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
Avalanche protection – some aspects of design and construction
Jón Skúli Indriðason
Línuhönnun Consulting Engineers, Suðurlandsbraut 4a, IS-108 Reykjavík, ICELAND
e-mail: jons (at) lh.is
ABSTRACT
Avalanches have posed a threat in Iceland. In the last decade a collective effort has been
made to alleviate these threats. Deflection dams, barriers and splitters have been constructed
at several locations. The material most commonly used for construction is scree material.
Scree material can be difficult to handle and can be very sensitive to moisture. This sets some
limitations on the utilization of the scree material. Other materials used for earth-fills include
material from rockslide formations and blasted rock.
Barriers have been constructed using reinforced fills. Aspects like appearance and maintainability,
as well as geotechnical factors, have to be considered carefully when selecting the
appropriate reinforcing system. Two types of systems, geocells/geogrids and steel strips/steelmesh,
have been used successfully in Iceland.
To increase or maintain the stability of dams and barriers, it is vital to keep groundwater at the
lowest possible levels. For that purpose drainage ditches are excavated to divert the water
away from the constructions.
1. INTRODUCTION
Avalanches have posed a major threat in Iceland throughout the centuries. However, no
large-scale protective countermeasures are known to have been taken until after the
avalanches of 1995. Few mounds and a small barrier had been built at Flateyri but their size
is dwarfed by the deflecting dams, later deemed necessary to protect the community. Prior to
1990, avalanche protection was studied at the Sudavik community using a computer software
developed by Verkfræðistofa Siglufjarðar. It revealed the necessity of a large barrier in the
mountainside above the town. A small community was in no position to build such an immense
structure so no action was taken at that time (Jóhannesson, 2008). After the avalanches
in 1995, a public decision was taken to protect communities subject to avalanche threat and
the Avalanche and Landslide Fund came in with financial backing. The first major project
was the construction of deflection dams at Flateyri. This was followed by projects at Siglufjörður,
Neskaupstaður, Seyðisfjörður, Ísafjörður and this year construction will start on
projects at Bolungarvík and Bíldudalur. Línuhönnun Consulting Engineers has had the
opportunity to be involved from the beginning, participating in most of these projects, either
during the design phase or the construction phase. In the decade that has passed since the
completion of the Flateyri project Línuhönnun has gained valuable experience. In this paper
some of the issues of design and construction will be addressed.
2. CONSTRUCTION MATERIAL
For construction of avalanche barriers and dams to be more economical than property
procurement in threatened areas, construction materials must be available within the site. The
188 Avalanche protection – some aspects of design and construction