Experimental study on deformation and failure characteristics of salt rock three-point-bending samples with impurities

In order to investigate the deformation and failure characteristics of salt rock under bending conditions and the influences of impurity content, the loading-and-unloading three-point-bending tests as well as the synchronous acoustic emissions (AE) monitoring are performed on two groups of salt rock single edged notched beam (SENB) samples with different impurity contents using the rock mechanics test system MTS815 in Sichuan University. The test results show that the bending tensile strength and the bending elastic modulus of the impure salt rock with polyhalite are higher than those of pure salt rock, and the impure salt rock is better to resist the crack propagation than the pure salt rock. And the deformation and failure process of the bending salt rock consists of four stages, elastic deformation stage, yield stage with plastic deformation and crack initiation, crack propagation stage at post-peak and residual stage. Moreover, the impurity has a great influence on the plastic deformation and fracture failure of the bending salt rock. By selecting energy count rate as the AE characteristic parameter, the deformation and failure of the bending salt rock can be well reflected. Corresponding to the process of deformation and failure, AE presents the periodical characteristics at different stages, and the AE activities are active at every stage except the elastic deformation stage. Compared to those of the pure salt rock, the AE activities of the impure salt rock are more active because of the friction effect and the plastic deformation weakening effect caused by impurities. What’s more, the AE source location in three dimensions well reveals the damage distribution of salt rock under the three-point-bending condition. And in the distribution, there are AE blank are asrelated to the stress state. For the distribution, its form is greatly affected by the impurities.