Un contributo all'individuazione e alla caratterizzazione delle frane interferenti con i ponti esistenti

This work aims to provide a useful contribution to the application of the recent Italian Guidelines on existing bridges (adopted with D.M. 578/2020 and replaced by the new version with D.M. 204/2022), for landslide risk. From the specific literature, field surveys and experimental studies, and the experience in the FABRE Consortium, relating to the application of the Guidelines and in particular to inspections and the compilation of sheets and reports, objectives are set to improve the identification and characterization of all types of landslide-bridge interference. It concerns: a)find criteria to determine the inspection area of the bridge that should be studied to identify all the landslides capable of interfering with the bridge; b)obtain a distinction between the various types of landslide-bridge interference; c)prepare a checklist for a better identification/characterization of the interfering landslides, with particular reference those that can hit the bridge from afar; d)define a methodology to characterize and quantify the material mobilizable by landslides in the catchment area, capable of contributing to the floating load and non-floating load of torrential debris flows. The study was structured in two phases: the first consisted of bibliographic research and the observations in different Apennine contexts for the elaboration of an operational methodology for the analysis of landslide-bridge interference, and a second phase dedicated to the validation of the methodology itself. The research for this second phase mainly concerns field surveys, experimental field studies and has been carried out in two areas with lithological contrast and with a fair number of bridges. These areas provide approximately 50 bridges each and are Garfagnana (LU), in the NW of Tuscany, and Materano (MT), in the NE of the Basilicata Region. The investigations in the study areas were carried out with basic equipment, drones, surface sampling and geotechnical laboratory tests. The studies allow to formulate the criteria for determining the inspection area useful for identification of interferences, to propose a classification of landslide-bridge interferences, to define a checklist to improve the identification and characterization of interferences and to estimate quality and quantity of mobilizable material from landslides that source of sediment, capable of providing a contribution to the torrential debris flows that threaten the bridges. The work contributes to the objectivity of landslide risk assessment for bridges and proposes procedures that are also useful for other types of structures, applicable to population protection, emergency management, and land-use planning.