The Brenner Base tunnel with its approximately 55 km length is a highly complex and ambitious project. The geomechanical design of such a tunnel system demands flexible tools to be able to cope with adoptions and modifications. The following paper describes the preprocessing of the given data, the setup of the database and the structure of the information processing. The different data are processed in order to get the full information for the tunnel system for each meter. This extensive information is used by the cost estimators. Then the data are condensed to have the information in the structure needed for the geomechanical design reports.
The Brenner base tunnel with its approximately 55 km length is the main building of the railway corridor between Munich andVerona. The current phase of the project covers the design stage to obtain the approval notifications in Italy and Austria for the construction. The Brenner base tunnel is a twin tube system consisting of two single track tunnels with an axis distance of 70 meters which are connected every 333m via cross passages. Inside the main tunnels the drainage adit is situated approximately 10m deeper (distance top of rail main tunnel and top of track drainage adit). These multifunctional stations include cross-over systems to change the track (i.e. the tunnel tube). In the area of the multifunctional station Innsbruck there are the junctions for the interconnection tunnels to the already operating bypass tunnel Innsbruck. The joint-venture PGBB (Planungsgemeinschaft BRENNER BASISTUNNEL / Progettazione GALLERIA di BASE del BRENNERO) was awarded the main contract for the design in decembre 2004 and works since on this demanding project.
During the preliminary design, which is the basis for the approval documents, the client requested a geomechanical design according to the Austrian guideline (ÖGG 2001). Since the available geotechnical and geological data are under constant refinement by another contractor, and the excavation method, alignment and the projected construction logistics are subjected to adaptions in the ongoing design process, the geomechanical design has to be worked out parallel to the available input data.
The given task comprises the following main items:
Primary support design for the subsurface buildings
Preliminary design of the inner linings, especially regarding the reinforcement requirements
Distribution of the support classes along the different alignments of the tunnel system according to the geotechnical homogeneous zones and the fault zones
Summary of the support distribution The results are then condesed into the respective reports.As mentioned before, these main tasks have to be performed with a changing data basis; that means that the constant updating of the data basis and the results have to be kept in mind when choosing an appropriate approach.
Approach Usually the geomechanical design at that design stage is done rather rough – some "representative" cross sections are taken as the basis for the support classification and the support distribution.