Uplift on Underground Slab
Uplift on Underground Slab
(OP)
I have a theory question I hope you folks can help answer.
We often have slabs under uplift conditions due to high groundwater (out to out of exterior walls footprint under uplift) . We extend the edges of the slab outward to engage the soil as part of the "righting" gravity load, this soil is assumed to be buoyant (120 pcf - 62.4 pcf = 58 pcf). There is some soil friction (granular backfill) that can also be taken into account isn't there? The effect of uplifting the slab results in an additional "wedge" of soil that must also be overcome due to this soil friction.
Do geotechnical engineers take this friction into account under uplift conditions? Or do they just suggest to use only the soil overtop of the slab directly? In the past, we have assumed a 2v:1h slope on this wedge to represent the soil friction. Can you point me to a good text book or research? I feel the way we've been doing this is somewhat unconservative.
Thanks,
A-
We often have slabs under uplift conditions due to high groundwater (out to out of exterior walls footprint under uplift) . We extend the edges of the slab outward to engage the soil as part of the "righting" gravity load, this soil is assumed to be buoyant (120 pcf - 62.4 pcf = 58 pcf). There is some soil friction (granular backfill) that can also be taken into account isn't there? The effect of uplifting the slab results in an additional "wedge" of soil that must also be overcome due to this soil friction.
Do geotechnical engineers take this friction into account under uplift conditions? Or do they just suggest to use only the soil overtop of the slab directly? In the past, we have assumed a 2v:1h slope on this wedge to represent the soil friction. Can you point me to a good text book or research? I feel the way we've been doing this is somewhat unconservative.
Thanks,
A-





RE: Uplift on Underground Slab
2) If I understand your point well, you are saying that granular backfill will be providing a reaction to the slab subjected to uplift forces. If so I understand the soil friction that may be accounted occur directly through a vertical line located on top of the slab edge up to the surface and may be calculated as effective overburden pressure times tangent of phi. Basically, the total resistance is obtained by the friction previously mentioned plus the wight of slab and weight.
Bowles book provide a good explanation together with names of researchers on the subject and suggested equations.
RE: Uplift on Underground Slab
RE: Uplift on Underground Slab
f-d
¡papá gordo ain’t no madre flaca!