Numerical study of granular debris flow run-up against slit dams by discrete element method

Abstract

Run-up of granular debris flows against slit dams on slopes is a complex process that involves deceleration, deposition, and discharge. It is imperative to understand the run-up mechanism and to predict the maximum run-up height for the engineering design and hazard mitigation. However, the interaction between granular flows and slit dams, which significantly affects the run-up height, is still not well understood. In this study, an analytical model based on the momentum approach was derived to predict the run-up heights of granular debris flows. A numerical investigation of granular debris flow impacting slit dams using the discrete element method (DEM) was then conducted. The influence of the Froude number (NFr) and the relative post spacing (R) on run-up height were studied. This study illustrates that the analytical model based on the momentum approach can predict the run-up heights well within a certain range of Froude numbers. There is a critical value of relative post spacing (RC): within the critical value, the maximum run-up height is insensitive to the relative post spacing; once R exceeds the critical value, the maximum run-up height decreases rapidly as the relative post spacing increases.