Despite extensive geological investigations, uncertainties in the ground model often remain. The residual risks associated with this during the construction phase cannot generally be estimated precisely enough in advance. Given such boundary conditions the use of the observational method in line with the principles of the Eurocode EC 7 is therefore required. In order to guarantee safe and economical tunnelling, especially in shallow tunnelling projects, it is vital that a qualified geotechnical safety management programme is implemented during the construction phase. Successful implementation of the geotechnical safety management programme during the construction phase is based on the designer completely defining the anticipated behaviour and on constant target-performance comparisons of the system behaviour by an on-site geotechnical engineer. Advanced data evaluation tools and methods support the continuous interpretation of system behaviour, the early detection of deviations and checking the results against warning and alarm criteria. This paper deals with the fundamentals, requirements and demands of such a management system and describes its practical implementation during the construction phase based on specific ÖBB-Infrastruktur AG project case histories.

The Koralmbahn railway line between Graz and Klagenfurt is an essential link in the Baltic‐Adriatic Corridor. The new high‐speed line will create new capacities and significantly better conditions for environmentally friendly goods transport by rail. The current journey times for passengers will be reduced considerably. The Koralm Tunnel with a length of 32.9 km is the most important section of the new Koralmbahn. The article reports on the current state of design, investigation and construction at the Koralm Tunnel and examples of further development are presented.Die Koralmbahn zwischen Graz und Klagenfurt stellt ein maßgebliches Teilstück im Rahmen des Baltisch‐Adriatischen Korridors dar. Mit dieser neuen Eisenbahn‐Hochleistungsverbindung werden neue Kapazitäten und deutlich verbesserte Voraussetzungen für den umweltfreundlichen Bahngüterverkehr geschaffen. Im Personenverkehr wird die derzeitige Fahrzeit erheblich reduziert. Der Koralmtunnel stellt mit einer Länge von rund 32,9 km das Kernstück der neuen Koralmbahn dar. Im Artikel wird über den aktuellen Stand der Planung, der Erkundung und der baulichen Umsetzung beim Koralmtunnel berichtet, und es werden projektspezifische Weiterentwicklungen exemplarisch vorgestellt.

Since the end of the 1980s, the Westbahn line has been undergoing successive upgrading to a modern high‐speed line. The aim is to considerably increase the capacity and the travel speed up to 250 km/h. Regarding the infrastructure, this entails the new construction or upgrading of many sections including a number of tunnels due to the extended route and the topographical conditions. The requirements applicable to railway tunnels have changed significantly since the start of tunnel construction activities for the upgrading of the Westbahn. At the same time mechanised tunnelling technology has made great progress. These two developments have led to the situation that mechanised tunnel boring has become increasingly established in Austria as a viable alternative to NATM as a construction method for rail tunnels. The present article describes the procedure at the responsible company of Austrian Railways, ÖBB‐Infrastruktur AG, in connection with these developments and explains the considerations leading to the selection of the tunnelling method. Seit Ende der 1980er Jahre wird die Westbahn sukzessive zu einer modernen Hochleistungsstrecke ausgebaut. Die Ziele sind, die Streckenkapazität deutlich zu steigern und die Fahrgeschwindigkeit bis auf 250 km/h anzuheben. Infrastrukturseitig sind dafür zahlreiche Neu‐ und Ausbauabschnitte notwendig, die wegen ihrer gestreckten Linienführung und der gegebenen topografischen Verhältnisse auch einige Tunnelbauwerke beinhalten. Die Anforderungen an Eisenbahntunnel haben sich seit dem Beginn der Tunnelbauaktivitäten für den Westbahnausbau wesentlich verändert. Gleichzeitig hat in dieser Zeitspanne die Technologie des maschinellen Tunnelvortriebs große Fortschritte erzielt. Beide Entwicklungen haben dazu geführt, dass sich der maschinelle Tunnelvortrieb in Österreich auch beim Bau von Eisenbahntunneln zunehmend als konkurrenzfähige Baumethode zum NÖT‐Vortrieb etabliert hat. Der vorliegende Beitrag erläutert die Vorgangsweise der ÖBB‐Infrastruktur AG im Zusammenhang mit diesen Entwicklungen und legt dar, welche Überlegungen bezüglich der Wahl der Tunnelbaumethode angestellt wurden.

The Koralm Railway Line represents an essential section of the Pontebbana corridor between Graz and Klagenfurt. It creates new capacities and significantly improved conditions for the freight transportation. Furthermore, the travel time of the passenger traffic will be considerably reduced. The heart of the Koralm Railway Line is the Koralm tunnel with a length of approximately 32.8 km. During excavation of the partly extremely demanding neogene sections of the investigation tunnels for the Koralm Tunnel, valuable experiences can be gained concerning the drainage and the closely related excavation behaviour, in addition to the geological-geotechnical insights. In the paper, the predicted mountain water conditions of the tunnel sections within neogene sediments as well as experiences with the implemented dewatering measures are described. These experiences strongly influence the detailed design of the future main tunnel structure. Systematische Entwässerungsmaßnahmen im

The St. Kanzian tunnel chain lies near the Völkermarkt reservoir and is part of the Mittlern-Althofen approval section of the Koralmbahn line in Carinthia. Of the six tunnels in the St. Kanzian tunnel chain, the 495 m long Kühnsdorf green tunnel (cut-andcover) has already been completed. The construction of the 230 m long Peratschitzen green tunnel (a cut-and-cover noise protection tunnel) and the 620 m long Srejach Tunnel (top-down construction) started in summer 2015. Work should start on the Untersammelsdorf, Stein and Lind Tunnels (all mined tunnels), in spring/summer 2016. The tunnels lie partially in challenging geological conditions (lacustrine sediments), all with shallow overburden, and require special measures for support and ground improvement (bored piles, jet grouting). Particular attention has been paid to later maintenance costs, which have to be considered in the course of the design work.