Abstract: The construction methods, longitudinal profile, cross-section layout, construction organization, shield type selection, and shield launching in ultra-deep shaft of the Shu′an tunnel are comprehensively analyzed using data research, engineering analogy, and experience summary methods. Findings are as follows: (1) The construction methods for urban railway tunnels should be based on a comprehensive comparison of geological conditions, construction environmental conditions, and construction duration. Shield method is a priority when there are applying conditions due to its high safety, minimal environmental impact, and fast construction progress. (2) When tunnels primarily pass through weakly permeable mudstone strata, the earth pressure balance shield is recommended. For locally highly permeable strata, measures such as surface dewatering, double-gate screw conveyor, and injection ports for modifiers could be adopted. (3) The phenomena of mud cake on cutterhead and segment floating can be avoided by optimizing the arrangement of cutting tools on cutterhead, enhancing the connection stiffness of the segments, and adopting synchronous dual-component grouting. (4) An advance pilot tunnel by mining method for shield launching shaft can realize high efficiency separate launching of shield.

Key words: urban tunnel, large-diameter shield tunnel, shield type selection, separate launching, segment floating