Numerical analyses of the influence of baffles on the dynamics of debris flow in a gully

Abstract

After the 2008 Ms 8.0 Wenchuan earthquake, a huge amount of loose debris materials were accumulated on the surface of slopes in the mountainous areas of Southwestern China. Under heavy rainfalls and earthquakes, these loose debris materials can flow, washed away, and subsequently enter the mountainous rivers due to landslides and debris flows. They can change the sediment supply of the river channel and result in the adjustment of riverbed. To mitigate the adverse impacts, baffles are usually installed on slopes in front of the protected areas to reduce the kinetic energy of incoming debris flows. In order to clarify the interacting mechanism between debris materials and baffles structure, the dynamics of granular transportation and deposition in a typical gully have been analyzed via the three-dimensional discrete element method (DEM). The numerical results indicate that the arrangement of baffles (e.g., spacing distance, layout row, and height) has a significant influence on the dissipation of debris energy and the final sediment deposition pattern. The kinetic energy, the velocity of granular flow, and the total mass of debris materials entering the river channel decrease with the increase of the baffles lateral spacing distance, layout row, and height. Correspondingly, the amount of debris materials retained by the baffles will increase. Thickness and volume of particle deposits in the upstream region increased with increase in lateral spacing, rows, and height of the baffles, but decreased in the downstream area. In addition, the baffle configuration can affect the particle size distribution along the channel. The results of this research can provide a theoretical basis for baffle designs and the prevention of debris flows in mountainous areas.