A semi-infinite soil mass is loaded with a load intensity of 300 kN/m² at the surface. The vertical stress at a depth of 0.2 m is equal to
- A30 kN/m²
- B60 kN/m²
- C300 kN/m²Correct
- D600 kN/m²
Solution
Concept
Stress under an infinitely wide load
Formula
Δσz = q (loading extends to infinity)
Step-by-step solution
1. When the loaded area is laterally infinite, the stress does not spread and does not decrease with depth. 2. Δσz = q = 300 kN/m².
Explanation
One-dimensional loading: the vertical stress equals the surface load.
Why the other options are wrong
Other values assume dispersion or amplification.
Shortcut
Infinite loaded area → Δσz = q at all depths.
Correct answer: C) 300 kN/m²