The Significance of Pore Pressure in Hydraulic Structures

By deductive reasoning it is shown that under and within any concrete structure founded below water level, or with water on one side (such as a gravity dam, even on rock foundation), hydrostatic uplift acts over the entire horizontal area, instead of over one half or two thirds of the area as commonly assumed. It is shown that it is the magnitude of the uplift force which is uncertain and which should be the subject of field observation and experimental investigation, not the area of application. It is also shown that the hydrostatic force against a dam is applied progressively along the route of seepage, instead of against the upstream face. Various implications of these fundamental principles are discussed.