Document Type : Original Research Paper
Authors
1 School of Civil Engineering, Collage of Engineering, University of Tehran, Iran
2 School of Mining Engineering, College of Engineering, University of Tehran, Iran
Abstract
Karkheh Dam, a 127-meter-tall earthfill dam with a central clay core in Iran, impounds the country’s largest reservoir with a capacity of 5.9 billion cubic meters. In April 2019, the reservoir experienced an unprecedented water level rise of 5 meters above its normal operating level, raising concerns regarding the dam’s long-term stability under sustained high-water conditions. To address these concerns, a comprehensive safety evaluation was conducted, integrating instrumentation data analysis, limit equilibrium analyses using SLOPE/W, and numerical back-analysis alongside nonlinear dynamic simulations utilizing Fast Lagrangian Analysis of Continua software with updated site-specific earthquake records. The numerical model was iteratively calibrated against observed deformations and pore water pressures to ensure appropriate representation of the dam’s behavior. While this methodology provides practical approximations for intermediate reservoir levels, statistical evaluations indicate that predictions at the normal water level (220 m) carry higher uncertainty and a lower confidence level. Nonetheless, within the limitations of this simplified framework, the results indicate that the dam maintains satisfactory stability under the investigated static and seismic loading scenarios. Under the Maximum Credible Earthquake (MCE), the analysis predicts a maximum crest displacement of approximately 1.35 m. Given the dam’s substantial freeboard of 14 m, this deformation poses no risk of overtopping. Furthermore, the analysis confirms that the upstream and downstream filter zones (5–6 m wide) retain sufficient residual width to prevent internal erosion following seismic deformation. Consequently, the study concludes that under the specified assumptions and modeling constraints, the Karkheh Dam meets the general safety requirements against catastrophic failure.
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