Rock Masses Characterization with Advanced Measurement Systems for Reliability-Based Design

Abstract

The design processes involving rock engineering problems must take into account the rock mass discontinuous nature, that strongly affects the mechanical response of this medium to any perturbation. Stress-strain behaviour of rock masses is linked to both the mechanical characteristics of rock matrix and to the rock mass degree of fracturing. The characterization of rock masses requires approaches at different scales (microscale, laboratory, site and, sometimes, regional scale), each of which provides different information that can be very relevant from a design point of view. At the microscale, information regarding petrographic and mineralogical features can be acquired and analysed in relation to the mechanical behaviour of rock matrix and discontinuities studied with laboratory tests. At the site scale, information related to discontinuity geometry, such as orientation, persistence and spacing, can be acquired by different measuring methods. Rock masses, by their nature, are discontinuous, inhomogeneous, anisotropic materials and the parameters characterizing them show a natural randomness due to both aleatory variability and epistemic uncertainties. In order to reduce the epistemic uncertainties a representative and sound number of measurements must be collected, and, simultaneously, probabilistic analyses are required to represent the aleatory nature of each variable. This contribution deals with the application of survey advanced techniques useable at different scale with the aim to measure the parameters necessary for a sound characterization of a rock mass useful to apply of reliability-based design approaches in line with the reference standards for the geotechnical design.