The undersea section is constructed of 8 prefabricated elements; the biggest element has length 134.50m., thickness of walls 1m and weight almost 15.000 tons. The elements are manufactured in a casting basin in Aktio with total area, 67.500m² The seabed is 11m under the surface of the sea. To keep the casting basin dry a network of perimetric drillings was used so as to lower the water level. The casting basin communicates with the sea through a channel that is manufactured by diaphragm walls. The communication is succeeded by the removal of the channel’s barriers.

In the next stage the elements were sealed with the use of barriers and the flood of the casting basin. The floating elements because of the buoyancy were towed into their final position. In the end the elements were immersed with the use of pumps and by increasing and reducing the water level thorough a temporary network of pipes, which was located in the internal area of the elements. The bottom of the sea trench is improved with the construction of 8.482 stone columns (diameter about 60cm and 12m length) in segments of 1,80m X 1,80m in a total length of 125 km.

This improvement was considered necessary in order to face the danger of liquefaction as a result of the seismic action in the area. The immersion of the elements (X1,X2,1,2,3,4,5 and 6) was carried out from Preveza to Aktio, starting with the element X1 and completed with the element 6. The last element 6, is placed totally in the communication channel between the casting basin and the sea. The connection joints are completed using two types of water proofing, Gina Gasket and Omega Joint.

Other parts of the undersea tunnel of total length 661m are composed of

Aktio Open Ramp (Cut and Cover), total length 152mPreveza Open Ramp (Cut and Cover), total length 509m. Aktio & Preveza open ramp is constructed following the Cut & Cover Method, that is after the diaphragm walls have been constructed the between of them ground material is removed and the tunnels cross section is completed.

Tunnel Cross Section

The tunnel cross section is rectangular with internal dimensions, width 10,60m and height 6,40m, the available surface for the traffic has width 8,0m (two traffic lanes) and height 5,0m. On the right and left of the traffic lanes a pavement (1,30 width) is been constructed for emergency situations and maintenance works.

Entrance – Exit Ramps

The entrance and exit ramps have a total length of 412m and the same dimensions as the traffic lanes of the tunnel.

Road Approaches and other Road Works

The Aktio road approach has a total length of 925m and width of road surface 9,10m. An exception was made in the Toll Station area, in which the road surface has three lanes in each direction. The Preveza road approach has a total length of 1914m and is composed by the Main Road with total length 1914m, speed limit 80km/h and width 12,50m. Note that the Main road in its total length is covered by an anti-slip layer (4cm thickness).