Numerical modeling of dam breach in concrete gravity dams

mosaddeghi, farshid
When a dam fails, a large amount of water is suddenly released that may create large flood waves capable of causing devastating impacts to downstream areas. This is even more important when the damage is caused by an earthquake, as it is unpredictable. The main objective of the research is a detailed simulating of the water surface profile from the first crack to the entire breaking of dams' body during earthquake using Finite Volume Method (FVM). The next objective is detecting of vulnerable zones on the dams' body during earthquake using Finite Element Method (FEM). Due to the complexity of the issue, it is necessary to first ensure the capability of the Flow 3D software in the field of dam failure simulation. For this purpose, pressure inside cracks during an earthquake is used and compared with the data available in literature to verify the Volume of Fluid method (VOF). Different motion types of solid objects due to the earthquake, is used to verify the General Moving Object method (GMO) in the scope of dam failure study. Finally, using the results and information obtained from the validation, models for the dam failure mechanism is presented in sudden and gradual forms. Firstly, an important result obtained from the simulation of the pressure inside the cracks is that by changing the length of the crack or its opening, the pressure distribution inside it changes. Therefore, considering that the failure of the concrete dam begins with the cracking of the body, modeling dam failure is almost impossible for small scales. Secondly, the failure of the dam in a sudden mode that is the result of terrible earthquake, is more dangerous than the gradual failure of the dam, which is very likely in concrete hydraulic structures. According to the discharge hydrographs of the two failure modes, for the gradual mode, the step-by-step increase to the maximum output flow rate occurs, while in the sudden failure of the dam, the discharge quickly tends to its maximum. Finally, by a closer look at the sudden failure of the dam, with decreasing oscillation frequencies for a constant magnitude earthquake, the probability of failure in the sudden state increases. However, after cracking of the body, higher oscillation frequencies will be able to break it in less time. from this perspective the earthquakes that start with small oscillation frequencies and end with higher frequencies are the most destructive ones.


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Citation Formats
f. mosaddeghi, “Numerical modeling of dam breach in concrete gravity dams,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.