Page 9 - Railways

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with +/- 3mm accuracy and the installation was carried out
by the above machine with the help of workers.
- Final Adjustment, where now the detailed tracing was
carried out with +/-0.9mm accuracy, manually and with
the appropriate tools for the micro-corrections.
- Inspection-acceptance (As Built) correspondingly, as
with the rails on the ground. Here, the identification of
any theoretical—constructed track deviations was more
frequent, since it could not exceed 1 km and the concreting
of the mounting of the rails intervened with the subsequent
micro-movements.

• 3.5km railway tracks on a slab inside the “Monastiraki –
Attiki” tunnel.
- The same methodology was followed here as with
the foundation rails before, during the rough and final
adjustment and the inspection-acceptance phases.
- Their difference, as regards the methodology, with those
outside the tunnel, pertains to an interim stage between
rough and final adjustment. After rough adjustment, and
certainly before the final adjustment, it was necessary to
inspect the tunnel’s clearance in real time.
Due to the small gauge of the tunnel, in width and height,
and therefore the narrow space, this was done in order
to determine with certainty and precision any interference
by any elements (supports, walls, cables, cable shelves,
electromechanical boxes, signals, signs, etc) within the
clearance that was provided for and should exist for the
correct construction of the project.
This inspection was carried out at sections of the line each
time, with the most advanced GRP 5000 control system.

Monitoring of micro-movements at the section of the
“Monastiraki-Omonoia” railway network.
The 850m-long (total length 1465 m) section of the ISAP
line between Monastiraki – Omonoia, is located inside the old
660m tunnel, which was constructed in 1893. Thus, due to
the age of the tunnel, one of the project’s objectives was to
support it, and therefore to take preventive measures during
the progress of the works inside it.
Our surveying support played an instrumental role in this
part, and pertained to monitoring the micro-movements inside
and outside the tunnel, i.e. underground and above ground.
• Underground:
Monitoring micro-movements included any convergence
presented by the tunnel walls. Before measurements started,
permanent controls had to be installed, which were targets
installed on tie rods embedded in the walls. After installation
and before the start of the works, “zero” measurements of the
controls were taken, in order to accurately observe their initial
position. Then, and simultaneously with the start of the works,
measurements were taken on a daily basis and their results
were sent directly to the construction company.

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