The biggest hard rock double-shield tunnel boring machine (TBM) in the world,
with a diameter of 12.4 m, is currently excavating the North-South Bypass, which
includes a crossing under the Brisbane River, Brisbane, Australia, to relieve
the often congested road traffic in the city centre. Ten years ago a 10.7 m
Mixshield giant helped to handle the Olympic Games in Sydney linking the airport
with the city centre for an improved transportation of fascinated visitors. In
Shanghai, currently the biggest TBM in the world with 15.43 m diameter presents
excellent performance rates; and in Paris a convertible Mixshield could be
quickly changed from earth pressure balanced (EPB) to slurry type in order to
handle the very heterogeneous ground conditions. In Madrid a 15.2 m EPB giant
finished its tunnel job four months ahead of schedule. Large-scale TBMs have
proved their economic and innovative potential to create the current and future
underground architecture of mega-cities.
TBM technology has made further large innovative steps in the last decade.
State-of-the-art is a TBM for very heterogeneous ground conditions comprising
hard and soft rock with additional high groundwater pressure. The machine
concept is adapted to the various ground conditions and allows for a quick and
flexible application. Ground treatment by means of additives developed to a
helpful tool in this connection.
To meet the special challenges of urban tunnel projects of nowadays it is of
very high importance, beside applying highest developed technology of TBM, to
have a comprehensive technical support during the project phase and to develop
positive relationships between all participants of the project which last longer
than only for one project.