The shearing strength of a cohesionless soil depends on:
Try it first: pick an option, then read the explanation.
Correct answer: D. All the above
Asked in SSC JE 2010
Detailed Explanation
For a cohesionless soil τ = σ′ tan φ. Anything that changes σ′ or φ changes the strength.
Why “All the above” Is Correct
Dry density: denser sand has more interlocking, so a higher φ. Confining pressure: strength is proportional to the normal (confining) stress. Rate of loading: very fast loading can change pore pressures and strength slightly. So all the factors listed affect it, and the expected answer is ‘all the above’.
Why the Other Options Are Wrong
- A. Dry density: Dry density matters, but so do the other factors.
- B. Rate of loading: Rate of loading has some influence, but it is not the only factor.
- C. Confining pressure: Confining pressure matters, but density does too.
Key Point
Sand: τ = σ′ tan φ, where φ depends on density, grading and shape.
Key Concepts for Students
- Rate effects are small in clean sands under normal test speeds.
- Dense sands show a peak and then soften to a residual value.
- Loose sands show no peak and reach strength at large strain.
Practice more: this is question 40 in Shear Strength of Soils MCQs – Part 3. Try the whole set and check every answer instantly.