Rock Mass Structure Characterization Considering Finite and Folded Discontinuities: A Parametric Study

The quantification of a rock mass’s internal structure and description of discontinuity properties is imperative for modern rock mass characterization. This study builds on decades of rock engineering development by reviewing and revising different parameters such as the rock quality designation (RQD), volumetric joint count (J_v), the Pij system and others. Analyses of these parameters are done by means of a Monte Carlo simulation that generated 5000 samples of discrete discontinuity networks including finite, folded and very low to very high discontinuity densities (J_v range: 0.5–117 discontinuities/m³), thus representing a wide range of possible geological scenarios. P10, P20, P21, P30, P32, RQD and the fractal dimension of the rock mass are virtually measured on these samples and a range of higher level parameters that are used in practical rock engineering computed and their relationships investigated. It is concluded that parameters which are based on subjective estimations of discontinuity spacing, the number of discontinuity sets or RQD are not suited to describe the rock mass structure in cases of demanding geological scenarios featuring many discontinuities, weak and anisotropic rock masses, metamorphic rock masses, folded rock masses, etc. By revising classical parameters and their relationships, this study contributes to basic rock mass characterization and furthermore paves the way for future developments by making the developed discrete discontinuity network dataset and all included codes openly accessible to the rock mechanics community.