Computer modelling of coal seams and their properties is standard geological practice for both underground and open cut mining. It is based on correlations of coal seams made between boreholes and the interpolation of relevant coal seam properties on the basis of the inferred coal seam boundaries. In the case of geotechnical studies, this same approach is not followed because there are insufficient geotechnical test results to form a basis for modelling and the geological models do not typically create boundaries for interburden rock types. Instead, geotechnical models tend to be based on coal seam geological models with test results shown as point data in the interburden intervals. This situation can be improved if geophysical logging data are used as the basis for geotechnical modelling. Appropriately analysed, these logs provide continuous measurements of lithological and geotechnical properties. In the case of natural gamma data, an analysis to show the variations in clay content allows sandstones to be separated from finer grained siltstones. If geophysical strata rating values are determined from the geophysical logs, they provide a measure of rock quality. From these analyses, 3D models showing interburden properties as well as boundaries of the relevant rock types can be created and used as a basis for mine design and control of geotechnical hazards.