Within few days at the beginning of July the experts at Euro Alliance Tunnels celebrated the break-through of two tunnels in Stuttgart, Germany. Both tunnels, "Veronica" and „Andrea“ are part of the famous project Stuttgart 21. This particular track consists of relocation of subway tracks for the U12 line. Nearly in the middle of the tunnels the parallel tubes which are 517 and 602 m long have been widened and branched off into 4 tubes on the whole. Now the southern sections have been finalized.
The tunnels were excavated with the New Austrian Tunneling Method using tunnel excavators. Although the experts and engineers at Euro Alliance Tunnels constructed more than 100 km tunnels in the company´s history, every project is a new challenge with unique conditions. So is this one. Because of the unstable geology the whole tunnels were driven by the use of pipe roofs. The construction site is in the very center of Stuttgart with narrow space conditions. The excavation works have to be mastered with special attention to the extremely low overburden, which is only 4 m in some areas. The tunnels cross below urban tower buildings, one of the city´s most important traffic axle and one existing rail tunnel still in service. Also unstable geology and high underground water level with ingressing water (5 l/s) combined with tight time schedule make this project so challenging.
Despite of its complexity and all difficulties the experts at Euro Alliance Tunnels excavated the main tubes in time and without incidents. Now they are proceeding with the excavation of the remaining parts - the two junction tubes in the North.
