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Flood flow beneath sand bags? 1

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CivilSigma

Structural
Joined
Nov 16, 2016
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US
The question : Could seepage under flood sand bags potentially cause scouring under foundation footings of a home?

Details: A home was subject to a flood. The home bears on sand using reinforced concrete footings. To mitigate flood water, sand bags were placed around the property, let's assume at a distance of 9ft from the the property line. Assume water flood levels peaked at approximately 2 ft on the exterior of the flood bags. Due to a difference in head, seepage and flow of flood water to the interior of the bags occurred, and water was constantly being pumped out. No signs of damage or soil erosion within the vicinity of the bags was observed.

Could it be possible that this flow of water scour the sand beneath the footings and induce home settlement, uplift, or damage?


I don't believe so, as if the flow was aggressive enough to cause scouring below the footings, it would have caused soil erosion near the flood sandbags.

What do you think?

All the best,
CS
 
This sounds more like a problem for a civil engineer. I will say I have seen sandbags undermined and/or completely blown away in the right circumstances.
 
Erosion is the general lowering of grade do to the movement of water. Probably not an issue here at all.

Scour is the localized removal of soil around a fixed object (pile, slab, etc.). I'm going to go with no, unless the sand bags were 50ft away from the building. It usually takes wave action or water flowing to cause these issues. They also start at the surface and work down. (Voids collapsing due to seepage and flow below grade is something else.) So if the bags were up close to the house, even if you have hydrodynamic forces at play outside the sand bag wall, the actions inside are going to be essentially static. The only exception I can think of would be if the pump intake was sucking up sand and exposing the foundation to some sort of localized flows.
 
@phamENG The pump intake was not aggressive and did not disturb the top soil. Thank you for your insight.
 
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