Abstract:
In the course of closing the gap between the Brandenburg Gate and Alexanderplatz, the Museum Island
station was built by Implenia Construction GmbH.
The tunneling for the platform hall took place on a length of about 106 m (347 ft) under the protection of a
major ground freezing measure and crossed the Spree canal as well as the listed castle bridge. The
approximately 20,000 m³ (4.54 E+06 US gal dry) frozen mass lay mainly in the Berlin sands. In order to
ensure safe tunnelling and to protect the adjacent buildings, the planners had defined requirements for the
mean freezing temperature and thickness of the frozen mass.
For a reliable conclusion on the dimensions of the frozen mass, we used innovative temperature sensors as
well as the new, web-based 3D measurement visualization and the associated site-specific evaluation
software. The largely automated evaluation enabled a quick and reproducible determination of the
temperature distribution in the frozen soil and its thickness in the relevant cross-sectional areas. The
measurements were validated by thermal calculations using the Finite-Element-Method. Thus, an objective
and clear assessment basis was available to ensure rapid coordination between stakeholders.
The evaluations provide new insights into the temperature influences from tunneling, the application of
shotcrete and the concreting of the inner shell. The newly implemented active thawing system is also an
interesting innovation.