Hydraulic characterisation of some arenaceous rocks of Molise (Southern Italy) through outcropping measurements and Lugeon tests

The hydraulic features of Miocene sandstones within the area between the Matese Mountains and the city of Campobasso have been investigated employing two methods. The first method included the analysis of the characteristics of persistent rock mass discontinuities on 12 significant outcrops. The second method included the processing of 125 Lugeon tests on the same rocks. p surveys have provided a model for rock mass characterised by a well-developed persistent discontinuity network, a high frequency of discontinuities and aperture values of generally less than 1 mm. These features correspond to a heterogeneous and anisotropic medium. The discontinuity aperture considerably influences the hydraulic anisotropy and heterogeneity of the sandstones. tests have also clearly shown the heterogeneous nature of the sandstones. Discontinuity aperture and rock permeability have been calculated with reference to the theory of Rissler and assuming a simplified hypothesis for relative roughness. These values (mean value of aperture = 0.35 mm; range of values of hydraulic conductivity = 10− 5 − 10− 2 m/s) are comparable to values determined from surface survey (mean value of aperture = 0.39 mm; range of values of hydraulic conductivity = 10− 6 − 10− 2 m/s).The convergent results obtained from the two methods of investigation are indicative of the complementary nature of the two approaches adopted when the hydraulic characterisation regards the portion closest to the surface of the rock mass.