Detailed Performance Analysis for Levees and Floodwalls in New Orleans During Hurricane Katrina
- C. R. Song (University of Nebraska) | A. Al-Ostaz (University of Mississippi) | H.-D. Cheng (University of Mississippi) | R. Mantena (University of Mississippi)
- Document ID
- American Rock Mechanics Association
- 52nd U.S. Rock Mechanics/Geomechanics Symposium, 17-20 June, Seattle, Washington
- Publication Date
- Document Type
- Conference Paper
- 2018. American Rock Mechanics Association
- 4 in the last 30 days
- 24 since 2007
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ABSTRACT: Hurricane Katrina flooded the New Orleans area in August 2005. Property damage was over $81B, and the number of lost lives was over 1,000 – it was recorded as one of the most disastrous hurricanes in the modern history of the USA. Several organizations such as IPET, NSF and ASCE published authoritative but expedited reports regarding failure mechanisms of levees and floodwalls. Four years of in-depth research conducted by the authors through field and lab tests, numerical simulations, model tests and state-of-the-art centrifuge tests provided detailed evaluation of the levees and floodwalls. The failure pattern of the floodwalls in the London Ave. Canal levee might be either a rotational or a translational failure with a slight variation in soil conditions. Failure did not always follow the rotational mode, which contrasts with previous research. Gap formation in the 17th St. Canal levee was found to be a potential result of the failure, again contrasting previous research. Underlain clayey soils in the London Ave. Canal levee were sensitive enough to cause shearing deformation and associated failure on wetting. Materials in the Inner Harbor Navigation Canal levee were erosive enough to cause a fast failure when subjected to overtopping.
After Hurricane Katrina, several researches such as Anderson et al. (2007), IPET (Interagency Performance Evaluation Task Force, 2007a, 2007b) and Rogers et al. (2008) evaluated the failure mechanisms of levees and floodwalls in New Orleans. In line with these researches, the Department of Homeland Security (DHS) initiated research primarily focused on devising resilient but cost- effective retrofitting techniques. This paper presents a part of those findings from four years of research.
To properly design the retrofitting techniques, effort was devoted to more meticulous evaluation of previously found failure mechanisms through field tests, lab tests, sophisticated analysis, and centrifuge tests. Detailed performance analyses of levees and floodwalls are presented here in.
2. GAP FORMATION
It was believed that the elevated water level of the canals in New Orleans applied high lateral pressure to floodwalls, opened gaps between floodwalls and levee soils, allowed water infiltration into levee soils, reduced the strength of foundation soils, and applied buoyancy force to levee materials (Rogers et al. 2008). This elevated water level eventually became one of the major failure mechanisms of the floodwalls of both the 17th St. Canal levee and London Ave. Canal levee as reported in IPET (2007a). A numerical study by Song et al. (2013) also indicated that the gap formation was the triggering mechanism for the failure of London Ave. Canal levee. Song et al. (2013), on the other hand, indicated that the gap could be the result of failure for the 17th St. Canal levee, as previously mentioned through a careful inspection of centrifuge test images (IPET, 2007b), numerical results by Adhikari (2012), and field sketches by Rogers et al. (2008).
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