subgrade modulus

[mosam2090]

what about subgrade modulus for clayey soil in case of zero settlement ?

 

[JAE]

There is no zero settlement.

For subgrade modulus, I usually try to depend on my geotechnical engineer. When I don't get anything from them I use the attached chart.



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[fattdad]

The modulus of subgrade reaction is a geotechnical engineering parameter that's used in the structural design of slabs on grade. The modulus of subgrade reaction has no relevance to soil settlement under sustained loading. Soil modulus (unsaturated overconsolidated soil), compression ratio, and recompression ratio can all used to calculate soil settlement under sustained loading.

So, I don't quite get your question. I do agree that "zero settlement" is not a reasonable goal.

f-d

¡papá gordo ain’t no madre flaca!

 

[mosam2090]

great thanks to you all ,appreciating your efforts

 

[Okiryu]

JAE, I normally use a chart from an old USACE Engineering Manual to determine k subgrade modulus. See the attached.

I like your chart also since it shows values for natural and compacted fine soils. From what reference did you take that chart?

 

[JAE]

Okiryu - honestly not sure where I got this - sometime back in the 1980's.


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[jba1082]

The chart is from Ch 3 of ACI 360R-92 Design of Slab-on-Grade. It may also be in the newest version of that same report.

 

[Okiryu]

jba, thanks for the info!

 

[dicksewerrat]

These are different from ASTM D3839

Richard A. Cornelius, P.E.

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[Mccoy]

I appreciate the fact that in one of those sheets (not the Usace where there is a handnote in red ink) it's clearly specified that the values refer to specific plate dimensions. It sounds weird but sometimes structurals, reading those tables, will use the k values of small plates for large mats as well, with no correction, vastly underestimating displacements and bending moments.