Rockfall threat assessment along railways in carbonate rocks in Croatia

This paper presents a methodology for estimating rockfall threats in carbonate rock cuts along railways in Croatia. The assessment is based on the Rockfall Hazard Rating System (RHRS). In general, the RHRS versions developed for Tennessee and Colorado are combined and modified to comply with Croatian carbonate rock mass properties, specific geological environments and values measured in the investigation area. The modifications are related to the classification parameters and corresponding adjustments of their classes. The exponential scoring of parameter classes is retained, but the calculation of final rockfall threat classes is modified. The proposed methodology is developed and applied to 366 cut segments along railways with a total length of 74.888 km. All rock cuts are located in the Dinaric karst area of Croatia, where carbonate rocks are locally susceptible to rockfalls, which mostly include sliding, toppling and ravelling. Rockfall threat is calculated for each cut segment with 15 different scoring models. The optimal scoring model is chosen according to the verification results. The verification is based on three different verification parameters: preliminary rockfall threat assessment, rockfall scars and cut stability, which are defined by the Regional Maintenance Administration of Croatian Railways. An ordinal logistic regression is performed to determine the threshold values for each rockfall threat class. The established methodology is used to detect the most vulnerable railway sections, which are selected for detailed inspection and reclamation. The research also enables a proactive approach of rockfall management along linear infrastructure in Croatia but also worldwide in similar geological environments.