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The Athens Metro construction
project is one of the largest and most complex in Europe. The
project was managed by Attiko Metro A.E. with a consortium of
25 Greek, German and French companies as the main contractors,
known as Olympic Metro.
The Metro, with a construction cost in excess of 2.2 billion
ECU, consists of 2 lines and 21 stations and will serve approximately
140,000,000 passengers annually.
Two 9.5m diameter tunnel-boring machines (TBM's) were used to
construct 11.7 km of tunnel, a further 2.5 km being excavated
by cut and cover methods.
The New Austrian Tunnelling Method (NATM) was used primarily
for the station galleries, subways and access ways. |
| The geology of the tunnels
was mainly heterogeneous fractured schist. There were also occurrences
of limestone and peridotite. Due to the nature of the strata
additional support was required in the roof, tunnel sides and
floor.
Fibregrip ® 22mm and 32mm fibreglass
rockbolts were used for both permanent and temporary support
in these areas. |
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In areas of
the roof where the strata was fractured 32mm and 22mm bolts
12m long were installed forward at the face of the drivage before
being excavated by the TBM.
In the areas where the station cross cuts thirled into the main
drivage the tunnel sides were reinforced by 22mm diameter Fibregrip
® rockbolts.
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Due to the ingress of water, particularly
in the areas of the tunnel where the limestone contained porous
limestone deposits, floor heave caused problems. This was overcome
by floor bolting using 22mm diameter Fibregrip
® bolts. These could be easily cut out when the floor was
regraded. |
The Fibregrip
® rockbolts used in this project were a polyester glass
fibre bars with tensile strengths of 470kN and 820kN and 275kN.
All bolts were installed into pre-drilled holes filled with
OPC grout.
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4.2 meg |
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Bar
& 'AT' Rockbolts
Ease of installation due to the products light weight.
