Discharge Capacity of Earth Dams Toe Drain with and without Clay Core

The objective of this study was to reduce the hydraulic gradient and consequently to weak the piping phenomenon. For this purpose, various models of geometric dimensions and hydraulic performance of clay core and toe drainage in earthen dams were investigated. Therefore, by using experimental modeling in both homogeneous and heterogeneous states, the seepage rate and the ferritic level in the earthen dam body with water level readings in seven observation wells and piezometric pressure measurement in 30 piezometers installed on the channel wall have been examined. Accordingly, three dimensionless ratios  with three heights (0.12, 0.20 and 0.28 m) at different angles (45, 60 and 90 degrees) were chosen to evaluate the performance and provide the optimal index  in the toes drainage design of earthen dams. Then the results of PLAXIS numerical model were validated by experimental data through calibration parameter and P-VALUE and RMSE statistical tests. The results showed that the optimal geometric dimensions of toe drainage due to direct relationship of reservoir water level with the position of the ferriatic line and its exit from the lower slope of homogeneous and heterogeneous earth dams are directly related to hydraulic conductivity and water level in the reservoir. In heterogeneous earthen dams, these values ​​are inversely related to the thickness of the clay core. By comparing and using regression analysis, an equation was proposed to predict the drain height of the homogeneous dam, which is more accurate for larger values of . Finally, the toe drainage size of homogeneous earth dam with an angle of 45 degrees and index of  and in heterogeneous state, the angle of 45 degrees with index of  have been reported as the optimal state.