Waterproof tunnel lining
1. First of all, 180,000 mounting bolts are set into the tunnel ceiling.
2. 200,000 square metres of membrane are hung on these bolts to create a diaphragm vault.
3. Precast wall elements are mounted on both side walls of the tunnel. Each of these 9,000 elements is 3x5 metres in size and weighs almost 6 tonnes.
4.60 truck-loads of reinforcing mats are mounted on the ceiling bolts.
5. A 10 cm thickness of shotcrete is then applied to these mats to create a free-standing and waterproof concrete vault between the wall elements. An escape route is located behind the elements on one side of the tunnel.
6. A conduit for all the electrical installations and fire suppression water pipes is created under the concrete walkway.
The “Förbifart Stockholm” bypass is a new three-lane motorway that links the south (Kungens Kurva) and north (Häggvik) of the city. To minimise the environmental impact, most of the 21 kilometre road will be underground. (Picture: Implenia)