---
title: "Index tests for soil"
subject: "Soil Mechanics"
chapter: 2
key: "semester_4/soil_mechanics:index-tests-list"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/index-tests-list
site: BCT Engineering
---

# Index tests for soil

Soil Mechanics · Chapter 2: Solids- Water –Air Relations and Index properties of soils

- Asked in: 2076 Baisakh, 1 marks; 2075 Baisakh, 2 marks (asked 2 times)
- Video: [Atterberg Limits - Consistency Limits](https://www.youtube.com/watch?v=BHqMqBOSWzs) — 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/index-tests-list
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-2

## Question

Name the index tests that are generally carried out to find the index properties of individual soil grains and of the soil mass as a whole.

## Short answer

Index tests for individual grains include specific gravity, sieve analysis, and hydrometer (or pipette) analysis for particle size. For the soil mass as a whole, tests include water content (oven-drying), unit weight (core cutter, sand replacement), calculation of void ratio/porosity, relative density, and consistency (Atterberg) limits (liquid limit, plastic limit, shrinkage limit).

## Answer

#### Tests for individual soil grains
- **Specific gravity** test (pycnometer or density bottle).
- **Particle size analysis** (sieve analysis for coarse grains, hydrometer or pipette analysis for fine grains).
- Particle shape and mineralogical tests (visual, microscope).

#### Tests for the soil mass as a whole
- **Water content** (oven drying, calcium carbide, sand bath, pycnometer).
- **Unit weight / density** (core cutter, sand replacement, water displacement method).
- **Void ratio, porosity and degree of saturation** (calculated from the above).
- **Relative density** test for sands (maximum and minimum density).
- **Consistency limits** (Atterberg limits): liquid limit (Casagrande/cone penetrometer), plastic limit, shrinkage limit.
- Sensitivity (unconfined compression) and field tests such as dilatancy and toughness.

## Check yourself

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

1. Which test gives the specific gravity of soil grains?
   A. Core cutter
   B. Pycnometer or density bottle
   C. Casagrande cup
   D. Hydrometer
   Answer: B. Specific gravity is found with a pycnometer/density bottle. (Key point: Grain tests)

2. Particle size analysis of fine grains uses:
   A. Sieve analysis
   B. Sand replacement
   C. Core cutter
   D. Hydrometer or pipette analysis
   Answer: D. Sieves handle coarse grains; hydrometer/pipette handle fine grains. (Key point: Particle size)

3. Which is a soil-mass index test?
   A. Pycnometer for G
   B. Atterberg limits (liquid, plastic, shrinkage)
   C. Microscope shape check
   D. Hydrometer
   Answer: B. Consistency limits describe the soil mass as a whole. (Key point: Soil mass tests)

4. The relative density test applies to:
   A. Clays
   B. Peat
   C. Rock
   D. Sands, using maximum and minimum density
   Answer: D. Relative density measures how dense a sand is between its extreme densities. (Key point: Relative density)

## Related in Soil Mechanics

- [Engineering vs index properties; index tests](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aindex-engineering-properties-index-tests) — Soil Mechanics, chapter 2
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