Research On The Erosion Damage Progress Of Hormogeneous Earth Dam After Overtopping

The research on dam-break problem can be divided into two aspects. On the one hand is the process of transmition and evolution when the dam-break flood wave is in downstream riverway, on the other hand is the process of the dam own breaking and bursting. In this paper, we put an emphasis on the latter one. Dam bursting caused by many causes such as reservoir overtopping caused by excessive flooding, infiltration and damage of dam body, landslide of dam body, and so on. The process of the dam bursting is not the same according to the factors which causes the damage. In this paper, simulation of the whole process in which the homogeneous earth dam body is eroded, destroyed and finally burst by the power of the overtopping current when the reservoir is overtopped due to the excessive flooding is projected, and some studies of the basic issues which are needed in the simulation is also paid attention to.The one dimension and two dimension mathematical model for the current movement on slope is established firstly, which provide a new method of calculation for the flow of the broken dam. On the basis, the mathematical models of scarp formation and development are established. The formula for starting shear stress and erosion rates which is educed by the examinnation is adopted to calculate the erosion of the dam. The establishment of scarp collapse mode and lateral collapse mode provide a theoretical basis for the simulation of the bursting breach formation and evolution in the process of eroding and destroying when the homogeneous earth dam is overtopped, considering the effects caused by the terrain random undulation and the the impact resistance property diffence which affect separately and synchronously on the dam overtopping. The paper mainly discussed the following issues:(1) The research purpose and significance of the simulation to the process of the homogeneous earth dam overtopping erosion and damage is described, the research status quo on the soil starting, erosion, dam breaking simulation and gullies network formation is reviewed, the main contents of this article is drawn up.(2) One and two dimensional water movement mathematical equations are deduced under the slope coordinate system, and the equations are transformed to the equations under the plane coordinate system. The equations are suitable for calculating the water movement under the condition of the large slope, equations are dispersed for programming. Three different slopes are selected for flood calculation, and the results of flow are analyzed and compared with or without equations amendment and the change of slope.(3) One dimensional mathematical model of the process of earth dam overtopping and break is established to simulate the formation and development process of the scarp. Earth dam gradually develops into the scarp during the process of overtopping and break, the collapse of scarp will lead to dramatically reduced crest elevation and the formation of dam breach. The scarp collapse mode is established in this model through mechanical equilibrium, and the sliding surface is not limited by the foot of slope. The effects of existence and nonexistence of scarp collapse on the earth dam overtopping and break are analyzed by means of calculation. A variety of soil samples are put in a rectangular pipe flume to experiment in the dam erosion trial. The corresponding relationship of incipient shear stress, erosion rate and their influencing factors is analyzed according to the experiment results, two formula of incipient shear stress and erosion rate are presented.(4) The two dimensional mathematical model of the process of earth dam overtopping and break based on two dimensional flow mathematical equations on the slope is established. Transverse collapse mode of the soil body is established in this model according to mechanical equilibrium, and the scarp collapse mode is adopted in longitudinal collapse. The formula of dam soil starting shear stress and erosion rate is adopted to calculate the erosion of the slope soil in the model. The effects caused by the terrain random undulation and the the impact resistance property diffence which affect separately and synchronously on the dam overtopping is analyzed by means of calculation, and the simulation of the deepening and widening process of earth dam crevasse with one and two diversion channels is processed by using the established model.