The 680km long Egnatia highway in Greece is gradually coming on stream. There have been some delays due partly to the extremely challenging ground conditions along the route, as well as archeological holdups and difficulties with the country’s sometimes Byzantine public works contract procedures. Environmental issues including protection of the habitat of rare European brown bears have also caused delays.
The route should now open in 2008 rather than 2006 as reported in T&TI three years ago (T&TI, May 2001). “But we are opening about 80km of new road every year, which is on schedule” emphasises Guy Hindley, project director for client and project control company Egnatia Odos and one of only 12 ex-patriate staff remaining at the organisation. Eight years ago there were 30 staff from consultant KBR [Kellog Brown & Root], which was appointed in 1995 by the Greek government to help create an organisation able to run such a huge scheme, both in design and construction, and eventually in operation. But as confidence has grown the outside advice has been scaled back.
And it is a huge scheme, nearly 700km of dual-two lane motorway running from Igoumenitsa port on the Adriatic coast, via Greece’s second city Thessaloniki, to Alexandroupolis port and eventually the Turkish border (figure 1).
On the way, it crosses some of Europe’s most difficult terrain, foremost being the Pindos mountain range, the “Greek Alps”, which rise to around 3000m, but also other high ground near the west coast and close to Thessaloniki. The region suffers from multiple landslides and slope instability as well as one of the highest seismicities in Europe.
The fertile but soft alluvial flood plains around Thessaloniki are a different challenge and then there is flatter ground to the east along the coast, though not without its own problems, including the crucially important Nestos river and its environmentally significant estuary.
Work on the project has moved focus since T&TI previously visited Greece. Much of the east sector from Thessaloniki is now running traffic and only the Nestos delta region and a section between the river Strimonas to Agios Andrea interchange at the west junction of the Kavala Bypass, are awaiting work. This latter section in fact includes one of the larger tunnels on the project, 1650m that would enable the road to take a more direct inland alignment. However, no funding has been agreed for the section says Hindley.
“They have not even done detailed design for the link yet” says Nikos Kazilis, Egnatia Odos’ head of tunnelling, “though we are about to let that and it will be starting soon.”
Interest in the west
Nearly all the tunnelling interest however is in the west where the majority of the project’s 77 mostly twin bore connections are needed to allow the road a modern, relatively straight, alignment through the mountainous areas. Some 15 of these are in a steeply climbing section of the road where it leaves the Thessaloniki plains heading westwards from Veria to join the already completed road at the Voskohori junction.
Three of the tunnels are cut and cover sections while the other dozen, ranging from 250m long to over 2km, are driven twin bores, each 80m2.
Like virtually all the tunnels on the project, the work has been done using drill and blast in staged excavation, usually with a top heading and bench, and in some places a two stage bench.
Much of this total 26km section is now complete, or nearly so, and it should be open by the end of this year, connecting the road all the way through to Grevena from the east. The section continuing the road across a central plateau has been open for some time, part of it for several years.
The biggest of the tunnels is a curved 2.1km long drive through the opheolites, gneiss and granites and despite a number of minor issues driving went well says Kazilis.
“The contractors have done pretty well given the constraints” adds Terry Jones, construction manager for this section. On the ground, management has been subcontracted to various consultants including in this case Parsons. Recent new contracts however will have direct construction management by the Egnatia Odos team itself, part of building up the overall experience of the organisation.
Geology for many of the tunnels was difficult with no really “massive” rock and in poor quality limestone or schists. The toughest tunnel on the section was a shorter one, designated simply Sigma 3 and found to be in a moving landslide. It suffered up to 400mm vertical and horizontal movement during construction. Heavy anchoring and grouting was needed inside the tunnel to stabilise it and also a row of substantial bored piles further up the slope, also anchored back at the top. “It has stopped moving” reassured Kazilis.
The next significant sector for tunnels occurs in the heavily wooded hillside forests beyond Grevena where a 35km long section of the route is still in preparation. The link crosses the habitat of the brown bear and was subject to extended legal and protest battling. Though a longer alternative route of some 60km was eventually ruled out, the agreed 35km alignment will now include 22km of tunnels and 6.5km of bridges.
Detailed design work is in progress and the bidding process will begin shortly with work to start next year. This section is likely to be one of the last to be completed in 2008.
Beyond the bears the road climbs again into the Pindos mountains where some of the longest and the most difficult of the tunnels have been located. The road leaps from valley to valley through the steep pass beyond Metsovo, heading towards the historic lakeside town of Ioannina.
Once again access problems and tough winter conditions have been major challenges, though in this area geology has come even more to the fore. Among the problems faced, even in the relatively good rock, has been areas or tectonic shattering, faulting and sometimes extraordinary degrees of twisting and changes in direction of the bedding.
Inevitably it means contractors have faced unexpected ground in most of the tunnels. “It is simply not possible for the designers to have taken rock and borehole samples every few metres,” says Hindley.
Among the most difficult issues has been squeezing ground. Small sections were encountered in the Driskos tunnel, the longest of all on the highway at 4.6km, and much more significantly in the shorter Anthochori.
The Driskos, which is the last of the bored tunnels before Ioannina, was a fairly straightforward if still largescale construction says Kazilis, and was drill and blasted mainly through Greece’s flysch, a particular rockform with alternating bands of siltstone, sandstone and conglomerate. It can be difficult enough especially as the rock is highly folded and the cover relatively high for the project at over 200m.
It is a job that was well organised and speedily implemented he says, by one of Greece’s best known contractors Aktor, which was subcontracted to a group of four other contractors, Efclides, Themeliodomi, HellinikiTechnodomiki and Pantechniki. Such separation between contract funding and implementation is commonplace in the Greek environment.
“We were expecting some squeezing ground and found it in short lengths” says Kazilis, “a 50m section in one bore and 200m in the other.” The squeezing developed slowly and resulted in cracking of shotcrete and buckling of steel members, “and we needed to come back and install extra support including prestressed anchors extra shotcrete and improved grouting.”
Lining work is currently underway on the second bore of the tunnel and a contract for completion – the initial contract did not cover the full extent of works – is due to be let very shortly.
Much greater difficulties have been experienced on the shorter 660m long Anthochori tunnel, back towards Metsovo, which experienced problems almost as soon as work began in 2000 with extensive deformations within the first 180m. Settlements were up to 360mm and horizontal movements as much as 200mm, with consequent overstressing of rock bolts, buckling of steel and cracking of the shotcrete.
“Our two expert advisers, Professor Paul Marinos and Dr Evert Hoek have described this as the most difficult tunnel in Greece” says Kazilis. “It has a medium overburden of about 90m but the geology is difficult – a flysch which is heavily sheared particularly in a 10m tectonic collision zone.”
Large sandstone boulders were initially thought to be usable as a solid rock mass but in practice were all floating. It was necessary to redesign, and eventually the five level support classification was abandoned because of frequent changeability, finally using just one heavy support.
“We also had a dispute with the contract in the first revision because it meant changes in the method of working, to forepoling, and a second design was produced. This used heavy support, 400mm of shotcrete and a temporary invert.”
Much of the tunnel has been completed and 70% is concreted says Kazilis, even while excavation is finishing at the centre. Along with four other tunnels and a number of high bridges this means an 8km length of the motorway will be open to traffic next year.
Lessons from these tunnels and earlier work have been incorporated into new methodology (T&TI, November and December 2000), which is informing the design for the 2km Anilio tunnel that continues the road eastwards from Metsovo.
Excavation at both ends has been largely completed but a 600m long central section, again in sheared flysch and with with over 220m overburden, is expected to suffer major squeezing and is being let as a separate contract. “It will use sliding sets for the first time in Greece,” says Kazilis, “a yielding support, which telescopes to allow high deformation.”
Meanwhile, a different problem besets two tunnels furthest towards the western end of the project, close to Paramithia. Here the contractor must deal with a limestone so shattered it comes in very small blocks and in places is so fine it is a flour texture. “It has no cohesion,” says Kazilis “and so you have to add it, essentially by forepoling and grouting.” The shorter of two tunnels, Sigma 2 has 40% of its 480m completed to primary lining and the longer 1100m tunnel has 60% complete.
“But the initial contracts were never going to be sufficient to complete the tunnels” says Kazilis. “New contracts have just been let, after some delay, for completion.”
