The Oberau tunnel project comprises the new construction of a twin tube road tunnel using conventional methods close to Garmisch-Partenkirchen, which aims to divert the existing road that crosses the town of Oberau. The excavation was performed with horizontal surface injections in order to prevent surface settlements due to low overburden. The ground water control was part of the scope of works.

The main parts of the project consist of:

• 2’750 and 2’830 m long (95 m²) twin tube road tunnel
• Cross connections every 500 m (14 to 36 m²)
• Shallow shafts for elevation-injections

Underground excavation, rock support and grouting work

• Excavation methods: drill & blast (80%) in hard rock, excavator advance (20%) in loose material
• Excavated length and volume: 5’580 m, 500’000 m³
• Grouting method: elevation-injections from the sur- face, sealing rings
• Standard rock support: shotcrete (60’000 m³) and systematic rock bolts (50’000 pcs)
• Additional rock support: spile umbrella and lattice girders

Underground water and frost protection work

• Umbrella seal and perimeter waterproofing systems: 160’000 m²

Surface- and groundwork

• Vibro pile column construction for 9’300 m
• Site access roads and main road works including ex- tension of existing tracks
• Collection basins including design
• Roadway separation walls including design
• Tunnel excavated material: dumping and processing services

Concrete work

• Tunnel concrete lining
• Four concrete portals totally 312 m long