Case History of Embankment Failure: Geological and Geotechnical Aspects of the Celotex Levee Failure, New Orleans, Louisiana

摘要

A section of levee along the Mississippi River near Marrero, LA, failed in a nonflood-related event. This report addresses the factors that contributed to that failure, which involved nearly 230,000 cu m, and the mechanisms of failure. The data examined during research on the causes of levee failure included geologic setting, historic bank migration and previous bank lines, thalweg profiles, width/depth ratios, scour pool movement, and river profiles. The geology within the pertinent river reach and Holocene chronology of changes in the river channel profile were critically important factors in revealing the cause of levee failure. The Marrero or Celotex failure occurred within sandy point-bar deposits from a former distributary channel of the St. Bernard delta system. During historic time, the river channel narrowed appreciably in the failure reach, while maintaining a near-constant cross- sectional area. The general failure mechanism involved scouring and erosion of sand from the toe of the river bank, causing an over-steepened slope and resultant instability of the upper bank. That is, severe scour at the toe resulted as the thalweg deepened through the sandy substratum. Flow failure in the sands then led to loss of the upper bank or batture.