Effect of large impacts against rockfall barriers

Abstract

High energy absorption deformable barriers represent one of the most common measure against rock falls. In order to define the performances of these fences, manufacturers may test their structure in accordance with the European Technical Guideline ETAG 027. The guideline describes all the procedure to perform full-scale crash tests. Moreover, it defines the parameters that must be recorder during the test in order to characterize the fence in term of energy capacity, maximum elongation, residual height and efforts transmitted during the impact to the different anchoring systems (lateral bracing cable, up-slope bracing cable and post foundations). According to ETAG 027, the foundations are not part of the “tested kit”, so designers must verify these elements taking into account the soil properties of the site and the different national design codes available. Difficulties can rise for the post foundations. These elements must be built where strong machineries cannot operate and where the material is very difficult to be transported. In these scenarios, the post foundations can be more expensive than the fence, thus the solutions with rockfall barriers might be reject because the global solution is not cost-effective. The paper describes, in the detail, a case study where very light post foundations where adopted on a 5,000 kJ rockfall barrier. Although the fence was impacted by several blocks able to develop energies higher than the nominal capacity of the fence, the barrier and its foundation system perform properly and they were able to dissipate all the required energy.