TYPES OF SOIL SAMPLE

 Soil Sample

Soil sample are obtained during sub-surface exploration to determine the engineering properties of the soils and rocks.Soil sample are generally classified into two categories:

1. Disturbed Sample
2. Undisturbed Sample

Disturbed Sample

Disturbed sample are the sample in which the natural structure of the soil gets disturbed during sampling.However, these samples represent the composition and the mineral content of the soil.Disturbed samples can be used to determine the index properties of the soil, such as grain size, plasticity characteristics, specific gravity.Disturbed soil sample do not retain in-situ properties of the soil during the collection process.Engineers do not consider these sample to be  representative of underground soils except for geotechnical testing that do not rely on the structure of the soil itself.Scientist commonly test disturbed soil samples for soil type and texture, moisture content nutrient and contaminant analysis, among other evaluations.

Undisturbed Sample

Undisturbed sample are the samples in which the natural structure of the soil and the water content are retained.However, it may be mentioned that it is impossible to get truly undisturbed sample.Some disturbance is inevitable during sampling, even when the almost care is taken.Even the removal of the sample from the ground produces a change in the stresses and causes disturbances.

Undisturbed samples are used for determining the engineering properties of the soil, such as compressibility, shear strength and permeability. Some index properties such as shrinkage limit can also be determined.The smaller the disturbance, the greater would be the reliability of the results.

Undisturbed soil sample retain the structural integrity of the soil and have a high recovery rate within the sample.Collecting a perfectly undisturbed sample is difficult and the samplers may contain a small portion of undisturbed soil at the top and bottom of the sample length. Undisturbed samples allow an engineer to determine the geotechnical properties of the strength, permeability, compressibility and fracture patterns among others.