An Analytical Model of Particle Impact Rate in Partially Dense Inclined Granular Flow Driven by Gravity

High-frequency seismic waves are generated by inter-particle collisions during granular flows travel downslope. However, the accurate estimation of particle impact rates over granular layers remains a challenging issue. Here, controlled laboratory experiments were performed to investigate basal dynamic pressures triggered by the impact of particles on an instrumented plate mounted on an inclined chute bed. For a similar set-up, the discrete element method was utilized to determine granular-flow characteristics and the rate of inter-particle collisions. From a thermodynamic perspective, we present a novel model for calculating the impact rate over the granular-flow depth. Our estimates agree with the simulated results and previous laboratory measurements of acoustic power, suggesting that the impact rate follows a Gaussian distribution across the flow depth and the exponential attenuation factor of radiated acoustic power may correlate with thermodynamic parameters of granular material. These findings may help better understand the source of the high-frequency granular-flow signals.