---
title: "Forces acting on well foundation"
subject: "Foundation Engineering"
chapter: 9
key: "semester_5/foundation_engineering:well-forces"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/well-forces
site: BCT Engineering
---

# Forces acting on well foundation

Foundation Engineering · Chapter 9: Well Foundations

- Asked in: 2081 Baisakh, 2 marks; 2072 Chaitra, 2 marks (asked 2 times)
- Video: [Force acting on well foundation par-1](https://www.youtube.com/watch?v=VBHh4OAQ1ig) — Mani Mahesh
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/well-forces
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-9

## Question

What are the different forces acting on a well foundation?

## Short answer

Forces include vertical loads (dead, live, self-weight, buoyancy), horizontal forces (braking, centrifugal, wind, water current, seismic), earth pressure (active/passive), secondary forces (temperature, shrinkage), forces during sinking (skin friction), and water pressure. The resultant horizontal force H and moment M at scour level must be resisted by soil.

## Answer

The forces acting on a well foundation are:

1. **Vertical loads:** dead load of the superstructure and the pier, live load on the bridge, self-weight of the well, and **buoyancy** (uplift).
2. **Horizontal forces:** braking/tractive force of vehicles, centrifugal force on curves, **wind** load, **water current** force on the pier and well, and **earthquake** (seismic) forces.
3. **Earth pressure:** active and passive earth pressure on the well, and surcharge on the soil, for abutments.
4. **Secondary forces:** temperature, shrinkage and friction at bearings.
5. **Forces during sinking:** skin friction of the soil, and the stresses from the weight and kentledge.
6. **Water pressure:** buoyancy and seepage forces.

The horizontal forces and their moments (force times lever arm) at the scour level give a resultant horizontal force $H$ and moment $M$, which the lateral resistance of the soil must resist.

## Check yourself

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

1. Which is a vertical load on a well?
   A. Wind only
   B. Braking force
   C. Earth pressure only
   D. Dead load, live load, self weight, and buoyancy
   Answer: D. Vertical loads include superstructure, live load, self weight and buoyancy uplift. (Key point: Vertical loads)

2. Horizontal forces include:
   A. Self weight
   B. Braking, centrifugal, wind, water current and seismic forces
   C. Dead load
   D. Buoyancy
   Answer: B. These act at the scour level and produce H and M. (Key point: Horizontal forces)

3. The horizontal forces produce at scour level:
   A. Only settlement
   B. Only buoyancy
   C. Horizontal force H and moment M resisted by lateral soil resistance
   D. Nothing
   Answer: C. The soil's lateral resistance must resist H and M. (Key point: Resulting effect)

## Related in Foundation Engineering

- [Components of well foundation with sketch](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awell-components-sketch) — Foundation Engineering, chapter 9, asked 9×
- [When well foundation is suitable](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awell-suitability-advantages) — Foundation Engineering, chapter 9, asked 2×
- [Remedies for tilt and shift of well](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awell-tilt-shift-remedies) — Foundation Engineering, chapter 9, asked 9×
- [Depth of well and sinking process](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awell-depth-sinking) — Foundation Engineering, chapter 9, asked 3×
- [Methods of lateral stability analysis of well](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awell-lateral-stability-methods) — Foundation Engineering, chapter 9, asked 2×
- [Precautions against tilt and shift of well](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awell-tilt-shift-precautions) — Foundation Engineering, chapter 9

## Related in other subjects

- [Forces acting on gravity dam](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Agravity-dam-forces-sketch) — Hydro Power, chapter 4
- [Well foundation: excavation, sinking, brick, PCC curb](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-d-four-items) — Estimating and Costing, chapter 6, asked 2×
- [Well foundation: sinking, brick, sand filling, PCC](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-g-sand-filling) — Estimating and Costing, chapter 6, asked 2×
- [Well foundation, 5 m internal diameter](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-5m-k) — Estimating and Costing, chapter 6, asked 2×