عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Monitoring and evaluating earth rock-fill dams during different stages of their lifetime including construction, impounding, rapid drawdown, and earthquake occurrences are important for improvement of dam monitoring, safety control, and stability. Historically, earthquakes had caused severe damages and human loss. The destruction of infrastructures such as dams is of concern because of financial and human losses caused from water flowing downstream into densely populated human settlements. Based on the world’s earthquake data, rock-fill dams showed different behavior under earthquake conditions, ranging from minor damage and deformation to complete destruction. Here we selected the Gotvand dam, one the largest rock-fill dams in Iran, as a case study. We modeled and evaluated the largest cross-section of the dam (the 4th cross-section) using a two-dimensional finite element software, FLAC4.0. We compared the results of back analysis with the data collected from instrumentation and characterized materials’ properties exactly. In numerical analysis, concerning the nonlinear nature of geo-mechanic materials such as soil, we used Mohr-coloumb constitutive models and hardening-softening models to simulate the behavior of materials in the foundation and the body of the dam, respectively. Under elastic conditions, the main assumptions include: 1) increasing the internal friction angle with increasing plastic strain; 2) dependence of material’s elastic modulus and dilation angle on confining pressure; and 3) bulk modulus of water dependence in a medium tension stress of the elements during the construction and first impounding to estimate the pore water pressure correctly and saturation collapse simulation during first impounding. We ran the model for five years after impounding until it reached a steady state. Using Mohr-coloumb nonlinear constitutive models through missing-Fin rules are adopted in this model, which can simulate nonlinear and hysteretic behavior of soil and rock-fill materials under earthquake condition, we performed dynamic analysis to predict the displacement of the Gotvand dam under maximum credible earthquake (MCE) condition. The type of acceleration time history and the magnitude of input acceleration are also investigated to predict the dynamic behavior of the dam including deformations on the design basic earthquake (DBE), the maximum design earthquake (MDE) and MCE. The maximum settlement of the dam core due to the application of the Manjil earthquake was equal to 1.94 meters and the maximum horizontal deformations were 1.30 and 1.19 meters in upstream and downstream shells, respectively. The results showed that the dam deformations were highly influenced by the magnitude of the earthquakes and acceleration time history.