Lining design for the district heating tunnel in Copenhagen with steel fibre reinforced concrete segments

The 3.9 km long district heating tunnel carries heating pipelines from a power plant on the island Amager into the centre of Copenhagen. A shaft on Amager and two shafts in the city centre provide access to the tunnel, which is located within the Copenhagen limestone at a depth between 25 and 38 m below the ground surface. The tunnel is excavated with an earth pressure balance (EPB) shield machine and is lined with steel fibre reinforced concrete (SFRC) segments without any conventional steel bar reinforcement. This represents an advantageous and innovative technical as well as cost-efficient solution. This paper presents the methods applied in the structural and durability design of the SFRC segmental lining for a specified service life of 100 years. Special attention is required due to the temperature increase in the tunnel to approximately 50 °C during operation of the pipelines. The experiences with the SFRC segments during construction of the tunnel are discussed.