An Experimental Study on Damage Propagation of Intact Granite

Microcracks during complex loading could result from the tensile stress concentration around such flaws as grain boundary microcracks, intracrystalline microcracks and microcavities. Therefore, detailed knowledge about microcracks substantially contributes to the interpretation of damaging process, microcrack-induced dilatancy and failure in intact rock. In the present study, a direct observation of actual damage propagation in intact granite specimens which are cut from a block of coarse grained granite was carried out by a newly developed experimental system. Microscopic observation shows that an incipient micro-damage is generated at two grain contact portion due to elastic mismatch of the two grains, and their morphologies are parallel or subparallel to the axial stress direction. The detailed observation of an incipient shear fracture in a granite specimen suggests that the fracture is formed by the coalescence through the inclined grain boundaries of links between echelon intracrystalline microcracks.