U-Bahn München/Lehel

The entire running and station tunnels with the exception of the passenger hall and parts of the staircase shafts were completed by mining means. The overburden ranges from 12 to 20 m. The tunnels are located in tertiary sands and marls of the second groundwater layer. They were driven via the shotcrete under compressed air construction method, with the pressure level in the sand layers bearing artesian water being lowered through partial relief through vacuum wells. In the vicinity of the eastern end of the lot, there is a special feature in the tertiary sands in the form of a free groundwater level of the second groundwater layer, which emerges on the right bank of the River Isar flowing towards the Isar. All the tunnels were provided with an inner lining of watertight concrete. As the running and station tunnels pass below areas with old historic buildings, the starting shaft had to be set up on Schwind Island between the western arm of the Grand Isar and the eastern arm of the Little Isar. Whereas the Grand Isar takes the form of a massive reinforced concrete channel at that point, rock packing secured with pile walls and steel girders has been installed on the river bed of the eastern arm of the Little Isar to protect it. These girders in some places extend down to the driven cross-section. In order to be able to master these areas, a tunnel support was driven, which is provided with a pressure wall with locks. Subsequently, the drive for both tracks in a western direction was carried out via a first cross-cut. For track 1, the drive was undertaken in the reverse direction past the starting shaft until underneath Schwind Island. Once the compressed air was released, the equipment for what was the 4th drive could then be completed via a pressure gate, which was set in the side of the starting shaft. Then it was possible to tackle the critical zone beneath the Little Isar in track 1 under compressed air and later track 2 was executed in the reverse direction via a cross-cut, which was located to the east outside the river bed.

• Country: Germany
• Region: Bayern
• Tunnel utilization: Traffic
• Type of utilization: Underground, urban and rapid transit
• Client: Landeshauptstadt München, U-Bahn-Referat
• Main construction method: Trenchless
• Type of excavation: Drill-and-blast
• Lining: Shotcrete
• Tunnel total length: approx. 2,900 m
• Cross-section: 38- 85 m²
• Contract Volume: 110 mill. DM
• Construction start/end: 1982- 1986