Reinforced Earth® rockfall bund withstands impact of 5000 KJ
Three years of research subjected to a few seconds of truth
The excitement was palpable at the Montagnole rockfall test site near Lyon, France on June 16.
Three years of collaborative research combining the expertise of Terre Armée and Gustave Eiffel University (formerly IFFSTAR) teams were distilled to a decisive moment of a mere five seconds.
The premise of thesis and the particularly slender rockfall protection bund using the Reinforced Earth® technique would either be shattered or withstand the test.
More than a dozen people stood and watched holding their breaths as the giant 12.4-tonne block was released from the crane at 41 m height with a clicking sound, then hit the structure a few seconds later, at no less than 103 km/h, resulting in an impact of 5.1 megajoules.
They saw all their hard work rewarded by a bund standing solidly; the big block – taller than an adult – now looking tiny in comparison, firmly embedded in the 15 m x 3 m x 6 m bund.
A world-record impact on a reinforced soil rockfall protection structure
The test, an important moment in Terre Armée history, confirmed a world-record in terms of impacting a reduced-footprint bund.
A very slender structure was tested with an impact representing more than 5000 kilojoules, pushing the known limits of soil-structure interaction to a new level.
After three years of research, development, and innovation works with Gustave Eiffel University, Terre Armée has developed a proven concept solution for reinforced soil rockfall bunds where site constraints require a small footprint, revolutionizing the market of protective structures.
In collaboration with other partners a new kind of test setup was implemented at the University’s test site near Chambéry, France.
A series of further impacts demonstrated the robustness of the studied solution beyond the test done by Terre Armée in June 2020.
Rockfall bunds: a great alternative to nets, fences, and barriers
With its very limited footprint and its great capacity to resist to multiple impacts at high energy, this rockfall bund solution will easily adapt to site constraints.
A series of tests and well calibrated numerical models resulted in a new in-house design capacity.
Reducing the footprint value opens the possibility for bunds to be used in applications that would typically require rockfall barriers, positioning this solution as a cost-effective, low-maintenance, and aesthetic alternative.
The numerous advantages of Reinforced Earth® mechanically stabilized earth rockfall bunds include:
- Site constraints are usually requesting solutions with very limited footprint and therefore solutions with low deformation after impact. While maintaining very high energy absorption, our double sided vertical face bund will address the right-of-way concerns. This unique and patented design will offer the market a new alternative.
- The structure can sustain multiple extreme impacts without compromising its stability nor the level of expected protection. The engineered soil as well as the soil-structure interaction are making the structure very resilient.
- Reinforced soil bunds offer an easy asset management and cost saving. Barrier systems require significant inspection and maintenance operations. The level of safety of flexible barriers can be compromised by the external conditions and deterioration over time caused by corrosion.
- Under impacts at service energy level, an easy and light repair of the skin components can be made while restoring the initial energy absorption performance. Removing the block elements can be done safely. Whenever needed, a full section rehabilitation is also possible in case of repeated severe impacts.
- The solution can be built reusing locally available materials. Environmentally friendly by nature, the soil structure blends into the environment and eliminates the risk to animals presented by nets.
- Rockfall bunds are easily scalable. The structure can be designed and optimized to address the project’s specific energy requirements.
- Should the requirements of a project change with time, the soil bund can be easily upgraded for both a taller interception height and a stronger impact resistance. The upgrade cost remains advantageous as compared to other systems that require a full demolition and reconstruction.
- We offer aesthetically pleasing structures that will blend into the local environment. A mineral / stone face or green steep slopes can be selected to suit the local landscape.
The Reinforced Earth® technique: solutions way beyond retaining walls and bridge abutments
The possibilities of the Reinforced Earth® technology, invented by Terre Armée founder Henri Vidal almost six decades ago are go, are far from having been explored.
The bund test confirms the tremendous resistance of Reinforced Earth® structures not only to static loads but also dynamic impacts.