نشریه سد و نیروگاه برق آبی ایران
پیاپی 27 (زمستان 1399)

In this study, the effects of diameter and location of drain pipe in uplift force and exit hydraulic gradient in the foundation of gravity dams are investigated. For this purpose, a numerical model of gravity dam foundation is simulated using finite elements method. The results indicate that drain pipe under the gravity dam reduces the uplift force and exit hydraulic gradient. Location of the drain pipe in 0.25L (L is the dam width), and 0.75L from the dam heel, causes to reduce for uplift force and exit hydraulic gradient in minimum value, respectively (optimum place). In addition with increasing the depth of drain, the uplift force at first decreases and then increases. The drain pipes diameter has little effect in uplift force and exit hydraulic gradient and thus its selection is dependent to construction cost considerations. By defining the best position for the location of drain pipes, it was observed that drainage pipes in these situations increase the safety factor up to 1.5 to 2 times against the structural overturning.

The Liroo Dam is one of the largest concrete dams in the country under study. The objective is to investigate and estimate the amount of water leakage from joints and fractures in dam abutments using numerical method. Interconnected fractures are the main pathways of water flow into the abutments and control the rock hydraulic behavior. Considering the stochastic properties of the geometric parameters of the joints, especially the persistence of the joints, and the presentation of a more realistic model is essential for hydraulic analysis. Therefore, geometric model of discrete fractures network (DFN) was prepared in 3D using 3D-DFN written code. Finally, after validation of DFN model constructed with the extracted values, it is found that the average fit for the different geometrical components and the values ​​of the joints intensities are over 90%. These results were used as reliable inputs of the geometrical model for modeling the hydraulic flow of the left and right abutments using the Discrete Element Method (DEM) in the UDEC software. The total leakage rate was calculated to be 135415 m3 / year. Compared to the useful volume of the reservoir, the total leakage from both supports comprises 0.03% of this useful volume.

The piano key weir (PKW) is a new type of hydraulic structure that has been of great interest to designers in recent years. In the present study, steady flow on the types A, B, and C PKWs was studied numerically using the FLOW-3D numerical model. Upon software validation using the experimental data, the 3D flow pattern on the types A, B, and C PKWs was studied, and along with the evaluation of the flow hydrodynamics, the differences in the flow behavior for different geometries were explained. The results showed that the wetted perimeter of the type B PKW was more than that in the types A and C PKWs. Therefore, the velocity of the approaching flow to the type A PKW was less than that in the other two types, which led to a more uniform flow distribution over different parts of the output key and hence, decreased the local submergence and increased the outflow percent from the output key crest. This finally led to an increase in the total output discharge as well as the discharge coefficient of the type B PKW compared to types A and C PKWs.

In this research, a seawater desalination system has been studied and simulated by magnetic-electric method. The electric field is considered to ionize seawater and the magnetic field to isolate it. The equations of motion of water and salt particles are modeled by the Euler-Lagrangian method. Particularly important for the separation of micron diameter salts, the magnitude of the electric and magnetic field, and the rate of seawater inlet to the separation system.

Additionally, if the materials at downstream of bucket spillway are erodible, the ogee spillway is likely to overturn by the time. Therefore, the prediction of the scour after bucket spillway is pretty important. In this study, the scour depths at downstream of bucket spillway are modeled using a new meta-heuristic model. This model is developed by combination of the Adaptive Neuro-Fuzzy Inference System (ANFIS), Particle Swarm Optimization (PSO) and Fuzzy C-Means Clustering (FCM). In addition, to assess the performance of meta-heuristic models, the Monte Carlo simulations (MCs) are used. Also in this paper, the k-fold Cross Validation is used for examination of the models ability. Moreover, the superior model was introduced using analyzing the numerical results. The model predicted the scour depth in terms of all input parameters. The model estimated the scour at downstream of bucket spillway with reasonable accuracy. For example, the mean absolute percentage error and root mean square error for this model were obtained 7.544 and 0.189, respectively. In addition, the superior model was compared with ANFIS model that analyzing showed the compound model had more accuracy.

Design of earth dams and their problems are important during construction and after it,because of their potential hazards and failure for downstream population. The dam foundation seepage control the the importance from the perspective of a major engineering project and explain the economic performance of each project is allocated. among activities that can be used to prevent piping phenomena and reduce seepage and exit gradient are installation of cutoff wall under hydraulic structures. In this study, using software Seep / 2D finite element method to evaluate and calculate the seepage from pays.Shamilearth dams in the Hormozgan province have been modeled. The effects of the thickness cut off wall of the dam, cutoff wall and foundation Homogeneous and heterogeneous conditions, Uplift pressure, hydraulic gradient, discharge of the dam covered. The results showed that in the absence of the screen cut off wall ofShamildam about 4 million cubic meters of water will seepage in the dam foundation. The wall also seal the heel to the toes to move freely in the line seepage is higher.

Acquiring optimal dimensions of concrete dams by reducing the cross section will reduce the volume of concrete used and consequently reduce construction costs. Due to multiplicity of constraints which leads to complexity of the decision space, meta-heuristic optimization algorithms have been increasingly used in optimal design of gravity dams. In this study, performance of Grey Wolf Optimizer was assessed in optimal design of Koyna concrete gravity dam and the results were compared to Particle Swarm Optimization. Results indicated that Grey Wolf Optimization was able to reach to a 5.2 percent lower mean optimal cost over 10 runs result with considerably a 61.5 percent smaller number of function evaluations compared to Particle Swarm Optimization and considering stability of the algorithm results obtained from Grey Wolf Optimization had smaller standard deviation than Particle Swarm Optimization. However, in 10 consecutive runs, the minimum optimal value reached using Particle Swarm Optimization was 1.6% smaller than the smallest optimal value obtained from Grey Wolf Optimization, considering overall performance of algorithms, Grey Wolf Optimization presented a promising performance having a faster and stable convergence