The process by which a mass of saturated soil, due to external forces, suddenly loses its shear strength and behaves as a fluid is called:
Try it first: pick an option, then read the explanation.
Correct answer: C. Quick condition
Asked in SSC JE 2015
Detailed Explanation
When pore water pressure in a saturated cohesionless soil rises until it equals the total stress, effective stress and therefore strength drop to zero.
Why “Quick condition” Is Correct
The soil then flows like a liquid. This is called the quick condition (quick sand, or liquefaction when caused by earthquakes or vibration).
Why the Other Options Are Wrong
- A. Piping: Piping is internal erosion: progressive removal of soil particles by seeping water, forming pipes.
- B. Slide: A slide is a mass of soil moving down a slope along a slip surface.
- D. Fluidity: ‘Fluidity’ is not the technical name of this condition.
Key Point
Quick condition: σ′ = 0, strength = 0, soil behaves as a fluid.
Key Concepts for Students
- Upward seepage at i = ic causes it.
- Vibration of loose saturated sand can also cause it.
- Piping can follow if a quick condition develops at the exit point.
Practice more: this is question 44 in Shear Strength of Soils MCQs – Part 3. Try the whole set and check every answer instantly.