Assessment of Stability Conditions for a Large Block Overhanging a Nabataean Archaeological Well at the UNESCO Site of HEGRA – KSA
Assessment of Stability Conditions for a Large Block Overhanging a Nabataean Archaeological Well at the UNESCO Site of HEGRA – KSA
This paper analyses the stability of a potentially hazardous rock block above a Nabataean archaeological well at Hegra, near the Al-Ula oasis in the Kingdom of Saudi Arabia, and proposes lowimpact intervention measures. The final design aims to preserve cultural heritage while ensuring safety during archaeological surveys and restoration works. The site is characterised by layered sandstone formations with variable strength, resulting in a banded erosion pattern that affects rock stability. A detailed 3D model of the area was generated using UAV photogrammetry, accurately reproducing the geometry of both the block and the slope. In-situ and laboratory tests on collected samples provided the required strength and deformability parameters. The developed model was used for static and pseudostatic analyses of increasing complexity, including limit-equilibrium assessments and 3D FEM stressstrain simulations, in which an elasto-plastic interface reproduced joint behaviour. Cohesive strength was progressively reduced to simulate the degradation of rock bridges, yielding a conservative unit safety factor under static loading. The proposed intervention method consists of passive low-impact dowels, modelled as embedded beam elements in the simulations. This study outlines a methodological approach suitable for comparable geological and geomechanical contexts and provides the first comprehensive physical and mechanical characterisation of local sandstone at site scale.
Edoardo Lusini; Daniela Boldini; Daniele Spizzichino; Claudio Margottini
4th International Symposium on the Preservation of Monuments and Historic Sites
Underground Monuments and Rock Engineering
https://doi.org/10.53243/tc301-2026-32