The Global Magazine of Leica Geosystems

4 | Reporter
Gotthard Base Tunnel
Length: 57 km
Scheduled completion: End of 2017
Construction costs (2008):
6.43 billion euro (8.62 billion US$)
Construction costs (2008) including Ceneri
Base Tunnel: 7.76 billion euro (10.41 billion US$)
Surveying:
Consortium VI-GBT c/o Grünenfelder und Partner AG
and ARGE LOS349 c/o BSF Swissphoto AG,
www.bsf-swissphoto.ch
This would have been way outside the accuracy of
10 cm horizontally and 5 cm vertically required of the
engineers working for the surveying consortium VI-
GBT today, because the new Gotthard Base Tunnel
is designed for a modern low-level, high-speed railway.
The highest point on the route is only 550 m
above sea level and the maximum gradient is limited
to 0.8 percent. This means that from the end
of 2017 (scheduled date), high-speed trains with
people, goods, and vehicles on board will be carried
safely through the Alps at speeds of up to 250 km/h.
Perfect alignment of the track is essential for this to
happen.
The hole in the right place
Ensuring that the alignment complies with these
requirements is the task of Ivo Schätti and his team
from Grünenfelder & Partner AG, the lead engineering
consultancy in the surveying consortium. As the
client's surveying engineers, they are responsible for
maintaining the correct position, height, and direction
as the mega-tunnel heading advances. “You
could say we have to make sure the hole is in the
right place,” grins Schätti during our visit to his office
in Domat-Ems, a small town near the Gotthard section
of the works. A map on the wall showing the
whole project gives rise to the suspicion that it might
be somewhat more difficult than that. “The special
aspects of this project naturally include its length,
Instruments used for tunnel surveying:
Precision total station Leica TCA2003
Digital level Leica DNA03
Nadirlot NL
Instruments used for monitoring :
Precision total station Leica TCA2003
Monitoring software Leica GeoMoS
Leica GPS System 500
Monitoring the Nalps dam wall
the five entry points out of which we work, and of
course the required accuracy,” he adds.
Great effort for control surveys
The mega-tunnel is being built from five places at
once – the two portals at Erstfeld (north) and Bodio
(south), and intermediate headings at Amsteg, Sedrun,
and Faido. The basic primary network was created
in 1995 and was completely resurveyed ten years
later. “In 1995 the use of GPS was still relatively new,
but our measurements confirmed that the points
were stable,” declared Schätti.
One of the principal tasks of Grünenfelder & Partner
AG at the moment is tunnel control. As the client's
surveyors, the team can take more time for its measurements,
but also work more intensely, using special
instruments such as a gyrotheodolite and enjoying
better working conditions than the contractor's
survey teams, who continuously monitor and control
the heading. Their measurements are usually taken
when the site is shut down. “This entails coming into
work over Christmas and on other public holidays,”
says Schätti.
The checks are necessary as errors can creep in
through many factors. One source of errors is temperature
fluctuations: ventilation equipment distributes
the relatively high temperatures uniformly