Modeling the Effect of Downstream Drain Geometry on Seepage through Earth Dams

Abstract

This research investigates the effect of downstream drain’s geometry on seepage through homogeneous earth dams founded on an impervious foundation. A permeability tank experimental model and SEEP2D numerical model are used in the study. The dam’s failure in the case of no drain is experimentally observed to point out the drain’s importance. The case of homogeneous earth dam with downstream slope protection is also studied experimentally to simulate the case of no drain while avoiding the dam’s failure. The effect of the drain’s geometry on the seepage characteristics is evaluated by considering different scenarios for its height, length, and angle. Three cases for reservoir filling are studied. Sensitivity analysis is also performed to evaluate the drain’s most effective geometrical parameter. The results show that the most effective geometrical parameter of the downstream drain is its length, while its height and angle have almost no effect. Increasing the drain’s length increases the seepage discharge and the distance between the phreatic line and downstream face and reduces the pore water pressure leading to more safety. Design charts and equations are provided.