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Coastal structures

Hybrid immersed tunnel element

A hybrid immersed tunnel element is a structure made up of a double steel shell filled with concrete. Inside the steel shell are steel plates and ribs in a crisscross arrangement. These steel plates and ribs transmit displacement between steel and concrete to one another, forming a hybrid structure (sandwich structure) that allows steel and concrete to move in mutual harmony.
One of the advantages of the hybrid structure is the extremely high rigidity and loading capacity of the composite materials, which cannot be expected from individual materials. Since the steel shell is a floating structure, element concrete can be applied to the floating steel shell.

Construction examples

Name of construction work
Shinwakato Road immersed tunnel (element No. 3) construction manufacturing work
Client
Ministry of Land, Infrastructure, Transport and Tourism Kyushu Regional Development Bureau
Purpose/Function
Immersed steel shell
Year completed
2007
Dimensions (m)
81 (length) × 28 (width) × 8.4 (height)
Quantity (/element)
Body weight: 1940 tons
Features
Steel-concrete full sandwich structure
Floating towing
Name of construction work
Osaka Port Yumeshima Tunnel immersed steel shell (element No. 1) manufacturing work
Client
Ministry of Land, Infrastructure, Transport and Tourism Kinki Regional Development Bureau
Purpose/Function
Immersed steel shell
Year completed
2004
Dimensions (m)
97 (length) × 36 (width) × 9.4 (height)
Quantity (/element)
Weight of steel: 3360 tons
Features
Steel-concrete full sandwich structure
Name of construction work
Naha Airport (Naha Wharf Zone) road (airport line) immersed steel shell (element No. 3) manufacturing work
Client
Naha Harbor and Airport Construction Office, Okinawa General Bureau, Cabinet Office
Purpose/Function
Immersed road
Year completed
2003
Dimensions (m)
Height = 8.7, width = 36.94, length = 90.0
Quantity (/element)
Dead weight = 2910 tons
Design overview
Installation water depth = '-24.0 m
Features
Full sandwich structure, high-fluidity concrete
Remarks
6-lane road (3 lanes on each side)
Concrete applied to floating steel shell