A drainage channel is an efficient debris flow countermeasure, but defects in practical function exist due to the non-peer exchange between post-geological hazard investigation and flow dynamics estimation. Especially in a drainage channel with a contracted entrance, the structural design depends on the peak discharge, the velocity of a debris flow, and the interaction between sediment and structure. This paper mainly explores debris flows interacting with a contracted channel before the drainage part through flume model tests. Results are illustrated as follows: i) In and after the contracted section, overflow and silting of debris flow are coexistent. Overflow grows with the increasing entrance inclination and the total debris flow volume. The silting efficiency keeps in higher quantity and drops roughly with increasing the total debris flow volume. Overflow and silting are both controlled when contraction angle β is reduced. ii) The debris flow in the entrance exceeds lateral wall height instantly when the contraction angle β is equal to 21.23° but falls down when β is smaller (equal to 19.14°). The deflection angle of the shock wave front φ varies in a small range with β. The normalization of maximum wave thickness in the entrance has a positive parabola correlation with the Froude coefficient Fr while decreasing β can reduce the normalized thickness. iii) The impact load of a debris flow on the lateral walls shows a hydrodynamic pattern analogy. The peak load has a positive linear relationship with Fr. Furthermore, the coefficient indicating the normalization of peak loadαneeds to be corrected according to the deflection angle of the shock wave front φ.

Huo Miao, Wang Xu, He Chuankai, Liang Yufeng, Zhao Jiangtao, Qi Lijian, Jiang Chenjie. A Preliminary Test Study on Debris Flows in a Contracted Drainage Channel at Mawan Valley, Chongqing. Academic Journal of Environment & Earth Science (2024), Vol. 6, Issue 1: 7-18. https://doi.org/10.25236/AJEE.2024.060102.

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