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GATE 2025 CE (CE2) – Question 47

Geotechnical Engineering · Shear strength, Mohr circle, stress-strain characteristics, stress paths · 2 marks · Multiple select

In the context of shear strength of soil, which of the following statements is/are CORRECT?

  1. The unconfined compression test is a special case of the unconsolidated-undrained (UU) triaxial tests.
  2. The shear strength parameters obtained from the consolidated-drained (CD) triaxial tests should be used to analyse rapid construction in clay.
  3. Vane shear test is commonly used for determining in situ undrained strength of saturated clay soils.
  4. In an unconsolidated-undrained (UU) triaxial tests, the angle of internal friction ($\phi$) is equal to zero.

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Show answer and explanation

Correct answer: (A) The unconfined compression test is a special case of the unconsolidated-undrained (UU) triaxial tests.; (C) Vane shear test is commonly used for determining in situ undrained strength of saturated clay soils.; (D) In an unconsolidated-undrained (UU) triaxial tests, the angle of internal friction ($\phi$) is equal to zero.

Explanation

The unconfined compression test is a UU test with zero cell pressure (A). Rapid construction in clay is an undrained condition, so the undrained (UU) parameters are used, not the CD parameters (B is false). The vane shear test measures the in-situ undrained shear strength of soft saturated clay (C). In a UU test on a saturated clay the failure envelope is horizontal, so $\phi_u = 0$ (D).