Contract SBT2.1 “Tunnel Fröschnitzgraben” has a value of about EUR 623 million, the largest contract for the Semmering Base Tunnel. The construction contract was awarded in autumn 2013 to the joint venture Tunnel Fröschnitzgraben Implenia – Swietelsky Tunnelbau. The contract includes altogether about 26 km of running tunnels to be driven by two mechanised drives and two conventional drives, with the works being undertaken at all four faces almost simultaneously. The particular challenge is that the entire supply to the underground activities and the clearance of excavated material has to pass through two shafts about 400 m deep. The construction of these two shafts with excavated diameters of about 12.4 and 9.9 m respectively and the selection of the shaft logistics are of decisive significance for the success of the project. These special requirements of the project faced a limited availability of flexible complete contractors for the construction and operation of shafts. Considering this situation, the joint venture partner Swietelsky Tunnelbau decided to solve the problem in‐house and follow new routes with innovative concepts.
Das Baulos SBT2.1 “Tunnel Fröschnitzgraben” ist mit einem Auftragswert von etwa 623 Mio. EUR das größte Baulos des Semmering‐Basistunnels. Im Herbst 2013 erhielt die Arbeitsgemeinschaft Tunnel Fröschnitzgraben Implenia – Swietelsky Tunnelbau den Bauauftrag. Für die im Baulos insgesamt aufzufahrenden ca. 26 km Streckenröhren sind zwei maschinelle Vortriebe (TVM) und zwei konventionelle Vortriebe vorgesehen. Die Arbeiten werden an allen vier Vortriebsästen großteils zeitgleich abgewickelt. Die besondere Herausforderung liegt darin, dass die gesamte Versorgung der untertägigen Aktivitäten sowie der Abtransport des Ausbruchmaterials über zwei jeweils ca. 400 m tiefe Schächte erfolgen müssen. Die Herstellung der beiden Schächte mit einem Ausbruchdurchmesser von rd. 12,4 bzw. 9,9 m und die Auswahl der Schachtlogistik sind für das Gelingen des Projekts von entscheidender Bedeutung. Den speziellen Anforderungen des Projekts stand ein begrenztes Angebot an flexiblen Komplettanbietern für den Bau und den Betrieb von Schächten gegenüber. Angesichts dieser Situation hat sich der Arge‐Partner Swietelsky Tunnelbau dazu entschieden, die Problemstellungen in Eigenregie zu lösen und mit innovativen Konzepten neue Wege zu beschreiten.
Contract SBT2.1 Tunnel Fröschnitzgraben is the central and longest construction section of the Semmering Base Tunnel, including 13 km of tunnelling from the intermediate access in Fröschnitzgraben towards Gloggnitz and Mürzzuschlag. The approx. 4 km long section towards Mürzzuschlag is being excavated by drill and blast, and the 9 km section towards Gloggnitz is being driven by two tunnel boring machines. Before the start of the actual construction of the running tunnels, the two shafts about 400 m deep had to be sunk using an innovative concept. Considerable changes are also noticeable above ground: the filling level of the landfill site in Longsgraben is rising constantly.
The Tiwag -Tiroler Wasserkraft AG -is replacing the entire fall to the powerhouse at the Kaunertal power station, which has been in operation for about 50 years, in 2012 to 2015. The new facilities are being constructed entirely underground in unusually difficult geology for high-pressure systems. Works to construct the 4,000 m of tunnels and shafts started in March 2012 and were completed by the middle of June 2013. Part of the construction work is based on the proven NATM and part is based on the modern technology of mechanised tunnelling. After the completion of the caverns, the core of the new system, the 1,430 m long penstock, will be lined with thick-walled steel armouring and backfilled with concrete.
Kaunertal power station -the new shafts in the fall to the powerhouse
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.
As part of the project "PPP Ostregion Paket 1", a tunnelling project is being constructed on the basis of a performance specification for the first time in Austria, with the entire geological risk being borne by the contractor. The two-tube Tradenberg tunnel, each tube carrying one traffic direction, is in the S1-West section of the 51 km long Y-Trasse to be constructed by the consortium Bonaventura. The overall length of the tunnel is 2,457 m or 2,423.5 m, of which 1,403.6 m or 1,359 m are to be mined underground. The entire section is to open for traffic in early 2010. The contract model has the effect of transferring competence to the contractor. This opens a wide range of organisational possibilities for the construction consortium, but accompanied by an enormous increase in responsibility and commercial risk.
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