Experimental Research On Overtopping Failure Of Cohesive Homogeneous Dams

Earth-rock dams, as the most popular kind of dam in the world, protect and promote mankind society as well as cause huge threat and damage on human lives and property. The failure of Earth-rock dams is complicated and affected by all kinds of factors. Experiment is the most effective method for the understanding of the mechanism of the dam failure. In this paper, experiments were carried out to study the influence of different factors on dam-failure process. Based on the results of the experiments, the failure mode is divided, the maximal outflow is studied as well as the critical time of dam-failures and the safety-assessement for the overtopping failue of earth-rockdams. The main contents are as follows:1?Background and significance of the research on earth-rock dams is described. Results of the research on breaching process, mechnism and modeling are summarized and analized. Research objective and method of this paper is also introduced.2?Overtopping failure tests are described, including the objective, generalized method of different influencial factors, preparation and detection of materials for test dams, test units, damming technology for test dams and test plan. The mixture of clay and sand is used for the test dams.Dry density, soil content and moisture content is strictly controlled in the damming process. The dry density, soil content and moisture content of the dam-material, the intial breach, inflow and dam height are studied as the influencial factors in the tests.3?The main dam-failure types, outflow processes are analized and summarized. Three main failure types are discovered, which are headcut erosion, shear erosion and block failure, as well as two outflow types, which are type of sudden increase-decrease and type of slow evolution. Based on the main failure type and the way that they are coupling, three failue-modes are discovered:Mode1(source-traced and erosive breach), Mode2(rapid shear-erosion and brock-failure breach) and Mode3(surface-denudation and no breach). The failure processes of Mode1include headcut erosion at the dam side in the breach initial phase and breach gradually in the breach deformation phase, while that of Mode2include rapid shear erosion in the breach initial phase and breach enlarge caused by block failure in the breach phase. Surface-denudation is the main process of Mode3. The differences between these3Modes are studied, as well as their cause of formation.4?The effects of the factors such as initial breach, damming material, inflow and dam height on the ratio between destructive power and the strength of the dam are analized. The influencial law and mechanism of these factors on breach mode and breach process is systematically discussed.5?Revised experical formulas for max-discharge are established based on the characteristics of different failure modes, as well as the safety-assessment for overtopping failure. The expressions of critical time and safty fators are built based on the influencial law of different factors on dam breach.6?Achievements and insufficiency of this paper are summarized and future works on this problem are discussed.