---
title: "Representative vs non-representative samples"
subject: "Foundation Engineering"
chapter: 2
key: "semester_5/foundation_engineering:representative-samples"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/representative-samples
site: BCT Engineering
---

# Representative vs non-representative samples

Foundation Engineering · Chapter 2: Soil Exploration

- Asked in: 2072 Chaitra, 2 marks
- Video: [Disturb Undisturb Sample🔥|Representative & Non Representative|Soil Sampling|Soil Exploration](https://www.youtube.com/watch?v=DzYOtr5Deqk) — DIPAK  MANDAL
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/representative-samples
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-2

## Question

Differentiate between representative and non-representative soil samples.

## Short answer

A representative sample contains all soil constituents in the same proportion as in situ, though it may be disturbed (e.g., auger cuttings). A non-representative sample loses some constituents or layers (e.g., wash boring cuttings), altering both composition and structure, and is only useful for a rough indication of strata change.

## Answer

| Point | Representative sample | Non-representative sample |
|---|---|---|
| Constituents | Contains all soil particles in the same proportion as the in-situ soil | Some constituents are lost or mixed (e.g. fines washed away, layers mixed) |
| Structure | May be disturbed, structure not preserved | Structure and composition both altered |
| Example | Auger cuttings, split-spoon sample, test pit sample | Wash-boring return water cuttings, percussion slurry |
| Use | Classification, grain size, Atterberg limits | Only a rough indication of strata change |

## Check yourself

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

1. A representative sample
   A. contains all soil constituents in the same proportion as in-situ
   B. has fines washed away
   C. is always undisturbed
   D. has only gravel
   Answer: A. Structure may be disturbed but composition is intact. (Key point: Representative)

2. Which gives a non-representative sample?
   A. Auger cuttings
   B. Wash boring cuttings with fines washed away
   C. Split-spoon sample
   D. Test pit sample
   Answer: B. Washing loses fines and mixes layers. (Key point: Non-representative example)

3. Representative samples can be used for
   A. consolidation tests
   B. triaxial strength tests
   C. classification, grain size and Atterberg limits
   D. permeability of structure
   Answer: C. These tests don't need natural structure. (Key point: Use)

## Related in Foundation Engineering

- [Disturbed vs undisturbed samples](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Adisturbed-vs-undisturbed-sample) — Foundation Engineering, chapter 2, asked 2×
- [Allowable load of 400 mm pile, layered soil](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apile-400mm-layered-soil-chart) — Foundation Engineering, chapter 8

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