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Milestone advance on Stuttgart-Ulm rail links 19 Jul 2018

Patrick Reynolds for TunnelTalk

Three-quarters of the total 120.4km of main underground excavations on the Stuttgart-Wendlingen-Ulm mega rail project in Germany is now complete. By early July, the project had advanced 89.5km or 75% of the tunnel elements on the project, adding 28.1km during the last 15 months and with several TBM and drill+blast breakthroughs marking milestone advance.

Breakthrough ends Bossler Tunnel drives in Germany
Breakthrough ends Bossler Tunnel drives in Germany
Precast lining behind the Herrenknecht TBM
Precast lining behind the Herrenknecht TBM

The new rail line for national rail company Deutsche Bahn (DB) is to be operational in 2022, reducing by almost half the journey between Stuttgart and Ulm in southwest Germany.

TBMs on Albvorland Tunnel at launch in late 2017
TBMs on Albvorland Tunnel at launch in late 2017

On the rural Wendlingen–Ulm section, a 11.34m diameter Herrenknecht TBM has completed the Bossler Tunnel and two additional Herrenknecht machines are approaching the one-third completed milestone for the parallel drives of the Albvorland Tunnel, which is the last major underground section contract awarded on the high-speed route outside the city of Stuttgart.

Within Stuttgart the project, known as Stuttgart 21, comprises several complex urban excavations, the largest of which, and for the entire project, is the Filder Tunnel. By late July, tunnellers are expected to finish the third of four drives, or 75%, of complex logistical juggle using a single multi-mode Herrenknecht TBM.

The longest section of the project for Wendlingen to Ulm, involves a total tunnelling distance of 61.6km. The halfway milestone was reached two years ago and by early July more than 48km, or more than three-quarters, or 78%, of all excavations had been completed.

Excavation of the parallel tube of the Bossler Tunnel by the Porr, Hinteregger & Sohne, Ostu-Stettin and Swietelsky JV broke through recently to complete the 8.8km full length of the second drive after the 11.34m diameter TBM was re-launched in April 2017.

Advanced lining work on the Albabstieg Tunnel
Advanced lining work on the Albabstieg Tunnel

According to a notice by Herrenknecht, better than expected geological conditions allowed the contractor to use the TBM to complete a majority of the first tube at 7.8km and all 8.8km of the second tube, instead of the 2.8km in each as originally planned. The TBM was launched on the first tunnel in April 2015 and after reaching advance rates of up to 38m/day, completed the drive in November 2016 before re-launch on the second tunnel five months later. Early drill+blast work completing the remainder of the total 19.1km alignment. Geology along the tunnel route comprised sandstone, limestone and claystone. The parallel TBM rail tunnels are linked by 17 cross passages.

Contractor Implenia launched twin 10.82m diameter Herrenknecht EPBMs at the east portal in October 2017 to excavate parallel 8km and 7.7km long x 9.6m i.d. tubes for the Albvorland Tunnel. By early July 2018, approximately 5km, or almost 30%, of the twin tube tunnel has been bored. The contract also includes excavation of two short twin tunnels – the 495m long Kleine Wendlinger Curve and a 520m long freight train link – for which excavation will be performed later.

Conventional excavation of the 9.5km Steinbuhl and 11.7km Albabstieg twin tunnels on the Wendlingen-Ulm link were completed by mid-2017. Final in-situ concrete lining of the Albabstieg Tunnel by JV contractor Zublin/Max Bogl was completed in May 2018.

Second TBM breakthrough on Filder Tunnel in mid-2017
Second TBM breakthrough on Filder Tunnel in mid-2017
Conventional tunnelling for Filder Tunnel transition zone
Conventional tunnelling for Filder Tunnel transition zone

Stuttgart 21 progress

By early July 2018 more than 41.3km or 70% of the total 58.8km of tunnel excavations on the Stuttgart 21 project within the city of Stuttgart was completed.

At 9.5km long, excavation of the project’s longest twin tube Fielder Tunnel is a combination of drill+blast and TBM work competed between 2014 and 2016. To start, the 10.82m diameter multi-mode Herrenknecht TBM completed parallel drives in closed mode for the 4km long southern portion of the alignment, each time stopping at a geological transition zone that was excavated in the middle of the route by conventional tunnelling.

Following the second drive the TBM was pulled through the 1.2km long, conventionally excavated transition zone and re-launched to bore the second pair of tunnels. Those next tunnels, on the north side of the geological transition zone, meet excavations near the city’s main train station.

The 3.8km long, third, drive was in open mode and is virtually completed. After breakthrough, the TBM will be turned around for the fourth, and final, 3.8km drive, this time back towards the middle cavern in the geological transition zone. JV contractor of the Fielder Tunnel, ATCOST21, is same Porr, Hinteregger, Ostu-Stettin Hoch- und Tiefbau, and Swietelsky JV team as on the Bossler and Steinbuhl tunnels.

Elsewhere on the Stuttgart 21 city section of the project, the total 12km of tunnelling for the Oberturkheim Tunnel by ATCOST21 is mostly complete. Parallel 5.25km long tunnels are almost finished, leaving 760m of double-track tunnels to excavate. Following a recent breakthrough, 90% of all excavations on the lot is now complete.

Of the almost 9.1km of tunnelling required for the Bad Cannstatt Tunnel, some 7.1km or 78% is complete. The main works for the parallel tunnels by the Hochtief, BeMo, Wayss & Freytag JV is nearly finished, following principal breakthroughs in late 2016 and 2017. The remaining works focus on a short section of these tunnels related to an S-Bahn link, plus 850m of other double-track excavation.

Breakthrough at Oberturkheim urban tunnel in Stuttgart
Breakthrough at Oberturkheim urban tunnel in Stuttgart
Celebration as works near end at Oberturkheim Tunnel
Celebration as works near end at Oberturkheim Tunnel

All 6km excavation of the Feuerbach Tunnel works is also almost complete following breakthrough of the first of the parallel tunnels in March 2018 and of the second tube in early July 2018. Only short sections of double-track tunnels and other excavations remain to be done and to be completed shortly.

Excavation of almost 7km in total of the project’s Airport Tunnels remains yet to start, although excavation of the twin 1.8km tubes of the Unterturkheim Tunnel are half completed and various short tunnel works for the 1.4km long S-Bahn section have started.

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