Which of the following is/are the demerit(s) of a Triaxial test? i. The specimen is free to fail on the weakest plane ii. Formation of dead zones takes place at each end of the specimen
- AOnly (i)
- BOnly (ii)Correct
- CBoth (i) and (ii)
- DNeither (i) nor (ii)
Solution
Concept
Demerits of triaxial shear strength test
Formula
NONE
Step-by-step solution
1. The freedom of the specimen to fail along its weakest plane is an advantage, not a demerit, of the triaxial test. 2. Friction between the end caps and soil specimen creates conical dead zones of restrained deformation at both ends, which is a key demerit. 3. Therefore, only statement ii represents a demerit of the test. Answer: B
Explanation
Allowing a soil specimen to fail freely along its natural weakest plane is an advantage of the triaxial test rather than a demerit. However, friction between the rigid end caps and the specimen causes non-uniform stress and creates dead zones at both ends. Thus, statement ii represents a demerit while statement i is a merit, making option B correct.
Why the other options are wrong
A) The specimen failing on its weakest plane is an advantage of the triaxial test rather than a demerit. C) Statement (i) represents a merit of the test, making option C incorrect. D) Statement (ii) is a recognized demerit due to end restraint friction creating dead zones in the specimen.
Shortcut
Failing on the weakest plane is a merit of the triaxial test, while end dead zones are a demerit.
Common mistake
Selecting option C by mistaking failure along the weakest plane as a demerit rather than a major advantage of the triaxial test.
Correct answer: B) Only (ii)