Dewatering in deep tunnel construction

3 min read

The Marmaray project, linking the European and Asian sides of Istanbul will be the world’s deepest immersed tube tunnel. The industry’s drive to create ever deeper tunnels has placed increasing demands on dewatering and construction equipment. Tsurumi rose to the challenge with its ‘puddle sucker’ LSC series.

During the construction of a 1.4 km tunnel under the Bosphorus, Tsurumi’s LSC series of pumps were used to dewater 15 caissons to create a dry working space before they are cast in concrete.
During the construction of a 1.4 km tunnel under the Bosphorus, Tsurumi’s LSC series of pumps were used to dewater 15 caissons to create a dry working space before they are cast in concrete.
An LSC series pump is seen in close up on the top of one of the caissons
An LSC series pump is seen in close up on the top of one of the caissons
The KTZ pumps were used for dewatering and pumping raw concrete. The series has a dry-running capability and feature a patented lubrication technology.
The KTZ pumps were used for dewatering and pumping raw concrete. The series has a dry-running capability and feature a patented lubrication technology.

Engineers have long dreamed of connecting the European and Asian sides of Istanbul by tunnel, an idea first proposed by Sultan Abdul Mecit in 1860. That dream is now being realised as part of the US$3 bn Marmaray project, one of the largest transportation infrastructure projects currently taking place anywhere in the world.

Planned by the Turkish Ministry of Transport, the rail tunnel is designed to ease heavy road congestion by providing the city’s 13 million residents with an effective transport alternative that encourages travel by train. Scheduled for completion in 2011, the Bosphorus tunnel will be 1.4 km long and its trains will carry up to 300,000 passengers per hour.

The link crosses beneath the Bosphorus Straits 58 m below sea level and will be the world’s deepest immersed tube tunnel. The tunnel is made of 11 pre-fabricated sections, which weigh 19,000 tonnes each. The sections are floated out and sunk 58 m into a trench on the sea-bed. The sections measure 135 m long, 15.3 m wide and 8.75 m high and are the largest immersed tube sections in the world.

As part of its plant contribution to the project, pump solutions provider, Tsurumi, has made 90 pumps available including 40 of its LSC series of residual dewatering pumps. With Parsons Brinckerhoff as the project’s main contractor, the pumps were supplied by local Tsurumi dealer Bilgi Mühendislik Tic. Ltd. Sti.

The LSC pumps are known as ‘puddle suckers’ because of their ability drive large amounts of water down to a depth of just 1 mm. Daniel Weippert, managing director of Tsurumi (Europe) GmbH, explains: “These pumps are not normally found on tunnelling jobs, but when the project details were presented to us, the LSC range looked like the best option.” The Marmaray project required the dewatering of 15 caissons to create a dry working space before they are cast in concrete. Weippert adds: “Due to the sheer volume of work involved to clear the caissons, we opted for the LSC series and these pumps have proved highly effective. This is only the second time we have used an LSC in this way, but seeing how successful it has been and with the industry’s drive to create ever-deeper tunnels, we certainly see applications for LSC pumps in other tunnel projects in the future.”

Typically, Tsurumi supplies its KRS and KTZ series pumps for tunnel projects and there are 50 of them on this job. The KRS series is a heavy-duty dewatering pump with a 4-pole motor for greater durability. The KTZ series is a submersible drainage pump for general applications.

These pumps have two specific applications on the Marmaray Project. Firstly, they are used to fill the ballast tanks attached to each of the 11 tunnel sections with water. These assist in the smooth placement of each section on the sea-bed. Secondly, once the pre-assembled tunnel sections are in place, they must be secured in position. The KRS and KTZ pumps are used in this application both for dewatering and pumping raw concrete.

The KRS, KTZ and LSC series are all part of Tsurumi’s contractor pump range. Tsurumi’s contractor pumps have a unique dry-running capability. Where most other pumps require a continual flow of water to remain cool, Tsurumi’s pumps feature a patented lubrication technology and will not burn out under dry operation.

Daniel Weippert concludes: “This is a huge undertaking is of great historical importance for the people of Turkey, but it is also very significant in terms of infrastructure and trade for the city. The Bosphorus tunnel is a highly technical, complicated and record-breaking project that requires a unique solution, not on the scale of anything seen before. We worked closely with our local pump dealer to come up with an innovative pumping solution for this record-breaking job.”