Which of the following piles is used for compacting loose granular soil?
Try it first: pick an option, then read the explanation.
Asked in SSC JE 06/06/2024 (Evening)
Detailed Explanation
Piles are named after the job they do. Most piles carry the load of a structure, but some are driven only to improve the ground.
Why “Compaction piles” Is Correct
When a pile is driven into loose granular soil, it pushes the grains aside and packs them more densely. Driving a group of such piles closely spaced densifies the whole area and raises its bearing capacity. These are compaction piles. They are not designed to carry load, so they can be made of cheap material, for example by filling the driven hole with sand (sand piles).
| Pile type | How it works / where it is used |
|---|---|
| End-bearing (point-bearing) pile | Passes through soft soil and rests on a hard stratum; carries load at its tip like a column |
| Friction (floating) pile | No hard stratum within reach; carries load by skin friction along its length |
| Compaction pile | Driven into loose sand to densify it and raise its bearing capacity; not meant to carry load itself |
| Tension (uplift) pile | Resists uplift, e.g. under towers, basements below the water table |
| Batter pile | Driven at an angle to resist inclined or horizontal loads |
| Sheet pile | Forms a wall to retain soil or water; not for vertical load |
Why the Other Options Are Wrong
- A. End bearing piles: End-bearing piles carry load to a hard stratum at their tip.
- C. Tension piles: Tension piles resist uplift forces.
- D. Friction piles: Friction piles carry load by skin friction along the shaft.
Key Point
Compaction piles densify loose sand; they are ground improvement, not load carriers.
Key Concepts for Students
- Compaction works well in sands and gravels, not in clays.
- Vibroflotation is another way to densify loose sand.
- Sand piles in clay act as vertical drains rather than compaction piles.
Practice more: this is question 3 in Shallow and Deep Foundation MCQs – Part 1. Try the whole set and check every answer instantly.