Special features of scheduling tunnel works - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 292

Construction according to bid and award. After checking the shortlisted bids, which
all offered faster construction than demanded in the tender, the combination of the tunnel-
ling works in contract sections 01 and 02 with a total length of 8,348 m was decided. The
constructions schedule, which the award was based on, can be found in Fig. 7-12. This is
based on the following average advance rates:
- West Tunnel about 130 m/month
- East Tunnel (start) about 200 m/month
- East Tunnel (enlargement) about 165 m/month
A fluent contract boundary was also agreed on this project. The boundary could move
500 m without changing the price.
Figure 7-12 Construction
schedule. Award of the
Arlberg Tunnel [10].
Construction. Collapsed areas and shear fractures already had to be overcome shortly
after the punctual start of the tunnelling works. In order to counter a threatened extension
of construction time, as extrapolation of the encountered conditions would have led to a
delay of 18 months, the following acceleration measures were agreed:
- Abandonment of the driving of the pilot heading in the east main tunnel (chainage
1,860 m), to be replaced by the driving of a pilot heading eastwards from the Rosanna
gorge.