Sediment mineral grain gradations on cavitation erosion of concrete material in high-velocity sediment-laden flow

This study investigates the effect of sediment mineral compositions on cavitation erosion in high-velocity flow within high-head flood release structures. The mechanisms by which different mineral grain gradations affect cavitation erosion on the concrete specimen were experimentally studied in a small looped water tunnel in this paper. Six primary mineral compositions (quartz, dolomite, feldspar, mica, calcite and pyroxene) were selected and sieved into coarse (d = 0.9–2.0 mm) and fine (d = 0.0385–0.154 mm) grain groups; the coarse and fine grains were categorized into mineral groups 1 and 2 with different Mohs hardness. Mineral grain water samples with mass percentages smaller than certain grain sizes (P < 15%, 33%, 50%, 68%, and 85%) were prepared, respectively. Pressures in cavitation and cavitation erosion zones were acquired in real-time by the pressure data acquisition system, and mineral grain concentrations were measured using the infrared suspended solid analyzer. The mass loss per hour of concrete specimen was used to represent cavitation erosion amount during a 4-h cavitation damage test. The experimental results showed that pressure and cavitation number in the cavitation zone decreased with a decrease in mass percentages smaller than a certain grain size of the mineral grain, and with increase in the Mohs hardness of the mineral compositions, while the pressure and cavitation number in the cavitation erosion zone increased. The accumulated cavitation erosion amount of the concrete specimen successively increased, and the extent of cavitation erosion on the concrete specimen surface aggravated, which exhibited a honeycombed morphology. It is concluded that both the decrease in mass percentages smaller than a certain grain size and the increase in the Mohs hardness of mineral compositions promoted the occurrence of cavitation in high-velocity flow, which led to the further development of cavitation erosion.