Last tunnel element Söderström tunnel immersed
On Tuesday 3rd of September the last element of the Söderström tunnel in Stockholm has been moved under water to its final position. This last element (TE1) was already immersed end July and temporary parked into the Jointhouse, to allow (early August) for the immersion of the second element (TE2) in-between TE3 (immersed early May) and TE1. All three elements of the sandwich type immersed tunnel are now in their final position within the extremely tight tolerance requirements. With the supervision of this final immersion related operation the involvement of TEC in this tunnel project has ended.
The tunnel in the Söderström is part of the Citybanan project and comprises a 340 m long immersed tunnel which is located between Riddarholmen and Södermalm. The immersed tunnel will be part of a 6 km long tunnel with two railway tracks and connects the rock tunnels at either side of lake Ridderfärden. The Söderström tunnel consists of three prefabricated tunnel elements, two short cut and cover tunnels and a joint house. Unique for Europe and due to the limited water depth the immersed tunnel is constructed as a sandwich tunnel with concrete and a double steel shell. The tunnel is placed partly above the lake bed on 3 pile groups due to the soft soil on top of the bedrock. After the immersion operations the three tunnel elements will be connected by means of prestress. The tunnel will be fixed at the southern end in the rock at Södermalm and has a free end at the joint house (at the northern end) where movements can take place.
In this project TEC is commissioned by the Swedish Transport Administration Trafikverket as independent reviewer of the marine works design of the tunnel and assists the Client in the supervision of the immersion operations. The works are executed by a Joint Venture between the contractors Züblin and Pihl.
Together with the stakeholders involved TEC is extremely satisfied about the success of the operations.