Tweet Share

• Send by email

  Send by email

  

  Passage under Lövstavägen at Bypass Stockholm – From Design to Realization

  The passage under Lövstavägen within the Stockholm Bypass Project has been the first real critical and sensitive area excavated during the construction phase of this important project. In this area, two access ramp tunnels pass under the fourlane road named Lövstavägen. Above the tunnel crown, 7-10 m of soil and no rock cover had been verified by several investigations. From the top down, the soil consists of man-made ground, a soft clay layer and a water-bearing moraine, followed by the bedrock with varying quality of the rock mass. These circumstances resulted in a very complex tunneling situation with mixed face conditions – competent rock together with soft soil and water. The design phase started in 2013 and resulted in a technical solution including a treatment of the soil with jet grouting from the surface prior to the tunnel excavation and the installation of a pipe umbrella. The temporary support in the tunnel consisted of rock bolts and fibre reinforced shotcrete and was planned to be applied immediately after every blasting round. Finally, a cast-in-place concrete lining was to be installed acting as the permanent ground support with drainage and waterproofing layer behind. Since the realization of the jet grouting from the surface began in early 2016, several adjustments and improvements to the design solution have been made in order to better fit the real situation met on the site and to allow a faster construction process. In March 2017, the excavation of the ramp tunnel finally reached the Lövstavägen area. This paper presents the evolution of the technical solution from the design to the as-built situation. In particular, an unexpected fault zone with low rock mass quality together with the 3D implementation of the real rock cover data from the jet grouting led to a partially new evaluation of the temporary rock support. Together with monitoring in and above the tunnel, this allowed a safe crossing under the road Lövstavägen.

  Recipient :

  Name ^* :

  E-mail address ^* :

  ^* Required fields

  Send   or  Cancel

• Print