Stockholm City Line

Published 2010-02-28 00:00:00

The Stockholm City Line will be a 6 km double-track underground railway in the capital of Sweden. The project cost is the largest railway investment since the Stockholm Metro was built 60 years ago. Nitro Consult has been involved in the project since the beginning, with ground investigations, measurements of vibrations, noise and structure-borne sound, risk analyses and much more.

The Stockholm City Line (Citybanan) is to be a 6-km double-track underground railway beneath central Stockholm, expressly for commuter trains, which will double the current north-south rail track capacity through the city. Currently under construction at an estimated cost of SEK 16.8 billion (USD 2.4 billion), the project is the biggest investment in the Swedish capital's railways since the Stockholm Metro. Scheduled to open in 2017, it will run mostly through 130 m2 double-track rock tunnels, which fork into 2 x 80 m2 tunnels at station approaches. Altogether the project will require about 1.5 million m3 of rock to be excavated sensitively by drill-and-blast. The scheme includes a parallel service tunnel, two 260-m x 220 m2 under-city stations, two underwater concrete tunnels and a 1.5 km railway bridge.

Nitro Consult's role in the project

Nitro Consult has been involved in this project from the outset, starting with ground investigations. We then participated in the design and drafting of construction documents for the rock-excavation work between Tomteboda (the northern portal) and Station Odenplan (beneath the city's Vasastaden district). Additionally, our Vibration Group has carried out a series of test blasts in order to determine the vibration limit-values for vulnerable buildings such as the Gustav Vasa Church at Odenplan, and other sensitive installations. We have also carried out risk analyses of the vibration-generating works along substantial lengths of the prospective tunnels.

Ongoing engagements

Nitro Consult is currently measuring vibrations, noise and structure-borne sound along the entire northern stretch of the main tunnels from Tomteboda to Station City (the planned main passenger interconnector station underneath the city center). We are doing this together in a joint venture, NCA, with a firm called Ansvarsbesiktning AB. We shall also be carrying out structural surveys of all buildings and other facilities within the risk zone before and after the vibration-generating works. Our assignment includes the handling of all related questions and enquiries from neighbors and other third parties. Vibration measurements are taken on buildings, equipment and the underground railways. Approximately 100 measuring points are active daily. All measured values are reported to a server via GSM link. The client and contractors can read these measurements continuously via the Nitro Consult NCVIB Web portal. Every morning the contractors post the day's scheduled blasting times in the NCVIB portal.

Tags: Technical and blasting consulting, Rockand ground investigations