软土地层盾尾注浆压力引起的地面隆起分析

Analysis of Ground Surface Heave Induced by Grouting Pressure at Shield Tail in Soft Soil Tunnel

目前已有盾尾注浆压力引起地面隆起的研究均假定盾尾注浆压力均匀分布,这与实际工程中盾尾注浆压力上小下大的形式不符。为更准确预测盾尾注浆压力引起的地面变形,在现有均匀注浆压力引起地面隆起分析的基础上,考虑软土地层盾构隧道施工中盾尾注浆压力上小下大的分布形式,将盾尾注浆对地层的压力效应视为半无限土体中柱形孔的扩张过程,利用镜像法和Mindlin解,推导出软土地层盾尾注浆压力引起的地面隆起计算公式,并通过工程实例,将本文解答、叶飞解答、林存刚经验公式解答、Vesic解答与数值解进行对比分析。结果表明:盾尾注浆压力引起的地面隆起横向曲线总体上呈高斯分布。在预测软土地层地面沉降时,忽视盾尾注浆压力引起的地面隆起是不合理的;用推导出的公式计算上小下大分布形式下盾尾注浆压力引起的地面沉降是可行的,Vesic公式和林存刚经验公式在应用时需要根据具体工程进行相应修正。

It is assumed that the grouting pressure at shield tail was uniformly distributed in existing researches of ground surface heave induced by grouting pressure at shield tail, which is not consistent with the actual situation. In order to precisely predict the ground surface heave, the computational formula of ground surface heave induced by grouting pressure at shield tail is deduced by image method and Mindlin Solutions based on analysis of ground surface heave induced by uniform grouting pressure. In the formula, the actual distribution of grouting pressure （ upper small and lower large） is taken into consideration, and the effect of grouting pressure at shield tail on the surrounding soils is simplified as an expansion process of cylindrical hole in semi-infinite elastic solid. And then, the solution deduced, Yefei Solution, Lincungang Solution, Vesie Solution and numerical solution are taken into comparison through case study. The results show that ： 1 ） The curve of the transversal ground surface heave induced by grouting pressure at shield tail shows Gaussian distribution. It is irrational to ignore the ground surface heave induced by grouting pressure at shield tail in prediction of ground settlement. 2） The above-mentioned formula is available in predicting the ground surface heave induced by grouting pressure at shield tail; and Vesic Solution and Lincungang Solution need to be modified according to actual project.