Drilled pier foundation for a house 4

[DoubleStud]

I have not done this in a while and forgot what my old firm did when we detail this. The geotech recommends 10" minimum diameter with 30:1 length to diameter ratio. I think all of the piers will end up being 10" diameter. Some may end up being 12" if I have to go deeper than 25 ft. What ties do I use? #3 @ 10" o.c.? I want to specify what people typically use. Most of these piers will be in compression. Some will be in tension at the end of the counterfort. This is for foundation in expansive soil.

Cheers!

 

[phamENG]

Yes. It probably could. We have a lot of fill around here (swamps turned into landfills turned into developments over the course of 200 years), and I imagine there are some parallel design philosophies. Where there is a significant settlement concern, sometimes site paving like sidewalks and slabs on grade will be turned into structural, pile supported slabs. I usually see it as a repair after everyone thought the geotech was being too conservative, but I have seen it done. So if you have large slabs on grade that need tight elevation control relative to the building floor, it should have a similar support structure. Otherwise, consider using a more stable fill under the slab or turning the slab edge down so it bears at a lower elevation than the void form and prevents the soil from filling that space.

Again, I don't design in expansive soils - anyone can feel free to tell me I'm crazy.

 

[MTNClimber]

DoubleStud - Ask the geotechnical engineer how much uplift force the piers should be designed for. I usually would tell the engineer X kips times the diameter in feet. It seems like they are missing this information in the report.

 

[dik]

If a #8 gives you 1%, I'd use a single #8 bar... it's a lot cheaper than 4 whateverz with ties.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik