Monthly TBM breakthroughs since August have brought main tunnelling on the Stuttgart-Ulm high speed rail line in Germany to completion. Developed by Deutsche Bahn, Stuttgart-Ulm has called for a total of 120.4km of main tunnel excavation, breaking down as 58.8km for Stuttgart 21 in the city and 61.6km for the Wendlingen-Ulm section.

The final TBM breakthrough took place on the Albvorland tunnel in the countryside section of the Wendlingen-Ulm portion in the east of the project and followed recent completion of complicated drives for the Filder tunnel for Stuttgart 21 in the city.

Stuttgart-Ulm called for multiple twin-tube TBM drives

Watch the Filder TBM take its u-turn

The end of TBM tunnelling took place when contractor Implenia completed the second of twin drives at Albvorland. The 10.82m diameter TBM had been boring the north tube since late 2017, and followed its sister Herrenknecht TBM which completed its 8.16km long drive for the 9.6m i.d. south tube in August. The parallel tunnels have a segmental lining of seven segments in each 2m long x 450mm thick ring.

Earlier tunnels completed in the Wendlingen-Ulm section are the 8.8km long TBM Bossler Tunnel, and the shorter conventionally excavated Steinbuhl and Albabstieg tunnels.

Excavation on the Stuttgart 21 western portion of the scheme in the city centre ended in September when a Herrenknecht TBM completed the last drive for the 9.5km long Filder Tunnel for the ATCOST21 JV of Porr-Hinteregger-Ostu-Stettin-Hoch- und Tiefbau-Swietelsky. Filder is the longest underground section on the project and the 10.82m diameter TBM completed the parallel tunnels in four separate drives with a u-turn in the middle of tunnelling to bore back toward the outskirts of the city.

The monthly TBM breakthroughs over August-October leaves the overall project with only minor underground works to complete. The project is to be completed and brought into operation in 2022.

TBM being disassembled and prepared for its u-turn

After successfully completing its third drive for the western tube of the 9.5km long twin tube Filder Tunnel on the Stuttgart-Ulm railway line in Germany, the 10.8m diameter Herrenknecht multi mode TBM is being disassembled underground and turned around to start the 3.4km final drive of the eastern tube.

The 120m long, 2,000 tonne TBM will be turned in a special cavern created by the crew for contract joint venture Porr, Hinteregger & Sohne, Ostu-Stettin and Swietelsky before starting work on the eastern tube this autumn, 2018.

"Such an about-turn underground with a TBM of this size is an example of the technical feats being achieved during the construction work on the Filder Tunnel," said Martin Herrenknecht, owner and CEO of the TBM manufacturing company.

Launch of the 10.8m multi-mode TBM for the western tube

The tunnel section is located in heterogeneous rock strata and overcomes a total height difference of 155m with a slope of up to 2.5%. Due to the complex project requirements, initially no mechanized tunnelling was planned for the Filder Tunnel but client Deutsche Bahn was persuaded of the advantages of mechanized tunnelling over a large part of the route using a convertible multi-mode machine.

In the upper section of the Filder Tunnel the TBM worked in EPB mode with screw conveyor muck removal and in the lower section in open single-shield mode with belt conveyor discharge. In the geological transition zone material was removed using diggers and loosening blasting.

TBM ready for start on the western tube at Filder

The Filder Tunnel is the longest on the new railway line between Stuttgart and Ulm, which will link the new central railway station with the Filder Plain. As a result of the railway project, travel times between Stuttgart and Ulm will be almost halved. Around ten million passengers per year will benefit from the scheme.

A Herrenknecht 10.8m diameter TBM is currently working on the Albvorland Tunnel and a Herrenknecht 11.3m diameter machine recently completed the 8.8km long Bossler Tunnel.