Test: Unconfined Compression - Civil Engineering (CE) MCQ

The unconfined compression test is a special case of tri axial compression test in which σ2 =σ3 =0.

The unconfined compression test is a special case of tri axial compression test due to the absence of confining pressure, the uniaxial test is called the unconfined compression test.

 In the equation σ1=2cu tan (45° + φu/2), for determining major principal stress, there are 2 unknowns cu and φu which cannot be determined by unconfined test. Therefore, the unconfined compression test is generally applicable to saturated clays for which the apparent angle of shearing resistance φu is zero.

In 1958, Goyal and Singh designed the first unconfined compression tester.

In the plastic failure, no definite maximum load is indicated. In such a case, the load corresponding to 20 % strain is arbitrarily taken as the failure load.