Context:
For various reasons, the top station of the Arcelle chairlift was at that time built along the path of the Signal du Grand Mont Cenis avalanche. This avalanche system can be huge. Thus the station has already been found several times filled and partially buried by the deposits of a large mixed avalanche.

Work provided by Engineerisk:

• - Flow analysis according to conditions and return period to numerically quantify the characteristics of potentially damaging avalanches.
• - Proposal of the different possible solutions, none allowing to obtain an ultimate level of protection.
• - Without being able to realize a deflective dam which would have required major earthworks, proposal of a hybrid solution to try to influence the dense phase even the layer of saltation. The residual aerosol phase is assumed to be acceptable regarding the industrial risk.
• - Numerical and expert evaluation of the different combinations of braking mounds (number, layout, geometry) and ultimate dam. The aim was to catch the first part of the avalanche in the labyrinth thus created to constitute a deflecting obstacle against the remaining flow. This deposit can then be shaped by the grooming machines to constitute a "natural" dam in the event of a subsequent event.
• - Decision with the Client for the construction of a first set of mounds, if any, to be completed in following years.
• - Interaction with the contractor at the time of construction to finalise the pyramid shape.

The following winter, during the famous month of January 2018, an avalanche, larger than those used in the analysis, has impacted the device which was certainly outdated but while preserving the chairlift.

Valcenis Telesiege Arcelle Avant 3



Valcenis Telesiege Arcelle 4

Case study