---
title: "Phase with supplementary core drilling"
subject: "Engineering Geology II"
chapter: 4
key: "semester_4/engineering_geology_ii:core-drilling-phase"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/core-drilling-phase
site: BCT Engineering
---

# Phase with supplementary core drilling

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

- Asked in: 2076 Baisakh, 1.5 marks
- Video: [How Diamond Drill Rigs Work](https://www.youtube.com/watch?v=VF3_TqN6AQA) — GeologyUpSkill
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/core-drilling-phase
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-4

## Question

In which phase of a civil engineering project is sub-surface site investigation carried out with supplementary core drilling?

## Short answer

Supplementary core drilling is performed during the detailed (final design) phase, after site selection. Closely spaced additional boreholes define foundation conditions, weak zones, RQD, depth of weathering, and permeability, filling gaps between earlier exploration points for final design and treatment.

## Answer

Sub-surface investigation with **supplementary core drilling** is carried out in the **detailed (final design) phase**, after site selection.

- In the reconnaissance and preliminary phases, only a few exploratory holes are used.
- In the detailed phase, additional (supplementary) core-drill holes are placed at closely spaced positions, to define foundation conditions, weak zones, rock quality (RQD), depth of weathering and permeability, and to fill the gaps between earlier holes and geophysical profiles.
- The results are used in the final design and for foundation treatment (grouting, excavation depth).

## Check yourself

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

1. Supplementary core drilling is done in
   A. Reconnaissance
   B. The detailed (final design) phase
   C. Preliminary phase
   D. After completion
   Answer: B. It follows site selection. (Key point: Phase)

2. Reconnaissance and preliminary phases use
   A. Dense supplementary holes
   B. No investigation
   C. Only a few exploratory holes
   D. Only core drilling
   Answer: C. Density increases with stage. (Key point: Earlier phases)

3. Supplementary holes are used to
   A. Select a country
   B. Measure rainfall
   C. Paint rock
   D. Define foundation conditions, weak zones, RQD, weathering and permeability
   Answer: D. They fill gaps between earlier holes. (Key point: Purpose)

## Related in Engineering Geology II

- [Direct methods of sub-surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Adirect-subsurface-methods) — Engineering Geology II, chapter 4, asked 3×
- [Surface versus sub-surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asurface-vs-subsurface-investigation) — Engineering Geology II, chapter 4, asked 3×
- [Indirect sub-surface methods: tunnel and dam](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aindirect-subsurface-tunnel-dam) — Engineering Geology II, chapter 4
- [Indirect methods of surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aindirect-surface-methods) — 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×

## Related in other subjects

- [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×
- [Drilling type and field tests, Kathmandu core](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Adrilling-field-tests-kathmandu) — Foundation Engineering, chapter 2
- [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×
- [Appraisal parameters for civil engineering project](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Aappraisal-parameters-civil-project) — Project Engineering, chapter 2