An integrated geostatistical-geomechanical approach for the characterization of a bimrock

Bimrocks are structurally complex formations made up by a fine-grained matrix including heterometric hard-rock fragments which deeply influence their mechanical behavior. A new approach for characterizing the morphological and spatial variability of rock fragments in bimrocks is introduced, based on the geostatistical analysis of bimrock outcrop pictures through a single-scale variogram analysis of the rock fragment indicator variable IB (x, y). The analysis indicated the presence, all over the field, of a nested structure characterized by three or four common elementary variogram models, each taking into account the variability of a specific size range of the rock fragments. A first attempt was also made in order to investigate the possible correlations between the bimrock strength parameters, obtained through in-situ non-conventional shear tests (BimTests), and the geostatistical indexes, which quantify specific spatial and morphological properties of the fragments, by means of a Cross- Covariance study of non-isotopic regionalized variables (ReV).