Investigation of Drainage Rates Affecting Stability of Earth Dams

The investigation described in this paper was undertaken for the purpose of studying the effects of increased rates of reservoir drawdown on the stability of an earth dam. Field observations of the rates of drainage of several dams were compared with rates computed from a method of analysis similar to procedures used in the theory of heat. Computed and observed rates agreed fairly well. To obtain a wider range of comparison, laboratory observations were made of models and sand samples under a variety of conditions. Both analytical and observed results indicated that the possibility of mass slides resulting from reservoir drawdown has been somewhat exaggerated, but that “sloughing” due to a process of flotation or “piping” induced by drawdown may deserve more attention than it has received. Limitations for the method of analysis are suggested.