Milano-Napoli High Speed Rail Link

Location: Bologna, Italy

Dates: 2004-2006

This project involved the design and construction of a new high speed rail link between Milano-Napoli. In particular, a section of the proposed rail link in Bologna passes beneath a number of previously existing railway bridges the most important of these bridges is a nine arch, 19th century masonary viaduct across Via Emilia. It was proposed that the rail link would pass underneath the existing viaduct by the construction of twin shallow overburden tunnels. Tunnel construction was within sandy gravels and was expected to generate large settlements and distortions, exposing the viaduct to serious structural damage and jeopardizing the services on the current Napoli-Roma-Milano railway line supported on it. The observational technique of compensation grouting was adopted as a flexible solution to safeguard the viaduct against adverse settlements.

GCG was engaged to provide specialist technical support to the Asset Owner and Designer. GCG’s remit included the design of compensation grouting works during the preliminary, detailed and construction stages, site support during construction and close-out reporting. For the compensation grouting, curved tube à manchettes (TAMs), installed by directional drilling, were used to provide access for controlled grout injection at a level between the tunnel and the viaduct foundations. The grouting induced heave, which reversed the tunnelling generated settlements. The net result was that the viaduct only experienced small and acceptable settlements and distortions. Real time monitoring was a key aspect of the technique, which allowed proper management of the grouting and tunnelling activities.


Iannotta, F., Pigorini, A., Mair, R. J., Facibeni, L., Harris, D. I., Menkiti, C. O., Leoni, F. (2007). Applicazione della tecnica del compensation grouting per il controllo dei cedimenti indotti dallo scavo di gallerie al di sotto di un viadotto ferroviario. Proc. XXIII CNG – Padova, Abano Terme