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Technical Visits

Technical Visits

WTC2023 Technical Visits

WTC2023 would like to invite you to take part in the technical visits on Thursday 18th of May and enjoy the experience of touring the most exciting tunneling and underground excavations projects that are currently taking place in Attica.

Technical Visits

on Thursday 18th of May

1. Athens Metro Line 4

The first phase of Line 4 (from Alsos Veikou to Goudi areas) is being constructed fully underground by the joint venture “AVAX AE – GHELLA SpA – ALSTOM TRANSPORT SA” following a tender award on 2021 from the Project Owner ATTIKO METRO S.A.

Main features of the Project

  • 8km line: double track TBM tunnel
  • 15 underground stations with platform screen doors
  • 9 intermediate or terminal shafts
  • 2km underground forestations, underground trumpet structures and connecting tunnels
  • A new Operation Control Center
  • A new repair workshop in the existing Depot area
  • Underground Train stabling and maintenance yards at both ends of the Line
  • Transfer connections at two existing Stations (Line 2 & Line 3)
  • 20 new 4-car automated driverless trains.


The Project’s estimated cost is 1,510,000,000.00 € and the estimated delivery time is 96 months.

Among the technical challenges of this Project is TBM tunneling under existing Metro tunnels and excavation of new stations close to operating Metro stations whose safety and activities should remain unaffected. Furthermore, boring or digging under or next to high buildings, sometimes old or historical ones in the city center, has to be performed securing their structural and serviceability standards. The risk of coming across archaeological findings during excavation works is always high in the Athens area and the issue of how to protect them while not impeding the works is of great importance.

The tour will start with a presentation of the Project at a construction site office. Delegates will then visit a number of worksites to view tunnelling works and construction of stations, shafts etc.
It is expected that by the time the Technical Visits take place, TBM tunneling works will have started and construction of cut & cover structures (stations, vent. shafts) as well as conventional tunneling will be in progress.

Photo Gallery

2. Underground Construction of National Railway Line in Athens

The Greek Public Railway Construction Company (ERGOSE) assigned in 2018 the construction of a four-track rail corridor, 2.36 km long of which approx. 1.9 km is fully underground, starting from the Athens Central Railway Station and ending at Sepolia area, in Athens Municipality. There the line connects to the new four-track rail corridor which was recently completed and opened to traffic. The rail corridor mostly runs within the occupation zone of the existing open air train tracks. The east half of the four-track corridor will serve suburban trains, whereas the west half will be used mainly for intercity services.

The project schedule has to provide for a number of constrains such as maintaining the existing surface train operation, safe construction close to adjacent buildings, close overpassing a Metro running tunnel and a Water Authority (EYDAP) culvert. The integrity and serviceability of all those structures is to be secured during the works, therefore modern instrumented monitoring is implemented.

When finished, the surface area above the underground corridor will serve 9 vertical streets which are currently interrupted due to the on-ground corridor. Moreover, landscaping will provide citizens with recreation areas of green (trees, shrubs).

Works are in full progress by the Contractor “J/V  INTRAKAT SA – SIDIRODROMIKA ERGA ATE” and Phase A is to be completed by 2024, while the whole project will be delivered by the end of 2025.

Following a brief presentation of the Project, we will visit a worksite to see construction work of the underground part of the Line. It will be a half-day visit.

Photo Gallery

3. The Hellinikon Project – Underground Coastal Road

The revitalization of the former Hellinikon Airport area is the biggest project of its kind in Europe and the most ambitious development project ever undertaken in Greece that will positively impact the local and national economy. It combines urban development, recreation facilities, a huge metropolitan park and seafront full accessible to the public. Access through metro and tram lines will be assured while the existing road along the shoreline will be reconstructed to become fully underground.

The Project of the Underground Coastal Road was assigned by the Owner LAMDA DEVELOPMENT to the Contractor AVAX SA and excavation works have already started. The underground road will begin at the area of Alimos and rise to surface at Ag. Kosmas marina. The purpose of this Project is to allow connection of the seashore front to the rest of the Hellinikon area.

The tour includes presentation of the Hellinikon Project at the Company’s office and then walk the delegates around the various worksites in the area especially in the underground coastal road.

Photo Gallery

4. DionyssoMarble – Underground exploitation of Pentelikon Marble

The famous marble that was used for the construction of the Parthenon in the 5th century BC is a deposit in the Mt. Pentelikon in Attica, about 20 km from Athens. In the ancient times, the huge pieces of stone had to be hauled to the building site by oxcart. The roadway used was a continual downhill, and followed the natural inclination of the land.

Pentelikon marble is currently exploited by Dionyssomarble who holds a leading position in the production, processing and trade of marble and other ornamental stone, marble dust and calcium carbonate filler. The increased demand for dimension stone in combination to quarrying in an environmentally sensitive area, has led the company to exploit part of its deposit using underground methods to minimize their environmental footprint.

To achieve this goal, the company participated in a three-year research program of the European Union, in the period 1999 – 2001. In cooperation with academic institutions and mining industries from EU countries, an integrated methodology of planning and programming for underground marble mining was developed.

The exploitation method is room and pillar with openings up to 15 meters wide, while the maximum height of the excavations is 30 meters. Following studies and simulations in collaboration with the School of Mining Engineering of the NTUA, preventive support measures (anchors) are implemented.

During the visit at Dionyssomarble, there will be an initial briefing by the company on site, its history and achievements and description of both the surface and underground mining methods. A visit to the quarry with emphasis on the underground excavations area will follow. A visit of the processing plant and the exhibition will conclude the excursion.

Photo Gallery