Investigation and Comparison of Saturated and Unsaturated Flow in the Gilan-Gharb Embankment Dam

Document Type : Research Article

Authors

1 Department of Water Engineering, Faculty of Agriculture, University of Tabriz

2 Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran

3 Department of Water Engineering

4 Department of Water Engineering, Faculty of Agriculture

Abstract

The purpose of this study is to investigate the characteristics of seepage flow in the Gilan-Gharb embankment dam in two saturated and unsaturated flow states using numerical simulation. The results of the numerical model for saturated flow and unsaturated flow indicated that the seepage flow rate in the unsaturated flow state is higher than the saturated flow state due to the addition of the amount of flow in the areas with capillary fringe flow. The comparison of the first flow line (phreatic line) in these two investigated states indicates that the phreatic line is in a lower location in the saturated flow compared to the unsaturated flow. The factor that has caused such conditions is the presence of suction in the areas above the phreatic line in an unsaturated state, which has provided the ability for the water flow to rise to a higher level. Also, the exit hydraulic gradient downstream of the dam was also evaluated in both cases, and the results of this study revealed that the highest values ​​of the exit hydraulic gradient occur nearly after the toe of the dam, so that the exit hydraulic gradient in the unsaturated state is 1.8 times of the saturated state. Since the exit hydraulic gradient is less than one for both saturated and unsaturated states, the sand boiling phenomenon does not occur in the investigated earthen dam. It should be noted that the hydraulic gradient in the dam body was also investigated for two saturated and unsaturated states and the results showed that the hydraulic gradient in both states are not meaningfully different from each other and the hydraulic gradient values ​​decrease significantly when exiting the dam core so that the value of this reduction in the state of unsaturated flow is more than that of saturated flow. The comparison of the results of the numerical model in both simulation modes indicates that the slope of the phreatic line in the central core is 0.947 for the unsaturated state and 0.905 for the saturated state, so the value of the phreatic line slope in the unsaturated state is 1.047 times of the saturated state.

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References

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Amirkabir Journal of Civil Engineering
Volume 57, Issue 5
2025
Pages 717-740

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