Stockholm bypass project – passage under the Lake Mälaren

Stille, B., Johansson. F., Ríos Bayona F., Batres Estrada, R. and Roslin. M. (2019) Stockholm bypass project – passage under the Lake Mälaren. In : Proceeding of the WTC 2019 ITA-AITES World Tunnel Congress (WTC 2019), May 3-9, Naples, Italy

In the last years, the Swedish Transport Administration has been working on improving and expanding road communications in Sweden. The Stockholm Bypass Project, one of the biggest projects in Swedish history, consists of a 21 km long highway that goes around the city from north to south. In order to reduce the environmental impact, 17 km of the total length will be excavated underground passing through several regional fault zones and subsea passages. One of the most difficult technical challenges in this project is the passage under the Lake Mälaren and the regional fault zone in the Fiskar fjord. This paper presents the utilized methodology to design the temporary rock support and to manage the risks and uncertainties for the excavation through the fault zone, which mainly originate from the limited information about the rock conditions and the relatively large width of the tunnels.