【摘要】 城市地铁工程建设中，常在地铁车站基坑建设后进行区间隧道建设，同时接入车站的出入场线隧道断面增大，对既有基坑结构造成严重影响.本文针对地铁大断面隧道出入场对既有基坑围护结构产生有害影响的工程问题，依托青岛市地铁4号线大河东站区间工程，研究既有基坑围护结构受隧道施工影响产生的挠曲位移.首先，综合全覆土压力与Terzaghi松弛土压力两种计算方法确定隧道断面垂直土压力及其对应的侧向土压力、掌子面土压力，并采用Mindlin应力解计算基坑围护结构上的附加应力；然后，计算并分析平衡状态下基坑围护结构上的横向附加应力；最后，考虑基坑围护结构的横向附加荷载，采用Midas GTS NX有限元软件构建隧道-土体-基坑围护结构3者共同作用的挠曲计算模型，分析基坑围护结构的挠曲位移变化规律.研究结果表明：随着大断面隧道向基坑方向的推进，基坑中下部围护结构会发生较大挠曲变形，在实际施工中应重点监测.研究成果可为车站基坑支护结构的设计优化、隧道接近与进站施工过程中的安全防控等方面提供理论依据.更多还原

【Abstract】 In urban subway construction, interval tunnel construction often follows the development of subway station foundation pits. The enlargement of the cross-section of entry and exit line tunnels connecting to the station can severely impact the existing foundation pit structures. This study focuses on the detrimental effects of large cross-section subway tunnel construction on the existing foundation pit envelope. Based on the interval project of Dahe East Station on Qingdao Metro Line 4, the de-flection displacement of the existing foundation pit envelope due to tunnel construction is investigated. Firstly,a comprehensive approach is employed to determine the vertical and corresponding lateral earth pressures on the tunnel section and the earth pressure on the face of the tunnel using both full-cover soil pressure and Terzaghi relaxation earth pressure. Mindlin stress solution is used to calculate the additional stress on the foundation pit retaining structure. Secondly, a semi-theoretical solution of lateral deflection of the retaining structure based on the beam-spring model is proposed to calculate and analyze the lateral additional stress on the foundation pit retaining structure under equilibrium conditions.Finally, considering the lateral additional load on the foundation pit retaining structure, a finite element model using Midas GTS NX finite element software is developed to construct the joint flexural calculation model of tunnel-soil-foundation pit retaining structure, thereby exploring the flexural displacement variation law of foundation pit retaining structure. The research results show that as the large cross-section tunnel advances towards the direction of the foundation pit, significant deflection deformations occur in the middle and lower retaining structures of the foundation pit, which should be monitored in actual construction. The research results of this paper provide a theoretical foundation for optimizing the design of the station foundation pit supporting structure, and enhancing safety measures during tunnel approach and entrance construction.更多还原