shear wave velocity vs Su
shear wave velocity vs Su
(OP)
Hello, I would like to ask you is it possible to correlate shear wave velocity Vs ( for instance, obtained from SDMT ) with undrained shear strength of cohesive soils. Maybe You know some articles or papers about it ?. I would be greatful for replies.
Paul
Paul





RE: shear wave velocity vs Su
If you are looking for Su, there are other cheap ways to fly: CPT, VST, SPT, or just oedometer results with an assumed typical shear strength ratio.
Oops. Fire alarm. Gotta go.
RE: shear wave velocity vs Su
if you have enough data point for a particular soil, then you could always do a generalized statistical analysis. but as dgillette notes there can be significant variability doing this. i've done such a thing with Vs and N-values in different geologies with similar results. however, there was significant variability overall since the Vs is a "broader" test while the spt is only across the 12" of the ss. but for very general comparisons it works well.
RE: shear wave velocity vs Su
I recently saw a SPT-based Site Class determination performed with a rope and cathead apparatus. Talk about blowing the standard of care to the client...
J
RE: shear wave velocity vs Su
RE: shear wave velocity vs Su
The NCHRP Synthesis 368 guide that was issued in 2007 listed a method for correlating the Vs and qt values from a CPTU test. (for clay like soils)
The formula:
Vs (m/sec) = 175(qt)exp 0.627 (qt in kPa)
To convert your qt values to Su we commonly use the this formula:
Su (kPa) = (qt - overburden stress)/Nkt (all units in kPa)
We have found that a Nkt value of 13 produces believable results.
I think the NCHRP formula was created in order to take into account most clayey soils on a global basis.
We have found that this formula can have up to 20% error for the soft, NC silty clays that we have in our of the west coast.
Best of luck with your estimates
Coneboy