Correlation of SPT & CBR to define subbase requirements for granular?
Correlation of SPT & CBR to define subbase requirements for granular?
(OP)
Hi, in the absence of CBR results, can anyone guide me to a document / chart where available SPT results of a granular material can be used to obtain an estimated CBR?
Thanks
Steven
Thanks
Steven





RE: Correlation of SPT & CBR to define subbase requirements for granular?
There are some correlations on the web but they are very approximate.
RE: Correlation of SPT & CBR to define subbase requirements for granular?
RE: Correlation of SPT & CBR to define subbase requirements for granular?
You can use Winterkorn & Fangs foundation engineering book (section 16.8) to convert stiffness to subgrade reaction.
By making these kinds of smaller steps you get a sense of how sketchy some of the correlations are. Keep in mind that CBR and SPT are both index tests, they're don't measure engineering properties of soils. I prefer using correlations between standard index tests and engineering properties (strength, stiffness).