ABSTRACT
Permeation and fissure grouting techniques were applied to volcanic rocks and soils within Rome and Naples metro projects to solve two difficult tunnelling problems. Two case studies are illustrated, both relevant to the widening of station platform tunnels starting from twin TBM tunnels, in the presence of improved soil by grouting. The first is relevant to Giglioli and Torre Spaccata stations at the new Metro Line C in Rome, where four platform tunnels were excavated through an alternation of pyroclastite and tuff, with a hydrostatic head of 5 to 8 m. The second case study is relevant to Duomo Station at the extension of Metro Line 1 in Naples, where four platform tunnels were excavated within Neapolitan Yellow Tuff, under a hydrostatic head of up to 30 m; at the same station four further tunnels for pedestrian access were excavated under the same conditions.
