基坑开挖空间效应对邻近隧道的影响分析

Spatial effect of foundation pit excavation on adjacent tunnels

基坑土体的开挖将引起周边土体的附加位移并对隧道等重要建(构)筑物造成不利影响。考虑基坑变形的空间效应,基于围护墙空间变形曲面表达式,在影像源法的基础上,推导了基坑开挖诱发坑外土体位移场的理论公式。基于两阶段分析方法,将隧道视为置于Winkler地基上的铁木辛柯(Timoshenko)梁,得到了计算隧道附加变形的表达式。通过与已有实测数据的对比分析,验证了本文计算方法的可靠性。进一步研究分析了隧道与基坑边距离、隧道埋深及围护墙最大变形等参数对邻近隧道附加变形、弯矩及剪力的影响。研究结果表明:随着隧道与基坑边距离的增加,隧道附加变形、弯矩及剪力均逐渐减小;当隧道埋深位置位于围护墙最大变形处深度附近时,隧道附加变形、弯矩及剪力均达到最大;围护墙最大变形的增大会显著增加隧道的附加变形、弯矩及剪力,应控制围护墙的最大变形以降低基坑开挖对隧道的影响。

Excavation-induced additional soil displacement outside the foundation pit poses adverse effects on the surrounding environment(e.g.tunnels).Utilizing the virtual image method and the deformation expression of the retaining wall that accounts for the spatial effect of excavation,a calculation method for soil displacement outside the pit was deduced.Employing a two-stage method,the tunnel was modeled as a Timoshenko beam resting on the Winkler foundation to obtain the tunnel deformation.The reliability of the method was verified by comparing with the measured data.The influence of the distance between the tunnel and the foundation pit,the buried depth of the tunnel and the maximum deformation of the retaining wall on the additional deformation,bending moment and shearing force of the adjacent tunnel were systematically investigated and analyzed.The research results show that with the increase of the distance between the tunnel and the foundation pit,the additional deformation,bending moment and shearing force of the tunnel are gradually reduced.The additional deformation,bending moment and shearing force of the tunnel reach the maximum when the buried depth of the tunnel is near the depth of the maximum deformation of the retaining wall.The increase of the maximum deformation of the retaining wall will significantly increase the additional deformation,bending moment and shearing force of the tunnel.Control measures should be implemented to limit the maximum deformation of the retaining wall and mitigate the impact of excavation on the tunnel.