## 3 Methodology for Evaluating the Effectiveness of Rock Fall Protections
### Hazard Scenario and Existing Protection Measures  
At first, information on what hazard affects the site of interest, regardless of any existing protection measure installed, has to be retrieved and expressed in terms of the hazard descriptors mentioned in Section 2, i.e., rock fall energy and return period--or frequency of occurrence. Then, the presence of protection measures has to be considered and their current conditions must be evaluated. This task is accomplished by carrying out site surveys to inspect the protections. For the purpose of filing relevant information in a systematic manner for any type of protection and environmental setting, a MS Excel spreadsheet tool was elaborated. The data collection tool features a preliminary section for the identification of the rock fall protection to be inspected (in terms of type, location, main characteristics and year of construction) followed by two main sections for recording information about the presence of potential factors, whose effects may negatively affect the performance of the protection. The first main section allows us to consider a category of factors, identified as Group 0, and is subdivided into:  
* Environmental factors--they are related to the site where the protection is installed and account for issues in connection with the interaction between the environment and the measure, such as: the presence of spring or torrents, which could generate erosion around the foundations of certain protections and make them unstable and/or expose them to other physical/chemical agents; possible frequent snow, which could fill up the nets of a barrier fence or reduce the effective height of an embankment; freezing and thawing cycles, which could affect the behaviour of some materials used for the protections, etc. A list of all factors of this type included so far in the methodology is shown in Table 1;  
Figure 1: Scheme of the methodological framework for evaluating the effectiveness of rock fall protections. * Factors related to the concept of the protection (general design and installation)--they represent potential issues generally common to most (or all) types of protections included in the methodology and consider effects such as: the possibility for structural measures of undergoing plastic deformations (e.g., barrier fences), possible redundancy of main structural elements which might help redistributing the efforts after an impact, consistency in the structure of the protection (e.g., such as in an embankment) as opposed to the presence of potential weak points (i.e., posts of a barrier fence rather than the steel wire mesh), respect of current norms, etc. These factors are also listed in Table 1.  
The second main section is dedicated to another category of factors, identified as Group N, more closely affecting the performance of each single type of protection (barrier fences rather than embankments, or anchors, or wire mesh nets, etc. ), due to specific flaws and causes of malfunctioning. Factors belonging this group were classified into four categories, according to the type of problem for which they account:  
* Category 1: flaws/faults due to lack of maintenance, e.g., posts of barrier fences damaged by impacts of blocks, barrier fences or embankments, or ditches partially filled up by blocks from previous events, nets of barrier fences or wire meshes loosened and/or damaged, corrosion on metal elements of the protections, etc. * Category 2: issues related to the original design of a given type of protection, including potential stability problems of embankments or barrier fences, inadequate protection against corrosion of the metallic elements of the protection, differences in the original positioning of the protection measure compared to the position required at present, as a consequence of the possible evolution of the events to be mitigated, etc. ;
* Category 3: causes of malfunctioning of the measures due to installation problems, such as sealing injections for anchors/nails, control of the applied stress in the anchors, etc.