High Dams: the Viewpoint of the Geologist

If rocks were entirely homogeneous it would probably rarely, if ever, be necessary to call upon a geologist to examine a site for a high dam. It could safely be assumed by the engineers that the rock exposed at the site continues unchanged in horizontal and downward directions, and that consequently the appropriate tests for strength, imperviousness, and other properties, applied to samples from the site, would determine whether a dam could safely be constructed at that locality. At first thought, the necessity for considering the effect of earthquakes might be regarded as an exception to the foregoing general statement, but serious earthquakes are a consequence of movement along faults, and faults are obviously departures from homogeneity.