ABSTRACT
Water-flow in hard rock-mass occurs through the main tectonic structures and the network of the ubiquitous discontinuities within each RMZ (Rock Mass Zone). A well-done field geological survey and geostructural characterization of these tectonic structures allow to exactly defining the tunnel chainage where they will be crossed by the tunnel, their width and permeability. The case history we present regards a new tunnel 7,528 m long, and with an excavation cross section of 15.87 m, to be executed in the Northern Apennine range. The tunnel will be driven through shales and bedded limestones; the water head can reach several tens of meters. A detailed well-focused geostructural field survey allowed collecting all the features of the ubiquitous discontinuity characterizing the RMZs crossed by the tunnel. Equations proposed in the last years by many authors let it possible to calculate the rock-mass permeability. On this base, by means of numerical analysis (Phase R7© Rocscience Inc.) we defined the water inflow due to the ubiquitous discontinuities along the tunnel. The analysis point in favor of a permeability for the different RMZs in the range of 1*10-5-1*10-8 m/s with a water inflow estimated in the range 1*10-3-1*10-4 l/s/m.
