Geotechnical investigations are performed to obtain information on the physical properties of soil and rock around a site to design earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions. Additionally, geotechnical investigations are also used to measure the thermal resistivity of soils or backfill materials required for underground transmission lines, oil and gas pipelines, radioactive waste disposal, and solar thermal storage facilities. A geotechnical investigation will include surface exploration and subsurface exploration of a site.

Subsurface exploration usually involves soil sampling and laboratory tests of the soil samples retrieved. Methods of observing the soils below the surface include test pits, trenching (particularly for locating faults and slide planes), boring, and in situ tests.

Soil (geotechnical) investigation shall include recommendations for foundation construction, foundation type, foundation depth, allowable or gross soil bearing capacity, remedial actions, design of side support systems, and dewatering systems.