Constrained Modulus from DMT

[nagatalluri]

Hi all:

We got constrained modulus (M) from DMT tests.I tried comparing it with the constrained modulus calculated using the CPT data. Though the procedures for calculating constrained modulus are similar, I am ending up with 2-3 times higher value using the DMT data. Did anybody face this type of situation.

Please advice.

Thanks
NT

 

[Mccoy]

Here in Italy it is a known fact that the DMT yields pretty high values of the constrained modulus, sometimes an order of magnitude more than lab oedometric tests. That's the rule, with a few exceptions.
It is also an observation of mine that oedometric lab tests tend to be on the lower bound of the parameter range.
So, the fact that the CPT runs in the middle is no wonder. It actually depends on the correlation coefficient adopted. You adopt an higher coefficient, you end up with data similar to the DMT.
Was that a mechanical or electrical cone? Which correlation did you apply? The multiplicative coefficient spans from unity to 8 and more. Its value should be adopted from local experience.
Bottom line, you might adopt the CPT data or half the DMT's even as Schmertmann did in a large bridge project, ending up overestimating settlement (so the DMT value was good after all). All this with great caution and reasoned choices.