Quick Undrained Shearbox Test

[groblert]

As far as I understand a shearbox test is a drained test(assumption that excess pore pressure is 0).
I do however have clients who require "quick undrained" tests on partially saturated soils.
This can surely, at best, be a total stress test?
Any recommendations on how quickly I should shear the samples? But more importantly:
How do you interpret the test data?

 

[dgillette]

Sounds like something to avoid unless the client can tell you which ASTM standard to follow (and I don't think there is one). In a typical shear box, I don't think you can shear it fast enough to actually be fully undrained, and how would you know if you had? Maybe if you had a hydraulic actuator that could shear it to failure in just a few seconds, instead of a typical mechanical drive? If the client is the engineer, get him to explain exactly how to do the test, charge your hourly rate for the nonstandard work and writing the disclaimer, and let him (or her) interpret the raw data.

There are DSS machines that simulate undrained tests by adjusting the normal force to keep the sample at constant volume, but that's for saturated samples where undrained means essentially constant volume. With partially saturated soil, undrained doesn't mean constant volume, because air is so much more compressible than water.

Thought-provoking question, if nothing else. Is this for stability of embankment slopes under construction?