Geotechnical surveys (or investigations) are performed for obtaining information on the physical properties of soil and rock around a site. This information is needed for design earthworks, foundations for proposed structures and distress repairs caused by subsurface conditions. Furthermore, the aim of investigations will be the measurement of thermal resistivity of soils or backfills for the design of underground transmission line, oil and gas pipelinesm radioactive disposal caverns and solar facilities.
Surveys include surface exploration and subsurface exploration. Surface exploration includes geologic mapping, sometimes geophysical methods and photogrammetry. Subsurface exploration is more complex and includes a combination of test pits, trenching, boring, in-situ and laboratory tests. One of the major task of investigations is the location of faults, slide planes and other unstable zones.
