Greece enlightening: Queen's Geology Engineering goes to Greece
From December 2nd to 7th, 2012, five Queen’s University students from the Department of Geological Sciences and Geological Engineering travelled to Greece for a technical tour of the geology, design and construction of tunnels with Dr. Nicholas Vlachopoulos of the GeoEngineering Centre in Kingston.
The Kingston ‘contingent’ joined approximately 30 Greek students from the National Technical University of Athens, the Aristotle University of Thessaloniki and their respective professors, Dr. Paul Marinos, Professor Emeritus, and Dr. Vassilis Marinos, Lecturer.
The professors are experts in the world tunneling profession and have extensive experience with the tunnel sites visited on the tour. Throughout the trip, students learned about industry-standard rock classification techniques and how to assess support for tunnels from the individuals who have been setting those standards.
The tour began in Athens and wound around the Greek mainland with overnight stops in Kamena Vourla, Platamonas, Thessaloniki, and Metsovo, before returning to Athens. S
everal sites were visited each day to allow students to observe tunnels in various stages of construction – from portal construction to completion – in the wide variety of ground conditions present across the Greek landscape. The map below shows the sites visited on the trip.
In very broad terms, tunneling conditions in Greece can be divided in to three major regions: the south, the northeast and the northwest. In the south, tunnel design must account for seismic activity, including crossing active fault zones. In the northeast, strong rock can change to weak rock and back again over very short distances due to the effects of weathering.
The northwest has rock types typical of Greece – including flysch and molasse, more on these later – which were encountered along the 670 km long east-west Egnatia Highway (or “Odos” in Greek) built across nearly every geological zone in the country. Stops in all three regions afforded students the opportunity to observe first-hand the rocks, ground support methods, and in a few cases, the construction process that went in to building the tunnels.
In the south, the Kakia Skala highway tunnels follow a rugged coastline formed along steep, active faults oriented parallel to the coast. “Kakia Skala” translates to “Evil Staircase”, for mythology tells of a man named Sciron who threw people off the steep cliffs into the sea below, until Theseus, a founder-king of Athens, arrived and defeated the tyrant and threw him into the water.
Thanks to careful investigation and planning, the tunnels do not cross the faults along this section of highway, and the tunnel continuity will not be affected by seismic events. North of Athens, on the Greek National Road 1, the Knimidas tunnel crosses a fault zone that experts have predicted could undergo up to 0.15 m of vertical displacement over the tunnel’s design life. This predicted movement was incorporated into the design by over-excavating around the tunnel, and then back-filled; if the fault moves, the concrete lining can simply be ground down, smoothed out, and the tunnel quickly reopened.
At the Olympus Mine project in the Chalkidiki region in the northeast, gold mining works are being developed and several tunnels are being excavated to facilitate these operations. Because of the tectonics in the area, rock previously located and weathered at the surface has been thrust down to tunnel depth in places. This can create extreme strength variations in the rock over short distances, making it very difficult for miners to predict what type of ground support will be required as the tunnel face advances. To anticipate upcoming ground conditions, the face is carefully inspected by geologists who record subtle changes in the rock after each 1m excavation step.
From Thessaloniki, the students travelled southwest towards Metsovo, following the recently completed Egnatia Odos - part of the trans-European road network - through many of the 100 kms of tunnels along the highway alignment. The project roughly follows the first Roman road built outside of Italy in the 2nd century B.C. and parts of the original pavement were encountered during construction.
Though the concrete linings of the finished tunnels prevented direct observation of the ground conditions, there were many rock cuts along the highway that afforded students a glimpse of the rock the tunnels were excavated through. These cuts included flysch: a sequence of siltstones and sandstones deposited in front of a future mountain chain and subsequently thrust upwards by tectonics, and found widely in Greece. Typical support requirements for tunnels in this rock type were discussed.
While the main north-east to south-west route of the Egnatia project has been completed, many north-south access roads are still under construction. The students saw the beginnings of the Ieropigi Tunnel, part of the road which will provide access from Albania to the Egnatia Odos. The tunnel is being excavated through molasse – a sedimentary rock sequence of siltstones, sandstones and conglomerates deposited in a tectonically ‘quiet’ zone behind a mountain chain. This rock type is uncommon in North America, but typical of Greece.
In addition to observing tunnel building in a variety of rock types, other issues affecting tunnel construction were also highlighted.
In Thessaloniki, the tunneling for the metro is proceeding relatively uneventfully; metro station construction, however, has been significantly delayed as archaeologists catalogue 2,700 years’ worth of the city’s history encountered as excavations proceed to the depth of the metro tunnels.
Along Egnatia Odos, designers were tasked with planning a road through rugged mountain terrain. However, slow-moving landslides along the originally proposed route necessitated realignment of certain sections where stabilizing the landslide wasn’t feasible. The options considered in these cases were either placing the road on the opposite side of the valley, often necessitating impressive bridge structures, or constructing long tunnels in the stable rock behind the moving ground. Many of these slide zones were pointed out to the students to explain external factors that contribute to the ultimate road location.
As part of this international technical course, the students also experienced a cultural exchange with their hosts. The Canadians were consistently impressed with the generosity and warmth of the Greek people, as well as their love for experiential learning.
Of particular note was the Greek ‘Name Day’ tradition, where individuals with a shared first name of a Saint, on that Saint’s calendar day, were expected to provide treats for all others (akin to a reverse birthday). As St. Nicholas’ day is on December 6th, a generous selection of treats was presented over the course of the day, as there were 3 Nicholas’ in the group, and a few others encountered en route!
By any measure, the course was a success. It is practical opportunities like these that make the educational experience at Queen’s exceptional, and help to create well-equipped future leaders.
Learn more about the Queen's Department of Geological Sciences and Geological Engineering.