Which one of the following has the least bearing capacity?
Try it first: pick an option, then read the explanation.
Correct answer: C. Loose gravel
Asked in SSC JE 2014 (Evening)
Detailed Explanation
IS 1904 (and the older National Building Code) gives typical safe bearing capacities for different soils and rocks. They are useful for preliminary design and are often asked in exams.
Why “Loose gravel” Is Correct
Rock is far stronger than any soil, and dense (compact) gravel is stronger than loose gravel. From the table, loose gravel has the least bearing capacity among the options.
| Material | Typical safe bearing capacity (kN/m²) |
|---|---|
| Hard rock (granite, trap) | 3240 |
| Soft rock | 440 |
| Compact gravel / sand-gravel mix | 440 |
| Loose gravel / sand-gravel mix | 245 |
| Medium clay | 245 |
| Soft clay, silt | 100 |
| Black cotton soil | 130–160 |
Typical values (IS 1904 / NBC). Use only for preliminary sizing; tests are needed for design.
Why the Other Options Are Wrong
- A. Soft rocks: Soft rock (≈ 440 kN/m²) is stronger than loose gravel.
- B. Compact gravel: Compact gravel (≈ 440 kN/m²) is stronger than loose gravel.
- D. Hard rocks: Hard rock has by far the highest bearing capacity.
Key Point
Rock > compact gravel > loose gravel > clays > soft clay/silt.
Key Concepts for Students
- Density strongly affects the bearing capacity of granular soils.
- Water table rise reduces the values for sand and gravel.
- Peat and made-up ground have no reliable tabulated values.
Practice more: this is question 32 in Shallow and Deep Foundation MCQs – Part 3. Try the whole set and check every answer instantly.