What is the maximum allowed temperature for drying soil during sample preparation?

50°C, to prevent altering the physical properties and clay mineralogy of the soil.

How should field soil clods be broken down?

By using a wooden mallet or a rubber-covered pestle to avoid crushing the natural individual particles.

Which IS sieve fraction is typically used for index properties like the Liquid Limit test?

The fraction passing the 425-micron IS Sieve.

What methods are permitted for reducing the bulk sample size?

Coning and quartering, or using a mechanical riffle box.

IS 2720 Part 1

: 1983

Methods of Test for Soils: Part 1 Preparation of dry soil sample for various tests

CurrentEssentialTesting MethodGeotechnical · Roads and Pavement

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This part of IS 2720 specifies the procedures for preparing dry soil samples from field-collected bulk samples. It covers the methods of drying, breaking clods, sample reduction via quartering or riffling, and sieving to specific fractions necessary for subsequent laboratory geotechnical tests.

Specifies methods for preparing representative dry soil samples suitable for various laboratory tests.

Quick Reference Values

Max oven temperature for sample preparation50°C

Sieve size for liquid/plastic limit tests425 micron

Minimum sample quantity for specific gravity test100 g

Minimum sample quantity for light compaction test6 kg (approx)

Practical Notes

Always use a wooden mallet or rubber-covered pestle to break clods to ensure that individual soil grains are not crushed.

Air drying in the shade is highly recommended over oven drying; if oven drying is necessary, the temperature must not exceed 50°C to prevent alteration of soil properties like Atterberg limits.

Ensure thorough mixing before quartering or riffling to obtain a truly representative subsample.