Project description

Milan Suburban Railway is an almost entirely underground infrastructure crossing the city from North-East to South-East. It integrates the Italian State Railways, Ferrovie Nord Milano and the urban public transport networks, in particular with the three Milan Undergroud lines. CEAS designed about 200 m of blind hole tunnel in the urban area, between the stops of Repubblica and Garibaldi. In this section the two lines got closer gradually separating and the tunnel sections included a first double track part with about 10 m of net section, followed by a second double track part with 13.74 m span. The last part included two single track tunnels with 6.02 m span. The consolidation and excavation project included in the tender project had to be basically reviewed due to a great rising of the water table level during the first work steps. It involved a low water table head that could be coped with through reinforcement and waterproofing injections from pilot hole. Therefore, the excavations were made below the water table head more than 6 m from the excavation bottom level. This required reinforcement and a preliminary lining specially designed to supply the necessary watertightness and resistance to buoyancy.