Mega-project in Singapore

The city state of Singapore in South-East Asia has constantly faced significant challenges in providing its five millionplus inhabitants with power. In order to avoid the threat of overload in the nation’s already congested electrical supply lines, the state energy utility Singapore Power initiated construction of two deeplying cable tunnels at the beginning of 2013, with MC injection systems very much integral to project progress.
The project with a total volume of 2 billion Singapore dollars (around 1.3 billion euros) is the biggest order ever awarded by Singapore Power. It involves the construction of two transmission cable tunnels, one following the north-south axis with a length of 18.5 kilometres, and the other tracking east to west over a length of 16.5 kilometres. The tunnels are being bored and blasted at a depth of 60 metres to an inside diameter of 6 metres – a Herculean task entrusted to five construction companies, with the specified time frame of six years ending in 2018.
Mock-up test provides compelling proof

The two tunnels with an overall length of 35 kilometres are currently being bored and then shored with tubbings. Problems have occurred in the form of leaks at the tubbing joints and both water-bearing and dry cracks elsewhere. This led Singapore Power to seek a solution capable of guaranteeing permanent, reliable sealing. The water pressure of 6 bar prevailing at depths of 60 metres presented a particularly difficult set of requirements. Subjected to a 1:1 mock-up test, a large-scale trial under site conditions, in order to prove its quality, the MC-Injekt system was ultimately selected as the runaway winner. Indeed, its sealing capabilities were considered to be so remarkable that the MC system received exclusive developer approval for the entire construction project.

Three-stage injection

The chosen solution with the MC-Injekt system involves first a curtain injection of the low-viscosity elastomer foam MC-Injekt 2033 in order to prevent water penetration along the tunnel lining. The secure temporary seal that this provides allows a second injection with elastomer resin MC-Injekt 2300 as a permanent elastic fill for the cracks, joints and cavities. An optimum finish is then achieved with a third and final injection of the epoxy-based duromer resin MC-DUR 1264FF. Offering high compressive and tensile strength, this ensures that the last fissures of the dry construction are permanently and rigidly sealed. In order to ensure optimum results, all applicators are required to have specific expertise in the field of IRP (Injection, Repair and Protection), with corresponding certificates to prove their competency acquired in practical courses provided in collaboration with MC by the building trades training centre BZB e.V. in Wesel, Germany.
Singapore’s backbone

With a good two years to go before completion, those responsible for the project are optimistic at its progress: “The deep cable tunnels will form the backbone of Singapore’s power supply, serving future generations to good effect,” assures Wong Kim Yin, Group Chief Executive Officer, Singapore Power. And MC systems are helping to ensure that this will be so.