Experiments of Debris Flow Damming in Southeast Tibet

In this paper, the formations of jammed dam by debris flow's injection and the influences on mainstream's riverbed by subsequent outburst of the dam are discussed based on a model test. The experiments lasted 3 months, together with 13 groups of tests in all. As the junctional angle is equal to 90, the critical index of jammed dam was established through the adjustments of density of debris flow, discharge ratio and momentum ratio between branch gully and main river; the jammed dams were easily formed when r >1001.16; the two events of damming in Peilong gully (1984, 1985) were discriminated. The shrinkage ratio of main river S and coefficient of velocity variation Fv have been defined, and the results indicate that there is a linear relationship between momentum ratio and shrinkage ratio of main river, and also an exponential relationship between ultimate average width of main river and coefficient of velocity variation. This model test can simulate the process of damming of debris flow, and the results that offer theoretic basis for the mitigation of debris flow are comparatively reasonable.