moment of settlement-reducing piles decrease with the increasing diameter or the decreasing pile spacing. At the same time, the isolation effects for the axial force and moment can be ignored when the pile spacing reaches 8D. The isolation effects for the axial force become better as distance S1 decreases, however those for the moment are not significant due to the variation of distance S1. The research achievements may provide a better reference for the application of isolation piles.