Saints fan, from the article you referenced, even that is in debate. Driving deeper does not automatically mean more strength--it all depends on the soil profile.
Worst case is that the water comes to the top of the sheet piling. The piling and depth are designed to withstand the worst case, and then some, called a factor of safety.
That the sheet piling failed below design strength points to either faulty design assumptions or to faulty construction or maintenance.
So far the theory is that the overtopping water scoured away supporting soil. We may yet find that connections were poorly made, or poorly maintained. Once the integrity of the sheet piling wall is broken, it cannot withstand the force of the high level of water.
The engineer in the article said that the number of soil borings was more than he had ever seen on any other project-so he felt he had an excellent picture of subsurface conditions, and designed the way he did. Whether the sheet piling went to 10.5 feet or to 17.5 feet doesn't matter if the soil profile matches the design criteria.
Bridges fail, walls fail, buildings collapse,dams fail--time and force take their toll.
Had there been proper maintenance, there would have been tell-tale signs that the sheet piling was undermined or in extreme stress prior to the storm. Since they were the key to the survival of NO in a storm, they should have been examined more often and more carefully.
We both know that didn't happen, and no surprise there, due to infamous NO money diversions and corruption.
The blame game can go on ad infitum, but the buck stops squarely in NO.
I appreciate your reasoned replies though. It must hurt to see your city come to this. As hard as it is to hear, this may yet be the best thing that has happened to NO in the long run.
That's exactly the point. The soil profile should have made it obvious that they should drill deeper. The sheet piles ended in the middle of a pocket of peat soil, a mixture of decaying biological matter. The canal bottom was 18 feet deep and the piles were only driven to 17 feet. The Engineering firm that did the soil samples called for a depth of 35 feet but was overuled by the ACof E. Corps engineers in Vicksburg, Mississippi questioned the designs, but the local Corps project leader again overuled. Water seeped under the piles and eroded away the base of the levee. The levees were not overtopped. I have talked to several witnesses who said the water level was a couple of feet below the top of the wall just before they broke. I am talking about the 17th street canal levee that is about 2 miles from my house. I am sitting in a 1 bedroom apartment as I type this because my home and everything that I worked 30 years to earn was destroyed when that levee broke. Perhaps it is too strong to say the feds destroyed my city but it is hard to amagine it was the best thing to happen to New Orleans. An investigating engineer from LSU called it the worst Engineering failure in the nation's history. I'll tend to take his word for it.
bkmk