Laboratory investigation of performance of a screen type debris-flow countermeasure

Abstract

Debris-flows are forms of landslides in mountainous regions that can potentially cause significant damage. Structural countermeasures to mitigate an entire debrisflow may become unrealistically large and expensive. If the flow cannot be stopped completely, one may alternatively consider reducing the impact and velocity of the flow using energy dissipating structures. A debris-flow screen is such countermeasure designed to dissipate energy. A screen is made by parallel grids, with some gap, placed in the direction of the debris-flow on an elevated foundation. This structure acts as a filter for separating water from the saturated debris-flow to reduce its flow energy. This work presents a laboratory model test investigating the effect of screen length (0.5 m and 1.0 m) and opening width (2 mm, 4 mm and 6 mm) in dissipating the debris-flow energy. The effectiveness of the screens was determined in terms of reductions in the run-out distance and flow velocity. The importance of the screen length and opening width is demonstrated. A hypothesis that the optimum opening size should be close to d50 of the solid material seems to be validated. The application of the laboratory observations to the field is indicated based on the energy line and scaling principles.

Flume Modeling of Debris Flows

“…As debris flows tend to consolidate rapidly, the residence time of the mixture in a storage container should be minimized to prevent separation of the solid and fluid phases, as this causes low test repeatability and gives rise to capillary stresses between soil grains (Song and Choi 2021). Some models include a mixer in the storage container (Ng et al 2022, Yifru et al 2018 to continuously disturb the solid-fluid mixtures and thereby hinder consolidation. Iverson (2015) noted that debris flows in the field are generally initiated from static sloping ground and in response to subtle and progressive changes in pore water pressures, which lead to force imbalances and slope instability, culminating in landslides (Iverson 2000).…”

Two-phase SPH modelling of a real debris avalanche and analysis of its impact on bottom drainage screens

“…To mitigate the potential destructiveness of these flow-like landslides, structural countermeasures are often used to reduce flow mobility or even retain the flow. There exist many different debris-resisting structures to cope with the threat related to debris avalanches and debris flows including artificial barriers Wendeler et al (2007), sabo dams Mizuyama (2008), check dams Popescu and Sasahara (2009), baffles Ng et al (2015), Geosynthetics-reinforced barriers Cuomo et al (2020), bottom drainage screen Yifru et al (2018).…”

“…The idea of installing bottom drainage screens along the propagation path of debris flows to reduce their impact was proposed by Hashimoto in Japan in the 1950s Kiyono et al (1986); Gonda (2009). Due to the effectiveness of this energy dissipating structure, several small-scale physical models have been conducted to have a better understanding of debris-flow screens and their mechanism including (i) the effects of different opening widths of permeable screens on the debris-flow run-out distance Gonda (2009), (ii) the effects of different bed sediments with different blocking and opening widths Kim (2013) and (iii) the effects of different location of debris flow screens, in the middle or at the end of propagation path, on the behaviour of debris flows Yifru et al (2018).…”

A two-phase SPH depth integrated model for debris flow propagation considering pore water pressure evolution

“…In the second simulation, the capacity of the proposed model was evaluated to reproduce a debris flow on a laboratory scale inclined channel, by comparing the numerical results with the measurements obtained from experiments and assessing the performance of the time-space evolution of pore-water pressure. The small scale laboratory test performed by Yifru at Trondheim (2019) [137] to illustrate the effect of the permeable debris flow rack and its working mechanism.…”