Winter 2015

Avalanche resistant

Geosynthetics such as TenCate Rock® PEC and TenCate Miragrid demonstrate their value when it comes to the building and service life of structures offering protection against snow and rock avalanches. They are an alternative to conventional building materials that is both environmentally friendly and economically attractive.

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Floods, mudslides, and snow and rock avalanches generating immense forces can occur in mountainous areas. A snow avalanche can reach speeds of up to 250 km an hour, while a rock avalanche can register even 300 km an hour.  A barrier can be erected against avalanches by installing reinforced retaining walls and slopes (mechanically stabilized earth). Site conditions impose specific demands on the design, the choice of material and the building of such constructions. Traditional solutions with only stone or concrete are economically unviable as the costs of both construction and the transport of building materials in poorly accessible terrain are high. The application of geosynthetics is an attractive solution.

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At Ísafjörður (Iceland) an avalanche barrier has been built that is 14 metres high and 330 metres long.
The system consists of a galvanised steel formwork, TenCate Polyfelt® TS geotextile to separate the fill from the slope and the stone front, and three grades of TenCate Miragrid GX for soil reinforcement. The fill material is composed of locally sourced gravel and small stones, which originate from the mountain itself and are ground on site – thus saving transport costs.  TenCate Polyslope® S is a tried and tested system. It consists of geosynthetics for reinforcement (TenCate Rock® PEC or TenCate Miragrid), a pre-formed steel grid, TenCate Polyfelt® Green erosion protection and locally available sand as fill material. In this way, a green vegetated bank with a natural appearance is quickly created.

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Avalanche barriers based on geosynthetics can also be found in Austria at Mühlau, Eiblschrofen, Lanersbach and Kappl (picture). A barrier 650 metres long and a maximum of 26.5 metres high has been built with geosynthetics halfway up the slope from Diasbach at Kappl, involving 285,000 m² of TenCate Polyslope®. When designing a wall at Lanersbach (Tyrol) to deflect avalanches, it was decided to fully integrate this in the surrounding landscape. Lanersbach is located at a height of 1,350 metres in the Ziller Valley. This is one of the largest nature reserves in Austria, which is why the authorities insisted that the wall be covered with vegetation.

Blue fabric (Tecawork Blue 65287)