Experimental study on impact signal frequency spectrum and energy distribution characteristics of water-stone flow

Understanding of impact characteristics is the basis of studying the hydrodynamic characteristics of water–rock flow. The impact and vibration characteristics of water-stone flow on protective structures were comprehensively studied in the research presented in this paper using an indoor large-scale test. Five groups (A–E) of graded crushed stone particles, combined with six levels of solid–liquid ratio (0.01, 0.05, 0.10, 0.15, 0.20, and 0.25) were used in this testing program. The spectrum and the energy spectrum of impact acceleration signal were analyzed and pertinent information was extracted using wavelet theory. The test results showed that the auto correlation curve of the impact signal had a maximum value when the delay of impact acceleration signal (τ) was zero, and the curves on both sides of the instant of impact were non-periodic, indicating that the periodicity of the signal was poor. However, two observed impulse signals were stable and they highly correlated. Maximum energy of the shock signal was located in the low frequency within an approximate coefficient a₈ band, and the maximum amplitude of each band decayed from a low frequency (a₈: 0–0.3905 Hz) to an high frequency (d₅: 3.125–6.25 Hz), while the attenuation amplitude decreased gradually. The real impact acceleration signal of the water-stone flow was in the band of 0–6.25 Hz, and the rest were a result of signal noise. The research provided a new and innovative methodology of studying the impact characteristics of such debris flow, and also provided some significant guidance for the design of water-stone flow disaster prevention structures.