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This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com


Wednesday, March 28, 2012

Man buried for four hours in 4' deep mud: thixotropic, rheoplectic, or something else?

Man immersed in mud for four hours in Atlanta, Georgia


An amazing event and rescue in Atlanta, Georgia, was briefly on the CNN.com news this morning. It's not clear how the story was pieced together yet, and the rescuers have no idea of the identity of the man involved or how he came to be stuck in mud.  At a construction site, there was a pool of mud estimated to be four feet deep. It appears that the man did not fall from the site, because it would have been a 30' fall and, aside from his mud trauma, had no other injuries.  He apparently wandered into the mud, and struggled to get out of it for a few hours before succumbing to cold and exhaustion (it was 50 F) in Atlanta this morning. Rescuers could not reach him without danger of becoming trapped in the mud themselves. Eventually a female paramedic reached him and kept his airways open until rescuers, using boards from the nearby construction site to fashion a bridge out to him, were able to pull him out. The video above shows his rescue, and he is apparently doing fine in the hospital.

The video compared this situation to quicksand, but I'm not sure that the analogy is correct. Quicksand is an example of a "thixotropic" fluid, one that starts as a solid and becomes weaker when it is shaken, aggitated or stressed. If my interpretation of the video is correct, this mud became stronger as he struggled so it may be an example of a "rheopectic" material, one whose viscosity increases the longer it undergoes shearing. Such materials are fairly rare, but of increasing interest in military and sports applications where a major goal is to create materials that reduce the stress due to impact. For instance, a shoe that incorporates rheoplectic materials in its cushioning might help protect the feet of runners, jumpers, and hurdlers. Helmets and body armors with such materials would reduce body trauma from projectiles.

Or it may be some other wonderful wierd behavior! Readers comments welcome!

3 comments:

Interested said...

I was very interested in your post since I'm trying to understand quicksand. I'm interested in why you think that the mud is thixotrophic or rheopectic. This would mean that it is a time dependent non-Newtonian fluid. I've read in other places that quicksand is dilatant which is a time independent non-Newtonian fluid. Could you explain why you think it is? Thanks!

Susan W. Kieffer said...

I'll research your question, but am on travel at the moment. If readers can help, please do so!!! This is not my area of expertise at all...I just thought that mud-man was interesting, and the implied fluid dynamics was intriguing to say the least!

Susan W. Kieffer said...

I'll research your question, but am on travel at the moment. If readers can help, please do so!!! This is not my area of expertise at all...I just thought that mud-man was interesting, and the implied fluid dynamics was intriguing to say the least!