triaxial test

Test results showed the internal friction angle is different from zero. If anyone has a paper about triaxial test failure conditions in clay, could share?

Soil Mechanics / Geotechnical Analysis Design Landslides - Slope Stability Groundwater Flow & Seepage

Asked 09/04/2018 10:02, updated: 1 day ago, 21:03

3 Answers

Votes: -1


This could easily happen in a clay if the clay is not fully saturated. Remember phi is equal to zero because, the increment of pressure goes into pore pressure, but if you are not fully saturated this will not happen.

Votes: 0

Michael Joseph Byle

You should look at your clay properties to assess all relevant conditions such as permeability, gradation (is it pure clay or does it contain silt and/or sand) degree of consolidation (OCR), and as the previous responder noted, degree of saturation.  If the test is run at a rate that permits drainage of excess pore pressures, you will see friction.  If your sample is very dense and dilating under shear, you may also see a frictional behavior. You should also check your shear device to assure that there is no frictional contact between the upper and lower portions of the shear box and that the load is centered over the sample without contacting the shear box.  Sometimes it's the little things that matter. 

Votes: 0


The angle of friction is equal to zero degrees it is in the case of soft clays. Generally, in this case, the percentage of fines to the sieve of 80 microns is between 90 and 100%, the plasticity index exceeds 30%, the VBS exceeds 2, the water content is greater than the limit of plasticity and the degree of saturation is almost 100%.