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WENG100 – Introduction to Engineering | Failures in civil engineering

   

Added on  2020-03-13

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1Author’s NameDepartment, City, CountryUniversity Name, City, Countryemail addressFailure analysis: Hurricane Katrina Levees and FloodwallsIntroductionFailures in civil engineering works and related structures have culminated into serious destruction of property and massive loss of lives and are a phenomenon that still lives with us[ CITATION Tif15 \l 1033 ]1. Just like any other professional fields, civil engineering is not left behind in experiencing failures of systems. In as much as civil engineering does not give a lot of room for errors besides the best efforts of its professionals, it still experiences errors that lead to loss of billions of dollars by the government and individuals resulting from destruction of property. In the design of any engineering structures, special and utmost attention should be given to the determination of the greatest magnitude of any given form of load that can successfully be applied to a structure without the structure failing[ CITATION Uni10 \l 1033 ]2. In sodoing it would be possible to estimate the safety factor against the failure. BackgroundBy 2005, reports indicated there were numerous floodwalls’ and levees’ failures that protected New Orleans and its surrounding resulting from the passage of Hurricane

2Katrina[ CITATION Com16 \l 1033 ]3. The New Orleans levee system project was designed and constructed by the United States Army Corps of Engineers while the maintenance was done by the local levee boards. Upon completion of the construction, the Corps handed over the project tothe local levee board. The project was 90% completed at the time it started experiencing failures.FailuresInvestigations were done by a team of experts that mainly consisted of civil engineers to establish the root cause of the failure[ CITATION Ada13 \l 1033 ]4. All the investigators came to a consensus that the failure resulted from inadequate design and construction of the floodwalls andlevee system by the Corps of Engineers. The engineers were found to have breached a number ofterm and conditions as outlined in the Orleans Parish[ CITATION New12 \l 1033 ]5. Improper design of the canal floodwalls at London Avenue Canal, 17th Street Canal and Industrial Canal( located on the east side north) was the primary cause of the failure of these canals.[ CITATION Tif15 \l 1033 ]1 Overtopping of floodwalls and levees by the surge of the storm was the failure mechanism of for the Industrial Canal while 10% of sand in place of thick Louisiana clay for the levees that protected the New Orleans of the east was the primary cause offailure on this end. Negligent maintenance of the Gulf Outlet of River Mississippi resulted into overtopping of the levees that protected St. Bernard Parish hence resulting into failure[ CITATION Uni10 \l 1033 ]2.Flooding of the Gentility neighborhood and the Lakeview neighborhood were also as a result of oversights from the Corps Engineers who were responsible for the design and construction of the levees and floodwalls. The team of engineers had two oversights. One of the oversights was an overestimation of the strength of soil during the design of the l-walls and the

3canal levees[ CITATION Com12 \l 1033 ]5. This meant that the strength of the soil that was used in the calculations of the design was higher than the strength that really existed near and under the levee at the time of Hurricane Katrina. This resulted in a destructive data interpretation since the soil that was underneath the levee was weaker than that which was applied in the design of the l-walls[ CITATION Uni11 \l 1033 ]7. Failure to consider the chances of a gap filled with water in the design of the 17th Street Canal was yet another critical engineering oversight[ CITATION San14 \l 1033 ]6. The gap filled with water emerged to be one of the fundamental causes of the failure of the canal. From research and analysis it was found that with the water-filled gap in place, the safety factor was reduced by approximately 30 percent. Having used a safety factor of 1.3 in the design and a decrease by 30 percent, then the safety factor would reduce to almost one which is basically a recipe for complete failure. The engineers misjudged the peat strength which was from the swamp remains on which some parts of the New Orleans were constructed. Borings of soil indicated that peat layer started at around 9.1 m under the surface and ranged from approximately 1.5 m to 6.1 m in thickness[ CITATION Uni11 \l 1033 ]7. The peat had very high water content and very low shear strength from the investigations that were carried out. As a result of the weak strength of the soil,the floodwall became very susceptible and vulnerable to the stresses that were caused by the large flood. The movement of water through the underneath soil and as the pressure of the water built up, the moving water overpowered the strength of the soil hence a sudden shift and carryingwith it all the materials including the wall[ CITATION Com12 \l 1033 ]5.

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