Performance of Levee Underseepage Controls: A Critical Review

摘要

The Federal Government through the U.S. Army Corps of Engineers (USACE) has a large investment in flood-control levees. Where such levees are built on pervious foundations, seepage beneath the levee (underseepage) during floods can produce pressure and flow conditions capable of initiating subsurface erosion leading to levee failure. Two adverse phenomena may occur; one is sand boils which involves the movement of subsurface sand to the surface by flowing water, and the other is heaving which involves the upward movement of a relatively impervious surface layer resulting from subsurface water pressures in excess of its weight. To prevent such occurrences, the USACE has developed a set of procedures to analyze underseepage conditions on a site-specific basis and a set of procedures to design underseepage control measures. For the most part, these procedures were developed in the 194Os and 1950s. Intensive construction of control measures was accomplished in the 195Os and l96Os. Several moderately large and major floods have provided data from which the validity of the procedures and the security of the constructed system can be inferred. Also, since the 195Os many technical advancements have been made in engineering analysis techniques and construction methods that may merit application to underseepage problems.