Flood Related Foundation Scouring

[msquared48]

Got a question...

Assuming that the foundation for a resiidential structure is still intact, are there any other easier or less costly methods other than pin pile and/or CDF to replace the material scoured from under the foundation?

With the flooding we had here in Dec/Jan, there are a lot of residences in numerous floodplains that have this problem.

Many of the areas that were initially scoured were later filled in to include areas under the foundation and will have to have this material removed and replaced/repaired some way.

Mike McCann
MMC Engineering

 

[RWF7437]

Have you researched all the FEMA publications dealing with this topic ?

 

[kslee1000]

Just a day ago in foundation engineering forum, some one mentioned flowable fill which may have 100 psi bearing value, and could be excavated later. It could work for certain cases.

 

[kslee1000]

By civilperson, under the subject "Sub-Foundation Excavation".

 

[Prepakt1]

We tackled this problem under a high school gym/ Where a burst watermain had washed out under the foundations and cracks of up to 1 inch had appeared in the block walls.
The walls were off plumb and the school was still using the structure in an earthquake zone( Some people do not think at all ) We took on the project and drilled and pressure grouted under the slab foundation.It all came back up nicely into place. We were not sure it would come back up properly. It was a case of try it and see what happened or demolish the building.
You could do it under other types of foundations but you may need to contain the grout by solidifying the ground around the structure or several ft below in the case of soft ground and then pressure grouting. Not easy, not cheap

Intrusion Prepakt /marineconcrete.com

 

[Ron]

Mike...not sure where "here" is, but a lot will depend on the soil conditions. In sandy soils, flowable fill might be an option (though most commercial flowable fills are higher in strength than that noted by kslee1000 (most are in the 500 to 1000 psi range). One obvious issue with any cementitious material is the shrinkage on hydration/drying. In clayey soils, continued drying shrinkage from the initial bulking from the flooding might need to be considered. Further, near surface effects of flooded clayey materials are a bit more difficult to predict than sandy soils.

One advantage to FF is cost. If you explore this option, you might consider making sure that the flowable fill is placed to maintain a few inches of head over the bottom of the foundation.

The Canadians have done quite a bit of research on flowable fill and you might check with the Canadian Institute for Research in Construction.

What do your local Geotechs say about the better alternatives?