Abstract
Just south of Oslo Central Station, the new high-speed Follo Line railway tunnels pass beneath the existing Ekeberg road tunnels. This paper presents the construction methods, numerical model, and monitoring program used to assess the stability of the E6 road tunnels during the excavation of the Follo Line tunnels only a few metres below. The construction of the Follo Line was approved subject to three conditions: (1) there should be no negative effect on the stability of the Ekeberg tunnels, (2) the traffic flow in the Ekeberg tunnels had to be maintained at all times and (3) any risk of instability in the existing tunnels must be detected beforehand, so that necessary precautionary actions could be taken in good time. To deal with the challenges, SINTEF developed a comprehensive analysis procedure, combining continuous rock stress measurements and displacement measurements with 2D and 3D numerical modelling. The rock stress change monitoring was used together with the numerical model to monitor the stability conditions in the Ekeberg tunnels as the Follo Line tunnels were excavated. This ensured that any risk of instability in the existing tunnels could be detected in advance to enable precautionary action to be taken. The successful completion of the new tunnels without any disturbance to the road tunnels shows that the procedure would be useful for dealing with similar applications in the future.
Highlights
In 2013, Bane NOR (Norwegian National Rail Administration) decided to construct the Follo Line Project, a new high-speed railway connecting Oslo and Ski
This paper presents the construction methods, numerical model, and monitoring program used to assess the stability during construction of the junction between Ekeberg tunnels and the Follo Line tunnels only a few metres below
A comprehensive monitoring program was established to obtain the information for numerical verification, but more crucially to monitor the behaviour of the rock mass between the existing Ekeberg tunnels and the new Follo Line tunnels (Trinh et al 2017)
Summary
In 2013, Bane NOR (Norwegian National Rail Administration) decided to construct the Follo Line Project, a new high-speed railway connecting Oslo and Ski. The Follo Line tunnels are designed for speeds up to 250 km/h and will form part of the future Oslo–Gothenburg high-speed railway (Kruse 2017). This paper presents the construction methods, numerical model, and monitoring program used to assess the stability during construction of the junction between Ekeberg tunnels and the Follo Line tunnels only a few metres below. This case is of special interest since a combination of "investigation", "numerical modelling", and "monitoring" were implemented smoothly to ensure the safety of new and existing tunnels
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