Vibration Characteristics of Rock Under Harmonic Impact

Modal analysis of rock is done in this study, and the results of numerical analysis are presented. Meanwhile, the amplitude-frequency characteristic curve of rock in steady state response is investigated based on the principle of vibration. In addition, indoor experiments are carried out to further analyze the vibration characteristics of rock under harmonic impact. Three main control parameters are considered, including drilling way, excitation frequency and impacting amplitude. Our investigations confirm that the rock has different resonant frequencies and vibration modes in different orders for free vibration system, and there is only one resonant frequency for a rock with one degree of freedom. Based on theoretical analysis and indoor experiments, it can be concluded that the vibration amplitude under resonant frequency of rock is significantly higher than that under non-resonant frequency and in conventional drilling. Also, the vibration response of rock is in the harmonic form by the harmonic impact, and increases with the increase of the impacting amplitude. The vibration characteristics of rock by harmonic impact are validated by numerical analysis and experimental results. Harmonic vibration impact drilling can greatly enhance the vibration amplitude of rock, and further improve the rate of penetration.