A sample that is as undisturbed as humanly possible, as distinct from a sample disturbed by boring tools. Special appliances are used to obtain such samples from boreholes, and the material is preserved in its natural state in airtight containers. Undisturbed samples are required so that the in-place (in situ) properties of the soil may be determined. It is difficult to obtain undisturbed samples of sandy soils without considerable preparation.