Fall Cone Method

[1Mperios]

What is the accuracy and reliability when determining the liquid limit and plastic limit using fall cone method, I know that it's used as an alternative to the casagrande cup method because it doesn't depend on human judgement, however is there any other reliabilities when using the test? In order to obtain an accurate result for the plastic limit the water content for the crumbling thread test should be repeated and the result averaged, is there anything else I should be aware of?

 

[BigH]

Are you going by any "standards" like ASTM/BS/IS??

 

[1Mperios]

Yes, BS.

 

[paganel]

From my knowledge, the results will be equivalent to the results from Cassagrande's apparatus.
As the shear strength is close to zero at liquid limit from both methods.

 

[dgillette]

Actually, research by Joe Koester at USACE WES (now ERDC) found a small difference (avg. 2-3 points?) between Casagrande cup and fall cone. A little Googling should find it for you. koester AND "liquid limit"

His work was aimed at the so-called "Chinese criteria" for liquefaction potential, (Wang 1979+/-), which have since been superseded. The criteria came from the Chinese version of the fall cone, and I don't know how closely that matches the BS fall cone.


Regards,
DRG