Assessment of tectonic-controlled rock fall processes threatening the ancient Appia route at the Aurunci Mountain pass (central Italy)

Abstract

This research addresses ongoing rock fall processes that affect the tract of the ancient Appia route crossing the Apennines at the Aurunci Mountain pass (central Italy). Elements of cultural heritage are endangered as calcareous blocks descending from the rock slope that delimits the route track were observed lying on the pavement. Based on cooperation between geologists and experts in remote sensing, a multi-disciplinary study was pursued to assess rock fall susceptibility. This study included aero-photogrammetric reconstruction of slope topography, field-based structural and kinematic analyses, terrestrial laser scanner and unmanned aerial system surveys and probabilistic rock fall modelling. This last was performed by simulating a large number of 3D trajectories and initially adopting a lumped mass approach, therefore tracking dimensionless rock blocks (kinematic modelling). The structural setting of the investigated rock slope shows evidence of four tectonic phases, including in chronological order folding, thrusting, strike-slip and normal faulting. Non-homogeneous joint sets distribution within the rock masses, due to the tectonic inheritance, was found to strongly condition rock failure mechanisms and sizes of detaching blocks. Different estimates of design rock block volumes and masses were integrated into kinematic modelling, finally achieving a dynamic 3D reconstruction of the rock fall process. Based on modelling results, a remediation plan has been drafted focused on positioning and sizing of elastic barriers.