Increase in vertical stress for flexible footing by Janbu, Bjerrum & Kjaernsli 2

[Hex_D]

Hello all - I hope all are doing well.

I'm looking for some guidance on the chart by Janbu, Bjerrum & Kjaernsli which shows the increase in vertical stress for flexible footing for various z/B ratio against L/B ratio.

I would like to re-create the equation to calculate the value shown on the chart, this is where i require some guidance. I have found little literature on the subject which fully explains the basis of the chart.

The original report gives the formula on the attached picture and I have translated the terms where;

C'o = Primary compression ratio
p'o & eo = Effective overlay pressure & pore number in the ground
Delta p = Increase in total vertical stress
Delta e = change in pore count for voltage (stress?) increase Delta p

The only values known to be are z/B ratio & L/B ratio.

Any help is very much appreciated!

 

[BigH]

Search for Poulos and Davis' book Elastic Solutions for Soil and Rock Mechanics . . . they give equations for the charts

Or check out:

http://research.engr.oregonstate.edu/usucger/PandD/PandD.htm

 

[Hex_D]

@BigH ,

Thankyou ever so much for your input and very useful reference.
Unless I've missed it it appears that the literature omits the `Janbu chart formula. Newarks work is covered in chapter 3 however which is similar but I don't think that is quite what I'm looking for.

Thanks!