Effects of Barrier Deflectors on Impact Mechanisms against Debris Flow

The implementation of a multiple barrier system has been recognized as an efficient approach for mitigating debris flows. To effectively reduce the impact forces on multiple barriers from overflow, a deflector can be installed at each barrier crest to redirect the flow front and facilitate energy dissipation. Despite the effectiveness of deflectors, a rational design approach for multiple barriers with deflectors is still lacking because of the complex impact dynamics during the flow-barrier-deflector interaction. In this study, a physical test was carried out using a deflector in a 28-m-long flume to calibrate a smoothed particle hydrodynamic (SPH) model with multiple barriers and deflectors against debris flow. Numerical parametric studies were then conducted using the calibrated SPH model to investigate the influence of a number of barriers on the impact dynamics of debris flow against multiple barriers installed with deflectors. A new equation was proposed and verified to predict the flow depth after landing for the development of an improved analytical design framework for multiple barriers with deflectors. This new framework can conservatively predict the overflow velocity, landing distance, flow velocity and flow depth after landing, as well as the impact force on multiple barriers. The computed results reveal that four multiple barriers installed with a deflector each can reduce the terminal barrier impact force by up to 60% relative to four barriers without using deflectors.