Threshold criterion for debris flow initiation in seasonal gullies |
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Authors: | Yang Wang Peng Cui Zhaoyin Wang Shuangqing Liang |
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Institution: | 1. Key Laboratory of Mountain Hazards and Earth Surface Processes/Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, China;University of Chinese Academy of Sciences, Beijing 100049, China;2. Key Laboratory of Mountain Hazards and Earth Surface Processes/Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, China;CAS Center for Excel ence in Tibetan Plateau Earth Sciences, Beijing 100101, China;3. Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China |
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Abstract: | A series of flume experiments were done to investigate the effect of grain composition on the critical gradient and discharge of debris flows initiated in seasonal gullies. The results indicated that the critical gradient and discharge for debris flow initiation decrease initially, and then increase as the mass content of fine particles (<2 mm) increases. As the mass content of fine particles increases, the angle of repose, permeability of widely graded gravel soils, and the incipient motion conditions of the coarse grains in non-uniform sediments decrease at first, and then increase. The mass content of fine particles of all inflection points is the same. The theoretical model based on the combination of hydrodynamic force and shear stress is more applicable to the prediction of the critical gradient for debris flow initiation. The critical discharge model considering the effect of non-homogeneity of the soil and the size of coarse and fine grains provides a more accurate prediction of debris flow initiation than other models based on the mean diameter. |
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Keywords: | Grain composition Seasonal gully Non-uniform sediment Debris flow initiation Critical gradient Critical discharge |
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