Building 40 metres under Copenhagen

It might look like an extension to Copenhagen's Metro, but it isn't. In fact it's a 4 km district heating tunnel, which we are currently building 25-40 metres beneath the streets of the capital.

Due for completion in 2009, the tunnel will provide the fastest and most direct district heating connection between Amager Power Station and Fredensgade in Copenhagen. In Adelgade and Fredensgade, it will be connected to the existing district heating grid.

The above photo looks rather like the boring for the Metro or the railway tunnel under the Great Belt. In fact we have applied many of the same techniques, as well experience gained from the latter project.

But it won't be trains that will run through this tunnel. Instead, it will carry district heating pipes that will ensure Copenhageners cheap and environmentally friendly district heating in the future. And down here - at up to 40 metres depth – the pipes will be much easier to inspect and maintain than many of the existing district heating pipes that lie just beneath the capital's roads and pavements.

Like a submarine under Copenhagen

The "Earth Pressure Balance Tunnel Boring Machine” we are using is of the same type that was used for the tunnel under the Great Belt. It weighs 500 tons and is 128 metres in overall length. When it moves ahead in the depths under the city, it is very reminiscent of a submarine.

The tunnel is not the only thing requiring boring and excavation work. We have also sunk three shafts into the capital's bedrock – 25-40 metres deep and up to 25 metres in diameter. It is between these three shafts that the tunnel itself is being bored.

Denmark's largest civil engineering project on a partnering basis

”Astrid”, as the boring machine is affectionately known, moves forward at 10-25 metres per day, while installing the 30 cm thick concrete elements that clad the tunnel wall. The tunnel has an internal diameter of 4.2 metres – about 30 cm less than the Copenhagen Metro.

The entire tunnel project is being carried out by KFT-JV – a joint venture between the German construction firm Hochtief and MT Højgaard. The tunnel construction is being carried out on a partnering collaboration basis, with KFT-JV, Københavns Energi and COWI focusing on meeting all the challenges in a sprit of togetherness.

The construction of the tunnel is the biggest civil engineering project in Denmark being carried out on a partnering basis, as well as the biggest underground construction in Copenhagen since the Metro.