Damage evolution characteristics and constitutive models of dry and saturated rocks under uniaxial compression: insights from AE and DIC techniques

To explore the damage behaviour and constitutive relationships of rocks, uniaxial compression tests with acoustic emission (AE) and digital image correlation (DIC) techniques were conducted on three rocks (granite, marble, and red sandstone) under dry and saturated conditions. The damage characteristics of these rocks were investigated from both the internal and apparent perspectives, and two damage constitutive models were proposed. Results indicate that granite exhibits the best mechanical properties, followed by marble, and red sandstone. Their mechanical properties degrade to varying degrees when exposed to water. The damage and failure process is accompanied by intensified AE activities and abnormal increases in local strains. High-strength rocks generally exhibit stronger AE activities and more severe apparent damage, characterised by higher peak and accumulated AE counts as well as larger peak and accumulated strain counts. Water suppresses the intensity and overall number of AE events, but promotes the apparent damage development. The stress–strain curves calculated from the models correlate well with the experimental data. The AE-based model is more suitable for high-strength rocks, whereas the DIC-based model is better suited to low-strength rocks because of the differences in rock properties and damage variables derived from accumulated AE counts and accumulated strain counts.