ML – Metropolitano de Lisboa
Geological and Geotechnical Study
Work’s Geotechnical Consultancy
The Lisbon underground station, located at the Terreiro do Paço, lies in the prolongation of the blue Line (Baixa-Chiado and Santa Apolónia). The station has a total length of 144m and a width of 24m. The excavation has a maximum depth of 28m, having a thick alluvial soft clay of about 22m, with the water table near the surface.
The peripheral secant pile wall consists of primary and secondary piles Ø=1,5m, distance away between axes of 1,75m and 35m of length, reinforced concrete crow beam, reinforced concrete lining with 0,8m thick and a raft of 1,7m thick. The peripheral wall was propped by five levels of steel struts strongly prestressed. In the wider area of the station, an additional slab of jet grouting with 3m thick was installed between 18 and 21m depth, disposed between the existing tunnel, previously filled with lean concrete, and the longitudinal pile wall.