Most construction projects require a geotechnical study, commonly referred to as a “soils report”. The purpose of the study is to identify the geological features and hazards of the site and to determine the engineering properties of the earth materials.
A geotechnical study begins with a review of geological maps and reports to determine the geological setting of the site and to identify any known faults, landslides, or other geologic features that may require further study.
Subsurface exploration allows observation and sampling of the subsurface earth materials. Geologists select exploration techniques based on the nature of the site geology and the planned construction.
Many geologic explorations employ hollow-stem auger, sonic, bucket auger, cone penetrometer, or other investigation techniques. Small test pits or larger trenches may be excavated with a backhoe to allow the geologist to directly observe the undisturbed geologic features. Seismic refraction, a geophysical technique, can evaluate the depth and hardness of bedrock concealed below soils.