Open-air zones

The open-air zone between the Tangen Tunnel and the Kopstad Tunnel
The existing rock cut by Bollerud, just south of the Tangen Tunnel, will be widened. The excavated rock mass will be used to build up the embankment in the existing brook valley just south of Bollerud. In order to ensure stability of adjacent terrain along the railway embankment, a counter fill will be established toward the line on both sides.

Profile of the line for rock cut by Bollerud

The open-air zone between the Kopstad tunnel and the Skottås Tunnel
South of the Kopstad Tunnel, straight west from Sletterødåsen, the line lies in a land cut of both earth and rock. In the south end of the fields at Moskvil, the line runs through a combined earth and rock cut before emerging on the fields by the Skaug farm. On the field west of the Skaug farm the line lies in an earth cut through a slope with a gradiant of 1:2.



Profile of the line north of Skaug towards the north portal of the Skottås Tunnel, looking southward

The open-air zone between the station area and the Gråmunk Tunnel
South of the station area, the line lies on fill or in an earth cut with some smaller rock cuts.  A service track will be established for Bane NOR at the south end of the station area.

The open-air zone between the Gråmunk Tunnel and Barkåker
South of the Gråmunk Tunnel the line lies partly in low rock and earth cuts and partly on low fills. In several places, intersecting tributaries to Sverstadbekken will have to be rerouted underneath and alongside the tracks.