ABSTRACT
The extension of the U5 metro line in central Berlin closes the gap between the existing metro line in East Berlin and the so called Chancellor Line U55 running between the Berlin main station and the Brandenburg gate. The last part of the project is the construction of the 110m long Museum Island station near the Berlin cathedral and the newly constructed Berlin castle. The station lies beneath the Spree canal in fully saturated sands with underlying marl.
Freezing is used to stabilize the ground for the subsequent sequential excavation of the platform tunnels. A new method for horizontal directional drilling has been used to install the freeze pipes from shafts on either side of the future station. Extensive monitoring of ancient and new buildings and bridges was carried out during the freeze period and excavation. Sequential excavation and lining was used to limit movements of both the tunnel and the surface. The paper deals with the challenges and experiences during freezing, excavation and concrete works.
