Peak Friction Angle
Peak Friction Angle
(OP)
Hello All,
The angle of friction that we get from the Mohr's circle envelope of a CU test, is that the peak friction angle?
Thanks
The angle of friction that we get from the Mohr's circle envelope of a CU test, is that the peak friction angle?
Thanks
RE: Peak Friction Angle
There are also undrained relations, which is a different topic.
The nature of your question is the basis why the ASTM standard for shear strength testing of soil excludes the preparation of the m-c envelope.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Peak Friction Angle
RE: Peak Friction Angle
Otherwise, yes, it's the work of an engineer. And, engineers should consider strain compatibility.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Peak Friction Angle
RE: Peak Friction Angle
This is all documented in a CGPR (Center for Geotechnical Practice and Research) publication from 2015 or so. I attended along with Tim Stark, Tom Brandon, Steve Wright, Mike Duncan and many others. (I studied at VT and have been involved with CGPR for quite a spell.)
Nice to see folks getting into these weeds.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Peak Friction Angle
Working in slope stability projects compression tests results are very common to see but understanding the failure plane through a clay layer is typically horizontal the results from direct simple shear testing are more applicable and will show lower shear strengths than compression tests.
RE: Peak Friction Angle
We have used the direct shear test results on remolded samples before on projects but we did not use that test on the current one. I will go through the CGPR publication that fattdad mentioned.
I read somewhere that undrained strength of clay varies with the orientation of the failure plane. Hence I think the comment from geg. But can we say the same for drained strength. I don't know. can you shed some light?
RE: Peak Friction Angle
The shear surface of the DDS is constrained; however. However; FSS at low normal loads renders this matter trivial.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Peak Friction Angle
RE: Peak Friction Angle
Can you explain, please.
Thanks.
RE: Peak Friction Angle
So, if the peak for one load is at 5 percent strain and all the others are at 15 percent strain, the, "Rule" is to strike a line parallel to the initial tangent modulus, but initiate the line at 2 percent strain. That parallel line will strike the stress strain curve at some point. Use that for M-C development.
In this manner, you will solve the strain incompatibility problem. . . and lower your friction angle.
f-d
ípapß gordo ainÆt no madre flaca!