The drainage systems of several tunnels in Austria are heavily clogged with calcite precipitates. Cleaning and water conditioning are cost-intensive for the operating company. The results of the case study Koralm tunnel show that the dissolved calcium in the drainage solutions derives from the ground water and especially from the dissolution of portlandite at the shotcrete. Accordingly, the drainage solutions are often strongly alkaline and as sufficient supersaturation with respect to calcite is reached, calcite precipitates. The carbonate in the calcite sinter is obtained from the ground water or from the absorption of atmospheric CO 2 . Extensive chemical, mineralogical, and isotopic analyses as well as hydrogeochemical modelling permit to decipher the effective parameters in order to develop recommendations for retaliatory action. In-situ experiments in the Koralm tunnel simulate the conditions for the designed drainage system, which should provide an appropriate evaluation of the sinter formation in the drainage and the application of inhibitors. Sinter formation will be reduced by using tailored construction materials. Koralmtunnel als Fallbeispiel für Versinterungen in Dränage-systemen -Ablagerungsmechanismen und GegenmaßnahmenIn den Dränagesystemen mehrer Tunnel in Österreich werden enorme Mengen an Kalzit abgelagert. Die Reinigung und Wasserkonditionierung sind für den Betreiber mit erheblichen Kosten verbunden. In dieser Arbeit konnte anhand der Fallstudie Koralmtunnel gezeigt werden, dass das gelöste Kalzium in dem Dränage-wasser aus dem Bergwasser selbst und insbesondere aus der Auflösung von Portlandit im Spritzbeton bereitgestellt wird. Die so erhaltenen Lösungen sind häufig stark alkalisch. Hierdurch kommt es zu einer Übersättigung an Kalzit, wodurch in weiterer Folge die Abscheidung von Kalzit eingeleitet werden kann. Das Karbonat im Kalksinter kann entweder aus dem Grundwasser oder aus der Absorption von atmosphärischem CO 2 erhalten werden. Durch umfangreiche chemische, mineralogische und isotopenchemische Analysen sowie hydrogeochemische Modellierungen wurden die jeweils wirksamen Faktoren identifiziert, um auf deren Basis Ansätze für Gegenmaßnahmen entwickeln zu können. In-situ-Experimente im Koralmtunnel simulieren die Bedingungen in der geplanten Dränage. Hierüber soll eine Beurteilung der Versinterungen im Dränagesystem und der Anwendung von Inhibitoren ermöglicht werden. Versinterungen werden auch durch den Einsatz maßge-schneiderter Baustoffe verringert werden. IntroductionThe formation of carbonate sinter is a natural phenomenon as well as a challenge in the fields of engineering [3] [4]. Carbonate precipitation in drainage systems may cause serious problems due to the reduction of the cross section of drainage tubes (Figure 1) and the pollution of receiving streams by suspended carbonates and ongoing sinter formation.The Koralm tunnel will be the longest tunnel in Austria and special effort is given to minimize costs for maintenance action such as cleaning of the drainage system and wat...

One of the main goals of the ground investigation for the Koralm Tunnel project was the detailed investigation of the Lavanttal fault systemwhich lies in the contact between the Koralm crystalline and the neogenic formations of the Lavanttal. The above-ground investigation programme (mapping, core drilling, geophysics) was able to deliver the first estimation of the geological, hydrogeological and geotechnical rock conditions of the fault zone many hundreds of metres thick ( fig. 1). The Paierdorf investigation tunnel, which has now been constructed, clarified the thickness and the internal structure of the fault zone as well as the hydraulic and mechanical rock properties along the tunnel. Equally important was the practical experience gained by tunnelling through the fault zone. The knowledge gained from the Paierdorf investigation tunnel will be used in further design work for the mechanical driving of this very heterogeneous region of rock.1 Knowledge of engineering geology gained from the investigation tunnel Main fault zoneThe prognosis Immediately to the East of the neogenic-crystalline boundary, a main fault zone of the Lavanttal fault system was forecast, with a thickness of several hundreds of metres. In this region, a sequence of softly plastic, finegrained and coarse-grained cataclasites was expected, alternating with less faulted, competent blocks of rock. The thickness of the cataclasites was supposed to be a few metres to many tens of metres. Steeply dipping faults were expected to be dominant, dipping towards and also against the advance direction.The groundwater table in this area is up to 270 m above the crown of the tunnel. In the main fault zone dry to damp conditions for tunnelling were expected with locally trapped water pockets. In the jointed competent rock and in the boundaries of steep faults trickling water ingress was expected. Isolated water or mud inflows with up to some tens of l/s were also considered possible. The conditions encountered

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 approx. 3 km long twin‐tube Rudersdorf tunnel is part of the Fürstenfeld Motorway S7. In addition to jet grouting and steel pipe umbrella sections, the excavation is mainly carried out according to the NATM. After the contract had been signed, the contractor proposed a value engineering concept including a stepped (almost) full excavation with a short ring closure. This concept avoids jet grouting sections and reduces sections with steel pipe umbrellas and the temporary top heading invert. A fair risk transfer between both contractual partner enables the full technical and economic potential of the project to be released and guarantees a win‐win situation. The modified construction methodology consequently also requires a change of tasks and responsibility for the contractual partners for the project. This paper highlights the main topics of the contractual modifications required and explains the handling of the ground risk with examples.

example drilling method, drilling length, gap between the pipes, overlap, type of injection or excavation advance. This article shows the decision making process based on an actual project. The experience gained during the exploration project was incorporated in the planning and tendering of the main project, thus leading to a successful application of the measures and to safe tunnelling.