Debris Flow Response Characteristics Of The Intersection Mechanism Of The Main Flow Of The River And Its River Bed

Firstly, series of experiments in 90° , 60° and 30° junctions are performed to study the mechanism of confluence between debris flow and the main river. Based on junction phenomena, four modes of confluence, three modes of erosion, one similar mode of equilibrium topography of degradation, and mechanism of confluence between debris flow and the main river have been found. Analytical criterion for blockage of the main flow is also obtained. The impacts of different ratios of water discharge to debris discharge have been analyzed. Secondly, the theoretical equations for deposition of debris flow and confluence between debris flow and water flow are worked out. Finally, theoretical solutions are found in good agreement with experimental data. The experimental study includes the following: 1. Deposition of viscous debris flow and subviscous debris flow in 90° ,60° and 30° junctions without water flow in the main river; 2. Confluence phenomena with different ratios of water discharge to debris discharge; 3. Unsteady erosion process caused by water flow; 4. River process when debris flows into the main river paved by sands, gravels and pebbles; 5. Step-Pool System due to unsteady water flow. The four modes of confluence between debris flow and the main river are as follows: 1. "Pounding the opposite bank " 2. "artial-complete blockage of water flow " 3. "Submerging into water flow" 4. "ixing with and submerging into water flow " Considering the impacts of different ratios of water discharge to debris discharge, three new concepts "ZHOU Line" "Ji Line"and their angle "erosion angle"have been introduced. Making use of the experimental data, it is found that "erosion angle"linearly increases with the ratio of water discharge to debris discharge. In addition, the relation between "diffusion angle"and junction angle should be studied when considering the effects of junction angle on confluence between debris flow and water flow. About the mechanism of confluence, the paper shows that debris flow is a movable submerged or non-submerged spur when it inflows the main river. If it blocks water flow completely, it is called ?Field Dam ? Furthermore, the concept ?debris head loss ?has been introduced and the debris head loss coefficient and water head loss coefficient have been deduced and the methods to compute the two coefficients are given. As debris deposits appear like a fan, polar coordinates are applied and ID theoretical equations are used to approximate the 2D deposition process. Theoretical solutions have been gotten considering and not considering the opposite bank effects. Comparison between experimental data and analytical solutions shows that the solution considering the opposite bank effects fits better than the one not considering the effects of opposite bank. The theoretical equations for the modes of confluence have been deduced and the simplified solutions are obtained. Finally, comparison between analytical solution and experimental data is made, which suggests that analytical solution is applicable when the discharge of debris flow does not vary greatly.