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The only technology that worked in Europe’s longest urban road tunnel

Download the Case Study as PDF-file:

Freeze hole drilling in Årsta, Sweden

Project Description:

The Södra Länken (Southern Link) highway in Stockholm is six kilometers long. Nearly five kilometers of the route consists of tunnel, making it Europe's longest urban road tunnel. Building the link was a complex job, and took nearly a decade to complete.

Dealing with water in projects such as this one is not entirely uncommon. To freeze the water flow in the rock, 17 horizontal freeze holes, each measuring 37 meters in length, were drilled in March of 2001. Cooling fluid was then circulated in the holes to freeze the water.

The work was carried out by Sven Andersson Brunnsborrning AB on commission by NCC, one of the major building contractors in Sweden.


Result:

Because pneumatic drilling would have disturbed the soil layers far too much, drilling using Wassara's water-powered system was the only technology that worked. The Wassara W150 drilling system made it possible to complete the job successfully.

Equipment used

DTH hammer Wassara W150
Drill bit Noex N-154
Pump Hammelmann 550 liter/160 bar
Drilling fluid Clean water
Casing OD 193,7 mm 
Drill rods 114 mm 
Bore hole length 37 meters 
Scope of drilling 17 horizontal holes 
Drilling formation Granite with fractured zones
Project year 2001