Experimental study on concrete-breaking by self-excited oscillating cavitation waterjet in a submerged environment

Self-excited oscillating cavitation waterjet (SOCW) has good prospects for application in concrete-breaking in the ocean. This study investigates the breaking mechanism of concrete subjected to SOCW in a submerged environment, with a focus on identifying damage characteristics at both macroscopic and microscopic levels using scanning electron microscopy and computed tomography. The breaking effect of concrete under the impact of SOCW at various impact times, jet pressures, impact distances, and strength grades was compared. It was found that (a) the best breaking effect of concrete was achieved by ensuring a 30 MPa jet pressure with a 5 mm impact distance. (b) Internal pores of concrete and the water wedge effect accelerated crack propagation. The formation of breaking pits was the result of closed loops formed by cracks leading to concrete spalling. (c) Microscopic analysis revealed plastic deformation pits on the concrete surface, forming through stages of cavitation collapse, pore expansion, and coalescence. This study provides a theoretical understanding and technical support for follow-up research on the parameter optimization and breaking efficiency of concrete-breaking technology.