Geogrids to reinforce earth dams for protection of reservoirs

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Axamar ski resort - Austria

TenCate Geosynthetics

In the ski resort of Axamer Lizum in Austria, two avalanche protection barriers were constructed to secure a storage reservoir against snow avalanche impacts. They deflect and/or prevent avalanches from entering the reservoir and creating a tsunami wave. Geosynthetics offer the best solution to create reinforced earth dam.

Reservoirs are located close to ski slopes to store water for artificial snow production prior to the starting of the ski season.

In the ski resort of Axamer Lizum , the storage reservoir and the pumping station are surrounded by steep slopes and rugged peaks. Various areas of avalanche danger were located, and scenarios were investigated and simulated to determine degree of risk. It was concluded that the most critical form of avalanche in the area was the ‘snow slab’ avalanche. This is where an extended weak layer is located within the snowpack and when this becomes unstable an avalanche can occur.

To protect the reservoir from the effects of avalanche flows it was decided to construct two protection barriers, one along the Southwest side of the reservoir and the other along the Southern side. These protection barriers were constructed up to a height of 9.5m on their upper sides and consisted of a Polyslope® S double-sided reinforced slope system which used Miragrid® GX110 geogrid reinforcement at 0.6 m vertical spacing in the reinforced slope.

Miragrid® GX geogrid reinforcement is ideal for long term reinforced soil applications because it has well-defined strength and strain properties over long time periods. The reinforced fill used was local granular material. On the upper sides of the protection barriers large rock was used at the base of the slopes to protect from erosion and other damage. The avalanche protection barriers were designed to primarily deflect avalanche flows away from the reservoir water surface.

The protection barriers can prevent design 150-year return period avalanches from entering the reservoir. This has resulted in the greatestpossible safety being achieved.

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