MICROCRACK GENERATION AND PROPAGATION IN GRANITE DURING STRESS RELAXATION UNDER WATER-SATURATED TRI-AXIAL CONDITION

Microcrack generation and propagation is an important phenomenon, which describes the long-term behavior of a crystalline rock. In this study, a progressive development of microcrack in granite and its proagation was observed using microscope under water-saturated triaxial compression. A series of triaxial relaxation tests was performed with fine and coarse grained granite. Results revealed that there exists a strong relationship between the stress relaxation and the microcrack propagation. Three stages of stress relxation rate were identified where stage one offers the maximum microcrack generation and propagation. The microcrack propagation in fine grain granite was found higher than the coarse grain granite because of higher number of contact points between the grain boundaries. Stress concentration occurs in these boundaries and microcracks are propagated through these contact points.