邻近开挖对既有软土隧道的影响

Responses of existing tunnels induced by adjacent excavation in soft soils

采用两阶段分析方法,提出了邻近开挖对既有软土隧道纵向受力变形影响的简化计算方法。针对软土隧道开挖情况,第1阶段采用Loganathan和Poulos提出的解析解计算开挖引起的土体自由位移场;针对基坑开挖情况,第1阶段根据Mindlin理论解计算邻近荷载作用引起隧道的附加应力;第2阶段基于Winkler地基模型将既有隧道视为弹性地基无限长梁,将土体自由位移或附加应力施加于隧道,并建立求解该问题的纵向变形方程,从而得到隧道纵向位移和内力的计算表达式。结合离心模型试验结果和工程实例进行分析,验证了方法的有效性。研究成果可为合理制定邻近施工对软土隧道的保护措施提供依据。

A simple two-stage method for estimating the longitudinal deformation of existing tunnels caused by adjacent excavation in soft soils is presented. In the first stage, the Loganathan and Poulos analytical solution is used to estimate the free-soil settlement induced by adjacent tunneling. The additional stress due to adjacent foundation pits excavation is calculated based on the Mindlin solutions. In the second stage, existing tunnels are considered as beams with infinite length based on the Winkler foundation model. The free-soil settlement or additional stress is then imposed to the existing tunnels. Displacements and internal forces of the existing tunnels are obtained. Finally, the accuracy of the proposed method is verified with centrifuge model test data and engineering case studies. The proposed method may provide a theoretical basis to establish rational protective measures of the existing tunnels influenced by adjacent excavation.