Rockfall threat assessment along railways in carbonate rocks in Croatia
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Rockfall threat assessment along railways in carbonate rocks in Croatia Iris Bostjančić 1 & Davor Pollak 1 Received: 22 July 2019 / Accepted: 24 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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. Keywords Rockfall . Rockfall threat assessment . RHRS . Carbonate rock . Railways . Croatia
Introduction Rockfalls are a type of slope movement process (Varnes 1978) that does not require a transporting medium (e.g. water) and predominantly occur under the influence of gravity (Dikau 2006). The detachment of a single rock block or a volume of blocks from steep slopes is followed by motions mainly through the air. Therefore, the fall trajectory is strongly controlled by the mean slope gradient, enabling different motion modes, such as free-falling, bouncing and rolling (Dorren 2003). Rockfalls are considered to be very rapid to extremely rapid events (Cruden and Varnes 1996). Therefore, rockfalls present an unpredictable source of threat, especially along
* Iris Bostjančić [email protected] 1
Department of Hydrogeology and Engineering Geology, Croatian Geological Survey, Sachsova 2, 10000 Zagreb, Croatia
highways and railways, and these events can cause damage to infrastructure or endanger human lives. Several transportation corridors in Croatia are
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