In my opinion, the best way to find a appropriate modulus of subgrade reactions for mats is to find the RATIO between the AVERAGE CONTACT PRESSURE below the mat foundation and the AVERAGE SETTLEMENT (according to geotechnical method; using the deformation characteristic of every layer in the influence bulb).

Petar, thak you for your reply. I think that your answer make sense.

The modulus is not just a simple value that can be obtained from plate bearing test and consequent correlations. It should be a soil-structure interaction problem as you stated.

Thanks again.

I agree with Petar but add that you can just start with a k1 value (for a 1 foot by 1 foot plate - by testing or picking a typical value), assume a deflected mat shape under columns (and an associated B value or "mat width" in the scaling equation by Vesic), calculate the scaled k value for the assumed B value, perform a structural analysis of the mat to determin the actual B value, and iterate until the B value converges.

That is the design process Terzaghi intended when he developed this design procedure in the 1950's - I read his original paper and add that it is brilliant and worth the read.

Palmahouse, thanks for the reply. do you have that Terzaghi paper availablE? I would like to have that.

You bet - please send me an email:  [email protected]

There is a great paper by George Aristorenas, PhD, PE & Jesus Gomez, DGE, PE titled Subgrade Modulus Revisited in Structure Magazine.

I saved it here for download: https://drive.google.com/file/d/0BynAMJy7cadrdTc2SU92a3RSYnM/view?usp=sharing

Hi Shana, would it be possible to add this link to my forum discussion on linkedin on subgrade modulus calaculation? see below for my link : https://www.linkedin.com/grp/post/2131828-6024956057267245058?goback=%2Egna_2131828

(NB you need to be connected to linkedin and to the forum to view it)

thanks