Back-fill grout with two component mix in EPB tunneling to minimize surface settlements: Rome Metro-Line C case history

摘要

The instantaneous filling of the annulus created behind the segment lining at the endof the tail shield during TBM advance is an operation of paramount importance. Its main goal is tominimize displacements around the tunnel and induced surface settlements due to lost volume at the tailshield. For correctly achieving these goals, the simultaneous back-filling system and the injected materialshould satisfy technical, operational and performance characteristics. The two-component injectionsystem for back-filling while excavating with shielded TBMs is progressively replacing the traditional useof cementitious mortars.In the paper different systems of back-filling grout and in particular the two-component system areanalyzed and discussed together with a description of the Rome Metro (Line C) case history where thistype of back-filling was widely applied.