Geotechnical drilling

Article By:

Sturges, Thomas B., III. Formerly, Pennsylvania Drilling Company, Pittsburgh, Pennsylvania.

Last reviewed:November 2019

DOI:https://doi.org/10.1036/1097-8542.091500

The drilling of holes for gathering and evaluating earth materials in order to design and monitor construction projects. Geotechnical data are required for the accurate, safe, and efficient design and construction of buildings, bridges, highways, dams, and mining sites. The data are derived from analysis of soil and rock samples obtained by drilling. Soil sampling usually is done with a split-spoon sampler, a tube that opens lengthwise to remove the sample. Rock cores are obtained by diamond drilling, using a hollow, diamond-embedded drill bit to cut an intact rock sample. The samples are tested in laboratories for compressive and shear strength, grain size, weathering properties, moisture content, and consolidation projections. The results are used to determine the materials' supporting characteristics, ability to resist transmission of fluids as with dams, and ability to stand without lateral support as in highway cuts or quarries. In addition, tunneling and mining are accomplished safely only with an understanding of the properties of the soil and rock above and below the projected opening. In-hole or in-situ testing through boreholes drilled in a formation is done to determine the material's permeability, water yield, movement (with inclinometers), and settlement over time (with settlement indicators). See also: Engineering geology; Rock mechanics; Soil mechanics

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