Ground Freezing for an emergency egress niche below a river estuary in Świnoujście, Poland.

The new 1.48 km long, bi-directional road bored tunnel connecting the islands of Uznam and Wolin in North-West Poland has been successfully excavated with a big diameter slurry TBM (outer diameter 13.46 m). The tunnel underpasses the Świna straits with the minimum overburden of approximately 8 m. The use of a slurry machine allowed to complete the excavation in these challenging geological conditions in compliance with the stringent construction time schedule. The project includes two lateral emergency egress niches. As they are excavated in permeable soil below the Świna straits, ground treatment with Artificial Ground Freezing (AGF) has been applied. The paper describes the design process and presents the monitoring data, also highlighting lessons learnt from the application of AGF in a complex geometry and a mixed face geology. [ABSTRACT FROM AUTHOR]