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?