TABLE OF CONTENTS An alternate approach to determining the undrained shear strength s u of the cohesive soil is to obtain the undrained shear strength in terms of the total shear strength parameters c and ?. The usual process is to perform triaxial compression tests on specimens of the cohesive soil. The triaxial test has been discussed in Sec. 9.2.
The shear strength ? f of cohesive soil for a total stress analysis can be expressed as follows (Mohr-Coulomb failure law):
| where ? f | = shear strength of soil, psf or kPa |
| c | = cohesion based on a total stress analysis, psf or kPa |
| ? n | = total normal stress acting on shear surface, psf or kPa |
| ? | = friction angle based on a total stress analysis, degrees |
Note that Eq. (9.19) is identical to Eq. (8.1), except that one equation is expressed in terms of effective stress [Eq. (8.1)] and the other is expressed in terms of total stress [Eq. (9.19)].
As previously mentioned in Sec. 9.2.1, the unconsolidated undrained triaxial compression test is rarely used in engineering practice. It is more common either to use the undrained shear strength s u from unconfined compression tests or vane shear tests, or to use the shear strength parameters ( c and ?) from consolidated undrained triaxial compression tests.
The unconsolidated undrained triaxial compression test specifications are presented in...
