A geotechnical borehole is a drilled hole specifically designed and executed to retrieve rock and soil samples for the purpose of characterizing subsurface ground conditions from an engineering and stability perspective, as opposed to exploration boreholes that primarily target mineral grade. In mining contexts — including bauxite, gold, iron ore, and diamond operations — geotechnical boreholes provide the raw data upon which slope stability analyses, foundation designs, groundwater models, and underground support systems are built. The drilling methodology for geotechnical boreholes differs from grade-control drilling; core recovery rates, sample integrity, and in-situ testing capabilities take precedence over drilling speed. Geotechnical boreholes are typically drilled using triple-tube core barrels to maximize core recovery in weak or fractured rock, and the resulting core is logged in detail using geomechanical classification systems such as the Rock Quality Designation (RQD), Rock Mass Rating (RMR), and Q-System. In-situ tests performed within geotechnical boreholes include Standard Penetration Tests (SPT), packer permeability tests, pressuremeter tests, and downhole geophysical logging. Piezometers and inclinometers are commonly installed within geotechnical boreholes to monitor groundwater levels and slope movement over time. For large open pit operations in iron ore and gold mining, a geotechnical borehole program spanning multiple drill campaigns over years may be required to adequately characterize the rock mass and support dynamic slope design as mining deepens.
