Study on the influence mechanism of material damage on the cavitation erosion properties of hydraulic concrete

Flood releasing safety is one of the three major safety problems of high dams due to the high-water head and large discharge, and the safety problems caused by cavitation erosion are increasingly prominent, which has become one of the challenging problems for the safety of high dam flood discharge. Particularly, flood discharge and energy dissipation structures are susceptible to varying degrees of damage under external loading and material performance degradation. However, the action mechanism of damage-cavitation erosion for concrete remains unknown and unclear. In this paper, the cavitation erosion properties of concrete with different damage variables and the influence mechanism of damage-cavitation erosion are systematically studied. Based on the ultrasonic cavitation erosion tests of undamaged and damaged concrete, it is found that the mass loss, harshness, volume of pits, and depth of damaged concrete increased rapidly at first and then slowly, the maximum loss rate is almost dependent on the degree of damage, and its relationship with the damage degree can be described by a piecewise linear function. More importantly, a damage variable threshold for the step surge of concrete cavi-tation erosion is suggested. The cementitious material in damaged concrete is more prone to cavitation erosion due to the potential microcracks caused by the damage. Compared with the results of tests and simulations, the incentive mechanism of the surge of concrete cavitation erosion due to the concrete damage -microcrack initiation -strength and fatigue life reduction -microjet impact -water wedge excitation in cracks -development, expansion, and penetration of erosion pits is revealed. The influence mechanism revelation of damage-cavitation erosion for concrete will enrich the theory and technology of cavitation erosion risk assessment for hydraulic concrete structures.