Page 10 - Railways

RAILWAYS The excellence of collaboration

It should be noted that the measurements were tied to the 3. WHY WAS THE GRP SYSTEM SELECTED FOR
already existing trigonometrical network within the tunnel, after THE SPECIFIC PROJECT?
it was first checked.
The project requirements and the large volume of the works
• Above-ground: necessitated highly precise measurements in the shortest
possible time. The GRP system and the appropriately trained
Here the monitoring of micro-movements pertained to the
buildings and any settlements of the paving above the specific staff made both these possible and the high density of the
tunnel. In order to proceed to the measurement stage, a new measurements, so that the final result reflects uniformity and
horizontal and elevation network had to be established and continuity, and the construction conforms, to the greatest
resolved first, this time above ground the tunnel. possible degree, with the study drawn up in advance.
Another advantage of surveying and concurrently tracing
Therefore, angle measurements and levelling of the established
fixed points-peaks on the road directly above the tunnel were with the GRP system, was that the survey crew could consist of
made. Then a secondary trigonometric network was established a single person, as the geodetic station operates automatically,
and resolved with the corresponding angle measurements, i.e. thus economizing human resources.
reference targets that were installed at points outside the zone
of influence of the works, where the control measurements
were tied. These controls were installed on all the buildings 4.) WHAT WERE THE PRESENTED PROBLEMS?
inside the zone of influence of the works and they were the a) The main problem that had to be dealt with was that
object of the measurements for any micro-movements. Their during the establishment of the trigonometric network along
results, respectively, were sent to the construction company the track, and the surveying of their existing conditions, the
daily. trains operated normally, and thus the surveying works were
carried out with increased risk because of the frequent routes
and the powered railway tracks.

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