In situ non conventional shear tests for the mechanical characterization of a bimrock

Six non conventional in situ shear tests were carried out in order to investigate the strength properties of the Shale Limestone Chaotic Complex bimrock at the Santa Barbara disused open-pit mine. The testing procedure ensures that the failure surface is free to develop in a tortuous way along block/matrix contacts, thus allowing for the evaluation of the bimrock strength parameters by taking into account the influence of blocks, and ultimately to overcome the size limitation of laboratory specimens. The evaluated operative strength parameters show an overall larger friction angle and a lower cohesion compared to that of the clayey matrix, in agreement with the common bimrock mechanical behaviour.