基坑上跨开挖诱发既有盾构隧道隆起变形研究EI北大核心CSCD

基坑上跨开挖将会引起既有盾构隧道隆起变形,危及既有盾构隧道的服役性能。目前基坑开挖引起的盾构隧道隆起变形的解析方法,通常将盾构隧道简化为埋置于弹性地基上的连续长梁,忽略了环间接头影响。针对前人研究的不足,提出带环间接头的盾构隧道计算模型,通过非线性Pasternak地基模型来考虑地基土变形的非线性特征,通过两阶段分析法,推导得到基坑上跨开挖作用下盾构隧道隆起位移和张开量简化解答。通过MINDLIN解计算基坑开挖引起的作用于盾构隧道上的附加荷载;建立基坑卸载下盾构隧道的隆起变形微分方程。利用有限差分法求解出基坑开挖引起的邻近盾构隧道隆起变形和内力分布。收集了三个工程实测数据,并将所提方法和实测数据、既有理论方法进行对比,验证所提方法的适用性。

HEAVE DEFORMATION OF EXISTING SHIELD TUNNEL INDUCED BY OVER-CROSSING EXCAVATION

Over-crossing excavation will cause the heave deformation of existing shield tunnels and endanger the service performance of existing shield tunnels. The current analytical methods for predicting the heave deformation of a shield tunnel due to excavation always consider the shield tunnel as an elastic continuous beam resting on an elastic foundation model, which overlook the effect of the joint between adjacent rings. Thusly, a shield tunnel model with adjacent joints is proposed. The nonlinear characteristics of soil deformation are considered by nonlinear Pasternak foundation model. Through the two-stage analysis method, the simplified solutions of heave displacement and opening of shield tunnel under the action of upper span excavation of foundation pit are derived. The additional unloading pressure on shield tunnel due to excavation is calculated using MINDLIN’s elastic solution. The differential equation of heave deformation of the shield tunnel due to exerted unloading pressure is established. The heave deformation and internal force distribution of the adjacent shield tunnel caused by excavation are obtained by using the finite difference method. The measured results from three well-documented published cases are collected, and then the prediction from proposed method is compared with the measured results and the prediction from existing methods to verify the applicability of the proposed method.