Mitigation of the effects induced by shallow tunneling in urban environment: The use of 'compensation grouting' in the underground Line B1 works in Rome

The new Underground Line B1 works in Rome involve the construction of three new stations and of about 7 km of single-track tunnels (i.d. 5.80 m) by means of two TBMs. The tunnels must be realized in heavily built-up areas, often with multi-storey buildings, both in masonry and in concrete. In the stretch near Bologna Station of the already operating Line B, the tunnels run at only few meters from building foundations. The settlements analyses carried-out in the design stage indicated the necessity of mitigation measures. Environmental constraints, building characteristics, geometric and geotechnical situations directed the choice towards the 'Compensation grouting' method as the best mitigation measure. Numerical analyses and one trial-field were used for exhaustive design definition. At the end of September 2010 the first tunnel under compensation grouting area was completed and the in situ monitoring data confirm the effectiveness of the chosen mitigation. © 2012 Taylor & Francis Group.