Bauer Spezialtiefbau has made progress on installing 35,000m of piles, including the deepest bored piles ever executed in Vienna, Austria, for Wiener Linien’s project to expand the city’s metro system.
The work is part of Vienna public transport provider Wiener Linien’s drive to modernise the city’s metro network.
The Austrian subsidiary of Bauer Spezialtiefbau was contracted to undertake the piling for nine shafts and station structures in the city centre by main contractor U2xU5 consortium - a joint venture of Hochtief, Swietelsky and Habau Hoch- und Tiefbau.
The metro expansion includes a new route layout for the U2 line and the construction of a new U5 metro line, which will intersect the U2 and replace it in some parts.
Bauer has so far completed approximately 75% of the commissioned services, undertaking piling works for contract sections U2/22 and U5/2 between Rathaus and Schottentor stations.
Work has involved installing piles with diameters of 620mm, 880mm and 1,180mm, and drilling depths of up to 61m.
Up to five large rotary drilling rigs have been mobilised to assist with the piling works in the period since April 2021.
The prevailing geology in the project area is characterised by deposits from the Vienna Basin consisting of Miocene soils. These are overlaid with backfill, loess loam and water-bearing quaternary gravel.
The tunnel axes in this area where Bauer is carrying out work are situated in the water-bearing quaternary layers.
These connected free bodies of water in the quartz gravel, in combination with the confined groundwater of the sandy Miocene layers, mean that bored piles embedded into Miocene layers must be constructed under water load.
The highlight of the work has been the construction of the deepest bored piles ever executed in Vienna on the Schottentor connecting structure – with pile diameters of 1,180mm and a drilling depth of 61m.
The high load concentrations resulting from the static side conditions and load redistributions make it necessary to construct a two-row pile group in the Universität Ost area of Vienna.
Construction of 55m long piles with a drilling depth of 61m in the area Universität Mitte will also be necessary – these will subsequently also form a part of the tunnel wall.
Based on the prevailing soil conditions in this partial section, the deepest piles in Vienna will be partially cased up to depths of approximately 30m, and beyond that under bentonite support.
Bauer is aiming to construct one 61m pile per working day on this section. It will operate under limited spatial conditions in two-shift work using a Bauer BG 45 drilling rig.
For the construction of the bored piles in most of the sections, compliance with higher tolerance requirements has been necessary.
This year, Bauer will carry out additional work between the areas of Universität and Votivpark, as well as on the shafts for Landesgerichtstrasse, Schwarzspanierstrasse and Frankhplatz Süd stations.
The U5 will be Vienna’s first fully automated underground line. It will take over the U2 section between Rathaus and Karlsplatz from 2027 and initially operate to Frankhplatz station.
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Tagged with: Austria Bauer Civil engineering Metro metro station Piling transport Vienna
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