High-speed railway tunnelling in soft granular Frankfurt ground

Two examples show the experience with highspeed railway tunnelling in Frankfurt soft ground. At the ’’Frankfurter Kreuz” the railway line Cologne-Frankftirt/Main crosses the highways Frankfurt-Basel and Cologne-Würzburg in a tunnel in near vicinity to the Frankfurt/Main airport. The construction of the tunnel was composed of a two step support. In the first step the crown was excavated under a jet grouted screen. The working face was reinforced with a support core and eight additional horizontal jet grouted columns. In a second step the lower part of the tunnel was excavated. To verify the soil parameters two series of in-situ large scale shear tests were performed. Within the project ’’Frankfurt 21” a new railway tunnel undercrossing the city of Frankfurt/Main is planned. For that various underground tunnels as well as numerous buildings and skyscrapers with their foundations, the river Main and the East docks will be undercrossed.