Control

Control Work

Avalanche Protection

Accidents and damage from interaction of avalanches with human activities can be prevented either by controlling the avalanches, by regulating the presence of persons, or placing structures out of avalanche paths. Methods include the following groupings of protective measures:

Temporary Control of Presence	Permanent Control of Presence	Temporary Control of Avalanches	Permanent Control of Avalanches
Choosing safe travel routes	Location of buildings, roads, ski lifts, etc. in safe areas	Compaction of snow in avalanche starting zones	Engineering works that retain snow in the starting zone
Temporary closures of roads and ski runs	Design of structures for avalanche forces	Release of avalanches by explosives	Engineering works that deflect &retard avalanches
Evacuation of buildings during hazardous times	Permanent closure of ski terrain	Time, snow pack settlement	Forests

Avalanche Control By Explosives

Detonating explosives in starting zones has two objectives: to release avalanches under controlled conditions and to test the stability of the snowpack.

One benefit of releasing avalanches with explosives under controlled conditions is that avalanche release is chosen when exposed areas are not occupied. The areas may be opened after avalanches are released; therefore, closures may be kept short. Another benefit is that frequent explosive control usually ensures that snow is brought down in several small avalanches, rather that a large destructive one. Also, frequent avalanche release prevents large unpredictable natural avalanches later when the snowpack can become unstable.

Effects of Explosions

Explosive charges are used to generate elastic stress waves to initiate shear fracture propagation and dry slab release. Stress waves attenuate rapidly in snow, but propagation is more efficient through the air and the ground. Explosions above the snow surface stress the snow over a wider area than those through the snowpack. Under favorable conditions, ground shock waves can be very effective. Avalauncher and artillery shells detonated on rocks have released avalanches on adjacent slopes and the opposite side of ridges.

Successful avalanche release by explosives depends on three parameters:

the stability of the snowpack (a function of the strength of the snow and stress already present)

the size of the explosive charge (mass)

the location of the explosion relative to the slope and the snow surface

The parameters may be combined to increase efficiency, such as when the snow stability is good , a large explosive charge might have to be applied or an explosion above the surface could increase the chances of creating the avalanche.

Using Explosives

Throwing Bombs

Avalauncher Snow Bird

Cornice Work

Bomb Under Arm-Cold Day