Experiments on granular flows to predict avalanche runup

Abstract

Design of deflectors or barriers to slow or stop snow avalanche debris in the runout zone requires estimates of runup height. In this paper, experimental data on runup of dense, dry granular flows in a flume are presented. The data are then compared with two one-dimensional theoretical equations for runup estimation: (1) a formulation based on following the leading edge of the flow up the barrier and (2) the traditional method adapted from equations presented by A. Voellmy for describing the centre of mass of the avalanche. The results show that the leading-edge model more closely matches the experimental results and, in field applications, the leading-edge model is expected to provide higher and, therefore, more conservative runup estimates. Key words : avalanche run-up, granular flows, avalanche defences, runout zone.

Experimental investigation on steady granular flows interacting with an obstacle down an inclined channel: study of the dead zone upstream from the obstacle. Application to interaction between dense snow avalanches and defence structures

“…Until now it is primarily the similarity with dry granular flows which has been exploited: sand (Chu et al, 1995), beads (Hutter et al, 1995), ping-pong balls (Keller et al, 1998). A dense snow avalanche is generally constituted of particles with various…”

Flume investigation of landslide debris–resisting baffles

“…9b). The granular jets impact the second row of staggered baffles, while runup and deposition simultaneously occurs upstream of the first row (Chu et al 1995;Gray et al 2003). A relatively symmetrical deflection pattern is observed between the baffles as granular jets deflect laterally into each other to promote additional energy dissipation.…”

“…Choking will lead to increase in upstream flow depth and minimum energy discharges through the constriction. Although the concept borrowed from hydraulic engineering may not entirely be applicable for transient surge granular flow because of the development of stagnant regions directly upstream of the baffles (Chu et al 1995;Cui et al 2007;Gray and Cui 2007), the concept of choking may serve as a preliminary assessment on whether overflow will occur if the Fig. 1b).…”

“…9c). Furthermore, increasing the number of rows of baffles may promote the deposition of sand behind obstacles, which may affect the impedance (Chu et al 1995;Gray et al 2003). Salm (1987) reports that energy dissipation from obstacles is proportional to half the fraction of blockage.…”

“…Interaction between flowing sediments and obstacles entails complex mechanisms, including the deposition and runup of material behind an obstacle (Chu et al 1995), formation of dead zones (Faug et al 2012), granular vacuum (Gray et al 2003;Zanuttigh and Lamberti 2006), and the deflection of jets between obstacles (Hákonardóttir et al 2001). These flow mechanisms are distinct for granular flows and cannot be captured by studying the interaction between water and baffles in hydraulic engineering.…”