Vane shear test

[Junkwisch]

Hi

I'm having a problem calculating the peak undrained strength, Suv. The problem I have is that I'm unsure of which equation I can use to calculate it (see attachment for equipment dimension and data (11.1m)). I have two equations with me, the first one is Suv=12T/(pi*D^2*(2D)+6H) and the second one is Suv=0.273Tmax(D^3)


For the first equation, I obtained an answer of 50.9kPa using the total torque for the depth 11.1m (combination of all torque in that column). For the second equation, my answer is 60.9kPa using Tmax of 37.1Nm. Can anyone tell me which is correct? Personally I believe it is 50.9kPa since the second equation seem to be the remolded strength instead of the peak undrained shear strength; due to the fact that I used the total torque in the column, I'm unsure of the correct result.


Best Regards

 

[Junkwisch]

Ok, I figure out that the equation Suv=0.273Tmax/(D^3) is to be used with the answer of 60.9kPa

 

[BigH]

I would suggest saying the undrained strength is 60 kPa - forget the decimals and I've never seen it reported as 61 - to that kind of accuracy - unless it was a very soft clay with Su less than 20 or so.