Experimental Study On Mechanism Of Debris Flow Modulated By Silt-Trap DAM

As one principal type of mountain hazards, debris flow gets an enormous menace to the exploitation of mountainous area, and it's imperative to mitigate it. Silt-trap dam is an important and effective debris flow countermeasure by the engineering technique, which is usually built in the forming region. The main function of silt-trap dam is to regulate the performances of debris flow (the velocity, the bulk density and the grain size etc.), reinforce the riverbed, protect the slope and so on. The research of that debris flow performances regulated by silt-trap dam aims at the issues of the dams'semi-empirical design, provides reference and basis to the quantitative design, enhances the comprehensive capacity of the control works, and gets a practical significance to the sustainable development in mountain areas.Based on the study on current situation, the practical investigation of the structure and application conditions of the dams, and the notion of the system collocate optimization, an experiment has been performed. In the experiment, bulk density, gross of the process, stock condition and the rate of the drainage hole were changed to simulate over-current situations of the multiple working conditions. The law of the capability parameters changed along with the control ones was analyzed, and the design optimization of the silt-trap dam was discussed. From the research some results can be shown as follows:(1) When the thinning and transitional slurry get past the empty dam, the drainage holes are unobstructed, and the value of the flux changing with a drainage hole rate 2.2% would be about twice to that with a rate 6.6%; when the capacity is half of the total, both hole over-current and overflow exist, and the former mode gets more proportion, as a result the flux's changing law still belongs to the hole rate; when the capacity is full, the drainage hole is being blocked till the end of the experiment, and the overflow becomes to be the major mode. To the viscosity debris flow's situation, the drainage hole will also be blocked. The flux is recorded 0 with the empty dam while the level keeps the same as the other two kinds slurry with the full capacity situation. (2) Bulk density reflects both the experiment's control and the result of debris flow's capability. When the density is growing up, the ratio will decrease firstly and then increase. The nature of the soil in the trough doesn't change the trend but the value of density. The two formulas "y=0.0034x2-0.1064x+1.7316" and "y=0.0045x2-0.1529x+2.2139" are used to fit the relation between density and its ratio after the dam, which are based on the recorded data of the experiment.(3) As the median size, the grain's D50 is used to characterize the sorting capability of the dam. When the capacity is empty, the ratio of the median size will grow up along with the drainage holes rate enlarged. In the three kinds over-current situations of the experiment, the ratio references are recommended to be 0.60-0.83,0.81-0.94 and 0.98-1.00. When the capacity is not empty, by the influence of the soil mixed with the water in the slurry, there will be a trend that thick grain gets increased.(4) Combined with the phenomenon, the parameters' changing and the consideration of abrasion, the optimization of the silt-trap dam is discussed, which include the flood control standard contact with the nature of the debris flow, the nature evolution's affect to the design calculations of the dam, the consideration of the granule to the quantity sharing and a tentative idea of prefabricated pipe based on the drainage holes'construction.