Athens Metro Line 3 Extension, “Agia Marina – Dimotiko Theatro” Section

Construction shaft with steel bracing, scaffolding, and a tower crane overhead

Location Athens, Greece

Project Duration 2012 – 2015

Industry Infrastructure Transportation

Client J&P AVAX, GHELLA SPA and ALSTOM TRANSPORT / ATTIKO METRO S.A.

Temporary Excavation Support Design, NATM Tunnel Works Design for the Athens Metro Line 3 Extension, “Agia Marina – Dimotiko Theatro” Section.

Technical Details

Metro Line 3 Extension “Agia Marina – Dimotiko Theatro” includes a 7.6 km long tunnel, six (6) new underground stations and seven (7) ventilation shafts. The Design and Build Project was commissioned in two phases in 2019 and 2022.

Obermeyer was appointed by the Design & Build Contractor as the nominated Consultant for Geotechnical Evaluation, Temporary Excavation Support Design, and Tunnel Works Design. The scope included the provision of geotechnical engineering services for the following stations, shafts, and associated structures:

Agia Varvara Metro Station
- 4-level Cut-and-Cover Station
- 415m-long retaining pile walls with a maximum retaining height of 30m

Aerial view of a deep urban excavation with concrete retaining walls, excavators, and a temporary access ramp — Aghia Varvara Metro Station - Main C&C Box

Deep excavation site with retaining walls, excavators, cranes and workers in a dense urban area — Aghia Varvara Metro Station - Main C&C Box

Korydallos Metro Station
- 4-level Cut-and-Cover Station with two independent Cut-and-Cover entrances
  - 340m-long retaining pile walls with a maximum retaining height of 30m for the main excavation and 145m-long pile walls with a maximum retaining height of 20m for the entrances

Aerial view of a night-time excavation site with retaining walls, earthworks, and construction machinery — Korydallos Station - Main C&C Box

Construction site with a tower crane, excavator, retaining walls, and a large concrete excavation in an urban area — Korydallos Station - Main C&C Box

Nikea Metro Station
- 4-level Metro Station comprising an 83m-long Cut-and-Cover Station Box, a 36m-long NATM Tunnel at platform level, a 57m-long Ventilation Tunnel, and two independent Cut-and-Cover entrances
- Retaining pile walls totaling 350m in length (240m for the main station box and 110m for the entrances)
- Platform Level NATM Tunnel (15.50m wide, 12.00m high) and Ventilation NATM Tunnel (7.6m wide, 6.7m high) excavated in stages under low overburden

Excavator and worker inside a tunnel excavation supported by concrete lining — Nikaia Station - Platform Tunnel

Tunnel excavation with workers and a boom lift inside a bored tunnel — Nikaia Station - Platform Tunnel

Excavated construction pit with excavators, retaining walls, and workers in safety gear — Nikaia Station - Main C&C Box

Dimotiko Theatro Station
- 4-level Metro Station comprising a 75m-long Cut-and-Cover Station Box, a 47m-long NATM Tunnel at platform level, two 44m-long access stair tunnels (concourse to platform level), two independent Cut-and-Cover entrances connected to the main box via tunnels, a 13m x 14m ventilation shaft, and a 31m-long ventilation tunnel
- Retaining pile walls totaling 534m in length (300m for the main station box, 160m for the entrances, and 74m for the ventilation shaft)
- Platform Level NATM Tunnel (16.20m wide, 13.20m high), Ventilation NATM Tunnel (7.6m wide, 6.2m high) and Access and Entrance Tunnels (8.0m wide, 7.3m high) excavated in stages under low overburden
- Custom-designed recesses were incorporated into the entrance tunnel walls to securely house archaeological discoveries within the site area
Ventilation Shafts (Taxiarchon St., Megalou Alexandrou St., Komninou St., Pisidias St., University Area)
- Approximately 30m-deep shafts retained using pile walls or shotcrete walls
- NATM ventilation tunnels connecting the shafts to the main metro tunnel

Looking up inside a concrete bridge pier under construction with scaffolding and a crane in the background — Dimotiko Theatro Station - Ventilation Shaft

Construction site with steel reinforcement in a concrete trench and two workers on the slope — Dimotiko Theatro Station - Entrance C&C

Urban construction site with deep excavation, retaining walls, cranes and surrounding apartment buildings — Dimotiko Theatro Station - Main C&C Box

Excavation pit with concrete retaining walls, excavator and crane in an urban construction site — Dimotiko Theatro Station - Main C&C Box

Services Provided

The geotechnical engineering services encompassed:

Surveys:

Elaboration of geotechnical reports and interpretative models to characterize ground conditions as well as geotechnical risk assessment
Estimation of ground settlements and displacements due to deep excavations and tunneling works in urban environment

Design:

Detailed Design and analysis of temporary retaining structures
NATM tunnel detailed design and analysis
Detailed Design of associated works (steel struts, retaining walls, tunnel linings)