Experimental Study On The Breaching Processes Of Debris Flow Dams

The debris flow dam is a particular kind of natural dam which forms when mud and debris reaches a river channel causing its blockage.Earthquakes often lead to a large number of collapses and landslides,which provide abundant material conditions for the formation of debris flows.As a secondary disaster,debris flow dams gradually appear.The rise of water level will lead to the inundation of upstream backwater,and the collapse of dammed lake will also set great threat to the lives and property safety of downstream residents.The large-scale debris flows will lead to the formation of barrier lake,and the rise of lake water level will seriously threaten the life and property safety of downstream residents.Therefore,it is significant to carry out the research on debris flow dam breach.In this paper,the representative debris flow dam events in different areas were investigated in the field and the data were consulted.The process and mechanism of debris flow dam break and the peak discharge after break were studied by combining model experiment and theoretical analysis.The main research work of this paper is as follows:First of all,the paper has carried on the field investigation and the related literature review,and has counted the representative debris flow blocking river and dam break cases in different areas.Based on the data analysis of debris flow dam,the formation and breaking process of debris flow dams are summarized,and the influence of upstream inflow,dam shape,dam height,clay content and debris flow viscosity on debris flow dam is mastered.Secondly,the experiments of debris flow dam break under different inflow,dam shape,clay content,dam height and initial water content are carried out.The main process of debris flow dam break is summarized,which includes slope erosion process(stage I),scarp erosion process(stage II),lateral erosion process(stage III)and decline process(stage IV).The influence of pore water pressure on the process of debris flow dam break is analyzed.And the evolution mechanism of the breach is studied,the starting mechanism of the landslide dam and the viscous debris flow dam on the slope is compared and analyzed,the erosion rate model of the dam with different materials is compared and studied,and a new erosion process tracking technology is proposed,which can better analyze the erosion process of the dam.Finally,There is a non-linear positive correlation between the peak discharge and the inflow.The peak discharge increases with the increase of the inflow,and the growth rate is faster and faster.The peak discharge increases with the increase of the backwater slope gradient.The peak discharge at the back slope gradient of 0.577(30 °)is about 1.7 times of that when the backwater slope gradient is 0.176(10 °).The peak discharge increases rapidly with the increase of dam height,and the peak time decreases with the increase of dam height.The flow rate decreased rapidly with the increase of clay content,and the collapse time increased rapidly with the increase of clay content.With the increase of soil initial moisture content,the peak discharge of outburst flood decreases slowly,but the range of change is small.According to the influence of different factors in the experiment on the discharge of debris flow dam break,the calculation formula of peak flow of debris flow dam break is established.