Select the incorrect statement.

Solution (By Examveda Team)

The correct answer is Option D: Unconfined compression test can be carried out on all types of soils.
Here's why:
Option A: In a direct shear box test, the plane of shear failure is predetermined - This is correct. The shear force is applied along a specific horizontal plane, so the failure is forced to occur along that plane.
Option B: Better control is achieved on the drainage of the soil in a tri-axial compression test - This is also correct. In a triaxial test, you can control whether the soil is allowed to drain or not, giving you better control over drainage conditions compared to, say, a direct shear test.
Option C: Stress distribution on the failure plane in the case of tri-axial compression test is uniform - This is correct. Triaxial test are designed to applied uniform stresses.
Option D: Unconfined compression test can be carried out on all types of soils - This is incorrect. An unconfined compression test is a special case of a triaxial test where the confining pressure is zero. It's only suitable for cohesive soils (like clays) that can stand on their own without lateral support. Granular soils (like sands) and very loose soils will collapse under their own weight in an unconfined state, so you can't perform this test on them.