|
Author:
yannick
|
2005-08-08 |
|
| |
|
|
| |
Can anyone please give me the theoretical explanation why, in a consolidated undrained test (CU) the effective stress path moves straight upwards (till the soil yields) in a (p',q) diagramma.
thanks,
Yannick
|
|
| |
|
|
Follow-up:
| |
Author:
johnnix
|
2005-08-31 |
|
| |
|
|
| |
The failure envelope of such a test is indeed a straight line of the form : t=c+sigma*tan(phi) where
t : shear strength
c : cohession
sigma : normal stress on failure surface
phi : friction angle
All the above parameters are expressed in terms of total stresses. In order to visualize why this is a straight line have in mind that the test procedure is done 3 times. Each time in a specimen of soil you apply a confining pressure allowing it to consolidate. At the end of consolidation an axial load is applied without allowing any change in water content. At failure the minor principal stress sigma3 = the confining pressure and the major principal stress sigma1 = the vertical stress are known thus you can draw the Mohr circle of failure. For the 3 tests sigma1,1<sigma1,2<sigma1,3 and sigma3,1 < sigma3,2 < sigma3,3.
The failure envelope does not pass through the peak point on a Mohr circle but is rather tangent to the three circles.
You may also refer in ASTM D 4767-95.
|
|
| |
|
|
Return
to subject 'Geotechnical research and education'
|
Follow-ups:
|
Subject:
CU Test 