Load path dependent static moduli and AE activity of a granite sample containing pre-existing damage

ABSTRACT: Static elastic moduli and acoustic emission (AE) activity are observed for a granite sample inferred to contain a pre-existing localized fracture. Bulk modulus, Young's modulus and Poisson's ratio are calculated along distinct load paths of varying mean and differential stress. The sample failed unexpectedly at a stress of nearly one fourth that of similar samples of the same granite material. Comparison with previous experiments along the same multipath testing routine shows significant differences in the elastic response of the sample included in the current experiment, including initial lower values of Young's moduli and higher Poisson's ratio. Bulk moduli however, especially during hydrostatic loading, remained consistent between experiments. AE data suggest the existence of a pre-existing localized fracture from a planar alignment of located events. This corresponds to the failure plane of the sample once it was recovered from the testing apparatus. The discrepancies between the three static elastic moduli are attributed to this presence of pre-existing damage, providing methods for detecting macroscale damage in experimentally tested samples using elastic response which are validated though the use of AE. This work highlights the dependence of compliance to damage and complexities associated with predicting behavior of damaged materials.