SPT N values in to phi for silt and clay, 1

[simonmarks]

I have a load of old boreholes, with SPT N values in Clay and Silt, i was wondering if there was a simple way of estimating soil perameters from these results, Phi, C etc. links would be good, thanks

 

[dgillette]

Forget trying to get phi' from SPT in that sort of material. You can get rough estimates of Su (undrained shear strength) using various correlations - see Terzaghi and Peck, NAVFAC DM-7, and others. Search around here for discussions in the last few weeks.

 

[BigH]

Best to look at the logs and see if you have the Atterberg limits - then, there are correlations that have been developed. But as in any correlation, you need to be able to use judgment.