Abstract

The characterization of rock masses is an essential component for the planning and development of engineering designs in rock mechanics and rock engineering. The Rock Quality Designation (RQD) is a widely used rock mass characterization system that is direction-dependent, i.e., the measurement of a core sample depends not only on the sample position but also on its orientation. This paper outlines the critical aspects of the determination of RQD and proposes a physically-based upscaling strategy from borehole samples to large blocks, based on block-averaging the RQD values corresponding to the same direction, then calculating the minimum value over all the directions. An anisotropy index indicating how much RQD varies between one direction and another is also derived. Using geostatistical simulation, our proposal allows interpolating and upscaling direction-dependent geotechnical variables like RQD at any place in the geographical space for any direction, avoiding directional biases. We illustrate this proposal by predicting RQD in a polymetallic deposit, achieving geotechnical zoning and comparing the results with those of the traditional approach where the directional dependence of RQD is ignored.