Undisturbed samples from a normally consolidated clay layer were collected during a subsoil exploration. drained triaxial tests showed that the effective friction angle was φ’ = 25°. the unconfined compressive strength, qu, of a similar specimen was found to be 133 kn/m2. find the pore pressure at failure for the unconfined compression test.

pre water pressure

Explanation:

given data:

frictional angle  25°

unconfined xompressive strength  qu = 133 kN/m2

for clay, unconfined compressive strenth is cu

cu = 133/2 =66.5 kN/m2

cell pressure is zero in uncomfined compressive strenth test

from principle effective stress we have

as this test is quick test i.e. undrained test therefore

pre water pressure

it breaks and dirupture other materials and other sencews from the bottom