Rock fall instabilities and safety of visitors in the historic rock cut monastery of Vardzia (Georgia)

This paper reports the main results of a feasibility project developed in cooperation with National Agency for Cultural Heritage Preservation of Georgia, and aimed at envisaging the stability conditions of the Vardzia Mon-astery slope (rupestrian rock cut city cave in the south-western Georgia). The site has always been affected by slope instability processes along the entire slope, including small block falls from the upper breccia layer and large block collapses from the middle layer. The study involves: rock mechanics characterization, geo-engineering survey, geo-structural and kinematic analysis, rockfalls modelling, geomatic acquisitions and elabo-ration. The geomechanical characteristics of volcaniclastic and pyroclastic rocks have been determined by means of geomechanical field surveys, rock mass classification through scan lines techniques, and laboratory tests on rock blocks and cores. In order to carry out a semi-automatic detection of discontinuities and to implement miti-gation activities, a 3D Terrestrial Laser Scanning survey has been carried out. Potential rockfalls have been sim-ulated by the 3D modelling code HY-STONE. The model, used both with a downward and backward approach, allowed the recognition of most critical sectors belonging to the upper part of the cliff (volcanic breccia) and to provide a support for designing both short and long-term mitigation measures. A general master plan for land-slide risk reduction and mitigation measures is actually under development for the entire rock cut city of Vardzia.