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US Army honours ICE vicepresident for Katrina work

ICE News

ICE vice-president Scott Steedman has been awarded the US Army's Outstanding Civilian Service Medal for his work in the aftermath of Hurricane Katrina.

Following the storm that devastated New Orleans in August 2005, Steedman led one of 10 teams commissioned by US secretary of defence Donald Rumsfeld to investigate why the city's ood defences failed (NCE 2 March 2006).

His work as part of the Interagency Performance Evaluation Task Force (IPET) centred on the physical modelling of New Orleans' levee and dwall performance using the world's most powerful geotechnical research centrifuges at the Engineer Research & Development Centre (ERDC) in Vicksburg, Mississippi.

The - al IPET report was published in June last year. It concludes that two-thirds of the water that owed into the city came through breaches in the defences that could have been contained if designers had taken into account New Orleans' subsidence and the poor quality of foundation soils (NCE 8 June 2006).

Geotechnical engineer Steedman was presented with his medal by his co-leader on the IPET project, ERDC director Mike Sharp, at One Great George Street last month.

The prize, the third highest honour the US Army can bestow on a civilian, came with a citation that said: fiDr Steedman's technical expertise and leadership provided critical -ndings, and a unique understanding and insight of failure modes benecial to other IPET analyses. fl Steedman said: fiI understand this is only the second time the medal has been awarded for centrifuge work so I'm obviously thrilled and delighted.

fiWhile the IPET report is now wrapped up, I anticipate that there will be a further study starting this summer looking at other levee systems in the US. fl Steedman will give an indepth presentation of his IPET work at One Great George Street on Wednesday 9 May.

One of his team's key - ndings was that storm surges in New Orleans pushed at least one sheet piled levee wall out of position before it failed (NCE 16 March 2006).

The surge exerted huge lateral forces on a whole section of sheet-piled levee wall on the city's 17th Street canal, causing a 139m long breach on its east side.

As canal water levels rose, the od wall moved landward. The movement created an underwater gap between the canal side of the oodwall and the clay embankment.

Water was then able to push down against the toe of the sheet pile, causing it to shift landwards (see diagram).

Weak shear strengths in the clay layer below the sheet pile and hydrostatic forces on the pile toe pushed the sheet pile vertically along a slip plane in the clay.

This crucial understanding of the 17th Street canal's ood defences' mode of failure was achieved by constructing one- ftieth scale models of the levee sections that failed for testing in the ERDC's centrifuge.

Accelerating the centrifuge to create a gravitational force of 50G increased effective weight, forces and stresses in the model, making it behave like its full-scale, real-life counterpart.

For more details of Steedman's talk at One Great George Street, please contact Jade Donovan on (020) 7665 2233 or email jade. uk

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