Avalanche Protection Systems:Static Defence Structures

Trumer Schutzbauten - safety by competence

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Trumer Schutzbauten is your experienced and competent partner interms of rockfall protection, avalanche protection and rock/slope stabilisation.Scientific research in perfect harmony with nature and the need for protectionof mankind are the forces that drive the development and are the basis of thecompany’s principles.

Different from rockfall catchment fences, anavalanche protection system, or snow net, is astatic defence structure that prevents snowavalanches from starting in their first stage ofoccurrence.

Static defence structures, along with forests,provide the primary method of mitigating avalanchehazards in many European countries and so havea long history of development. In other parts of theworld, these systems - especially systems usingflexible netting - are becoming more common.

In Europe, the design and installation of avalancheprotection systems follow the guidelines set by theSwiss Federal Institute for Snow and AvalancheResearch entitled “Defence Structures inAvalanche Starting Zones: Technical guidelines asan aid to enforcement”.

Avalanche protection systems by TrumerSchutzbauten provide an environmentallyfriendly, low maintenance and highly effectivemethod of mitigating avalanche hazard whereapplicable.

The extreme flexibility and minimal amount of material used make these systems moreeasy to install than other traditional measures such as terrace walls and snow bridges.

Various avalanche mitigation structures on the peak of a ridge as well as below, in a gully. The upper most structuresare avalanche systems by Trumer Schutzbauten and replace older, more costly structures like the adjacent snowrakes.

The use of snow net systems is becoming common place for ski areas, as well as protectingbuildings, roads, railways and utility corridors.

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View of avalanche protection system with snow bridges in the background.

Unlike other avalanche mitigation methods such as control throughtriggering with explosives or engineering works that mitigate theeffects of an avalanche in progress, static defence structuresprevent an avalanche from ever occurring. If properly designed, thishas many obvious benefits, including but not limited to:

Virtually no maintenance throughout the year;

Not weather dependent (i.e. unlike helicopter bombing or otherartillery methods);No exposure of personnel to hazardous situations;Encourages reforestation;Eliminates hazard from furthest point away from elements atrisk.

Though the initial investment in an avalanche protection systemmay be higher than, for example, the annual maintenance cost foravalanche forecasting and mitigation for a site, over the lifespan ofthe structure the cost benefits are often far greater. This isespecially true when considering the secondary costs resultingfrom the closure of infrastructure being protected.

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No need for costly road, rail or facilities closures;

Schematic showing the placement and effects of avalanche protection systems. The structures are installed in the expected initiation zones of the avalanche (A), far above the elements atrisk (E) that are to be protected. Because the avalanches no longer occur after mitigation, the avalanche tracks (T) are allowed to re-vegetate, thus providing another layer of protection.

Avalanche protectionsystems are normallyused on slopesbetween 30 - 50degrees. The spacingof individual rows isdetermined accordingto the Swissguidelines and rangesfrom 8 - 35 metres.

AA

T

T

E

Downsloperetainingrope of head

Upper bearing rope

Omega-Net

Upper bearing ropefor triangular net Lower bearing

rope

Upslopeanchor forlower bearingrope

Base plateAnchor

Side anchor forupper bearing rope

Downslope anchor

Post

The Omega-Net is a vital component of avalancheprotection systems, which makes them unique in theirstrength and flexibility.

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Avalanche protection system showing net deflection at less than half capacity.

The cornerstone of the avalanche protection systems by TrumerSchutzbauten is the unique net material used to form the primarysupport structure for retaining the snow masses: the Omega-Net.

Though its roots are with rockfall catchment fences, the highflexibility, small mesh size and high strength of the net allows theforces exerted by the snow mass to be evenly distributedthroughout the system, with no need of a finer, supplementarymesh layer.

The Omega-Net used for avalanche protection systems is a 7 wiredspiral rope with a diameter of 6.0 to 7.5 mm and which is pre-bentwith a curve diameter of approximately 125 to 150 mm.

Omega-Net - the catchall for rock and snow

An avalanche protection system under full load conditions.

Due to the Omega-Net’s small mesh size, no supplementary mesh layer is required.

Unlike rockfall catchment fences, the net components are mountedon the upslope side of the system and are stretched by the lowerbearing rope.

During the winter, snow deposition on the slope causes the nets todeflect. The forces exerted by the snow mass are distributed withinthe avalanche protection system and led into the ground via theposts, bearing ropes and anchors. In this manner, the downslopeforces of the snow layer are compensated, allowing the snow toremain in place, where it has come to settle.

As the snow melts, the nets will return to their initial geometry,ready for the next seasons snow fall.

Side profile of an avalanche protection system. The coloured dashed lines representsequential loading of the net over time with increasing snow depth.

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The use of the Omega-Net as the primary mesh component eliminates theneed for shackles to attach the mesh to bearing ropes.

Each avalanche protection system is designed based on parameters collected atthe site of installation, these include (but are not limited to): slope, snow height(normal to slope), snow density, and glide coefficient. Calculations are thencarried out internally to dimension each of the components of the systemaccordingly.

Once designed, fabrication of the components is carried out to yield a uniquesystem specially designed for the conditions on the slope intended. In thisregards, three types of base plates/foundations are available to best suite thelocal geotechnical conditions.

Structural components are dimensioned on aper site basis, yielding a cost efficient andtechnically correct solution.

Structurally Sound - its all in the details

Posts for an avalanche protection system, showing the socket coupling on the post base and thesaddled post head with extra flange and mounting tube to aid installation.

Base plate showing the ball portion of the ball-and-socketcoupling to the post.

Additional stability within the system is achieved throughclamping the bearing rope at the head of the post.

View of a post and baseplate installed. In this instance, a base plate utilizing a single monobaranchor is used as the foundation.

When it comes time to build the structure, the lesspieces there are, all the better.

Putting It All Together - simple is better

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Avalanche protection systems by Trumer Schutzbauten have a modularconfiguration that can easily adapt to local topographic features as wellas simplifies the installation.

Individual components of the system can be assembled into packagesprior to installation. This greatly reduces the amount of helicopter orcrane time required during the erection of the fence and the amount ofmanpower required.

Connections between components are designed to be as simple aspossible to aid in the construction of the fence and the redistribution offorces throughout the system.

Pre-flight preparations as seen here greatly reduce the amount of time and manpowerrequired for installation.

Similar to rockfall catchment fences, the posts and net packages are erected together,before stringing the bearing ropes through the system.

Systems by Trumer Schutzbauten are designed to help minimizethe amount of helicopter or crane support required, thus reducingthe overall cost of installation.

Once all posts are positioned, net packages can be opened and sewn together,thus completing the system.

Avalanche protection systems by Trumer Schutzbauten offersuperior performance in rock and snow.

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Avalanche protection systems that utilize the Omega-Net are extremely flexible and durable,while at the same time light weight. This combination yields a structure that is easy to install ineven the most adverse terrain.

Where local snow conditions make these types of defence structures permissible, avalancheprotection systems offer a cost effective mitigation method that is in operation 365 days ayear. They help eliminate other more costly and sometimes dangerous maintenance-centredapproaches that are reliant on weather, available resources and expertise.

Avalanche protection systems by Trumer Schutzbauten is the answer to your need ofprotection for infrastructure, permanent structures and loss of life from snow avalanches.

A Complete Solution - its character speaks for itself

A flexible anchor is used for the lower (upslope)bearing rope in order to maintain maximal elasticity ofthe system.

Maximum surface area is achieved through the use oftriangular nets at the edge of systems.

Due to the spring effect between the upper and lower bearingropes, avalanche systems using the Omega-Net can easilyconform to irregular topography.

Avalanche protection systems by Trumer Schutzbauten usethe same components as their rockfall catchment fences andso have the highest resistance to rockfall of any othersystem.

Avalanche net systems aremuch less obtrusive than otherstatic defence measures suchas snow bridges and snowrakes. Even in the summer,they are virtually transparentand have minimal impact on theaesthetic environment.

During the winter, the systemsbecome even more transparentas they fill with snow.

Weissenbach 1065431 Kuchl

AustriaTel.: +43 6244 20325

Fax: +43 6244 20325-11E-mail: office@trumer.cc

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5162 Obertrum am SeeAustria

720 - 999 West BroadwayVancouver, BC

Canada V5Z 1K5Tel.: (604) 732-0325Fax: (604) 521-0324

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