An experiment of attenuation law of vibration and evolution mechanism of damage of granite under cyclic blasting

To investigate the dynamical response of rock under cyclic blasting, the small-scale blast tests of biotite granite were carried out. By using the acceleration transducer and ultrasonic testing apparatus, the attenuation law of particle vibration and the evolution mechanism of cumulative damage of the granite subjected to cyclic blasting were analyzed, respectively, and the crack propagation and fracture shape of the rock block under different charges were further compared. Results show that the Sadowski’s formula has a good applicability to describe the attenuation law of rock particle vibration in laboratory blasting, and the values of fit goodness are above 0.90. The blast damage of the granite increases with the blast number. Besides, the damage decreases with the increase of the distance from explosive center, and the rock damage of the near area decreases rapidly, with a decreasing amplitude of 1.46/m, while those of the middle area and far area decrease slowly, the amplitudes being 0.57/m and 0.13/m, respectively. The charge amount has a high correlation with the degree of rock damage. When the charge is smaller, the blast number for rock fracturing is higher. When the charge increases to a certain extent, the rock block might be destroyed under a lower blast number. In addition, the number of rock fractures increases as the increase of charge. For example, the sample breaks into 2 pieces when the charge is low, while it breaks into 3 or 4 pieces under a high charge.