---
title: "Situations demanding pile foundation"
subject: "Building Technology"
chapter: 2
key: "semester_6/building_technology:pile-situations"
source: https://www.bctengineer.com/q/semester_6/building_technology/pile-situations
site: BCT Engineering
---

# Situations demanding pile foundation

Building Technology · Chapter 2: Foundations

- Asked in: 2076 Bhadra, 2 marks; 2072 Asoj, 8 marks (asked 2 times)
- Video: [From Bored to Driven: Demystifying Pile Foundation Choices](https://www.youtube.com/watch?v=6S1LjSphWBA) — The Brazilian Engineer in Australia
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/pile-situations
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-2

## Question

Enumerate the situations demanding the use of piles as foundations.

## Short answer

Piles are required when surface soils are weak or compressible, for heavy loads from tall structures, to control settlement or uplift, in high water tables, scour-prone or expansive soil sites, and to avoid disturbing adjacent buildings or excavation.

## Answer

Pile foundations are used when shallow foundations are not suitable or economical. The situations are:

1. **Weak surface soil**: A thick layer of soft clay, loose sand, peat or fill above, with hard stratum or rock at a lower depth; piles carry load to the firm layer (end-bearing piles).
2. **Heavy loads**: Tall buildings, bridges, towers and industrial structures whose loads shallow footings cannot carry.
3. **Large settlement expected**: Compressible soils, where settlement of shallow footings is excessive.
4. **High water table or submerged site**: Excavation of shallow foundation is hard (river, marine, bridge piers).
5. **Uplift or overturning loads**: Transmission towers, chimneys, basement under water pressure; piles resist tension.
6. **Lateral loads**: Wind, earthquake, or water pressure on retaining walls, jetties, and docks (raked piles).
7. **Scour risk**: River bed erosion around foundations of bridges.
8. **Expansive soils** (black cotton): Piles go below the zone of seasonal change.
9. **Liquefaction-prone soil** in earthquake areas.
10. **Adjacent structures or very deep excavations**, where shallow footings would disturb nearby buildings.
11. **Compaction of loose sand** (compaction piles).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. When are end-bearing piles used?
   A. Soft soil above with a hard stratum deeper down
   B. Hard rock at the surface
   C. Uniform firm sand at the surface
   D. Light single-storey buildings
   Answer: A. Piles carry load through weak soil to a firm layer. (Key point: Weak surface soil)

2. Why are piles used for transmission towers?
   A. They resist uplift or tension
   B. They reduce tower height
   C. They are cheaper than footings always
   D. They stop corrosion
   Answer: A. Piles resist tension, which shallow footings cannot. (Key point: Uplift)

3. Why are piles used for bridges in river beds?
   A. To increase the water level
   B. To avoid any load
   C. To reduce span
   D. To go below scour from bed erosion
   Answer: D. Piles extend below the scour depth. (Key point: Scour)

4. How do piles help in black cotton soil?
   A. They absorb the swelling
   B. They keep the soil wet
   C. They go below the zone of seasonal change
   D. They compact the soil near the surface
   Answer: C. Piles bypass the active zone where swelling and shrinkage occur. (Key point: Expansive soil)

## Related in Building Technology

- [Deep foundation types and use of shallow foundations](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Adeep-shallow-types-079a) — Building Technology, chapter 2
- [When pile and mat foundations are chosen](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apile-mat-scenarios) — Building Technology, chapter 2
- [Foundations on black cotton soil](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ablack-cotton-foundation) — Building Technology, chapter 2
- [Common problems of existing foundations](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aproblems-existing-foundation) — Building Technology, chapter 2, asked 2×

## Related in other subjects

- [Classification of pile foundations](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apile-classification-material-load) — Foundation Engineering, chapter 8
- [Piles for Foundations: suitability for apartments](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Apiles-for-foundations-apartments) — Communication English, chapter 2
- [Pile spacing for 100% efficiency, 16 piles](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apile-spacing-100-efficiency-square-30cm) — Foundation Engineering, chapter 8, asked 2×
- [Types of pile by use; tension piles](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apile-types-use-tension) — Foundation Engineering, chapter 8