Characterization of rock response in vibro-impact drilling

ABSTRACT: Vibro-impact drilling (VID) is a promising efficient rock-breaking technology in hard-rock drilling. This technology is designed to break rock with vibration or impact loads and its ultimate goal is to break rock in resonance state. Characteristics of damping and gravity have a significant influence on the realization of rock resonance. So a rock response model considering these two characteristics is established and the rock micro-vibration equation based on the model is obtained. Then the response of the rock under periodic non-harmonic impact are presented by analytical method and Fourier series approximation. Finally, the numerical analysis is conducted to verify the model. It is confirmed that the maximum vibration displacement of the rock can be obtained when the excitation frequency is equal to the natural frequency of the rock. And the damping characteristic reduces not only the frequency, but also the amplitude of the rock resonance. The natural frequency of rock decreases with the increase of the density, while the density has positive effect on the amplitude of the rock resonance. The vibration response of the rock is also related to the impact parameters. The research of this paper is of great significance to the development of VID.