Modulus of Subgrade reaction and spring constant

[IHcal]

Hi

I am designing mat 12'x9' mat on soil. In the geotech report following values are given
qa= net allowable bearing capacity of 2.5 ksf
Ks= modulus of subgrade reaction of 215 ksf (not kcf)for 1'x1' plate. Even tells to modifiy based on the size of the foundation, ie K's=Ks(1/B)

Question is how do I calculate spring constant
1. Is it ok if I use k= qa/deflection
2. Or K's = 215ksf/(9')= 23.88 ksf assuming 1'' deflection and my mesh being 1'x1' can I apply spring constant of 23.88 k/in on the inner and 23.88/2 on the edge and 23.88/4 on the corner nodes.

I know there is lot of information in the forums regarding this but I could not specifically found what I am looking for .

Appreciate your response in this regards...

Thanks

 

[271828]

I think I'd go back to the geotech and see what's up. Those should be in units like ksi/in. like you suggest.