Triaxial compression experiments on intact veined andesite

• Five intact veined andesite specimens were tested in triaxial compression with AE.
• Experiments demonstrated that intact veined rock behaved differently than intact rock.
• High C′/C ratios were observed in tests with confining pressure of up to 30 MPa.
• The onset of AE correlated with damage initiation stress, not with crack initiation stress.
• Experiments showed a short stage of unstable fracturing, atypical of intact rock.

A comprehensive experimental program was instigated to test intact veined andesite from the El Teniente Mine (Chile) under triaxial compression with confining pressure ranging from 2 to 60 MPa. The experimental program established that the veins acted as weak mechanical components in the specimens, promoting rock fracture under stress. The experimental results indicated that the stress thresholds identifying the onset of dilatancy and the transition from the stable to unstable fracturing were higher in intact veined rock than in intact rock. The observed behaviour illustrated a significant departure from intact rock where the onset of Acoustic Emissions (AE) correlates with the onset of specimen dilatancy. The experimental results from intact veined rock indicated that the onset of AE correlated with the crack damage stress. The departure from the behaviour of intact rock is attributed to the presence of veins.