Undisturbed soil samples are obtained by: -

Concept:

Soil samples are classified as disturbed and undisturbed samples.

Undisturbed samples: The soil samples in which original soil structure and mineral properties have not undergone any change are called undisturbed samples.

It is important in the identification of soil properties such as shear strength, water content, soil structure, consolidation properties, etc.

Disturbed sample: The soil samples in which original soil structure and mineral properties are destroyed during sampling operation are called disturbed samples.

They are used to study soil grain properties, in CBR test for highway construction, etc.

The extent of disturbance depends on cutting edge and inside wall friction of soil sampler.

The sampling tubes are of two types:-

a) Thin-walled sampler: These are used to obtain undisturbed samples. The sampler tube is pushed into the soil without any twisting.

b) Thick-walled sampler: These are used to obtain disturbed but representative samples. The sampler tube is twisted and pushed into the soil.

Important Points:

Direct excavations: It is a method of soil exploration. This method is generally used in small works and produces disturbed samples.

Augers- It is a boring method in which the boring is carried by an auger that is held vertically and pressed down shearing the soil around the auger.