Experimental and SPH Modeling of Debris-Flow Impact on Dual Rigid Barriers with Deflector

Multiple barrier system has become a widely adopted method to mitigate debris flows, which consists of smaller barriers that progressively retain the debris to reduce the acceleration and carbon footprint. Different from single barriers, the impact force on multiple barriers depends on the overflow from the upstream barrier. Overflow may substantially accelerate the flow by converting potential energy into kinetic energy with limited energy dissipation. While installing a deflector at the crest of a single barrier suppresses overflow, the efficacy of a deflector in reducing impact force in a multiple barrier system is not well understood yet. In this study, physical tests were conducted using a 28-m-long flume to investigate the impact dynamics of debris flow against dual rigid barriers with a deflector installed at the first barrier. A smoothed particle hydrodynamic (SPH) model was calibrated by back analyzing the flume tests. A numerical parametric study was then conducted to investigate the efficiency of a deflector in reducing impact force from different volumes of debris flow against dual barriers. Newly modified equations are proposed that can reasonably predict the overflow velocity, the velocity after landing, and landing distance considering a deflector. Physical and numerical results reveal that a deflector at the first barrier can efficiently reduce overflow by redirecting the flow to roll back and reduce the landing distance by up to 75%. A deflector at the first barrier can reduce the impact force at the second barrier by up to 90%.