For developing a new system for use in tunnel pre-exploration Dr. Rüdiger Giese from the GeoForschungsZentrum Potsdam (GFZ) and his team have received the Technology Transfer Award 2008 from the Technology Foundation Brandenburg.
ISIS (Integrated Seismic Imaging System ISIS) is a method that enables the
preliminary exploration of the rock mass in a tunnel. The technical innovation
here is that with this procedure, sounding explosions no longer are necessary,
and the system can be employed while actual tunnel construction is taking
spite of all the progress to date, tunnel construction still is a risky
undertaking. The biggest challenge is that an exact pre-exploration of the rock
mass in which the tunnel-drilling machine has to drill is essential. To
investigate the rock material ahead of the tunnel drill, seismic procedures
usually are applied: A small explosive charge is ignited, and the propagation
of the explosion’s sonic waves are evaluated. Under these circumstances, the
tunnel drill has to stop operation, and construction work is interrupted – at a
is where the ISIS comes into use. The ISIS allows for the forecasting of the
geological characteristics of the rock mass in the surroundings of tunnel
excavation in advance and without disturbing drilling procedures to any great
extent – similar to ultrasound in medicine.
idea is to use the tunnel-anchor, to install a measuring system for seismic
three-component receivers with their antenna in such a way that a
high-resolution seismic image of the rock mass during excavation is possible,”
says Dr. Rüdiger Giese. “Small earth-microphones (geophones) serve as
receivers, which are implanted in the pinnacles of the rock anchor. Herewith
the different seismic waves can be super-sensitively compiled. The data gives
information on changes in the rock mass, and eventually on water-bearing
anchors are cemented in 3-feet-deep boreholes. They can be fixed radial to the
tunnel, or in the direction of tunneling. The seismic impulses are triggered
with a pneumatic hammer or an electromagnetic vibration source, whereby the
impulses radiate in the specified direction and can be repeated in intervals of
all this can take place during the ongoing tunneling procedure.
The system already has
been applied during the construction of the new St. Gotthard tunnel and in the
tunneling of Lough Ness.