Effect of Drain Pipes on Uplift Force and Exit Hydraulic Gradient and the Design of Gravity Dams Using the Finite Element Method

The effects of diameter and location of drain pipes on the uplift force and exit hydraulic gradient for a gravity dam are investigated. A numerical model of a gravity dam is simulated using the finite element method. The results indicate that drain pipes under a gravity dam reduce the uplift force and exit hydraulic gradient. The optimal location of the drain pipe with respect to reducing uplift force is 0.25 L (where L is the dam width) from the dam heel, and is 0.75 L with respect to the exit hydraulic gradient. In addition, with increasing drain depth, the uplift force first decreases and then increases. The drain pipe diameter has little effect on uplift force and exit hydraulic gradient and thus its selection should depend on other considerations. When the drain pipe is located at its optimum location with respect to minimizing the uplift force, the volume of dam materials is reduced similar to 30-50%.