Analysis of Surrounding Rock Deformation in the Expansion Excavation Construction Process of Metro Interval Tunnel with Connecting Passage into Forming New Station

Objective The Cruise Home Port Station on Chongqing Rail Transit Line 9 is constructed from in-situ expansion of the existing interval tunnel (including a connecting passage). Due to the complex geological conditions, the initial stress field of surrounding rock, and the structure of the existing interval tunnel, analysis and research of the complex mechanical behavior of the interval tunnel during construction is essential to ensure engineering safety. Method After outlining the overview of the excavation project, a three-dimensional finite element numerical model, utilizing an anisotropic jointed rock mass elastoplastic model, is established. The model geometric features, geological characteristics, structural features, and procedural characteristics are further determined. Three measurement lines (connecting passage centerline, left-line large-mileage interval tunnel centerline, right-line small-mileage interval tunnel centerline) are selected for analyzing land subsidence above these three lines and defor