Analysis of the block-size distribution in the Shale-Limestone Chaotic Complex (Tuscany, Italy)

The Northern Apennine chain in Italy is characterised by scattered outcrops of many oligo-miocenic clay-limestone melanges. The Shale-Limestone Chaotic Complex (SLCC) is one of these melanges and it outcrops in the Valdarno Basin, eastern part of Tuscany. From a geotechnical point of view the SLCC represents a typical bimrock, made up of a highly sheared and tectonized, scalyfabric, clayey matrix containing marly-calcareous blocks from a few millimetres to tens of meters in size, randomly distributed. In this paper focus is given to high artificial slopes (a few hundred meters) of a dismissed pit-mine cut in the SLCC bimrock. An accurate characterization of the block size distribution in the matrix was carried out by means of photographic surveys on natural and artificial outcrops, that allowed a high number of georeferenced images to be collected. Images were analyzed with an image processing technique, providing important indications about the block-size distribution in the studied bimrock.