Mechanical behaviors and acoustic emission characteristics of fracture of granite under different moisture conditions

The three-point bending tests on Beishan granite under different moisture conditions are carried out by using the MTS815 Flex Test GT and acoustic emission (AE) three-dimensional positioning monitoring system to obtain the load-LPD curves, AE ringing count rates and curves of AE hitting number. The results show that there is significant influence of water on the fracture mechanics and AE features. The average fracture toughness of the water-saturated samples is 87.5% of the dry ones, and the stiffness and strength decrease apparently. The water-saturated granite shows greater deformation and weaker stiffness. At different stages of the tests, the AE ringing count rate of the water-saturated samples is far less than that of the dry ones, and the water-saturated samples show obvious Kaiser effect. The main failure of the samples is the tensile failure with v-shaped cross-section features. The AE events of the water-saturated samples are more than those of the dry ones. The results of this study are of important theoretical and practical significance for the design and construction of the deep granite geotechnical engineering influenced by aquifers.