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Undercutting question

Undercutting question

Undercutting question

We received a soils report on a project that says the following:

Recommends that structures, where shallow slab-on-grade foundations are being considered due to tolerance for some foundation movements, utilize preparations recommended herein to reduce the PVR to on the toher of approximately 1-inch.

Undercutting the natural expansive soils at this site and replacing them with properly compacted select fill soil will reduce the PVR. The resulting reduction in PVR at this site, utilizing undercutting and replacement operations, are included in the following table:

Required undercut depth (ft) - 4
Minimum select fill thickness (ft) - 5
Approximate design PVR (in) - 1

Does that mean undercut below the slab on grade foundation 4' and then put fill to 5' below the foundation? How can the required fill thickness be more than the undercut?


RE: Undercutting question

Seems like a typo. Call the engineer to confirm.

RE: Undercutting question

I interpret the comments as take out 4 feet and backfill with 5 ft meaning you will be 1 ft above grade.

RE: Undercutting question

I'd want to know what data they have to claim the soils expansive.


ípapß gordo ainÆt no madre flaca!

RE: Undercutting question

I think GeoEnvGuy is correct. SOG is usually placed on fill, which in turn, is placed over the grade. The edge of the SOG needs to have turn-downs to confine the fill in this case.

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