Investigation into the characteristics of rock damage caused by ultrasonic vibration

• The idea of the limited incident energy is put forward for analysis of the rules of the formation of rock crack instead of the spall stress in the critical normal stress criterion.
• The degree of rock damage and the percentage of strength degradation increase smoothly with the duration of vibration when the incident energy is bigger than the limited incident energy.
• The curve of preloading against compressive strength is concave since both impact energy and strain rate were affected by preloading.