Interstitial Pressures on Rock Foundations of Dams

The reservoir water that percolates through the rock foundations of concrete dams causes uplift pressures that affect stability. It may open the joints and produce piping of the filler materials. Measurements of water pressures inside rock masses have indicated the complexity of the phenomena involved. As the permeability of rock masses is mainly caused by the existence of joints, the examination of the laws of filtration of water through fissures is of primary importance. A theory for the nonsteady state of percolation is established considering the variation of the opening of the joints with the stresses, the volumetric compressibility of water, and the existence of air in the water. Variations of the coefficients of permeability may be expected. The importance of grouting and drainage in controlling seepage is discussed as well as the stability of rock slopes near dams.