---
title: "Methods of improving bearing capacity"
subject: "Building Technology"
chapter: 2
key: "semester_6/building_technology:improving-bc"
source: https://www.bctengineer.com/q/semester_6/building_technology/improving-bc
site: BCT Engineering
---

# Methods of improving bearing capacity

Building Technology · Chapter 2: Foundations

- Asked in: 2078 Chaitra, 5 marks; 2076 Bhadra, 4 marks (asked 2 times)
- Video: [How to Increase Bearing Capacity of Soil? || By CivilGuruji](https://www.youtube.com/watch?v=YERCZQs8MLY) — The Institute of Construction Managment 
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/improving-bc
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-2

## Question

What do you mean by the bearing capacity of the soil? Explain the different methods of improving the bearing capacity of soil.

## Short answer

Bearing capacity is the soil's ability to support loads without shear failure or excessive settlement; safe bearing capacity is the ultimate capacity divided by a factor of safety. Improvement methods include compaction, drainage, soil replacement, deep compaction with sand piles, grouting, stabilization, and using deeper or wider foundations.

## Answer

**Bearing capacity** of soil is the ability of soil to carry load from the foundation without shear failure or excessive settlement. **Ultimate bearing capacity** ($q_u$) is the pressure at which the soil fails in shear; **safe bearing capacity** is $q_u$ divided by factor of safety (usually 2.5 to 3), and also limited by permissible settlement.

#### Methods of improving bearing capacity
1. **Compaction**: Rollers, rammers or vibrators raise the density of loose, granular soil in layers.
2. **Drainage**: Lowering the water table by sumps, well points or sub-soil drains increases effective stress and strength.
3. **Replacement**: Poor soil is excavated and replaced with compacted sand, gravel or murrum (sand cushion).
4. **Increasing depth and width of the foundation**: A deeper and wider footing gives better capacity and reduced pressure.
5. **Confining the soil**: Sheet piles or a ring wall keep loose soil in place.
6. **Sand piles and stone columns**: Holes bored and filled with sand or crushed stone, compacted; raise the density of soft soil.
7. **Chemical treatment / grouting**: Cement, lime or chemical grout injected into soil voids.
8. **Stabilisation**: Mixing cement, lime, bitumen or fly ash with soil.
9. **Pre-loading and geosynthetics**: Surcharge to pre-consolidate soft clay; geotextile and geogrids reinforce.
10. **Vibroflotation** for deep compaction of sand.
11. **Pile foundations** for transfer to a deeper stratum, if the above are not sufficient.

## Check yourself

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

1. How is safe bearing capacity obtained from ultimate?
   A. Dividing q_u by a factor of safety of 2.5 to 3
   B. Multiplying q_u by 2.5
   C. Adding the factor of safety to q_u
   D. Dividing by the footing width
   Answer: A. q_safe = q_u / FS, also limited by permissible settlement. (Key point: Safe bearing capacity)

2. How does lowering the water table improve bearing capacity?
   A. It reduces the soil density
   B. It adds weight to footing
   C. It increases effective stress and strength
   D. It removes the need for a footing
   Answer: C. Lower water table raises effective stress. (Key point: Drainage)

3. What is replacement as a method?
   A. Injecting grout in pores
   B. Driving piles
   C. Excavating poor soil and replacing with compacted sand, gravel or murrum
   D. Mixing lime with soil in place
   Answer: C. The poor soil is replaced by a compacted cushion. (Key point: Replacement)

4. What is pre-loading used for?
   A. Compacting dry sand
   B. Lowering the water table
   C. Pre-consolidating soft clay with a surcharge
   D. Confining soil
   Answer: C. A surcharge consolidates soft clay before construction. (Key point: Preloading)

## 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
- [Soil exploration, safe bearing capacity, improvement](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aexploration-bc-065s) — Building Technology, chapter 2
- [Factors affecting foundation design, improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Afactors-design-improve-bc) — 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×
- [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

## Related in other subjects

- [Bearing capacity from plate load curve](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abc-from-load-settlement-sand) — Foundation Engineering, chapter 6
- [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×
- [Mat bearing capacity: cohesive vs cohesionless](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Amat-bc-cohesive-vs-cohesionless) — Foundation Engineering, chapter 7, asked 2×
- [Skempton's findings on clay bearing capacity](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Askempton-net-safe-bc) — Foundation Engineering, chapter 6