Levees were 'heaved' upward from below

Total411.info
Oct. 05, 2005

Do you know what can heave the ground over and upwards 8 feet?

Military-grade explosives for one.

From Times-Picayune Oct. 4:
"A child's clubhouse, built about 25 years ago by a civil engineer for his son, provides another clue pointing to possible design or construction flaws in the structural failures that breached two canal floodwalls and inundated the city during Hurricane Katrina.

Engineer Gus Cantrell, 60, and son Daniel Cantrell, 33 -- now a structural engineer himself -- returned to the family's Pratt Drive house last week for the first time since Katrina struck. They discovered the old clubhouse sitting a few feet from its original location next to the London Avenue canal levee -- on top of a pile of mud and silty sand about 8 feet high.

The Cantrells believe that extreme pressure from high water pushed soil under the base of the floodwall away from the canal and upward in an arc, something known as a heave. That appears to have raised a mound of earth into the back yard under the clubhouse. The wooden clubhouse's base is now even with the edge of the house's roof, Daniel Cantrell said.

"Once that happened, the wall would have been compromised, not have been able to support itself," he said.

That is different from initial theories offered by the Army Corps of Engineers that the floodwalls were topped by storm surge and raises more questions about design and construction.

[...]

A similar heave may have occurred at the breach in the 17th Street canal, where soil also appears to have been pushed forward and upward.[...]

The Cantrells' clubhouse is virtually undamaged. It was built sturdily, Gus Cantrell said. . . "It appears that the structure had not gotten wet at all."

That suggests the heave occurred first, precipitating the wall's failure.

[...]













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