The Effects of Deflection Walls on Debris Flow Deposition Features in the Main Channel

To diminish the risk of debris flow to the infrastructures along the runout path or in the accumulation area, deflection walls are commonly constructed as the last element of a systematic torrent training control measures, which could direct debris flow into the main channel. The deposition characteristics of debris flow in the main channel with the effects of deflection walls in different deflection angles are varied and have not been systematically analyzed. Therefore, a series of flume experiments were performed in this study to investigate the deposition features of debris flow in the main channel. The results indicate that the spread range of debris flow deposition will be limited by water in the main channel, and the finer sediments of the deposition will be transported downstream by the main flow. When the weight and velocity of the debris flows reach certain values, the relative magnitude and cross section of the debris flow depositions will not change significantly. More than half of the debris flow will be transported into the main channel under the effect of deflection walls. The variation of deflection angles will remarkably change the debris flow deposition features. With the increase of deflection angle upstream or downstream, the weight and cross-section area of debris flow deposition decrease, and the obstruction degree of the main channel also reduce. These experimental results could provide both references for the design of deflection walls and essential data for further study on the interaction between debris flow deposition and river system.

Keywords: Debris flow; deflection walls; deposition features; main channel; deflection angle.