— Project Description:

The underground section of Line 2 crosses a portion of the city center of significant prestige and includes 4 underground stations, approximately 2.9km-long, twin tunnels to be excavated with TBM, a launching and a retrieval shaft. The ground conditions are very heterogeneous consisting mainly of alluvial deposits with generally poor geotechnical characteristics and very high water table. The tunnels (9.70m of excavation diameter) have an overburden ranging from 10 to 28m and a groundwater pressure up to 3.5MPa. Stations are conceived with diaphragm walls with thickness ranging from 1.00 to 1.50m, strutted up progressively using a top-down construction method and with no use of soil anchors. Bottom plug typically with jet grouting columns is also included. Ventilation is managed from the station with no need for additional inter-station ventilation shafts. One of the interesting aspects of the project is the request of the public owner NCA to guarantee a minimum of 70% of the volume of excavated material to be routed to the disposal sites via sea barges for which a study has been undertaken.

— Description of Services:

Geodata Engineering has provided the tender design for all the civil works (including geotechnical, hydrogeological and surface water management), architecture design, alignment design, station equipment and tunnel ventilation study as well as the risk analysis and planning.