Flume investigation of the interaction mechanisms between debris flow and slit dams

Abstract

Slit dams are designed to mitigate debris-flow hazards. However, according to field surveys and past experimental studies, slit dams constructed using currently prescribed design methods usually become blocked, which then leads to the loss of capacities of the slit dam’s capability to mitigate debris-flow hazards. In this study, a series of flume tests were conducted to investigate the interaction mechanisms between debris flows and slit dams. This work aims to contribute to the design of slit dams more reliable. The influence of debris-flow water content (w) and the slit-dam relative post spacing b/dmax (b: post spacing; dmax: maximum particle diameter) were examined. Experimental results reveal that when w<22%, dead zones and pile-ups occur during the interaction processes. When w≥22% and b/dmax≤2.3, run-up, overtopping, and backwater effects can be observed, and with no apparent formation of dead zones. Moreover, when w≥26% and b/dmax>2.3, majority of the granular-water mixtures pass through the slit dam in the form of jet flows with no obvious overtopping.