Numerical Simulation of Effect of Drain Pipe in Uplift Force and Exit Hydraulic Gradient in Gravity Dams

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.