Geotechnical Characterisation from Geophysical Logs for Longwall Coal Mining

This paper presents examples of geotechnical characterisation from geophysical logs at various coal mines. The methods used include the constrained 2D/3D modeling of geophysical logs for strata geotechnical characterisation, and automated lithology/geotechnical interpretation of geophysical logs. The outcomes of these methods can be visualized in 3D space and used for identifying the key geotechnical strata units that affect caving behaviors during longwall mining. This could assist site geologists, planning and production engineers predict and manage mining conditions on an ongoing basis. Both conventional logs such as density, natural gamma and sonic and less common logging data such as full waveform sonic, televiewer and the SIROLOG spectrometric natural gamma logging data are examined for geotechnical interpretation. The geotechnical strata classification and rock strengths predicted from the geophysical logs match with the laboratory tests, drill core geotechnical strata classification, core photos and the mining condition/behaviour observed. This illustrates the usefulness and effectiveness of geophysical logs in geotechnical characterisation.