Bologna Tunnels

The project comprises two 6.1-km tunnels for which two Earth Pressure Balance tunnel boring machines of 9.4-m diameter were used. The excavation of the tunnels in an intensely urbanized context and the heterogeneous ground conditions required a particular methodology in order to minimize the effect on the existing structures and facilities on the surface. 

This project featured the world’s first experiment with earth-consolidating injections and compensation with guided boring along a curved line. Other innovations included metal rings with doors for connecting galleries, designed by ACCIONA.