confined and drained test

[ketanco]

in a question i am solving about triaxial test, it says:

"In a drained triaxial test, a specimen is confined under pressure and axially loaded until failure."

but drained means, we let the specimen to drain, which means it must be unconfined isnt it? why do they say confined? what am i missing here?

 

[JMT]

"In a consolidated drained test the sample is consolidated and sheared in compression with drainage. The rate of axial deformation is kept constant, i.e. is strain controlled. The idea is that the test allows the sample and the pore pressures to fully consolidate (i.e. adjust) to the surrounding stresses. The test may take a long time to allow the sample to adjust, in particular low permeability samples need a long time to drain and adjust strain to stress levels."

 

[ketanco]

here is a very good source i found on this triaxial test :

http://www.geocities.ws/dominic_trani/paper4.html

i read CERM and All in one, but here, it is explained much better. Hard to believe when the two most popular books on the market can not explain this good enough....

 

[PE_Guy]

If you are taking Geotech depth, you can't expect detailed topics in CERM or All in one for it.You can refer Das, Braja M., book for geotechnical engineering.