# Calculation of the ultimate depth of a scour pit after debris flow through drainage canal ribs

Vol13 No.2: 246-254

### 【Title】Calculation of the ultimate depth of a scour pit after debris flow through drainage canal ribs

Author】LIU Shu-liang1,2,3;YOU Yong1,2;ZHANG Guang-ze4;WANG Dong4;ZHAO Hai-xin1,2,3; SUN Hao1,2,3

Addresses】1 Key Laboratory of Mountain Hazards and Earth Surface Process, Chinese Academy of Sciences, Chengdu 610041, China; 2 Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; 3 University of Chinese Academy of Sciences, Beijing 100049, China; 4 China Railway Eryuan Engineering Group co. LTD, Chengdu 610031, China

Corresponding author】yyong@imde.ac.cn

Citation】Liu SL, You Y, Zhang GZ, et al. (2016) Calculation of the ultimate depth of a scour pit after debris flow through drainage canal ribs. Journal of Mountain Science 13(2). DOI: 10.1007/s11629-015-3551-5

DOI】10.1007/s11629-015-3551-5

Abstract】Drainage canals are engineering structures widely used for debris flow mitigation. When passing through a drainage canal, debris flow usually scours the gully bed at the back of the rib sill of the drainage canal, which leads to failure of the rib sill. Therefore, the scour depth at the back of the rib sill is an important design problem and it is related to the economic benefits of engineering and service years. To explore the law of the depth of the scour pit after debris flow through drainage canal ribs, we first proposed a formula for the calculation of the maximum scour depth at the back of a rib sill based on energy conservation. We then conducted a series of simulation experiments to test the proposed formula. The experimental results show that the scour depth, trench slope and the distance between ribs all increase with a decrease in debris flow density. We then compared the results of experiments and formula calculations. Through the testing analysis, we found that the calculation results of the conducted formula correspond with the experimental results better. Finally, taking Qipan Gully as an example, we designed the ultimate depth of a drainage canal for debris flow using the calculation formula.

Keywords】Debris flow; Drainage canal; Scour depth; Energy conservation method; Flume experiment