Modeling and simulation of the effect of rock grain sizes on vibration characteristics when rock drilling

A numerical simulation method and an experimental method were employed to investigate the relationships between the mineral particle sizes and spectral characteristics of the sound or vibration signals generated during rock drilling processes. Several rock models with different aggregates were generated by means of determining the locations of aggregates randomly. The modal analysis of the rock models was conducted to reveal their vibration characteristics. Simulation results indicated that the smaller the aggregate size, the larger the high-frequency composition of sound and vibration. Several drilling experiments were performed on the rock specimens of different aggregate sizes. By using an indoor signal acquisition and analysis system, data from the sound waves and vibrations were collected, and characteristic signals were extracted. Moreover, the spectral characteristics of the sounds and vibrations of different aggregate sizes were identified. The experiment results are consistent with the conclusion of the simulation. The study provides a possibility for developing a method to evaluate the rock structure information collected from drilling vibration or sound signals for a fine exploration of geological surveys.