Abstract
Debris flows are one of the perilous landslide-related hazards due to their fast flow velocity, large impact force, and long runout, in association with poor predictability. Debris-flow barriers that can minimize the energy of debris flows have been widely constructed to mitigate potential damages. However, the interactions between debris flows and barriers remain poorly understood, which hampers the optimal barrier installation against debris flows. Therefore, this study examined the effect of barrier locations, in particular source-to-barrier distance, on velocity and volume of debris flows via the numerical approach based on smoothed particle hydrodynamics (SPH). A debris-flow event was simulated on a 3D terrain, in which a closed-type barrier was numerically created at predetermined locations along a debris-flow channel, varying the source-to-barrier distance from the initiation point. In all cases, the closed-type barrier significantly reduced the velocity and volume of the debris flows, compared to the cases without a barrier. When the initial volume of source debris was small, or when the flow path was short, the barriers effectively blocked the debris flow regardless of the source-to-barrier distance. However, with a long flow path, installation of the barrier closer to the initiation location appeared more effective by preventing the debris volume from growing by entrainment. Our results contribute to a better understanding of how source-to-barrier distance influences debris-flow behavior, and show that the methodology presented herein can be further used to determine optimum and efficient designs for debris-flow barriers.
Highlights
Debris flows are defined as massive flows of debris mixed with water, which occur when debris, such as soils, gravels, boulders, and drift-woods, is entrained by surface water flow due to heavy rainfall
This study investigated the effect of barrier locations on the characteristics of debris flows by using numerical modeling based on the smoothed particle hydrodynamics (SPH) method
For a debris-flow event with a short flow path (e.g., Site 1), the debris flows can be readily terminated by the barrier regardless of barrier location, owing to the sufficiently large barrier compared to the small debris volume
Summary
Debris flows are defined as massive flows of debris mixed with water, which occur when debris, such as soils, gravels, boulders, and drift-woods, is entrained by surface water flow due to heavy rainfall. Numerical simulation of these debris-flow events using DAN3D requires the determination of input parameters, including the friction coefficient, the turbulence parameter, and the channel erosion rate These parameters were back-calculated from the source volume, final debris volume, and depositional area. Owing to the erosion-induced entrainment process, the total debris volume gradually increased as the source-to-barrier distance increased This result demonstrates that the installation of barriers nearer the initiation (or source) location is more effective as it interrupts flow before the debris grows substantially by entrainment, when the location of initiation can be predicted. This highlights that identifying debris source locations is a prerequisite for barrier location determination
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