Development of a new-type flexible joint for submerged tunnels was described. This joint called Crown-seal joint can absorb larger deformation in a submerged tunnel element than other conventional flexible joints. Crown-seal joint mainly consists of rubber, which was reinforced by plastic fibers. Its applicability to actual submerged tunnels was examined through some experiments using a full-scale model of tunnel section including Crown-seal joint. From the experimental results, it was made clear that no harmful deformation and local distortion were observed on the surface of rubber even if the displacement at the joint occurred in the direction parallel and perpendicular to the tunnel element. Water-tightness of the joint was confirmed through the seepage tests utilizing water pressure.
　The deformation behavior of Crown-seal joint was numerically evaluated by 2-D and 3-D non-linear finite element analyses. The maximum principle strains in the components of the joint were calculated, and compared to their ultimate and allowable strains. Consequently, no local strain beyond the allowable level was detected in any components, indicating the adequate safety of Crown-seal joint even if the displacement at the joint occurred under water pressure applied.
　Therefore, the applicability of Crown-seal joint to actual submerged tunnels was satisfactorily verified based on the experimental and analytical investigation.