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Title: Performance of levee underseepage controls : a critical review
Authors: Wolff, Thomas F.
Keywords: Critical gradient
Flood-control levee
Internal erosion
Levee design
Mississippi River
Relief well
Sand boils
Seepage berms
Publisher: Geotechnical and Structures Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: ERDC/GSL TR ; 02-19.
Description: Technical Report
Abstract: 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 1940s and 1950s. Intensive construction of control measures was accomplished in the 1950s and 1960s. 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 1950s many technical advancements have been made in engineering analysis techniques and construction methods that may merit application to underseepage problems. The Federal Government’s levee system will be expected to provide flood protection for many centuries, regardless of its so-called economic life. It will undoubtedly be subjected to floods equaling and exceeding those already experienced. Conditions along the levees are not static but are subject to periodic natural and man-made changes. Such changes may necessitate review, reanalysis, redesign, reconstruction, and/or modification of the system. Several researchers have prepared voluminous evaluations of the performance of particular levees in particular floods. This report draws on those previous assessments to summarize in one source what has been learned from observations during floods up to 1986. Using that knowledge, the analysis procedures and the performance evaluation procedures are reviewed to identify possible areas of improvement.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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