Vienna Underground Railway- U1 /1 Kagraner Platz

Contract section U 1/1 of the Vienna-Kagran Underground was built between autumn 2001 and spring 2005. A roughly 41 5 m long route section consisting of 2 single-track tunnel tubes represents part of this contract. The tubes were excavated by means of a hydro-shield with a shield diameter of 6.80 m from June till December 2003. The overburden fluctuated between 3.40 and 12.00 m. ln addition to supply and disposal lines, a number of multi-storey residential buildings and a historic church had to be undercut without causing major Settlements. The logistics and the extremely constricted space conditions presented major challenges. The tubes were lined with segments made of water impermeable fire protected concrete B 500 with the addition of polypropylene fibres. The segments were fitted with EPDM gaskets dimensioned for 3 bar water pressure. A segmental ring is on average 1.3 m wide and consists of 6 segments and a small wedge-shaped keystone. The route is located in the Danube valley and entirely in the vicinity of recent meanders. The geological sequence revealed that close to the surface there were fills varying between 0.50 and 3.00 m thick as well as in parts, riverbank sands and loams. The underlying Danube gravel layers, which are practically devoid of fine grains, form the bulk of the subsoil. They were encountered over the entire contract section and possess a thickness of from 6.00 to 1 5.00 m. They cover young tertiary Upper Pannonian layers, largely composed of silts and sands. The tertiary upper layer possesses an irregular relief on account of erosion. As a result, the underlying silty-clayey sequence below the quaternary gravels was expected at depths of between 9.00 and 17.00 m. The part of the excavated cross-section located in gravel and a 2.00 m thick "coat-shaped" marginal zone outside the cross-section were stabilised in advance over the entire length of the route by means of pore space injections on a cement and bentonite basis. These injections are intended to help avoid uncontrolled soil displacements or cave-ins and provide compensation for major settlement differences or a flattening of the settlement troughs on the ground surface. In addition, the gravels lacking in sand have to be cemented to ensure that the ground is sufficiently stable to permit a shield passage and prevent sudden losses of supporting fluid in permeable gravel layers.

Country: Austria
Region: Vienna
Tunnel utilization: Traffic
Type of utilization: Underground, urban and rapid transit
Client: Wien er Linien GmbH & Co KG
Consulting Engineer: Schick & Partner
Contractor: Bilfinger Berger AG; BB Bauges. m.b.H, Wien
Main construction method: Trenchless
Type of excavation: Shield machine (SM)
Lining: Fire protected concrete B 500 with PP fibres
No. of tubes: 2
Tunnel total length: 1.2 km, including 2 tunnel stations, each 415 m
Cross-section: 36.3 m²
Contract Volume: € 45.8 million
Construction start/end: 2001 to 2004