The Underwater Tunnel of Aktio-Preveza

The tunnel is 4.710m and the underwater part has a length of 1.570m. the tunnel is 4.710m and the underwater part has a length of 1.570m. (no1 on the map). The contractor was the "Joint Venture of Christiani Nielsen and Technical Company of General Construction S.A. (T.C.G.C. S.A.), now EMPEDOS S.A.".

A dry dock and were submerged into the exact place with dredged. Each part has a length of 134,50m and a weight dredged. Each part has a length of 134,50m and a weight of 10.000 to 15.000 tons.of 10.000 to 15.000 tons.

In this photo you can see two diaphragm walls with pined beams. Those are the entrance of the dry dock. From this site the precast parts are guided to the place were they will be sink.

More about the Tunnel?

How each precast part is placed and stabilized next to the other

Each pre-cast element is sunk next to the other with the use of GPS technology (to find the exact position) and the use of a hydraulic pump which pumps water from the tunnel. Of course, first, the sides of the tunnel are closed with a steel slab (you can see the supports in photo1). The element is sunk next to the other so that they fit. Then the water which is in the tunnel (so that it can be sunk) is pumped out, and because of the hydrostatic pressure, the one pre-cast element compresses the other. Between the two parts there is a plastic liner which protects the concrete portions from being damaged. (see photo 2). No other support exists for the connection of the pre-cast elements with the exception of a pre-stressed concrete slab.

Then gravel material is placed on the outer side of the tunnel. From the inner part, the connection is supported with concrete (photo 3).

Photos of the prestressed concrete slab of the floor of the tunnel

In this picture you can see the floor between the connected precast parts.