Crown Seal Joint (New Type Flexible Joint for Immersed Tube Tunnel)

Generally, conventional flexible joints for immersed tube tunnels are comprised of rubber gaskets attached around the circumference of the submerged tube at its end and connection cables. This type of joint accommodates resist forces on the joint. The Crown Seal Joint adapts a mechanism to “dodge” these forces and accommodates large deformation between tunnel elements. The joint consists of a rubber block installed on the exterior of the bulkhead of the joint, stopper cables (PC cables) that cope with excessive tensile displacement, and secondary seals, which provides a fail-safe system in the event of leakage around the rubber gasket.

Since no resisting members are present, large deformation due to earthquakes or ground settlement can be absorbed.

Water tightness is of concern primarily at in the locations of steel attachments, and seal noses below the rubber block also provide a fail-safe system for leakage as they are deformed by water pressure.

Stress from immersed tube tunnels due to earthquakes can be reduced much more than in the conventional PC-rubber gasket type of flexible joint.