---
title: "Soil exploration and improving bearing capacity"
subject: "Building Technology"
chapter: 2
key: "semester_6/building_technology:soil-exploration-improving-bc-nepal"
source: https://www.bctengineer.com/q/semester_6/building_technology/soil-exploration-improving-bc-nepal
site: BCT Engineering
---

# Soil exploration and improving bearing capacity

Building Technology · Chapter 2: Foundations

- Asked in: 2079 Chaitra, 8 marks
- 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/soil-exploration-improving-bc-nepal
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-2

## Question

Define soil exploration. Explain the methods of improving bearing capacity of soil. Which method is commonly used in Nepal? Discuss.

## Short answer

Soil exploration studies soil strata via borings and tests. Bearing capacity is improved by replacing weak soil with compacted sand/gravel, compaction, drainage, increasing foundation size, stone columns, grouting, or piling. In Nepal, replacement with a sand-gravel cushion is most common for ordinary buildings.

## Answer

#### Soil exploration
**Soil exploration** (site investigation) is the process of studying the soil and rock at a site by borings, sampling, field tests and laboratory tests, to find the type and thickness of strata, groundwater level and the engineering properties (bearing capacity, settlement, strength) for safe foundation design. Methods are test pits, auger boring, wash boring, percussion boring, rotary drilling, SPT, cone penetration, plate load test, geophysical methods.

#### Methods of improving bearing capacity
1. **Compaction** of loose soil by rolling, ramming and vibration.
2. **Drainage** of ground water (sumps, well points, sub-soil drains).
3. **Replacement** of weak soil with sand, gravel or murrum, compacted in layers (sand cushion).
4. **Increasing size and depth** of foundation.
5. **Sand piles, stone columns**, to densify soft soils.
6. **Grouting and chemical injection** (cement, lime, silicate).
7. **Soil stabilisation** with cement, lime, bitumen or fly ash.
8. **Pre-loading** and use of **geosynthetics**.
9. **Confining the soil** with sheet piles or sheeting.
10. **Piles** to reach firm strata.

#### Method commonly used in Nepal
The most common method is **replacement with a compacted sand or gravel cushion**, along with **compaction** and increasing the footing size, for ordinary buildings, because it is cheap, uses local materials and manual labour, and needs no special equipment. For larger works in soft soil, sub-soil drainage, stone columns and pile foundations are used. For many Kathmandu valley sites with soft clay and a high water table, these methods plus raft foundations are adopted.

## Check yourself

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

1. What is the purpose of soil exploration?
   A. Select paint colours
   B. Plan the roof
   C. Measure rain
   D. Find strata, groundwater level and properties for safe foundation design
   Answer: D. It gathers soil data for design. (Key point: Soil exploration)

2. Which BC improvement is most common in Nepal for ordinary buildings?
   A. Vibroflotation
   B. Freezing
   C. Replacement with a compacted sand or gravel cushion
   D. Jet grouting
   Answer: C. It is cheap, uses local materials and manual labour. (Key point: Common method)

3. Why is the sand cushion method preferred in Nepal?
   A. It needs heavy machinery
   B. It is the most expensive
   C. It needs imported material
   D. Cheap, local material and no special equipment
   Answer: D. It is cheap and simple. (Key point: Reason)

4. For Kathmandu sites with soft clay and high water table, what is adopted?
   A. Only shallow strip footings
   B. Nothing
   C. Only plastering
   D. Drainage, stone columns, piles and raft foundations
   Answer: D. Those methods plus rafts are adopted. (Key point: Kathmandu)

## Related in Building Technology

- [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
- [Methods of improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aimproving-bc) — Building Technology, chapter 2, asked 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
- [Need for soil test / soil exploration](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asoil-test-need) — Building Technology, chapter 2, asked 2×
- [Define soil exploration](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Adefine-soil-exploration) — Building Technology, chapter 2