Munich:

Underground Railway Line U5/9, Construction Lot 9.2

Description

On account of the considerable depth of the overlying ground (20 m - 35 m) the section was tunnelled in the zones with tertiary sands and marl. The transition from the two single-track tunnels to the twin-track tunnel was extended into an access shaft, from when cecompressed air drivage was effected. The single-track tunnels were driven with a crown excavation 2 m in advance of the succeeding breasting excavation. The twin-track tunnel was first driven as a rising wall gallery; the remaining excavation was carried out with a 15 m offset from the working face.

The outer shells were reinforced with arches and steel mesh before being shotcreted with a thickness of 15cm - 30 cm. The inner shells consisted of watertight concrete with a thickness of 35 cm and 50 cm; they were placed every 10 m using a form work transport wagon. The station was constructed with 25 m deep diaphragm walls using the cover-and-excavation method because of the restricted space available.