Hybrid immersed tunnel element
Immersed tunneling is a method of constructing relatively shallow undersea tunnels. For ease of construction and economic efficiency, immersed tunnels are divided into several elements (immersed tunnels), which are fabricated at docks and other fabrication yards. The structure of the immersed tunnels is generally a composite structure consisting of steel shells and concrete, and can be either full-sandwich or semi-sandwich (open-sandwich).
Construction method features
- 1High rigidity and high load-bearing capacity
- 2Steel shell is a floating structure and concrete can be cast at sea.
- 3Reduction in the amount of reinforcement, formwork and support works.
- 4Rapid on-site construction
Hybrid immersed tunnel element (Overview of construction method)
1.Overview
Hybrid immersed tunnel elements are adopted for navigation channels and canal crossings in port areas.
(Compared to immersed tunnels, bridge and shield tunneling methods have longer approaches and higher total costs.)
- Full-sandwich types
-
- 1No reinforcing steel is used.
- 2Filled with high flow concrete
- Semi-sandwich (open-sandwich) type
-
- 1Partially reinforced with steel reinforcement.
- 2Placing ordinary concrete.
Construction examples
Sumida River (downstream of Azuma Bridge) right bank terrace construction (No. 2-2)
| Client | Tokyo Metropolitan Government |
|---|---|
| Purpose/function | Water-friendly revetment |
| Year of construction | 2012 |
| Dimensions | 62.0 m (length) x 3.75 m (width) x 4.2 m (height) |
| Number of units manufactured | 1 unit |
| Weight | - |
| Steel weight | 265 t |
| Concrete volume | - |
| Design overview | Installation depth - 2.35 m |
| Features/functions | Steel pipe pile foundation |
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 of construction | 2007 |
| Dimensions | 81 m (length) × 28 m (width) × 8.4 m (height) |
| Quantity (/case) | Body weight: 1940 tons |
| Features/functions | Steel-concrete full sandwich structure Floating towing |
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 of construction | 2004 |
| Dimensions | 97 m (length) × 36 m (width) × 9.4 m (height) |
| Quantity (/case) | Weight of steel: 3360 tons |
| Features/functions | Steel-concrete full sandwich structure |
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 of construction | 2003 |
| Dimensions | Height = 8.7 m, width = 36.94 m, length = 90.0 m |
| Quantity (/case) | Dead weight = 2910 tons |
| Design overview | Installation water depth = -24.0 m |
| Features/functions | Full sandwich structure, high-fluidity concrete |
| Remarks | 6-lane road (3 lanes on each side) Concrete applied to floating steel shell |
