Mid-Adit Breakthrough of the Second Hallandsås Tunnel in Sweden

The project, which is part of the renovations to be done to the railway line running between Malmö and Göteborg, aims to considerably increase traffic on the line and to double the maximum weight of freight trains using this route.

The Åsa tunnel boring machine was designed to drill into very heterogeneous terrain (highly altered or instable firm rock) in which water seepage can reach high levels (up to 400 l/s). An entire range of terrain treatment processes (in particular, injection), allowing to overcome these difficulties while being in compliance with the water laws applicable to this project, can be carried out at the tunnel boring machine level.

In order to help the tunnel boring machine make its way through the northern segment of the second tunnel that is yet to be dug, injection work is currently being carried out from two branches. The purpose of this injection work is to reduce water seepage into the 800-metre-long highly aquiferous area known as Lya.

At the same time, the freezing of the Mölleback fault, made up of altered, fractured and heterogeneous rock, started on the first 85 metres. Digging a gallery in the frozen ground is ongoing in order to allow the freezing of the next 115 metres. The Åsa tunnel boring machine is scheduled to start excavating in the Mölleback fault in early summer, 2013.

85 % of the two main tunnels have been completed. The remaining 3 kilometres of tunnel to be dug should be completed by the end of 2013, and the project is set for commissioning in 2015.

In 2002, VINCI Construction Grands Projets, along with Skanska, was mandated to design and build these two tunnels, each 5,500 metres long, with an inside diameter of 9.04 metres, through the Hallandsås hillside, as well as twelve inner tube tunnels (four measuring 39 metres long, and eight measuring 21 metres long). The first two tunnels were bored on August 25, 2010.