ABSTRACT

The central section of new metro line M4 in Milan cross an high-density urban area with a lot of issues cause by historical and archaeological building, one of the most complex case is the St. Ambrogio station. The initial solution for the connection between existing metro line M2 and the new one M4 in St. Ambrogio station was to build a 100 m long rectangular open-air tunnel placed above and practically on the same axis with the existing tunnel of M2 built in the 80s with a traditional excavation method, with a gap between the two facilities being quite strait, of about 1.50 m. Such a solution created problems for the further development of the overall project in terms of the traffic/construction site organization, because the connection had to be placed exactly along an important traffic corridor making part of internal ring road of the city of Milan. An alternative engineering and architectural solution has been developed in collaboration with the archeological supervision authorities. The integration and utilization, in the tunnel connecting M2 and M4, of the belowground part of the complex of Pusterla of St. Ambrogio, built in XII century a.C. and under protection of the archeological supervision authorities, helped to avoid a complete surface traffic block, to resolve a number of critical issues from the geotechnical and structural points of view, and to revaluate the archeological site that was incorporated into the connection between the M2 and M4 metro stations.