Statistical Characteristics of Basal Forces Generated by Experimental Debris Flows

Abstract

Debris flows are fast-flowing, high-energy mixtures of sediment and water that are difficult to monitor. Seismic monitoring instruments can be placed safely outside the channel, but it is an indirect method that needs the application of theory-based inversion to obtain quantitative information on flow properties and rheology. Such inversion methods do not currently exist for debris flow dynamics because the essential understanding of the relationship between the basal force and physical properties of debris flow at the channel bed is lacking. In this study, flume experiments are used to investigate the distribution of basal forces of dual-phase solid-liquid flows. We systematically varied particle size, bed slope, dynamic viscosity, particle dosage, and slurry dosage and measured the forces generated on the bed at high temporal resolution. We analyzed the probability density function of the basal impact force to identify distribution parameters relating to the physical properties of the flow. Evaluation of 10 fitted distributions showed that the Cauchy distribution and Dagum distribution best described the normalized basal force under different variables using objective criteria based on the Sinkhorn and Wasserstein distances. We found that the Cauchy and Dagum distributions' parameters correlate with the dose ratio and Bagnold numbers (R² ∼ 0.588–0.844), showing the significant influence of the sediment concentration and particle collision rates on the distributions. The study contributes to developing a theoretical underpinning of debris-flow seismic inversion.