Major milestone progress has been reached on Stuttgart-Ulm rail project in Germany with half the total tunnelling of 120.4km now completed, and more tunnelling about to start. Crews and fleets of equipment working across the multiple tunnels of the project are being joined by two more TBMs for use by Implenia to bore most of the Albvorland Tunnel, the last major twin-tube tunnel to start excavation.
The Albvorland Tunnel is the second longest underground section on the eastern Wendlingen-Ulm part of the multi-billion railway investment scheme. The German division of Swiss contractor Implenia was awarded the €380 million contract in December 2015 and has recently taken delivery of two 10.87m diameter Herrenknecht EPBMs for the parallel bores of up to 8km each, which are scheduled to launch from the east portal later this year (2017).
The Stuttgart-Ulm project is one of the largest investments among many new infrastructure projects across Germany for Deutsche Bahn (DB) and one of the country’s largest tunnelling endeavours. The entire Stuttgart-Ulm scheme comprises two large projects: Stuttgart 21 (S21) in the heart of the city involving a total 58.8km of tunnelling, and the Wendlingen-Ulm link with 61.6km of underground alignment. Each is financed through separate arrangements.
The S21 project involves major changes to the main station in Stuttgart plus excavation of long twin-tube network tunnels. With a budget of €6.53 billion the project is funded mostly by DB with contributions also from the European Union, the city’s airport operator, and the Federal, State and City governments. Key tunnels on the project are the Filder, Oberturkheim, Bad Cannstatt, Feuerbach, and Unterturkheim Tunnels plus the Airport and S-Bahn Tunnels, and smaller tunnels of less than 1km each (Fig 1).
The Wendlingen-Ulm link runs east from Stuttgart to improve regional rail capacity. Once completed, the new high-speed line will cut travel time between Stuttgart and Ulm by almost half to 28 minutes. The new line is a lynchpin on a priority European rail route to link Paris and Strasbourg, through to Vienna, Bratislava and Budapest. The project is half the cost of Stuttgart 21 at about €3.5 billion, and is funded mostly by the Federal Government and EU resources, with about a fifth from the Baden-Wurttemberg State. The key rail tunnels on the line are the Albvorland, Bossler, Albabstieg, Steinbuhl Tunnels, with additional relatively short tunnels (Fig 2).
Cutting through the city and across the surrounding countryside in southwest Germany, much of the Stuttgart-Ulm scheme is aligned underground. Only slightly more runs at grade, following the A8 motorway (Figs 1 and 2). By early April, DB reported that tunnelling on the project had reached the halfway milestone with a total 61.4km, or 51%, of the running tunnels excavated.
On S21 the distance excavated by early April was just reaching its halfway milestone with a total of 27.3km, or 46.5%, of the various tunnels, that link into the main station from different quadrants of the city, excavated.
At 9.5km long, and the longest underground section on the entire project, the Filder Tunnel links the new central station to the airport with twin tubes running about 30m apart and connected every 500m with cross passages. Together with 700m of non-track tunnel works, total excavation on the lot to 19.8km.
Tunnelling methods include open-face excavation, including and particularly at junction zones, and the operation of a single TBM undertaking multiple drives. Contractor on the lot is the ATCOST21 JV, comprising Porr Bau, G Hinteregger, Ostu-Stettin Hoch- und Tiefbau, and Swietelsky Tunnelbau. Construction supervision is by ILF Consulting Engineers.
The TBM is boring four separate drives either side of a middle geological transition zone that comprises unleached gypsum Keuper containing anhydrite that is susceptible to swelling. With open-face tunnelling excavating the middle zone, the TBM has launched twice on closed mode drives from the southern portal, first in late 2014 and again in early 2016, after partial disassembly and retraction as a single unit from the dead-end drive using a system developed by Herrenknecht. By early April, the 10.82m diameter multi-mode Herrenknecht machine had bored a total of 8.48km and will soon complete its second drive when it will be pulled through the excavated middle zones tunnels and prepare to launch once again, this time in open mode for the first of the northern side tunnels towards the main railway station.
In brief summary, progress on the other key tunnels on S21 by early April was as follows:
Oberturkheim Tunnel: A total of 12km of tunnelling, approximately 7.6km (63%) of which has been completed.
Bad Cannstatt Tunnel: A total of almost 9.1km of tunnelling and just more than 6.1km (67%) is complete.
Feuerbach Tunnel: Some 6km of tunnelling with 3.73km (62%) completed by early April.
Yet to get underway are the various tunnelling works for the Airport Tunnels, of almost 7km in total, and the Unterturkheim Tunnel at 1.8km long. Tunnel works for the 1.42km of S-Bahn alignment is more than half completed.
Tunnelling on the Wendlingen-Ulm link reached the halfway mark almost a year ago, in mid-2016.
From the city centre, the Albvorland Tunnel takes the railway out of Wendlingen on the east side of Stuttgart, and after a section of surface alignment, the route enters the Bossler and Steinbuhl Tunnels that take the new railway to the high point of its alignment. Only a few short tunnels then remain, along with mostly surface tracks, to take the route gently downhill towards the last Albabstieg Tunnel close to Ulm.
Excavation progress on the tunnelling works by early April is as follows:
TBM tunnelling will commence later this year for the two Herrenknecht EPBMs that contractor Implenia has procured for the project. One tube will be bored to its full 8km length while the parallel tube will be 7.7km with the balance excavated by open-face drill+blast tunnelling.
“The TBMs will launch and operate in closed EPB mode during their parallel drives of about 1.5km underneath the A8 highway,” explained Jens Classen of Implenia Construction GmbH. “The remainder of the TBM drives are expected to require open mode only, but still using the screw conveyor to extract material from the excavation chamber.” The 9.6m i.d. running tunnels will be segmentally lined with seven segments in each 2m long x 450mm thick lining ring.
“The drives are expected to finish after 18 months,” said Classen, “with the southern TBM breaking through at the west portal and the northern TBM breaking into a cavern previously excavated by drill+blast.” Drill+blast excavation is being used to excavate the contract’s link to the Kleine Wendlinger Kurve rail line on the Stuttgart-Tübingen route and a freight train connection at the west portal of the Albvorland TBM drives.
The twin tubes of the Bossler Tunnel are being excavated using an 11.34m diameter Herrenknecht EPB machine, following early drill+blast works for the two 8.7km drives. Boring began in early 2015 and the east tube was completed in late 2016. Excavation has yet to start on the parallel running tunnel and on the 17 cross passages that will link the twin tubes. Just more than half of the 19.15km of the excavation of the Bossler lot is complete to date.
Excavation by drill+blast of the 9.8km of tunnelling for the twin tubes on the Steinbuhl Tunnel is almost complete.
Drill+blast excavation and shotcrete lining for the twin tubes of the Albabstieg Tunnel have been completed. The tunnel is the third longest on the Wendlingen-Ulm project, requiring 12.45km of tunnelling, and is the last on the link into the city of Ulm. Construction started in early 2014 and excavation progressed in both tubes simultaneously with faces advancing from access at Dornstadt and an intermediate adit closer to Ulm. The final lining is cast-insitu concrete with a waterproof membrane behind and 11 cross passages will link the two tubes.
The rail tunnel in the remaining five lots on Wendlingen-Ulm are each less than 1km in length. Much of the excavation works are finished, with the shortest 253m Rastplatz vor dem Aichelberg Tunnel yet to complete.