A triaxial shear test is preferred to direct shear test, because:

Question

Question

This question was previously asked in

OSSC JE Civil Mains Official Paper: (Held On: 16th July 2023)

It can be performed under all three drainage conditions with complete control
Precise measurement of pore pressure and change in volume during test, is not possible
Stress distribution on the failure plane, is non-uniform
None of these

Answer 1

Concept: -

A triaxial shear test is preferred over direct shear test because of following reasons –

1. Triaxial test has complete control over drainage conditions. Test can easily be conducted for all three types of drainage conditions.

2. Precise measurement of pore pressure and change in volume during the test is possible.

3. Stress distribution is uniform on the failure plane.

4. The specimen will fail along weakest plane while in direct shear test failure can occur along the plane which is not the weakest.

5. Mohr circle can be drawn as the stresses at all the intermediate state is known up to failure.

Note: -

Demerits of triaxial test –

The following are the demerits of triaxial test -

1. Takes longer period under drainage condition than direct shear test.

2. Uneconomical

3. No accurate measurement of cross-section area of specimen under large strains.

4. Soil is assumed isotropic while in actual anisotropic in nature.