Experimental and numerical study on the cracking characteristics of repetitive electrohydraulic discharge shock waves

The application of repetitive electrohydraulic shock waves (EHSs) is a developing underwater discharge technology; however, its cracking characteristics on rock under different loading modes are rarely studied. In this paper, an experimental platform of electrohydraulic discharge is built, and test results show that repetitive EHSs can cause obvious macroscopic cracks on samples. A fitting method is proposed for the time-domain waveform of the EHS. The mechanism of the EHS cracking process (liquid-solid interface transmission process, cracking process in rock) is analyzed, and the cracking criterion and fracture zone range of a single EHS on rock are given. In addition, PFC(3D)simulation is used to establish a three-dimensional numerical model of the test sample under the experimental conditions, and the development characteristics of the damage shape and crack density inside the rock under the action of repetitive EHSs are deeply analyzed. Under different repetitive loading modes with the same loading total energy, the simulation results show the following cracking characteristics: in single-level mode, the crack density is mainly related to the energy of the single loading. The higher the single-loading energy, the more conducive it is to the growth of the number of main cracks, but it will form a crushing zone to cause energy loss; lower single-loading energy is more favorable to the length of main cracks. In the multi-level loading mode, the degraded loading mode has a higher crack density than the upgraded loading mode. Compared to the single-level loading mode, the multi-level loading mode can effectively promote the development of the number and length of main cracks, and effectively reduce the range of the crushing zone. This paper provides theoretical and simulation guidance for the research and application of repetitive EHSs.