Abstract: To investigate the deformation behaviour and the brittleness evolution characteristics of Linghai granite, a series of conventional triaxial compression tests was performed. Complete stress-strain curves under various confining pressures were analyzed in detail. The relation among the specimen surface deformation, damage law and microcrack propagation was discussed on the basis of static strain measurement data. Typical microcracking modes were captured dynamically. Based on the improved post-peak energy method, the brittleness of Linghai granite under triaxial loading conditions was evaluated. The results indicate that there are localised deformations that correspond to the positions of crack initiation and propagation, which are revealed from the multiple long strain gauges showing larger compressive strains in the strain-time curves. Several microcrack propagation modes at the post-peak failure stage, which are related to the stress-controlled loading type to some extent, are observed from dynamic strain monitoring results. Brittle failure of Linghai granite is observed at the confining pressure up to 70 MPa. As the confining pressures increase, the brittleness of the rock decreases initially, and then increases and finally decreases. Experimental results provide an insight into the study of rock failure mechanism and are useful for stability analysis of underground engineering structures.

Key words: Linghai granite, brittle failure, post-peak deformation, brittleness index, microcrack propagation