Strategy for the Foundation Design of Rockfall Barriers

Abstract

European Technical Approval Guideline (ETAG 027) defines the functionality of a rockfall barrier and describes all the procedure to carry out the full scale tests and consequently outline the deformability, the resistance, the performances and the forces acting on the foundations of a deformable rockfall fence. But it must be remarked that foundations are not considered part of the tested kit of ETAG 027. Designers must design the anchoring systems considering the different national standards and the geotechnical characteristics of the site. Many times problems arise for the post foundations, because they should be built where heavy machineries cannot operate and where the material transportation is very difficult. Because in these cases, the posts foundations become more expensive than the fence, the solutions with rockfall barriers might be rejected due to the high global cost of the intervention. When a severe impact strongly damages a barrier, for safety reasons the whole structure, foundations included, should be replaced. Then the basic question becomes whether strong posts foundations make sense. The paper presents a case study of a Maccaferri rockfall barrier impacted by several blocks. Despite of the fence was installed with unusual light post foundations, it was able to withstand impacts exceeding its nominal capacity. The analysis of the structure suggests that in certain conditions displacement and settlements on the post foundations represent a benefit.