Analysis of precursor response characteristics and time-frequency vibration parameters of rock failure: a laboratory experimental method

To explore the vibration characteristics of rock failure precursors, a vibration optical force combined monitoring method was adopted. In this study, quasi-sandstone and granite samples were selected for uniaxial loading experiments to monitor the surface crack propagation and vibration. The variations in acceleration, displacement, energy, and waveform characteristics of quasi-sandstone and granite were studied from the perspective of the time domain. Additionally, a warning parameter SKE (Skewness, Kurtosis and Energy) based on waveform characteristics and energy was proposed. From the perspective of time-frequency analysis, a warning parameter CFEFD (Center Frequency Energy and Frequency Difference) is proposed by comprehensively utilising short-time Fourier analysis and statistical methods. The prediction effectiveness of both parameters was evaluated. It was observed that the vibration acceleration, energy, and displacement of rocks can all reflect the propagation of rock cracks. Prior to reaching the peak stress, the vibration acceleration and energy of rocks undergo sudden changes. The development of rock fractures releases energy, leading to high-energy frequency diffusion. Before reaching the peak stress, the range and energy level of high-energy frequency diffusion show significant improvement. Finally, it was found that both the SKE and CFEFD warning indicators can provide a certain degree of warning effect.