PSI - Issue 84

Nicola Perilli et al. / Procedia Structural Integrity 84 (2026) 805–812

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and landslide, A Overall, the proposed refinements—including structured operational rules for evaluation primary and secondary parameters, and the incorporation of the potentially unstable slopes and incipient landslide category— provide inspectors with a standardized, transparent, and reproducible solutions. BC These improvements enhance operational clarity, and consistency in landslide CdA assessments, while the hierarchical separation among Susceptibility , Slope Instability, Slope Instability Degree and Slope Instability Class - along with clearly defined secondary parameters- ensures reliable assessment of CSI and CdA assignment in compliance with multilevel logic of LLG 2020. D Overall, this approach delivers a coherent, practical, and internationally aligned framework for slope assessment, supporting early detection, informed decision-making, and effective risk management. Table 7 . Operational classification from Stable slope to instability/ landsides Slope Type Degree of Instability State / Phase Scale of Investigation Outputs

Susceptibility analysis (regional) Detailed remote and field analysis of potential landslide source areas Volumes not quantifiable (slope scale) Magnitude not quantifiable

Instable slope and Landslide susceptibility models Landslide susceptibility models refined with updated landslide inventory

Stable slope

Low Susceptibility

Absence of

movement

Potentially unstable slope High Susceptibility

Disturbed /deformed -presumably unstable -areas

Presence of observable precursors

Incipient landslide

Geolocalizzation of precursors

Estimation of P A + P V + P M and of Reliability of primary parameter estimation, Status of mitigation works

Slope instability/ Landslide

Active or dormant landslide

Ongoing or past movement

Assessment based on indicators (L1) (slope scale)

5. Conclusion The application of the LLG 2020 to monitor landslides threatening or affecting bridges revealed ambiguities in key terms and conceptual and operational weaknesses in the estimation of primary and secondary parameters during periodic field inspections (Level 1), thereby reducing the robustness and reproducibility of CdA assessment. In compliance with the LLG-2020, this study proposes the following refinements: • Replacing Slope Instabily (SI) with SI Degree and Susceptibility Class with SI Class ; • Refining the secondary parameters Reliability of primary parameter estimation and (ii) Status of mitigation works ; • Eliminating the term potential landslide and the primary parameter criticality level ; • Introducing operational categories (i) potentially unstable slopes and (ii) incipient landslides . A These refinements enhance methodological transparency, reduce arbitrariness in assessing SI Degree and SI Class , and improve consistency, reliability and operational clarity of landslide CdA assessment, while preserving the conceptual foundations of the LLG 2020 framework and ensuring full compatibility with the multi-level approach. B Field validation confirmed the robustness of the proposed procedure and tools and strengthened confidence in decision-making. Acknowledgements This study was supported by FABRE – Research consortium for the evaluation and monitoring of bridges, viaducts and other structures (www.consorziofabre.it/en). Any opinion expressed in the paper does not necessarily reflect the view of the funder. Additionally, this research was supported by the project “Methodological Approaches for RIsk assessment in the framework of landslide bridge IntEraction (MARIE)”. References Ministero delle Infrastrutture e dei Trasporti, 2020. Adozione delle “Linee Guida per la classificazione e gestione del rischio, la valutazione della sicurezza e il monitoraggio dei ponti esistenti” . Decreto Ministeriale 17 dicembre 2020, n. 578. Roma, Italia.