Special features of scheduling tunnel works - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 287

with optimal construction costs. This does, however, demand precautions and the provi-
sion of measures in case of problems. The development of costs resulting from an inter-
ruption for a limited time is illustrated in Fig. 7-7 and this shows how adjustments of
capacity can lead to cost overruns.

Figure 7-7 Cost development resulting from interruptions of the advance [122].

7.6 Examples of construction schedules

7.6.1 Construction schedule for the City Tunnel, Leipzig
The core of the future S-Bahn urban rail network in the metropolitan area of Leipzig/
Halle is an altogether 4.1 km long north-south link through the inner city of Leipzig,
which provides an underground connection between the main station, which was opened
in 1915 and recently extensively rebuilt, and the Bayerischer Bahnhof station. Both
these stations previously were termini and were linked underground by a 1.8 km long
tunnel driven by a shield machine. This underground link consists of two single-track
tunnel bores with single-pass watertight segment linings, bored by a shield machine.
In order to ensure an optimised traffic utilisation of the connection, the tunnel was de-
signed to provide two lines for both S-Bahn urban rail and express trains. The external
diameter of the tunnel bores is thus 9.00 m. The tunnel cross-section is designed for a
travel speed of 80 km/h.

The implementation of the mega-project is displayed clearly for all participants in a
framework schedule. This contains the planning procedures, the permits, tender and
award, the project management itself as well as acceptance and trial operation (Fig. 7-8).