International Symposium on Mitigative Measures against Snow ...

<strong>International</strong> <strong>Symposium</strong> on Mitigative Measures against Snow Avalanches
Egilsstaðir, Iceland, March 11–14, 2008
during the summer, at least in the northern part of the country where all the projects have been
taking place to date. It is therefore of vital importance to always have access to materials that
are not as moisture sensitive, such as sand, gravel or blasted rock, to use as layers sandwiched
between the scree material for drainage and to be able to maneuver equipment. Early in the
construction phase at Flateyri, a large deposit of sand was encountered within the excavation
site and a considerable amount of sand was used in the dams for the aforementioned purposes.
The following photographs are from the Flateyri construction site (Línuhönnun, 1998).
Sand being laid out on top of scree material,
Flateyri deflection dam, 1997.
Scree material being laid out, Flateyri
deflection dam, 1996.
After the slopes have been constructed it is important to start the vegetation process as soon as
possible. The vegetative layer minimizes surface erosion potential, dust pollution and gives
the surface a far more appealing appearance.
4. CONSTRUCTION – REINFORCED FILLS
The first avalanche protection construction in Iceland using reinforced fill was a barrier
constructed below Drangagil ravine at Neskaupstaður. That project also involved 13 splitters
using same method. The barrier was 17m high with a reinforced part of 14m. The splitters
were 10m high. Since then, both deflective dams and barriers have been constructed utilizing
reinforced fills at Seyðisfjörður and Siglufjörður. Similar constructions are planned this
summer at Bolungarvík and Bíldudalur.
The market offers a variety of types of systems to reinforce fill material. When choosing the
most suitable system certain things need to be taken into consideration. It is important that
the fill material has good compaction characteristics to minimize movements, since that will
distort the front of the wall and the systems are not equally suitable to account for such
distortions. The fill material has to be screened or processed in most cases, since the reinforcements
require a certain maximum diameter and grain size distribution in order to maximize
the friction between the fill and the reinforcement. Some other reasons also play a pivotal
role when choosing the system. The walls are in some cases enormous and appearance obviously
is important. Cost is another factor that always plays a major role. Maintenance and
the ability to repair damages by avalanches or rock fall is also of importance.
When designing the barrier and the splitters at Neskaupstaður in 1999 an analysis of certain
systems (geotextile/geogrid with two different fronts, gabions, steel strips/steel mesh front,
192 Avalanche protection – some aspects of design and construction