Auswirkungen der geometrischen Lage der Tunnel auf die Gebirgsplastifizierung und die Spritzbetonschale beim Brenner Basistunnel

Effects of the geometric position of the Brenner Base Tunnel on rock mass plastification and the tunnel's shotcrete shell

The Brenner Base Tunnel will be, at 64 kilometres, the longest underground railway connection in the world. A preliminary exploratory tunnel is being excavated in segments about 11 metres under the two main tunnels in order to prospect the rock mass. The geometric position of the exploratory tunnel varies, with respect to the main tunnels, near Innsbruck and Fortezza. This horizontal displacement and the possible plastification of the rock mass are the focus of this study. The aim of the analyses was to evaluate the impact of the various geometric positions of the tunnel on the thickness of the shotcrete shell. Exhaustive finite element simulations were carried out and the mechanical and geometric data of the shotcrete shell were determined for the first time by a large series of tests in situ. A statistic analysis verified the required thickness of the shotcrete shell on the basis of probabilistic observations. The study also examined whether the thickness of the shotcrete used on the exploratory tunnel would also be sufficient if the tunnel were in an off-center position (including underneath the main tunnels) or for an additional tunnel running down the center axis.