Investigation of the effect of depth and distance between cutoff walls on uplift force for gravity dams

摘要

The purpose of this study was to investigate the effect of the location of cutoff walls, the number of walls (or their spacing), and their depth in the foundation of dam on the uplift force and the exit hydraulic gradient. The solutions are obtained with the finite element method; the effect of depth and location of the walls was studied. In addition, multiple cutoff walls at six different depths and separations were considered. As the depth of a cutoff wall at the heel of dam increases, the uplift pressure and the exit hydraulic gradient decrease if there is only one cutoff wall. The uplift pressure was 51.58% and the exit hydraulic gradient was 49.33% lower than the non-cutoff wall state and for a ratio ofd/D = 0.96. In the case with two or three cutoff walls, reducing their distance from each other decreases the uplift pressure, while increasing the distance reduces the exit hydraulic gradient. The results indicate that when multiple walls are used, their spacing should be such that the length of the water flow path is prolonged. In order to validate the present study, the present numerical model was evaluated against analytical calculations for a given condition. The results showed excellent agreement between the numerical calculations and the expected results, thereby adding confidence in the results.