Landslide, flood and snow avalanche risk assessment for the safety management system of the railway Trento -Malè -Marilleva

The railway line Trento - Male -Marilleva in Trentino (Northern Italy) is a meter gauge line with 65 km distance travelled taht connects the town of Trento to Marilleva by passing through the Rotaliana plain, and Non and Sole valleys. The line was opened to the public in 1909, completely reconstructed in its own place at the end of the fifties and extended 10 km at the beginning of this century to the current configuration. It is a typical example of a mountain railway: has a total rise of 700 m, a path made partly along the hillside, hairpins, 5783 m of tunnels (of which 2670 m in one tunnel), 2580 m of bridges and viaducts , curve radius of 80 m and track gradients up to 50 ‰. Since 2009 Trentino transport S.p.A. (Tt) is a quango to which the Autonomous Province of Trento has devolved the power for the management, implementation and maintenance of the rail and fixed infrastructure. The environmental context in which the railway is inserted implies Tt, among its various functions to ensure the safe operation of the railway, the task to carry out monitoring of risk conditions that can interfere with the line, such as those typical for an alpine environment, ie the risk of landslides, avalanches and flooding, and construction and management of the works for their mitigation. From an operational point of view, Tt uses a group of adepters (about 18 people), which is currently divided into three teams based locally and coordinated by a Chief Engineer. Every day each team carry out maintenance and surveillance of the track, its structures and its appurtenances. The constant presence of workers on the line allows to identify immediately, even with the help of drivers in service on trains, any suspicious situations of potential danger. In particular, just before, during or after exceptional events (heavy rain, floods, heavy snowfalls, earthquakes, etc.) the workers are required to intensify the inspection activities of the line. For some sites identified by Tt as "sensitive", because with greater hazard, the workers are asked to intervene even before the passage of the first train of the morning (no night trains operate on the line). They have also to adopt, if necessary, appropriate measures, such as the establishment of the march slowdowns or interruption of train rides and the subsequent implementation of mitigation works, always in order to ensure the safety of the railway. In relation to the causes and severity of events that have originated the hazard, the workers are supported by the service personnel of Tt and consulting technical experts. In parallel in 2011-2012, Tt with the internal resources of the Technical Service, based on the concept of risk and assuming, in this first phase, the same level of elements at risk along the line, has developed a method that defines five classes of " Criticality "C (none, mild, moderate, high or very high), which has zoned the whole rail. The method, which now Tt uses as the tool of planning and programming, defines the criticality C as the product of the hazard P and the factor "works" O (C = P x S). The hazard P of an event of landslide, flood or avalanche is calculated as P = I x F, where the intensity I and the frequency F are given in relative terms and on the basis of the information published by the local authorities or available in the archive of the company. The hazard P is amplified by the factor works O, that is greater than one in the case of structures obsolete (ie not effective and / or functional to mitigate the risk) or even absent. In this way Tt is constantly aware of the dangerous conditions present on the line, as well as of the presence, the effectiveness and functionality of the remedial works. Accordingly to the Criticality classification, Tt may plan the actions of intervention required on the line and their priorities. The classes of Criticality vary from null, which corresponds to the absence of dangerous phenomena, to very high, which corresponds to phenomena very intense and in the absence of mitigation works, and for which it is inevitable to stop the railway traffic and to adopt pertinent countermeasures. For each class of Criticality Tt has defined the actions to carry out for its management. To date, along the entire railway line 35 critical situations have been recognized, from mild to high, for a total length of about 7 km (ie more than 10% of the track). Since 2012, for 14 situations of them, considered a priority, Tt has already worked in various ways with further analyses, and consultancy for the design of remedial works. This paper illustrates the method, the way in which it was implemented and how in some sites the Cricality values were updated after the depth studies (the method was preliminarly applied with the data already available to the company, from previous studies or maps carried out by the local government), or as a result of the construction of remedial works. It is also given an indication of the future goals that Tt has planned to pursue in security management system, such as the implementation of monitoring systems with remote control and refinement of the method by adopting different levels of element at risk.