Simplified calculation model for longitudinal equivalent bending stiffness of shield tunnel and its influence factors' analysis

As shield tunnelling method is applied widely,the longitudinal uneven settlement of shield tunnel has emerged because of the comparatively large settlement after construction,and the designing method has been emphasized gradually,which can consider the longitudinal structure characteristics of shield tunnel. For the purpose of determining the longitudinal equivalent bending stiffness,a 3D calculation model has been established,considering the longitudinal bolts' characteristics and the ring seams' true splaying states. The results show that some factors related to the ring seam,for example the amount of longitudinal bolts,the assembly pretightening force and segment ring width,influence the longitudinal bending stiffness largely,which increases linearly with the amount of longitudinal bolts and the segment ring width,and which nonlinearly increases with the assembly pretightening force. Other factors related to the longitudinal seam,for example the transverse effective rigidity ratio,influence it less. The results provide key parameters for the longitudinal design method of shield tunnel.