Investigation of block geometrical properties of the Shale-Limestone Chaotic Complex bimrock of The Santa Barbara open pit mine (Italy)

The exhausted Santa Barbara open pit mine (Tuscany, Italy) has some high slopes excavated in the Shale-Limestone Chaotic Complex Formation (SLCC). The slopes suffer large gravitational sliding movements. From a geotechnical point of view the SLCC can be classified as a typical block-in-matrix rock (bimrock), made up of a gray scaly-fabric clayey matrix including heterometric calcareous blocks. Since the geometrical dimensions of blocks influences the mechanical behaviour of a bimrock, an accurate study was carried out in order to determine these properties by means of indirect non-destructive characterisations: image analysis and geostatistical approach to the data. The volumetric ratio between blocks and the matrix is also investigating by means of in-situ large sized sieving tests.