The Stockholm City Line
The new Stockholm City Line (Citybanan), currently under construction, is to be a 6-km double-track railway under central Stockholm expressly for commuter trains. With a main tunnel cross-section of 110 m2 and an estimated cost of SEK 16.8 billion (USD 2.4 billion), it is the biggest investment in the capital’s railways since the Stockholm Metro, which opened in 1950.
Nitro Consult has been appointed together with consultants Ansvarsbesiktning AB to carry out vibration, noise and structure-born sound measurements in connection with the excavation of the main tunnels in the scheme. We are also charged with the surveying of buildings and other infrastructure within the affected area, both before and after the vibration-generating rock excavation work. Our contract includes the handling of all third-party questions and enquiries. Citybanan is the largest single project in which Nitro Consult has participated to date.
Prior to winning the contract, our Design and Planning Department had, together with international engineering consultants SWECO, assisted with the designing and planning of the rock-excavation contracts at Tomteboda (where the northern portals are located). We also participated in the design and planning of the Vasa Tunnel (beneath the city-center district of Vasastaden) and Station Odenplan (one of the two 260-m x 220 m2 downtown underground stations that will connect passengers with the overlying Stockholm Metro and other modes of transport). Our initial responsibilities included preparing descriptive technical documentation for the construction of the 65m2 single-track and 110 m2 double-track rock-tunnels and carrying out site investigations in the form of diamond core drillings, which became the basis for preparatory geotechnical work. Additionally, our technical blasting team performed a series of test blasts in order to establish the limit values for sensitive buildings, such as the Gustav Vasa Church, Stockholm’s largest. Nitro Consult also prepared risk analyses for large portions of the Citybanan tunnel route with regard to the proposed vibration-generating blasting and other works. The Citybanan scheme, which requires over 1 million m3 of hard rock to be excavated sensitively by drill-and-blast, includes a parallel service tunnel, two underwater concrete tunnels and a 1.5 km railway bridge.