Abstract: Bailong River drainage basin is an area subjected to the most severe debris flow hazard, with debris gully density and debris flow frequency ranking top in China. Despite many treatments, debris flows have caused large casualty and property losses. In this paper, the current engineering mitigation works in Ganjia gully of Bailong River basin were analyzed through field investigation, and on this basis, the particle gradations, rheological behaviors, and shear strengths of debris deposits in the upstream and downstream of check dam were compared through particle size test, rheological test and direct shear test. Results suggest that check dam plays an insignificant role in adjusting the particle size of debris flow, but apparently alters the mechanical properties of debris flow. The shear stress of debris deposit slurry in the downstream of check dam is smaller than that in the upstream; while shear strength in the downstream is slightly larger than that in the upstream. In addition, the difference in grain size distribution of debris flow is an important factor that affects the rheological properties and shear strength. The results could be used as reference for the type selection and parameter design of check dam.

Key words: check dam, debris flow deposits, rheological behavior, shear strength, engineering mitigation