ABSTRACT
The soil upon which dams are founded is porous and consists of a skeleton framework of solid particles with pores throughout. The penetration and movement of water through the porous medium, under the action of the gravitational potential occurring after the construction of water-retaining structures and the filling of the reservoir, is called seepage. Seepage may occur in the foundation beneath the dam (Fig. 3.1a), and in the banks beside the dam, as well as through the dam itself if it has been constructed with earth material, such as an earth dam (Fig. 3.1b). Owing to seepage, the following harmful effects may occur:
a) Loss of water in the impounding reservoir. b) Pressure at the bottom of the dam, directed from below upwards and perpendicu-
lar to the bottom, which is called uplift pressure; this force is rather unfavourable, since it lightens the dam and reduces its resistance against the action of the horizontal forces.
