---
title: "Importance and stages of site investigation"
subject: "Foundation Engineering"
chapter: 2
key: "semester_5/foundation_engineering:importance-stages-site-investigation"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/importance-stages-site-investigation
site: BCT Engineering
---

# Importance and stages of site investigation

Foundation Engineering · Chapter 2: Soil Exploration

- Asked in: 2078 Bhadra, 4 marks
- Video: [Stages of Site Investigation/Soil Exploration Programme](https://www.youtube.com/watch?v=oeCW3D4e9Sc) — GeotechnicalEngineering ShortClasses
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/importance-stages-site-investigation
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-2

## Question

Describe in detail the importance of site investigation and the stages of site investigation.

## Short answer

Site investigation is essential to choose safe, economical foundations, obtain design parameters, and identify problem soils and groundwater. Stages are reconnaissance, preliminary exploration (few borings for general strata), detailed exploration (sampling and testing for design), supplementary investigation during construction, and final report.

## Answer

**Site investigation** (soil exploration) is the process of finding the nature, extent and properties of the soil and rock and the groundwater at a site.

#### Importance
- To select a safe and economical foundation type and depth.
- To get design parameters for bearing capacity and settlement.
- To find problem soils (soft clay, peat, swelling, collapsible, liquefiable soil) and groundwater.
- To plan the construction method, dewatering, excavation support.
- To find construction material sources and the stability of slopes.
- To avoid failures, delay and cost increases from unforeseen conditions.

#### Stages
1. **Reconnaissance (desk study and site visit):** study maps, geology, aerial photos, past records, and walk over the site.
2. **Preliminary exploration:** a few borings/test pits and simple tests to learn the general strata, groundwater and the likely foundation type.
3. **Detailed exploration:** more boreholes, undisturbed sampling, field and laboratory tests to get the design parameters.
4. **Supplementary exploration (during construction):** extra tests where unexpected conditions appear.
5. **Report preparation** with recommendations.

## Check yourself

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

1. A main purpose of site investigation is to
   A. select a safe and economical foundation type and depth
   B. avoid any design calculations
   C. increase construction cost
   D. choose building colours
   Answer: A. It gives bearing capacity, settlement and problem-soil data. (Key point: Importance)

2. The first stage of site investigation is
   A. detailed exploration with undisturbed sampling
   B. reconnaissance (desk study and site visit)
   C. supplementary exploration
   D. report preparation
   Answer: B. Maps, geology and a walkover come before any drilling. (Key point: First stage)

3. Detailed exploration is carried out to
   A. learn the general strata only
   B. walk over the site
   C. get the design parameters using more boreholes, undisturbed sampling and tests
   D. replace the report
   Answer: C. Preliminary gives the general picture; detailed gives design values. (Key point: Detailed exploration)

4. Supplementary exploration is done
   A. before the desk study
   B. only after the building is complete
   C. never
   D. during construction when unexpected conditions appear
   Answer: D. Extra tests deal with surprises found while building. (Key point: Supplementary)

## Related in Foundation Engineering

- [Contents of site investigation report](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Asite-investigation-report) — Foundation Engineering, chapter 2, asked 5×
- [Investigation details for bridge foundation](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abridge-foundation-investigation) — Foundation Engineering, chapter 2

## Related in other subjects

- [Detail stage of EG site investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Adetail-stage-investigation) — Engineering Geology II, chapter 4
- [Purposes of site investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asite-investigation-purposes) — Engineering Geology II, chapter 4, asked 7×
- [Types and methods of site investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asite-investigation-methods) — Engineering Geology II, chapter 4, asked 7×
- [Methods of surface and subsurface site investigation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Amethods-of-surface-and-subsurface) — Engineering Geology I, chapter 1, asked 4×