Longitudinal Equivalent Bending Stiffness and Bending Performance of Rectangular Segmented Tunnel

Abstract:

Based on the equivalent continuous model， this paper deduces the longitudinal equivalent bending stiffness of rectangular shield tunnels under the combination state of compression and bending. Considering the cross-sectional characteristics of rectangular shield tunnels， the closed-form solution of the equivalent bending stiffness under four neutral axis positions is discussed， based on which， a parametric analysis， using the new analytical solution， is conducted to investigate the effect of key parameters on the longitudinal bending stiffness， including the ratio of compression to bending， the number of bolts， the ratio of width to thickness and so on. The critical value of N-M ratio for different positions of the neutral axis is further obtained. The results show that the longitudinal bending stiffness efficiency increases with the increase of the compression-bending ratio， the number of bolts and the ring width-to-thickness ratio， but decreases with the increase of the sectional width-to-thickness ratio and aspect ratio. The position of the neutral axis is not only related to the size of the cross-section and material properties， but also to the compression-bending ratio. The critical value of N-M ratio decreases with the increase of sectional width-thickness ratio and is sensitive to the change of sectional shape. The conclusion has important theoretical reference for optimal selection and design calculation of rectangular segments.