Immersed Tunnels

TUNNELS
IMMERSED TUNNELS At WSP, we have been involved with multiple immersed

tunnel projects on all continents, in a variety of ground
Immersed tunnels consist of very large pre-cast concrete conditions, and we have been at the forefront of this
or concrete-filled steel tunnel elements fabricated in dry technology since its earliest years, including the design and
docks and then installed underwater. construction of the Detroit-Windsor Tunnel between US and
Canada in 1930, the first crossing between two countries
WSP has pushed the limits of tunnelling technology with under international water, where we have been serving as
landmark projects that shaped the course of tunnel the Owner’s Engineer ever since.
engineering and defined industry practice. Our achievements
over more than 130 years cover every aspect of tunnels from PUTTING OUR EXPERIENCE
program management to design and construction TO WORK FOR YOU
management.
Immersed tunnels consist of very large pre-cast concrete or
We serve clients in the rail, highway, offshore/maritime, concrete-filled steel tunnel elements fabricated in dry docks
utilities, and power and energy industries. Our designs have and then installed underwater. They are first fabricated in
resulted in record-setting advances with tunnel boring convenient elements in dry docks, shipyards, or in
machines (TBMs) and we have employed innovations such as improvised floodable basins, sealed with bulkheads at each
earth-pressure-balanced (EPB) and slurry-face tunnelling end, and then floated out.
techniques, and fibre-reinforced sprayed concrete liners
Once they reach their final location, the elements are
(SCL).
immersed, lowered into a prepared trench, and joined to
Immersed tube tunnels are used in situations where building previously placed tunnel elements. Immersed tunnels
a bridge is undesirable, unsightly, or environmentally elements are then backfilled and the bottom bed reinstated.
unacceptable, to provide road, rail, or utilities across bodies
There are two main types of immersed tunnel: steel and
of water. As such, these tunnels are extremely rare, with just
concrete tunnel elements. Steel elements use structural steel,
over a hundred having been constructed worldwide.
usually in the form of stiffened plates, working compositely
with the interior concrete as the structural system.
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TUNNELS
Concrete elements, on the other hand, rely on steel

reinforcing bars or prestressing cables. WSP is one the few
CONCRETE IMMERSED TUNNELS
firms in the world who have experience with both types of In Istanbul, we worked on the concrete/steel sandwich
immersed tube tunnels and the tunnel was opened to traffic construction Marmaray Tunnel, the first tunnel to connect
a few hours after the earthquake. two continents. The rail and transit tunnel is 1.4km long
consisting of 11 elements, each weighing up to 18,000 tons.
STEEL IMMERSED TUNNELS
At 60m (200ft) under the water’s surface, it is the deepest
In San Francisco, US, we designed the steel immersed tunnel immersed tunnel in the world.
for the Cross Bay Tunnel, a part of the BART public transit
In Virginia, US, the Elizabeth River Tunnel (Second Midtown
system. The tunnel consisted of 57 elements totalling 5.8km,
Tunnel) was delivered as part of a Public Private Partnership
the longest of its kind in the world. Thanks to innovative
procurement process and was opened to traffic in 2016. The
seismic retrofitting, the tunnel was able to survive the 6.9
tunnel consists of 11 concrete elements fabricated in
Richter scale Loma Prieta earthquake without any damage.
Sparrows Point, Maryland and towed down the Chesapeake
In Baltimore, US, we designed the notable steel immersed Bay to the project site in Portsmouth, Virginia for immersion
Fort McHenry Tunnel which was the widest immersed tunnel and placement under the Elizabeth River.
built at that time. It was the first immersed tunnel to have
WSP is also performing the Independent Design Review of
double tubes, carrying a total of eight lanes of traffic, laid
the Fehmarn Belt Fixed link between Denmark and Germany.
immediately side-by-side in a single trench under Baltimore
Upon its completion, it will reduce the journey from
Harbor.
Hamburg to Copenhagen by an hour and thirty minutes. At
WSP also designed the bridge-tunnel crossings of Hampton 17.6km long, it will be the longest immersed tunnel in the
Roads, Virginia, where immersed tunnels were built between world. The precast concrete tunnel sections will have a
two artificial islands that connected to the mainland via rectangular cross-section of 42m wide by 10m high,
viaduct bridges. This approach was later adopted by other consisting of four separate passageways, two for vehicles and
projects in the world, including the Oresund Bridge-Tunnel two for rail.
between Denmark and Sweden.
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TUNNELS
WSP IN ACTION
In Singapore, we designed the Tuas Undersea Cable Tunnel,
the only use of on-end casting of immersed tunnel elements
in the world. The tunnel is 2.1km long, 11.7m wide by 4.3m
high, and the elements were cast vertically on-end in
segments of 4m long each, to minimize shrinkage cracking
and ensure a watertight structure. The segments were then
rotated, assembled, grouted, and pre-stressed to form 100m
long elements.
Our Research and Development programs have produced
tools of the trade, including our tunnel engineering
handbook and practical guide to tunnelling beneath open
water which are considered to be authoritative resources for
tunnel design, risk management, and site investigation
guidance worldwide.
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Immersed Tunnels

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Immersed Tunnels

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TUNNELS

IMMERSED TUNNELS At WSP, we have been involved with multiple immersed

Concrete elements, on the other hand, rely on steel

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