Okan, Merve
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merve.okan@ieu.edu.tr
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05.03. Civil Engineering
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6
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6
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2
Documents
4
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59
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7
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3
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2
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6
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1
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0.29
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| Journal | Count |
|---|---|
| -- 10th IAHR International Symposium on Hydraulic Structures, ISHS 2024 -- 2024-06-17 through 2024-06-19 -- Zurich -- 215612 | 2 |
| Bulletin of Engineering Geology and the Environment | 1 |
| International Conference on Civil, Structural and Transportation Engineering | 1 |
| Journal of Innovative Science and Engineering (JISE) | 1 |
| Proceedings of the IAHR World Congress | 1 |
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Conference Object Citation - Scopus: 1Application of Artificial Neural Network for Predicting Peak Discharge from Breached Embankment Dam(International Association for Hydro-Environment Engineering and Research (IAHR), 2024) Okan, M.; Bor, A.; Tayfur, G.Estimation of peak discharge is a key parameter for risk assessment in case of dam failure, and has attracted great attention from researchers in recent years. Many formulas are available in the literature, but these cannot cover all experimental scenarios. Existing models are typically inadequate to address the complexities of dam breaches. This research attempted to predict the peak discharge in the breached embankments with an artificial neural network (ANN) model, which is effective in nonlinear problems, using datasets obtained from various dam breaches cited in the literature. The ANN model is useful in the preparation of emergency action plans since it enables prediction of peak discharge. Multilayer Perceptron (MLP) with Levenberg-Marquardt (LM) and Bayesian Regularization (BR) algorithms was used to predict peak discharges from breached embankments. The dataset was divided into three: 56% for training, 20% for validation and 24% for testing. Different scenarios were created using different input combinations. Performance evaluation was based on the root-mean squared error (RMSE), percent bias (PBIAS), determination of coefficient (R2), Nash-Sutcliffe efficiency (NSE) and RMSE-observations standard deviation ratio (RSR). A comparison of training algorithms revealed that LM showed the best performance when the best ANN was selected from 1000 networks. Volume of water above the breach bottom (Vw) had a greater effect on model performance than the depth of water above the breach bottom (Hw). The best performance was obtained when both Vw and Hw were used as input. © 2024 ISHS. All Rights Reserved.Article Numerical Study of Breaching at Upper Parts of Homogenous Earthen Dams(Springer Heidelberg, 2025) Dumlu, Emre; Guney, Mehmet Sukru; Okan, Merve; Ozden, Guerkan; Tayfur, GokmenIn this study, time-dependent finite element analyses of the breaching process in two homogenous earth-fill dams were performed using the finite element method. Breaching was initiated at the middle and corner sections of the upper part of the dam bodies. The numerical results were compared with the findings of the experiments realized on dams 60 cm high, 2 m wide at bottom, 20 cm wide at crest with 1 V:1.5H side slopes at upstream and downstream faces. This numerical study combines time-dependent hydraulic gradient distributions and groundwater flows to assess breach areas, velocities, and flow rates. A Python algorithm was integrated with the Jupyter console, allowing the simulation of the breach mechanism in multiple runs to determine breach parameters. Both numerical and experimental analyses revealed that the dams were exposed to backward erosion, starting at the downstream side of the dam and progressing inward. The compatibility between experimental and numerical results was sought by means of the parameters RMSE, MAE and the statistical performance of the numerical approach was evaluated by using RSR, NSE, and PBIAS. A fairly good agreement was obtained between the experimental and numerical results.Conference Object Comparison of the Evolutions of Internal Erosion When Seepage Is at Top, Bottom or Middle Part of the Homogeneous Earth-Fill Dam Built With Fine Sand and Clay Mixture(International Association for Hydro-Environment Engineering and Research (IAHR), 2024) Güney, M.S.; Dumlu, E.; Okan, M.; Kalyoncu, Y.One of the most prominent failure reasons for earth-fill dams is internal erosion resulting from piping. This failure mode may cause irreversible weakened structural integrity, loss of properties, and even loss of lives. Therefore, it is important to understand the breaching process due to piping by providing reliable data for the decision-makers in case of emergency. This study was supported by the Scientific and Technological Research Council of Turkey with project number 119M609 and involves experimental investigation on piping under three different weak zone scenarios to examine the breach process and provide the data for more realistic numerical evaluations. The experiments were conducted in the hydraulic laboratory of Izmir University of Economics and Dokuz Eylul University. The initiation of piping was triggered from seepage in weak layers at the bottom, middle, and upper parts, along the centerline of homogenous earth-fill dams in a rectangular flume. As a result of the experiments, the magnitude of the peak discharges and their durations as well as the eroded breach areas were found to be affected by the locations of the seepage and initial water heads acting on the weak zones. Also, in the experiments, at the beginning of the breaching, initial cascading surface flow resulted in sheet and rill erosion. © 2024 ISHS. All Rights Reserved.Conference Object Citation - Scopus: 2Experimental Study of the Evolution of the Breach and the Discharge Through the Breach Resulting From Piping Due To Seepage at the Earth-Fill Dam Bottom(Avestia Publishing, 2022) Guney M.S.; Dumlu E.; Okan M.; Bor Türkben, Aslı; Aklık P.; Tayfur G.Piping is one of the main causes of the earth-fill dam failures. Most of the researchers realizing numerical analyses make some simplified assumptions concerning the shape of the breach and the discharge of water flowing through the breach. The aim of this study is to realize experiments to provide data needed to perform numerical analyses by making more realistic assumptions. The dam having a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m is built in a channel 1 m wide, 0.81 m high and 6.14 m long. The evolution of the breach and the discharge through the breach resulting from piping due to seepage at the earth-fill dam bottom was investigated experimentally. The evolution of the dam failure is recorded by six cameras located at different locations. The time-varied of the breach areas at upstream and downstream sides are determined by applying the Gauss Area functions. The discharge of water through the breach and average outflow velocity are determined by using the continuity equation. © 2022, Avestia Publishing. All rights reserved.Article Comparison of Levenberg-Marquardt and Bayesian Regularization Learning Algorithms for Daily Runoff Forecasting(2025) Bor, Asli; Okan, MerveIn this study, Multilayer Perceptron (MLP) with Levenberg-Marquardt and Bayesian Regularization algorithms machine learning methods are compared for modeling of the rainfall-runoff process. For this purpose, daily flows were forecast using 5844 discharge data monitored between 1999 and 2015 of D21A001 Kırkgöze gauging station on the Karasu River operated by DSI. 6 scenarios were developed during the studies. Our findings indicate that the estimated capability of the Bayesian Regularization algorithm were close to with Levenberg-Marquardt algorithm for training and testing, respectively. This study shows that different network structures and data representing land features can improve prediction for longer lead times. We consider that the ANN model accurately depicted the Karasu flows, and that our study will serve as a guide for more research on flooding and water storage.Conference Object Citation - WoS: 2Citation - Scopus: 3Experimental Study of the Evolution of the Breach and the Discharge Through the Breach Resulting From Piping Due To Seepage at the Earth-Fill Dam Top(International Association for Hydro-Environment Engineering and Research, 2022) Güney, Mehmet Şükrü; Okan, Merve; Dumlu, E.; Bor Türkben, Aslı; Aklık, Pelin; Tayfur, G.Internal erosion, also known as piping, is one of the most important causes of earth-fill dam breaks. Many researchers dealing with numerical analyses in this area make some simplified assumptions about the shape of the breach and the discharge of water flowing through the breach. This study was conducted in the scope of the project supported financially by the Scientific and Technological Research Council of Turkey and it consists of experimental study which aims to provide data needed to perform numerical analyses with more realistic approaches. A dam with a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m was built in a flume 1 m wide, 0.81 m high and 6.14 m long. Before the construction of the dam, some common soil mechanics tests were carried out. The dam was constructed by using a mixture consisting of 85 % sand and 15 % clay. A circular tunnel with a diameter of 2 cm was created along the centerline at 6 cm below the dam crest. In the closed system, water was pumped from the lower reservoir to the upper channel. Six cameras located at different locations recorded the evolution of the dam failure. Gauss Area formula was applied to determine the time-varied of the breach areas at upstream and downstream sides. The discharge of water through the breach and average flow velocity were determined by using the continuity equation. The changes in water depth in the channel were also recorded. © 2022 IAHR.Article Experimental Study of Evolution of Breach Resulting From Piping at Upper Part of Earth-Fill Dam(Turkish Chamber Civil Engineers, 2025) Guney, Mehmet Sukru; Tayfur, Gokmen; Bor, Asli; Okan, Merve; Dumlu, Emre; Aklık, PelinPiping and overtopping are the most important causes of earth-fill dam failure. Such dams may erode under seepage, causing a reduction in the structural strength. The aim of this study was to investigate the temporal evolution of the breach and flow rate from the breach resulting from the piping in earth-fill dams. The experiments were carried out at Hydraulics Laboratory of Civil Engineering Department of İzmir University of Economics. The dam was constructed by using a mixture consisting of 85 % sand and 15 % fine (low plasticity clay). In the first scenario a circular tunnel with a diameter of 2 cm was created along the centreline at 6 cm below the dam crest whereas in the second one it was located at the upper edge. Six cameras at different locations recorded the evolution of the progress of the breach formation. The pump flow rate was measured by magnetic flow meter, and the continuity equation was used to calculate the flow rate values from the breach. The time-varied values of the total breach areas were determined using the Gauss Area formula. The image processing method was also applied in the determination of the breach areas. The time-dependent changes of water depth in the channel were also recorded. The obtained experimental findings are presented and commented, together with the universal dimensionless curves. The failure of the dams occurred mainly because of the head cut erosion developed from downstream to upstream. When breaching started, the orifice flow was converted to open channel flow where breach bottom behaved like a broad crested weir. In the second scenario, the rigid lateral side considerably influenced the flow rate and the development of the breach. The peak flow rate corresponding to the first scenario was found approximately 2.3 times greater than that of the second one. The maximum values of all the breach parameters were reached earlier in the case of the seepage along the centerline. The ratios between the values corresponding to the first and the second scenarios were found as 3.25 and 1.75 for maximum breach areas at downstream and at upstream sides, respectively. These ratios were 2.44 and 1.37 for the average breach widths at downstream and upstream sides, respectively. A very good agreement was found between the area values obtained from Gauss area method and image processing technique, in both scenarios. This fact demonstrated that either of these two approaches can be used to determine the time-dependent breach areas. These experimental findings provide the opportunities for the calibration and validation of the numerical models used in the relevant numerical investigations. This study also offers guidance for the strategies concerning emergency action plans related to the failure of homogeneous earth-fill dams when the piping starts at upper part of the homogeneous earth-fill dams.
