Multiple Lines of Rockfall Net Fences: A Design Proposal of the System

Net fences constitute a valuable and widely adopted solution for mitigating rockfall risk. Nevertheless, in complex morphological situation with several rocky cliffs, a single line cannot be effective, and a double line of net fences is thus often required. At present, the existing design procedure has been conceived for a single line, only. In the present work, a design procedure for double line of net fences is introduced, considering the double line as a system, in which the upslope line stops, or at least decelerates, the great majority of the blocks, while the downslope line stops the remaining part. As a system, the effects of actions and resistances should be evaluated as a whole. The integrative trajectory analyses are required to optimise the design in terms of necessary energy absorption capacity, height of the lines, and maintenance planning. This system is suitable for mitigating rockfall risk, especially in very complex situations.