---
title: "Field tests for sand and clay"
subject: "Soil Mechanics"
chapter: 3
key: "semester_4/soil_mechanics:field-tests-sand-clay"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/field-tests-sand-clay
site: BCT Engineering
---

# Field tests for sand and clay

Soil Mechanics · Chapter 3: Soil Identifications and Classification

- Asked in: 2078 Baisakh, 2 marks
- Video: [Field Identification of Soil](https://www.youtube.com/watch?v=JvU-OXOyiTU) — Elementary Engineering
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/field-tests-sand-clay
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-3

## Question

Name the tests generally done to identify sandy soil and clayey soil in the field.

## Short answer

Sandy soil: gritty, crumbles easily, quick dilatancy, settles fast, no thread. Clayey soil: high dry strength, slow/no dilatancy, rolls into 3 mm tough thread, sticky and shiny, stays suspended.

## Answer

**Sandy soil**
- **Visual and touch:** coarse, gritty, grains visible to the naked eye.
- **Dry strength test:** crumbles easily; no strength.
- **Dilatancy test:** quick reaction with water rising to the surface (for fine sand).
- **Sedimentation test:** settles in less than a minute.
- Does not form a thread (no plasticity).

**Clayey soil**
- **Dry strength test:** high strength; hard to crush.
- **Dilatancy test:** no or very slow reaction.
- **Toughness (thread) test:** rolls into 3 mm thread; tough and cohesive.
- **Stickiness/shine test:** sticky, smooth, with shiny cut surface.
- **Sedimentation test:** stays in suspension for a long time.

## Check yourself

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

1. Sandy soil in dry strength test
   A. crumbles easily with no strength
   B. has high strength
   C. forms a hard lump
   D. is sticky
   Answer: A. Sand has no cohesion. (Key point: Sand dry strength)

2. Which test shows clay is cohesive?
   A. Quick settlement in water
   B. Rolling a 3 mm thread that stays tough
   C. Gritty feel on teeth
   D. Water rising on shaking
   Answer: B. Clay forms a tough thread; sand does not. (Key point: Clay thread)

3. In water, clay
   A. settles in less than a minute
   B. shows quick dilatancy
   C. stays in suspension for a long time
   D. does not mix with water
   Answer: C. Sand settles quickly; clay remains suspended. (Key point: Sedimentation)

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