Rock mass characterization is based on information gathered at different levels that all together concur to the understanding of the rock mass behavior. Geological, geostructural, geomechanical information are needed to set up a reliable model of the rock mass. All these different sets of data are utilized to set up a rock mass model to study the rock mass hazard. According to the kind of phenomenon that can affect the rock mass, different studies are required: stability analysis to determine the factor of safety of a certain rock volume or to study the rock blocks instability in terms of blocks path and kinetic energy. The quality and the quantity of needed data are correlated to the kind of analysis to be performed. However, in all cases a sound set of data is needed and a large number of discontinuities must be measured, although reaching the slope can be difficult or dangerous. The development of advanced survey techniques, such as digital photogrammetry and laser scanning, has supplied powerful instruments in several fields including rock mechanics, where a huge number of researchers have dedicated their efforts to improve the quality and the quantity of geometrical information achievable on the rock mass structure. This work is aimed to show how, thanks to the research development in non-contact techniques applied to rock mass characterization, geometrical data, such as rock discontinuity planes and traces, can be acquired by means of dedicated codes and processed to perform statistical analysis.

A well-documented case history will be used to illustrate the application of these procedures.

1. Introduction

Any engineering design is based on the knowledge of the materials involved and on the set up of a design model: in rock engineering the knowledge of the rock mass is based on experimental testing and in situ survey and the scheme of analysis is based on the kind of phenomenon we expect. The geometry of the discontinuities determines block shape, size and kinematic (Cruden & Varnes 1996).

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