An application of geostructural and seismic investigations in a granite quarry in Sardinia, Italy

In Sardinia most of the granite quarries occur in the north-eastern region (Gallura) though several are presently unexploited because of rockmass heterogeneity. Indeed their exploitation and productivity is strictly related to the compositional homogeneity and mechanic parameters of the stone quarry. The present study was carried out on a granite quarry in the Bassacutena district in order to assess the suitability of the raw materials for exploitation by integrated geostructural and seismic investigations. Detailed investigations evidenced the chemical-mineralogical homogeneity of the rockmass. A surface geostructural study was performed to define the geometric features (orientation, spacing, persistence and filling) of the discontinuities and provided the basis for seismic refraction investigations. The results showed the heterogeneity of the granite rockmass, which was due to an increase in the discontinuities in some sectors. In this context, refraction seismic techniques have allowed to predict in depth the rockmass quality for exploitation purposes. The interpretation of the refraction seismic profiles carried out on a partially exploited sector of the quarry, showed that the rockmass quality improves at a depth of a few meters. From the results of the integrated analysis of the surface geology and from the structural and seismic data so far obtained, it seems that this multimethod approach can be an efficient investigation tool to locate the sectors that can be more productive, thus allowing proper planning of the exploitation activity.