The Geological Model Reliability in Tunnelling and Its Influence on the Geomechanical Model: A Quantification Attempt

The construction of a geotechnical model for a tunnel is a challenging process, often complicated by the limited quantity of available data compared to the extension of the project. In this process two main activities concur to determine the result: i) the geotechnical characterization and ii) the geological characterization. The first one derives the materials properties, the second allows the extrapolation of these properties at the large scale. In this paper, after some preliminary considerations on the interplays existing between these two activities, the attention is principally focused on the second one, that is, on the construction of a geological model and on the possibility of obtaining a quantitative estimate of its reliability. Elements contributing to the capacity of the model of providing appropriate forecasts are considered and their mutual interactions are explored. A multistep computation process is illustrated leading to the derivation of an index called GMR, whose dimension is related to the reliability of the geological model.