The report presents two German railway tunnel projects, the construction of which demanded high-quality engineering work regarding the given geotechnical, hydrogeological and administrative conditions. The report will concentrate on actual results of the geotechnical monitoring. The Wandersmann-Tunnel North is part of the new 184 km long new high speed railway line Cologne - Frankfurt which is planned with a maximum operation speed of 300 km/h. Two single-tracked pipes, each of which is about 900 m long, are driven protected by a groundwater-lowering by means of a shield machine with mechanical support of the face. At the line a total of 18 bridges (total length = 6 km) and 30 tunnels (total length = 47 km) are under construction at the present. In the course of the extension of the railway line Mainz-Mannheim the double-tracked New Mainz Tunnel is under construction. The tunnel undercrosses the city centre of Mainz with a length of about 1,250 m. Regarding the actual ground conditions and the existing settlement-sensitive structures at the surface the driving is carried out in shotcrete tunnelling method with sequential excavation steps. A sidewall drift hurrying on ahead was chosen as construction method.
The Wandersmann-Tunnel is part of the branch line that connects the District Capitol City Wiesbaden with the new high speed railway line Cologne-Frankfurt. A highway has to be undercrossed in an acute angle, the allowed deformation at its surface is limited to a maximum of 5 cm. The shield diameter is 11.50 m; the preliminary fitting is done with reinforced concrete segments. The final lining consists of a water-tight internal formwork. Due to geomorphological and geotechnical conditions, starting and exit pits up to 220 m long and up to 22 m deep on both portals were constructed.