Multi-Scenario Analysis of Rockfall Hazard for a Historical Vaulted Masonry Building in Sumela Monastery

Sumela Monastery located in the northeast city of Trabzon is one of the most-visited touristic places in Turkey. As it is located in a mountainous area, rockfall hazards have become a crucial problem that the Monastery complex faces, especially in the last decade. Due to several rockfall cases, the monastery was closed for visitors in 2015 to take preventative measures. The current study examines the whole stages assessing and eliminating rockfall hazards that a historical Vaulted masonry building in the Sumela Monastery is exposed to. First of all, field studies were conducted to determine the kind and type of rockfall hazard. For this purpose, the regional geology of the area was evaluated and due to the inaccessibility of the region, industrial climbers were recruited to climb the slope above the Historical Vaulted building to determine the locations, dimensions, and risk level of the risky blocks that threatened the building. After that, the terrain of the risky area was modeled with Unmanned Aerial Vehicle (UAV) using the digital photogrammetry method. In the last step of the field studies, samples were taken to determine the mechanical and physical properties of the rocks and several laboratory tests were conducted. In the second part of the study, probabilistic analyses of 2400 rockfall simulations with eight different trajectories were conducted to calculate the maximum run-out distance, velocity, kinetic energy, and bounce heights of falling blocks. In the third part, to evaluate the damage status on the vaulted building, six different possible rockfall scenarios determined by the rockfall analysis were simulated using the Finite Element Method. After determining the rock block size that would not cause significant damage to the building, the cleaning and controlled removal method of the risky blocks was determined. In the last stage, controlled crushing and removing practices for risky rock blocks were carried out and the building was restored. Consequently, the rockfall hazard for the historical Vaulted building was eliminated and the monastery complex opened for visitors in 2021.