Geotechnical logging is the systematic recording and classification of physical, structural, and mechanical properties of rock core or soil samples retrieved from drill holes, as well as observations made at exposed rock face outcrops and underground excavation surfaces, for the purpose of geotechnical engineering analysis. In mining operations — including bauxite, gold, iron ore, and diamond — geotechnical logging produces the primary dataset from which rock mass classification, slope stability analysis, and ground support design are derived. The process is performed by trained geotechnical engineers or engineering geologists and follows standardized logging protocols specific to the project and commodity. Core geotechnical logging involves the measurement and recording of core recovery percentage, Rock Quality Designation (RQD), fracture frequency, discontinuity orientation, spacing, persistence, roughness, aperture, infill, and weathering grade. Rock strength is assessed through field index tests such as the Schmidt Hammer, point load index tests, or simple scratch and break tests. Discontinuity sets identified during geotechnical logging are plotted on stereonets for kinematic stability analysis of bench, inter-ramp, and overall slopes. In underground mining, geotechnical logging of development headings and stope walls is used to update support recommendations and identify areas of overbreak or spalling. Digital geotechnical logging tools — including tablet-based software and photogrammetric core scanning systems — are increasingly deployed in iron ore and gold mines to improve logging consistency, reduce subjectivity, and enable integration with 3D geological models. Geotechnical logging data is stored in relational databases for use in resource and geotechnical modeling workflows.
