基坑底部抗拔桩对下卧隧道群竖向变形影响分析

以杭州市某河道开挖为背景,利用ABAQUS有限元软件建立了三维数值模型,研究了河道开挖过程中,抗拔桩对抑制下卧隧道群隆起的作用效果。结果表明,抗拔桩长度越长,隧道隆起越小,当桩长超过一定长度,其抑制隧道隆起的作用削弱;隧道纵向一定范围内的隆起受抗拔桩的影响,此范围外几乎无影响,且隧道埋深越大,其受影响的范围越小;基坑两侧抗拔桩对抑制隧道隆起作用较小,因此适当减小基坑两侧抗拔桩的长度,形成长短结合的抗拔桩,对于减小隧道隆起,同样效果显著,且在一定程度上降低了工程造价;推导非等长抗拔桩下,隧道抗浮验算公式,计算简单,便于应用。

Analysis of vertical deformation of underlying metro tunnels by uplift pile at the bottom of foundation pit

A 3-D model for channel excavation is constructed in ABAQUS. The influence of uplift piles on the apophyses of tunnels in the process of foundation pit excavation is analyzed. The results show that, with the length of uplift pile increased, the vertical deformation of tunnels decreased . When the uplift pile reaches a certain length, the effect of uplift piles on displacement of tunnels would be weakened. There is certain range of the influence on the uplift piles. The range is related to the buried depth of the tunnels; the greater the buried depth, the smaller areas would be affected. The uplift piles on both sides of foundation pit have little effect on restraining tunnel uplift.The length of the uplift piles is appropriately reduced and form long-short piles, which have the same effect as original design and reduce engineering cost . The formula for checking anti-floating of tunnel under non-equal-length uplift piles is deduced, which is easy to calculate and easy to apply.