Experimental study of viscous debris flow characteristics in drainage channel with oblique symmetrical sills

In this study, experiments were performed in a 6-m-long flume to determine the characteristics of viscous debris flows in a new type of drainage channel with oblique symmetrical sills. The debris flow velocity was measured and subsequently used to characterise the viscous debris flow. The influences of the channel slope, transverse length of sills, and row spacing of sills on the debris flow velocity and the velocity reduction ratio P were investigated. The experimental results indicated that the viscous debris flow velocity increased as the channel slope increased from 0.10 to 0.15. However, the velocity decreased as the ratio of the transverse length of sills to the row spacing of sills increased from 0.13 to 0.53. Different combinations of the channel slopes, transverse lengths of sills, and row spacing of sills reduced the velocity by 14.2%-51.1% compared to the velocity in a smooth channel. The effects of the channel slopes, transverse lengths of sills, and row spacing of sills on P could be described using a power-law equation. Most of the errors in P prediction ranged from − 25.0% to 25.0%. A comparison of P in drainage channels with different deceleration measures indicated that P increased with an increase in the length of a channel with deceleration measures. These experimental results serve as a useful reference for the design of drainage channels with oblique symmetrical sills.