| Debris flow, with big specific gravity, high velocity, large discharge, and strong destructive power, carry a gteat amount of sediment, especially the large-size one, into the Main River. The composition of flow and sediment and the boundary condition within the conjunction area is changed in a short time, which will seriously affect the movement characteristic of sediment and flow, and even the evolvement of the Main River. The water level of the Main River will be blocked up and the solid material of debris flow will be deposited in the conjunction area. This causes a serious change for the bed form and the flow condition in a long distance near the conjunction area. A dam and barrier lake will be built under even more serious condition. As an effect, the grain field, railway, highway and all of the construction along the river in upstream will be submerged. Even terrible, if the water overflow, it will lead to backward erosion; And if the dam outburst, major outburst flood will come forth. Because of the long distance uncommon scour, the grain field of downstream and construction along the river will be destroyed, which is a secondary disaster. It will be crowning calamity for downstream inhabitant. Thus it can be seen that to study the mechanism of debris confluence with the Main River has operation significance. Moreover, it is a complex interaction between non-Newtonian flow andNewtonian flow when debris flow joines into a Main River. To study the movement mechanism of flow and sediment under the complicated condition has theoretic significance.In this paper, based on the experiment, the movement characteristic of flow and sediment in conjunction area is studied. The height of back-water in Main River, the deposit law within the conjunction area, the critical condition of river blocking and the re-incipient of wide-size distributed non-uniform sediment have been studied in depth through theoretical analysis on the basis of experiment. The paper consists of 6 chapters. The main contents are as follows.The research status of debris flow and conflow are introduced in the firrst chapter. It shows that the interaction between debris flow and Main River is a complex problem of interaction between non-Newtonian flow and Newtonian flow, which is lack of systemic study by now. It is also be pointed out that the complex problem, especially, the flow and sediment movement characteristic in conjunction area, should be studied based on the experiment.A series of experiments aimed at exploring the mechanism of the confluence between debris flow and the Main River are introduced in the second chapter. The arrangement, equipment, and condition of the experiments are dealed with. The experiment phenomena are described in detail by charts, figures and photos. Meanwhile the relation among the relative factors is analyzed and summed up. Through the description of the conjunction experiment phenomena of debris flow with different specific gravity, it shows that specific gravity of debris flow is a main factor that influence the turbulence intensity of conjunction area. The lower debris flow specific gravity, the higher joined velocity, and correspondingly the stronger turbulent intensity. Vice versa. According to the rule of the experiment of different discharge ratio, discharge ratio is a main factor that reflects the contrastive relation of discharge of debris flow and the Main River. The bigger discharge ratio, the stronger action of debris flow to the Main River. As a result, with low debris flow specific gravity the turbulent intensity will be increased. When debris flow specific gravity is high, the structure of it is maintained, and river blocking will be producedeasily. But if the discharge is equiponderant, it will stir strongly for both high and low debris flow specific gravity. Conjunction angle is found to be another important factor which influences the mechanism of debris flow joining into the Main River. The bigger conjunction angle, the higher block-water in the Main River, and the easier rive...
|
PDF Full Text Request