Aerial photogrammetry used as a quick procedure for rock mass stability analysis in a nature reserve

The geostructural characterization of rock clusters, located in poorly accessible areas of nature reserves, represents a challenge for the specialized technicians who carry out field rock mass measurements. This paper aims to highlight the advantages in adopting a quick approach that introduces the photogrammetric technique to overcome the limitations of conventional field measurements. In this study, the aerial photogrammetry, combined with the powerful algorithms of the Structure from Motion technique, allowed generating a detailed rock mass model of a sub-vertical cliff affected by instability features threatening the safe fruition of a nature reserve. Quantitative and qualitative data on the spatial orientation of discontinuities and on location of major structural elements were achieved. The digitally derived spatial data were used to perform a kinematic analysis of the rock mass, highlighting the most recurrent unstable failure patterns, for which the stability and the probability of failure were numerically calculated in both static and dynamic conditions.