---
title: "Accessible and inaccessible exploration methods"
subject: "Foundation Engineering"
chapter: 2
key: "semester_5/foundation_engineering:accessible-inaccessible-exploration"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/accessible-inaccessible-exploration
site: BCT Engineering
---

# Accessible and inaccessible exploration methods

Foundation Engineering · Chapter 2: Soil Exploration

- Asked in: 2079 Bhadra, 2 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/accessible-inaccessible-exploration
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-2

## Question

Differentiate between accessible and inaccessible methods of exploration.

## Short answer

Accessible methods like test pits permit direct observation and undisturbed block sampling but are limited to shallow depths (~3–6 m). Inaccessible methods such as borings can reach any depth but strata are inferred from samples and cuttings.

## Answer

| Point | Accessible methods | Inaccessible methods |
|---|---|---|
| Meaning | Soil can be examined directly by a person entering the excavation | Soil is examined only by samples brought up from a hole |
| Examples | Test pits, trenches, shafts, drifts | Auger boring, wash boring, percussion, rotary drilling |
| Depth | Shallow (up to about 3-6 m) | Any depth |
| Observation | In-situ strata, structure, fissures visible; undisturbed block samples possible | Strata inferred from samples/cuttings |
| Cost | Costly for depth, dewatering needed | Cheaper per metre of depth |
| Use | Small, important sites; check of weak zones | Routine investigation of buildings and bridges |

## Check yourself

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

1. In accessible methods
   A. soil is seen only from samples
   B. a person can enter and examine the soil directly
   C. only geophysics is used
   D. no soil is examined
   Answer: B. Test pits, trenches and shafts allow direct inspection. (Key point: Accessible meaning)

2. Which are inaccessible methods?
   A. Test pits and trenches
   B. Auger, wash, percussion and rotary boring
   C. Shafts and drifts
   D. Open excavation
   Answer: B. Soil is examined only through samples or cuttings. (Key point: Inaccessible examples)

3. Accessible methods are practical only to
   A. any depth
   B. over 100 m
   C. shallow depths of about 3-6 m
   D. depths of 50 m
   Answer: C. Cost and dewatering limit depth. (Key point: Depth)

## Related in other subjects

- [Geophysical and geotechnical exploration](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Ageophysical-geotechnical-exploration) — Engineering Geology II, chapter 4, asked 3×
- [RL of tower top, base inaccessible](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atower-inaccessible-base-rl-two-stations) — Surveying II, chapter 3