---
title: "Factors affecting foundation design, improving bearing capacity"
subject: "Building Technology"
chapter: 2
key: "semester_6/building_technology:factors-design-improve-bc"
source: https://www.bctengineer.com/q/semester_6/building_technology/factors-design-improve-bc
site: BCT Engineering
---

# Factors affecting foundation design, improving bearing capacity

Building Technology · Chapter 2: Foundations

- Asked in: 2074 Bhadra, 8 marks
- Video: [Selecting Type of Foundation from Type of Soil?](https://www.youtube.com/watch?v=ddkroD9aIAQ) — Engineering Motive
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/factors-design-improve-bc
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-2

## Question

Describe the factors affecting the design of foundation. How can we improve the bearing capacity of soil?

## Short answer

Foundation design is affected by soil bearing capacity, loads, depth, settlement, ground water, structure type, seismic zone, adjacent structures, soil problems, topography, construction and codes. Bearing capacity can be improved by compaction, drainage, sand cushion replacement, increasing depth/width, sand piles/stone columns, grouting, stabilisation, preloading, geotextiles, sheet piles or piles.

## Answer

#### Factors affecting the design of foundation
1. **Bearing capacity of soil** and the type of soil (clay, sand, rock).
2. **Loads on the structure**: Dead, live, wind, seismic and their eccentricity.
3. **Depth of foundation**: Depends on bearing strata, frost, shrinkage zone, scour, water table, and depth of nearby foundations. Rankine's formula gives minimum depth $D = \frac{q}{\gamma}\left(\frac{1-\sin\phi}{1+\sin\phi}\right)^2$.
4. **Settlement**: Total and differential settlement must be within limits.
5. **Ground water table**: Affects bearing capacity, excavation and uplift.
6. **Type of structure**: Sensitivity to settlement, e.g. framed or load-bearing.
7. **Seismic zone** and liquefaction risk.
8. **Adjacent structures and underground services**.
9. **Soil problems**: Expansive, collapsible or filled soils; sulphate in soil and ground water.
10. **Site topography**: Slope, drainage and erosion.
11. **Construction methods, materials and economy**.
12. **Building codes**: Nepal National Building Code, IS 1904, IS 6403.

#### Improving the bearing capacity of soil
1. Compaction by roller, rammer or vibration.
2. Drainage of water by sumps, well points, sub-soil drains.
3. Replacement of weak soil by a sand or gravel cushion.
4. Increasing foundation depth and width.
5. Sand piles or stone columns.
6. Grouting or chemical injection.
7. Stabilisation with cement, lime or fly ash.
8. Preloading with surcharge, and geotextile reinforcement.
9. Confining soil with sheet piles.
10. Using pile foundation.

## Check yourself

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

1. Rankine's formula gives
   A. Minimum depth of foundation
   B. Maximum load
   C. Water table
   D. Settlement
   Answer: A. D = (q/gamma)((1-sin phi)/(1+sin phi))^2. (Key point: Rankine)

2. Which affects depth of foundation?
   A. Frost, shrinkage zone, scour and water table
   B. Colour of paint
   C. Number of doors
   D. Roof pitch
   Answer: A. Depth depends on bearing strata, frost, shrinkage, scour, water table. (Key point: Depth factors)

3. Settlement must be
   A. Ignored
   B. Maximised
   C. Within limits, both total and differential
   D. Zero total only
   Answer: C. Total and differential settlement must be limited. (Key point: Settlement)

4. Sumps, well points and sub-soil drains
   A. Raise the water table
   B. Reduce density
   C. Lower the water table to improve bearing capacity
   D. Increase settlement
   Answer: C. Drainage raises effective stress. (Key point: Drainage)

## Related in Building Technology

- [Soil exploration and improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asoil-exploration-improving-bc-nepal) — Building Technology, chapter 2
- [Sub-soil exploration, improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asubsoil-exploration-improve) — Building Technology, chapter 2
- [Methods of improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aimproving-bc) — Building Technology, chapter 2, asked 2×
- [Soil exploration, safe bearing capacity, improvement](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aexploration-bc-065s) — Building Technology, chapter 2
- [Safe and ultimate bearing capacity, improvement](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Abc-define-improve-066j) — Building Technology, chapter 2
- [Methods of determining bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Abc-determination-methods) — Building Technology, chapter 2, asked 2×

## Related in other subjects

- [Factors affecting bearing capacity; water table](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abearing-capacity-factors-water-table) — Foundation Engineering, chapter 6, asked 5×
- [Soil moisture forms; factors affecting CWR](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Asoil-moisture-forms-cwr-factors) — Irrigation and Drainage Engineering, chapter 2
- [Traffic capacity; factors affecting capacity and LOS](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Atraffic-capacity-factors-los-timing) — Transportation Engineering II, chapter 1
- [Highway capacity; factors affecting capacity and LOS](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ahighway-capacity-factors-level-of-service) — Transportation Engineering II, chapter 1