the design of rockfall barriers requires analytical simulations of the trajectories of the falling blocks along the slope. The easiest way to design these structures is by comparing the energy level defined by the numerical analysis with the results of the full-scale test carried out according to ETAG 027/2008 ("Guideline for European Technical Approval of Falling Rock Protection Kits"). This is the guideline used by the manufacturers to test their rockfall fences. Unfortunately this approach has a lot of uncertainties because it does not take into consideration all the technological limits of the rockfall barriers and the installation issues. This paper illustrates the procedure of a new design approach based on the Italian norm UNI 11211:12, the European Guideline ETAG 027/2008 and the in-situ experience of Maccaferri in the rockfall protection field.
Rockfall barriers are generallycomprised of a number of components:
steel posts (support structure), spaced from 8 to 12 m;
upper and lower longitudinal steel cables;
lateral and upslope steel bracing cables;
energy dissipation devices, able to increase the energy absorption of the fence;
an interception structure (steel mesh).
The barriersare then anchored to the soil by foundations. These elements have the function to transmit the loads of the impact to the ground.
ETAG 027/2008 (reference paragraph 18.104.22.168 of ETAG 027/2008) classifies asa deformable rockfall barrier, a structure able to absorb an energy no lower than 100 kJ (350 kg travelling at 90 km/h). It does not define any upper energy limits, but at the present the record for the highest energy capacity fence belong to the RMC 850/A, which is able to absorb an energy higher than 8500 kJ (27 t travelling at 90 km/h).
Rockfall barriers are passive measures used to protect structures and infrastructures from rockfall events. Their main advantages are: they are able to protect largerock surfaces, which would be impossible, for economic reasons, to cover with drapery mesh, they are able to absorb high energy levels, they can be installed in most location and morphological conditions, they can be easily installed on vertical slopes, and they are systems that have been tested and certified byrecognized Approval Bodies.