Rockfalls are often associated to mountainous zones where cliffs are present, but they are also very common along roads where areas of natural escarpment or excavation exist.
Small volume rockfalls and rock avalanches are among the most common ground movements. When these blocks reach residential areas or access roads, they represent a direct threat for the communities. The number of equipment and infrastructure has thus greatly increased in mountainous territories with strong natural constraints.

Rockfall barriers are required when it is necessary to stop rocks which are rolling down a slope. In view of new regulations which will potentially limit the use of metallic nets, smaller soil or concrete barriers designed to stop rockfall for low ranges of energy must be “reviewed”.

Instead of simply developing a highly reinforced protective concrete wall, a multilayered structure was considered in Julien Lorentz's PhD-work.
The dissipative process takes place in two steps:

• The first layer made of a regular concrete slab is impacted. In this case, the destruction of this slab is accepted because a part of the impact energy is dissipated within the plastic deformation of the reinforcement steel bar.
• Simultaneously, the slab spreads the load on a second layer which is made of granular material conditioned in specific manners. It is the deformation of this granular material which will dissipate the major part of the impact energy. 

We are grateful to:

•  IMS-RN company for its financial support,
• “Léon Grosse” company for the experimental test site.
• Thanks are also extended to Pascal Perrotin for his major experimental contribution.

Comparison between experiment and  SDEC-DEM numerical model  (single dissipative layer)
Julien Lorentz Ph.D. thesis
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