Triaxial Test apparatus

Advantages of Triaxial Test

1. The stress distribution on the failure plane is uniform.
2. The specimen is free to fail on the weakest plane
3. There is complete control over the drainage.
4. Pore pressure changes and the volumetric changes can be measured directly.
5. The state of stress at all intermediate stages upto failure is known. The Mohr circle can be drawn at any stage of shear.
6. This test is suitable for accurate research work and the apparatus adaptable to special requirements such as extension test and tests for different stress paths.

Disadvantages of Triaxial Test

1. The apparatus is elaborate, bulky and costly.
2. The drained test takes place a longer period in comparison with a direct shear test.
3. It is not possible to determine the cross sectional area of the specimen at larger strains, as the assumption that the specimen remains cylindrical does not hold good.
4. The strain conditions in the specimen are not uniform due to frictional restraint produced by the loading cap and the pedestal disc. This leads to the formation of the dead zones at each end of the specimen.
5. The consolidation of the specimen in the test is isotropic, whereas in the field, the consolidation is generally anisotropic.