Geosynthetics in reinforced avalanche barriers secure village of Mittenwald
Location of work/project:
Mittenwald - Germany
In the mountain above Mittenwal, two huge avalanche barriers were built during one summer thanks to the simplicity of a system that combines geosynthetics and green facing solution. Thus, the safety of the population could be guaranteed during the following winter with snow falls of magnitude not seen in decades.
Mittenwald is located in Bavaria, near the Austrian border at the Southeast of Garmisch-Partenkirchen. In February 1999 an avalanche came very close to destroying houses and roads, and from that date community leaders pursued the goal of providing an effective avalanche barrier to protect againstfuture avalanche flows. Simulations have shown that an extreme avalanche can have a flow width of 100 m, a flow height of 4 m and a downslope velocity of 40 m/s. Such a destructive avalanche threatens various residential areas of Mittenwald, its road infrastructure and high voltage power lines.
To ensure effective protection of Mittenwald, two protection barriers were constructed. The protection barriers used the PolyslopeR S reinforced wall system which included the wire mesh facing set at a 70° face angle, Miragrid® GX geogrid reinforcement and compacted reinforced fill.
The construction of the two avalanche protection barriers resulted in large structures, but not at the expense of visual appearance. Planting vegetation on the face ensures that they are not perceived as “foreign bodies” in the landscape. In spite of the 70° steep face, a simple and quick implementation of surface greening was found by using locally grown willow cuttings. The insertion of these plants already resulted in vegetation growth during construction.
The layers of Miragrid® GX geogrid reinforcement ranged in tensile strengths from 35 kN/m to 160 kN/m and were used in different embedment lengths depending on their levels withinthe barrier walls.
Within a few days during the winter after the constuction, the Northern side of the Alps experienced fresh snowfall of a magnitude not seen in decades. For the combined avalanche measures in Mittenwald it was the best opportunity to put their interaction to the test. Several times, the threatening snow depth was reached and blasted off in a targeted manner. The snow masses were slowed down, successfully deflected and deposited by the avalanche protection barriers.