The tunnel was excavated partly in a trench, for short sections at the entrances, then backfilled, and partly in a blind bore, within a very deep and extensive paleo-landslide mound. The tunnel is, relativeto the slope, generally parallel to the wall, given the great steepness of the overlying slope, as well as of low coverage. The tunnel was afflicted by significant deformative and fissuring phenomena that strongly conditioned the transit of trains. The proposed intervention consists essentially of reshaping the tunnel, following advanced consolidation of the surrounding ground according to the following phases:
- creation, through injections of specially designed chemical mixtures, of a self-contained, cylindrical shell-shaped, waterproof screen, external and coaxial to the lining;
- sealing of the cracks on the intrados of the current lining to prevent internal leakage of the aforementioned cement injections, as well as preventing external leaks with the aforementioned closed shell;
- creation of a thick resistant shell through cement injections within the aforementioned cylindrical crown between the current lining and the remote barrier;
- milling of the old lining to achieve the desired shape for the cavity; this last dimensioning implicitly includes the goal of obtaining, for the entire development of the work, a sufficiently large regular section to allow for the planimetric and altimetric adjustments that will be necessary in the coming decades;
- formation of a new thin, resistant, elastic inner lining, composed of shotcrete and electro-welded mesh, to make up the finished surface of the new lining
