Relationships between some geotechnical properties of the Genoese area's clayey rock formations and the instability problems that affected the historic tunnels between Polcevera and Scrivia Valleys (Ligurian Appennines) [Relazioni fra alcune caratteristiche geomeccaniche delle formazioni argillose del genovesato e le problematiche evidenziate in gallerie storiche fra le valli Polcevera e Scrivia (Appennino ligure)]

The results obtained during the first part of a study focussed on the geomechanical characterization of the clayey rock masses outcropping in the Polcevera Valley, in the Genoese area, are presented in this paper. Since 1852 a great number of railway and highway tunnels have been bored inside them. Many of these tunnels have been affected by serious instability problems both during the tunnelling and afterwards, caused by the pressure acting on the lining. The study, so far, includes mineralogic/petrographic analysis and Point Load Tests on both surface and underground rock samples. The results of the mineralogic and petrographic analysis suggest that the studied formations would be characterized by a visco-plastic behaviour (squeezing rocks) rather than, as previously believed, by a swelling behaviour (swelling rocks). The Pont Load Test’s results allows to estimate the uniaxial compressive strength’s characteristic range of the different types of rocks forming the clayey formations. The carried out analysis constitute only the first step of a series of investigations that could lead to a geotechnical zoning of the area.