Spatio-Temporal Distribution Characteristics of Debris Flow Impact Pressure and Impact Velocity on the Check Dam Upstream Surface

Debris flows endanger humans living and property in mountainous regions all over the world, so it must be prevented and controlled by engineering. It is one of the quick and effective measures to build gravity check dam in the gorge from the formation area to the circulation area. Check dam often plays a controlling role in debris flow control. Check dam controls the development of debris flow, reduce the scale and frequency of debris flow. The consequences of the instability and destruction of check dam are extremely serious. However, debris flow hazard poses a great threat to check dam, especially the impact of debris flow on check dam is often the important cause of its stability damage. Accurately calculating the impact pressure and impact velocity of debris flow on check dam is a key scientific problem to be solved in the field of debris flow engineering prevention. Taking the drainage channel slope, the check dam slope ratio and the debris flow density (the clear water impact as the comparison experiment) as the experimental variables, eight pressure sensors are arranged at different positions on the upstream surface of the check dam to receive the debris flow impact signal, and the high-speed continuous data acquisition is adopted. The impact signal is collected and transformed by the instrument and the acquisition system. The time history curve of the impact pressure of the debris flow on the upstream surface of the check dam is obtained. The distribution of average velocity of debris flow along the vertical and lateral directions of the check dam is studied under different drainage channel slopes, different debris flow densities, and different check dam slope ratios. The results show that (1) at the same position on the upstream surface of the check dam, the average value of the debris flow velocity nonlinearly increases with the slope of the drainage channel, the slope ratio of the check dam, and the debris flow density increasing. (2) The average flow velocity of the debris flow decreases along the lateral direction of the check dam from the overflow section to the dam shoulder. (3)The debris flow average velocity directly affected is greater than the top position along the height direction of the check dam. The study results are of great significance for providing data and technical support for the structural design of the check dam.