Page 6 - Tunneling

TUNNELING The excellence of collaboration

Project for the Diversion of the Acheloos River –

Acheloos River Diversion Tunnel to Thessalia

1. SHORT HISTORY: frames, etc.
The partial diversion of the Acheloos River to Thessalia is a In more detail, the following works took place: Establishment
complicate and complex Technical project, whose construction of trigonometrical network (horizontal and leveling) inside and
design studies started thirty years ago. outside the tunnel with high accuracy for the correct guidance
of its excavation.
In 1995, after annulling decisions, a new Total Environmental
Impact Study was drawn up, and the initial design was amended - Horizontal Network :
as follows: The horizontal network depended on fixed points, which existed
A) The quantity of the diverted water was decreased to 600 before the original opening of the fronts, establishing at least
million cubic meters annually two new ones at their entrances.
B) The currently applicable Diversion Scheme was formulated, • Internally
and the diversion works are now as follows: Approximately 350 metal brackets (stations) were installed
- The Sykia Dam and the namesake Hydroelectric Plant inside the tunnels, soundly embedded and checked
before the angle measurements started in order to
- The 17.5 km long Acheloos River Diversion Tunnel with intake eliminate any errors or failures due to incorrect installation.
at the Sykia Reservoir
These stations considered also as the peaks of the new
- The Hydroelectric Plant of Pefkofyto at the exit of the diversion Trigonometric Network, and were placed at every 100 and
tunnel every 200 meters on both sides of the tunnels where the
tunnel alignment was straight line, and more densely in
- The Reregulating Reservoir of Mavromati. curved alignment parts. Particularly regarding the entrance
2. AIM OF PROJECT: from Argithea, for approximately 1.5 km the bases were
The project’s primary aim was the irrigation and the increase more closely installed due to the existence of many curves
of agricultural production and by extension of water supply to and angles in order to achieve visibility between peaks.
housing complexes - improvement of the quality of the water of Approximately 2800 x 6 measurements were carried out
River Pineios and the generation of energy. from all brackets (stations) towards back and front aiming
to at least 7 prisms placed on an equal number of bases,
3. OUR CONTRIBUTION TO THE PROJECT: depending on visibility. Three routings were made, the first
Establishment of surface - underground horizontal and from the entrance of the Drakotrypa to Argithea tunnel, the
levelling network inside and outside the open tunnels, as second from the entrance of the Petroto to Argithea tunnel,
well as the compilation of tunnel cross-sections. and the third from the entrance of the Anthiro to Argithea
tunnel for 1.5km and then it diverted left to the Argithea –
The tunnel’s excavation works were performed from both fronts Petroto front and on the right to the Argithea – Drakotrypa
(Drakotrypa and Petroto) using a Tunnel Boring Machine (TBM) front.
and conventional excavation method. An access gallery of
aprox. 2 km in length began at the village Anthiro and ended at • Externally
the main tunnel (Drakotrypa-Petroto) forming a “T”. This created With regard to the horizontal network outside the tunnels,
3 tunnels as depicted below. both the new base plates that were created and those
Taking into account that the tunnel construction requires that pre-existed used as survey points 11 single & double
specialized survey support through all its stages, our contribution frequency GPS geodetic receivers, taking measurements
was crucial for its smooth development and for reaching the simultaneously.
set aim, pertaining to the entire length of the Diversion Tunnel - Elevation Network:
of the Acheloos River. Essentially, our main responsibility was
to depict the data necessary to achieve accurate joining of The elevation network was tied to two fixed points with known
the 2 tunnels constructed, between Drakotrypa-Argithea and elevation (reperes) located near the entrances of each tunnel.
Petroto-Arghithea, by using accurate information in 3D form Surface and underground levelling was carried out.
(horizontal and level) . • Internally
Our responsibilities did not end there. After succeeding in the With regard to levelling inside the tunnels, there were
correct joining of the tunnels, and before supporting the final loops at every 500 meters, which included the fixed metal
tunnel with gunite , a complete survey of its condition was carried bracketsstations, thus determining their accurate elevation.
out, using laser scanner method in order to compile cross
sections and calculate the quantity of concrete, membranes,

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