This set of Geotechnical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Unconfined Compression Test”.
1. In unconfined compression test the value of σ2 and σ3 is equal to ____________
a) 1
b) 0
c) 0.5
d) ½
View Answer
Explanation: The unconfined compression test is a special case of tri axial compression test in which σ2 = σ3 = 0.
2. The unconfined compression test is derived from _____________
a) Direct shear test
b) Vane shear test
c) Tri axial compression tests
d) Drained test
View Answer
Explanation: 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.
3. The unconfined compression test is generally applicable to ____________
a) Unsaturated clay
b) Saturated clay
c) Fine grained soil
d) Coarse grained soil
View Answer
Explanation: 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.
4. The unconfined compression test was first designed by _________
a) A. casagrande and Goyal
b) Singh
c) None of the mentioned
d) All of the mentioned
View Answer
Explanation: In 1958, Goyal and Singh designed the first unconfined compression tester.
5. In plastic failure, load corresponding to __________ strain is arbitrarily taken as the failure load.
a) 10 %
b) 5 %
c) 20 %
d) 50 %
View Answer
Explanation: In 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.
6. When the Mohr circle is drawn in confined compression test, its radius will be equal to ____________
a) Cu
b) qu
c) Ru
d) None of the mentioned
View Answer
Explanation: When the Mohr circle is drawn, its radius is equal to σ1/2,
Since, σ1=2cu
σ1 /2 = 2cu/2
Therefore, radius=cu.
7. Stress condition in the Unconfined compression test represents ____________
a) Drained test
b) Un-drained test
c) Quick test
d) All of the mentioned
View Answer
Explanation: The stress condition at failure, in the unconfined compression test which is essentially an un-drained test, if it is assumed that no moisture is lost from the specimen during the test.
8. Which of the following parameter is used to represent unconfined compressive strength at failure?
a) τf
b) cu
c) qu
d) Au
View Answer
Explanation: τf= qu/2
Where, qu=unconfined compressive strength at failure.
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