---
title: "Detail stage of EG site investigation"
subject: "Engineering Geology II"
chapter: 4
key: "semester_4/engineering_geology_ii:detail-stage-investigation"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/detail-stage-investigation
site: BCT Engineering
---

# Detail stage of EG site investigation

Engineering Geology II · Chapter 4: Engineering geology in site selection, investigation & construction/excavation

- Asked in: 2076 Bhadra, 3 marks
- Video: [Site Investigation](https://www.youtube.com/watch?v=S-IU_XN1KLk) — BSCE 2A
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/detail-stage-investigation
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-4

## Question

Describe the detail stage of engineering geological site investigation.

## Short answer

The detail stage produces final design data through large-scale (1:500–1:1000) geological mapping, closely spaced core drilling, geophysics, in-situ and laboratory tests, rock mass classification (RMR, Q), and groundwater monitoring, culminating in a final report with foundation treatment recommendations.

## Answer

The **detail stage** (detailed design stage) is the final stage of investigation after the site or alignment has been selected, and gives the complete and accurate geological data for the final design and construction.

#### Activities
1. **Large-scale engineering geological mapping** (1:1,000-1:500) of the site, with detailed structural study.
2. **Dense sub-surface exploration:** closely spaced core drilling (including supplementary holes), test pits, trenches, shafts and adits.
3. **Geophysical surveys** to fill the gaps between holes.
4. **In-situ tests:** permeability (Lugeon), plate load, shear, flat-jack, SPT and in-situ stress tests.
5. **Laboratory tests** on rock and soil for strength, deformability, durability and index properties.
6. **Rock mass classification** (RMR, Q, GSI) and design parameters.
7. **Groundwater study:** observation wells, piezometers.
8. **Detailed investigation of construction materials** and their reserve.
9. **Geological sections and 3D model;** final report with recommendations for foundation treatment, slope support, grouting, excavation and monitoring.

Scale and spacing are chosen from the importance of the structure and the geological complexity.

## Check yourself

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

1. The detail stage is
   A. The final stage after site selection giving complete data for design and construction
   B. The first desk study
   C. Site selection
   D. Post-construction monitoring
   Answer: A. It follows reconnaissance and preliminary stages. (Key point: Purpose)

2. Detailed mapping scale is
   A. 1:100,000
   B. 1:1,000 to 1:500
   C. 1:50,000
   D. 1:250,000
   Answer: B. Large scale is needed for detail. (Key point: Mapping scale)

3. Sub-surface exploration in detail stage is
   A. A single borehole
   B. None
   C. Closely spaced core drilling with supplementary holes, pits, trenches and adits
   D. Aerial photos only
   Answer: C. Dense data defines foundation conditions. (Key point: Exploration)

## Related in Engineering Geology II

- [Detail stage: bridge and reservoir](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Adetail-stage-bridge-reservoir) — 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×
- [Tunneling and site investigation process](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunneling-site-investigation-process) — Engineering Geology II, chapter 4
- [Geological investigation of tunnel and road](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunnel-road-investigation) — Engineering Geology II, chapter 4
- [EG map versus geological map](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aeg-map-vs-geological-map) — Engineering Geology II, chapter 1
- [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×

## Related in other subjects

- [Engineering geological map and site investigation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-geological-map-and-site) — Engineering Geology I, chapter 1, asked 3×
- [Site investigation for dam and reservoir](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Asite-investigation-for-dam-and) — Engineering Geology I, chapter 1, asked 2×
- [Importance and stages of site investigation](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aimportance-stages-site-investigation) — Foundation Engineering, chapter 2
- [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×