Study on the characteristics of debris flow movement in the transition section of inlet drainage channels

This study investigates the factors influencing debris flow movement characteristics in the inlet transition section of drainage channels through laboratory flume experiments. Debris flow bulk density, contraction angle, and channel slope were selected as key variables to systematically analyse their effects on flow velocity and mud trace height. The results indicate that channel slope is the most influential factor, with an increase in slope significantly enhancing both flow velocity and mud trace height. In contrast, the increase in debris flow bulk density inhibited flow velocity and mud trace height, primarily due to the increase in internal friction and fluid viscosity, which reduced flow mobility. The contraction angle has a relatively minor impact, with a slight reduction in both velocity and mud trace height as the angle increases, though the overall influence remains limited. Based on the experimental data, a regression equation for mud trace height ratio was established, quantifying the effects of slope, contraction angle, and bulk density. This model provides theoretical support for drainage channel design. The findings suggest that in engineering applications, optimising channel slope should be prioritised, while adjusting the contraction angle based on debris flow bulk density can further improve drainage efficiency and mitigation performance.