Trelleborg to supply seals for Chinese immersed tunnel project

Dalian, China – Trelleborg’s marine and infrastructure operation has been awarded the contract to supply all of the closure joints for the construction of Dailian Bay immersed tunnel in Liaoning, northeastern China.

The ‘longest immersed tunnel in northern China’ will cover 5.1 kilometers and consists of 18 large tunnel elements, with some weighing as much as 60 kilotonnes, said Trelleborg 20 July.

For the 18 tunnel elements and 219 segment joints, Trelleborg will provide a mixture of its Waterstop seals, Gina gaskets, Omega seals and a new closure joint seal. 

In addition to the 18 immersed elements, Trelleborg said it will also supply 14,000 metres of Waterstop and 7,000 metres of Omega seals for the cut and cover section at the north and south shores of the tunnel.

The solution, it said, will seal the construction joints and expansion joints and help speed up the construction time of the project as it enables all works to be prepared on the drydock.

In traditional construction, bulkhead and concrete pouring would take two to three months longer underwater. 

“This exciting and large-scale project aims to help relieve local traffic pressure in the area by connecting the two banks of the Dalian Bay,” said Zhang Haiying, chief engineer of the Dalian Project at CCCC First Harbor Engineering Co.

The seals used in the project must be able to withstand a maximum 1700mm movement under a 35-metre water head, he explained.

Trelleborg, he added, was selected for the project as their seals have the ability to handle immense weight and demonstrate strength against extreme environmental factors.

Furthermore, Trelleborg has developed an entirely new closure joint structure for the immersed tunnel. 

“Although this closure joint structure will consist of many units, a section of this joint will be an entirely new Membrane seal design, made especially for this project and the first of its kind,” Zhang Haiying explained. 

According to the official, Trelleborg’s new seal passed a performance test “to an extremely high standard” and will also help speed up construction work by allowing to prepare works on the drydock. 

Once in use, the new membrane seal will be the widest seal ever used in an immersed tunneling project, according to Eddy Chen, sales director at Trelleborg’s marine and infrastructure operation in China.

“One of the main challenges for the development of this seal was ensuring that it not only had a wide movement of 1700mm, but that it could simultaneously handle the challenge of high-water pressure,” Chen explained.

As the original seal design has a capacity to withstand a wide movement of 1000mm, the seal had to be redesigned and tested for 1700mm. 

“The seal passed the design requirements with a high-performance and high safety rate,” he concluded.