Study on construction mechanics behavior of extra-large span continuous variable cross-section tunnels using "dual guide tunnel advance + central column reverse excavation" method
WANG Shengtao1, CHEN Pengtao2, LIU Aiwu1, SUN Wenhao3, ZHANG Junru2*
(1.China Tiesiju Civil Engineering Group, Hefei 230002, Anhui China; 2.Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, Sichuan China; 3.China Railway Siyuan Survey and Design Group Co., Ltd., Wuhan 430063, Hebei China)
Abstract: Using the section where the main line and ramps merge into the super-large span continuous variable cross-section of the second Qingdao Jiaozhou Bay Subsea Tunnel, this paper proposes a 'dual guide tunnel advance + central column reverse excavation' construction method under specific conditions to ensure the excavation construction stability of shallow-buried, large-span, continuously variable cross-section tunnels. The method's rationality and effectiveness are validated through finite element analysis and field monitoring data. The results showed that: Maintaining the original design's excavation partitions and using the proposed method could significantly enhance construction efficiency, with deformation and stress on the tunnel support structure within acceptable limits, ensuring structural safety and stability. Numerical simulation analysis showed that the reverse excavation of the central guide tunnel caused a rapid increase in the uplift of the invert, and stress concentration was likely to occur at the side walls of the tunnel, especially in the large-span section. During lateral excavation, the excavation of the lower bench significantly increased the load on the temporary support gantry, and stress concentration was prone to occur at the joints of the steel beams. During lateral expansion construction, the crown settlement and clearance convergence stabilized at approximately 9 mm, the initial support and surrounding rock contact pressure reached up to 70 kPa, and the maximum axial stress on the lining calculated empirically was about 0.354 MPa, with surrounding rock deformation and support stress meeting the standards. The 'dual guide tunnel advance + central column reverse excavation' method had been successfully applied to the entrance section of the second Qingdao Jiaozhou Bay Subsea Tunnel, providing a reference for the construction of subsequent continuously variable cross-section tunnels formed by merging forked tunnels.
王圣涛, 陈鹏涛, 刘爱武, 孙文昊, 张俊儒. 特大跨连续变断面隧道“双导洞超前+中柱反向扩挖”施工力学行为研究[J]. 隧道与地下工程灾害防治, .
WANG Shengtao, CHEN Pengtao, LIU Aiwu, SUN Wenhao, ZHANG Junru. Study on construction mechanics behavior of extra-large span continuous variable cross-section tunnels using "dual guide tunnel advance + central column reverse excavation" method. Hazard Control in Tunnelling and Underground Engineering, 0, (): 1-11.
