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

On the whole Line B1, the typical excavated soils consist of fluvial-lacustrine recent sedimentary formations. The geological sequence comprises a base deposit of fluvio-palustrine gravel of Pleistocene age, overlain by a layer of clayey silts and sandy silts, both of Pleistocene age. Frequent and relatively deep ancient ditches filled by alluvial silty-clayey and sandy deposits cut into the Pleistocene deposits. A layer of made ground of varying thickness including relicts of ancient structures covers everywhere the natural soil profile. The piezometric level is few meters below ground level.