WANG Zu-xian, SHI Cheng-hua, GONG Chen-jie, et al. Analytical method to estimate the influence of foundation pit excavation adjacent to the station (working shaft) on the underlying shield tunnel[J]. 2022, 43(8): 2176-2190.
WANG Zu-xian, SHI Cheng-hua, GONG Chen-jie, et al. Analytical method to estimate the influence of foundation pit excavation adjacent to the station (working shaft) on the underlying shield tunnel[J]. 2022, 43(8): 2176-2190.DOI: 10.16285/j.rsm.2021.2108.
既有用于基坑开挖引起下卧盾构隧道纵向变形计算的解析模型,往往将盾构隧道视为两端自由的无限长梁,限制了此类模型的适用范围。针对邻近车站(工作井)基坑开挖引起下卧盾构隧道纵向变形问题,将车站(工作井)―隧道连接节点对盾构隧道的约束视为一转动刚度为 Kθ 的旋转弹簧和一竖向链杆,建立了开挖卸荷作用下邻近车站(工作井)盾构隧道纵向变形分析的Winkler地基 - Timoshenko 梁模型,基于力法基本原理严格推导了解析模型的差分解。通过与一维弹性地基梁有限元数值解和邻近车站基坑开挖诱发下卧盾构隧道纵向变形的整体有限元计算结果的对比,验证了解析模型的可靠性和适用性。进一步的参数分析结果表明:车站(工作井)―隧道连接节点转动刚度 Kθ 对隧道纵向变形和内力具有显著影响,连接端处隧道内力随 Kθ的增大而非线性增大,而隧道横截面转角的变化却恰好相反,且车站(工作井)-隧道连接节点采用柔性连接时能更好地保障此节点处盾构隧道的工作性能;当基坑中心距车站-隧道连接节点的距离在4~5倍的基坑宽度(沿隧道轴向)范围内时,连接节点对隧道端部的约束效应不可忽略,应采用该模型进行盾构隧道纵向性能评价;上覆基坑开挖对下卧盾构隧道的影响主要集中在自基坑中心2倍基坑长度(横隧道轴向)以内。The shield tunnel is typicallysimplified as an infinite beam with two free ends in existing analyticalmodels
which are used to calculate the longitudinal deformation of the underlyingshield tunnel induced by the excavation of a foundation pit. However
the applicabilityof those analytical models is limited due to the simplification. The currentstudy is aimed at estimating analytically the longitudinal deformation of the underlyingshield tunnel induced by the excavation of a foundation pit adjacent to thestation (working shaft). The constraint on the shield tunnel generated by the jointbetween the station (working shaft) and the tunnel is treated as a rotationspring with the rotation stiffness of Kθ and a verticalrod support. The Winkler foundation – Timoshenko beam model for calculating thelongitudinal deformation of the shield tunnel adjacent to the station (workingshaft) induced by the foundation pit excavation is proposed. The finite differencesolution of the proposed model is strictly derived based on the basicprinciples of the force method. The reliability and applicability of the proposedanalytical model are verified via the comparison with the finite elementnumerical solution of one-dimensional elastic foundation beam model and theglobal finite element simulation results of the longitudinal deformation of theunderlying tunnel induced by the excavation of a foundation pit adjacent to thestation. The parametric studies indicate the following conclusions. (i) Thelongitudinal deformation and internal forces of the shield tunnel aresignificantly influenced by the rotation stiffness
Kθ
of the joint between the station (working shaft)and the tunnel. The internal forces and the longitudinal deformation (i.e.rotation angle) at the end of the tunnel increase and decreases nonlinearlywith a increasing Kθ
respectively. In addition
when the flexibleconnection is adopted at the joint between the station (working well) andtunnel
the working performance of the shield tunnel at the joint can be betterguaranteed. (ii) The constraint effect of the joint on the end of the tunnel isnon-negligible
when the distance from the center of the foundation pit to thestation-tunnel joint ranges from 4 to 5 times the width of the pit along thetunnel axis. In this condition
the proposed analytical model should be adoptedto evaluate the longitudinal working performance of the tunnel. (iii) Theinfluence of the overlying foundation pit excavation on the underlying tunnelmainly exerts within 2 times the length of the pit perpendicular to the tunnelaxis away from the center of the pit.