Investigation on energy characteristics of shock wave in rock-breaking tests of high voltage electric pulse based on Hilbert-Huang transform

High voltage electric pulses (HVEPs) can damage hard rocks with electrical energy as the driving force. Fracture process of rock and energy characteristics of shock wave (SW) can better explain the fracture mechanism of HVEP. Self-developed HVEP system fractures rocks. By using high-speed camera technology, the extension of cracks can be shown in form of pictures. The Hilbert-Huang transform (HHT) is utilized to characterize the instability of rock fracture in terms of time domain-frequency domain-energy deposition. The results show that increased voltage leads to structural transformation of rock interior to instability. The peak energy of SWs occurs near 0 s, and decreases rapidly within 0.1 s 0–20 Hz is the region of concentrated distribution of SWs energy. In addition, instabilities occur at the moment of rock fracture, including an increase in the vibration frequency range of SWs and a shift in the main frequency of vibration. The occurrence of cracks suppresses waves propagation.