PT Slab on Grade & Liquefaction 2

[laymfpres]

I was given a soils report where expansive soils are not a problem, instead the project site is subject to liquefaction. The jurisdiction is requiring that we design the foundation as a post-tension slab on grade. Has anybody ever heard of this?

I'm not sure how to go about my design because the software that we use to analyze the slab requires input for expansive or compressible soils.

 

[mitchell54]

http://www.building.org/profiles/98475.html

Here is a web site that might help. I have heard of this technology and have yet to use it. The sites that I have constructed on have not required it. I know that these type of slabs can get a bit pricy, have you inquired about a dewatering system?

Please keep me posted on your progress I would like to know how things work out for you since I think that this technonlogy can offer a wide variety of applications in saturated soil environments.

 

[cvg]

suggest you post this on the geotechnical engineers foundation engineering forum for better response

 

[dirtsqueezer]

Yeah, that is pretty strange. I would personally push for a structural slab (thickened edges), which usually go with either augercast or steel piles. You might just ask your jurisdiction as to their reasoning on the subject. P/T decks are generally suspended by compressional members, are they not? Where would this support come from were you to lose ground bearing due to liquefaction?

This sounds a lot more like a pile job to me. I'd find out whose idea this was and go make an appointment to see them. They aren't the ones designing in the end, and I'm not sure that P/T is compatible with a SOG.

Best of luck.

 

[laymfpres]

thank you for your responses;

I will check out that link, hopefully meet with the plan checker, and keep you posted.

 

[RCEJD]

IN So Cal we use this approach all the time. There is extensive discussion on the web. Essentially the geotech is calculating the settlement related to dry and saturated soils during a seismic event. Your computer program can treat the soil as "compressible" for the magnitude of settlement. CDMG 117 and SCEC guidelines recommends that the foundations be designed for 2/3 the total settlement rather than the traditional 1/2.

If you want some of the web sites and links let me know.

 

[BigH]

RCEJD - do you have a URL for the discussion?