Abstract: The field monitoring data demonstrate that longitudinal pressure of each crosssection between launching and reaching sections of shield tunnel is very small, which would lead to water leakage. As a result, the distribution of longitudinal stress is proposed by solving differential equations describing tunnel deformation characteristics, and based on which, the design method of the longitudinal tie component is proposed. The results show that: (1) The longitudinal stress near the tunnel portal is the smallest(close to zero) without longitudinal tie. (2) The longitudinal stress increases with the distance from tunnel portal increase. (3) The longitudinal stress can be effectively increased between the launching and reaching sections by adopting longitudinal tie. The minimum crosssectional area of longitudinal tie component is determined by the tunnel stiffness and the closure pressure of the annular joint waterstop gasket, and the minimum length is determined by the tangential bonding stiffness between the tunnel and stratum.

Key words: shield tunnel, longitudinal stress, launching and reaching sections, longitudinal tie, design method