Avalanche release with a cable car
If an avalanche is triggered by a cable car , the explosives are transported by cable car and thrown from there. It can be an existing installation (e.g. passenger cable car ) or an avalanche detonating cable car specially built for this purpose.
Cable cars for avalanche explosions
With the approval of the competent authority, passenger ropeways may also be approved for carrying out avalanche explosions.
Avalanche blasting cable car (short blasting cable car or railway Avalanche blasting, Engl. : Avalanche blasting ropeway , French. : Câble transporteur d'explosif , abbr. : CATEX) are special material ropeways . They serve the sole purpose of delivering explosive charges to one or more predefined target points so that they can detonate there and trigger an avalanche .
Detonating ropeways can be equipped with manual or machine drives.
advantages
- Over-snow blasting with a large load (up to 5 kg) creates a maximum effective area (up to 260 meters in diameter ),
- With one system, several avalanche starting areas can be approached under certain circumstances,
- Weather-independent release
- there are no personnel in the danger area,
- the breakpoint can be freely selected along the rope line according to the requirements of the snow situation.
disadvantage
- The disadvantage of blasting cable cars is that they are often too slow to be able to deploy several loads in the limited time (e.g. in the morning before the opening of operations or slopes),
- Due to their infrequent use and exposure, detonating ropeways are prone to hoarfrost , icing and the effects of wind.
- Access to the drive station can sometimes be complex and dangerous due to the exposed nature of the system.
Demolition
The sharp explosive charges are thrown or roped out of the cable car cabin by hand in the case of passenger ropeways, or in the case of the avalanche detonating ropeway, they are brought into position and detonated with a lowering device or drop device (see also: manual release of avalanches ). The ideal detonation point is between 0.5 and approx. 3 m above the snowpack. Most charges are between one and five kilograms.
In the case of the detonating ropeway , the charge may have to be armed in the drive station and the time detonated. The time fuse is then to be dimensioned so that the actual transport time and lowering time or dropping time of the explosive charge coincides with the burning time of the fuse (110 to 130 sec / m). A further delay may have to be added due to snow and ice formation. It should also be taken into account that employees must be able to go to a safe area if the charge is ignited but does not reach the destination. In Austria, explosive charges may only be detonated electrically when an avalanche detonates from a passenger cable car.
In Austria, at least two authorized persons must be employed by cable car companies. For the operation of a detonating cable car, a machinist who can also be a blasting assistant must be employed. Blasting with the detonating cable car may only be carried out if it has been established and ensured beforehand that all parts are functional and that safe access to the system is possible.
Charge ejector
Charge ejectors on explosive ropeways allow two to four explosive charges, each weighing up to 5 kg per charge, to be individually dropped at the respective target point with a single radio command. Double detonation can also be activated during the fall of the explosive charge. After being dropped, the cargo hangs on a string above the snow cover. The cord is thrown off after the detonation so that it cannot get stuck somewhere when the dropping device travels back.
Lowering device
A lowering device makes it possible to bring the explosive charge so close to the ground that the maximum effect is achieved. The route of explosive cableways usually runs at different heights above the ground. Here, the Absenkgerät is on the hanger of the conveying cable is mounted, and the explosive charge on the rope of Absenkgerätes. An electric motor is switched on via an adjustable timer, which lowers the cord on which the explosive charge is attached to the surface of the snow. After automatic determination of the relief when the explosive charge is placed on the snow cover, the rope is automatically rewound until the explosive charge hangs about 2 to three meters above the ground. After a specified time, the cord is rewound after the detonation - or with the failure - and the hanger is moved into the drive station.
Avalanche explosives
The explosive used commercially for the purpose of avalanche detonation in Europe is selected and suitable for these purposes, particularly with regard to handling safety even at low temperatures and insensitivity to moisture. The explosive should trigger the strongest possible shock wave, which is why, as a rule, only highly explosive explosives that have a high detonation speed are used. Explosives that have a high detonation speed but also a high blasting oil content (e.g. Knauerit-Alpinit etc.) are unsuitable because of the low ambient temperatures, because blasting oil solidifies at around −6 ° and the explosive loses its handling safety. In Germany, only powder explosives (e.g. sytamite ) that do not contain explosive oil but are sensitive to moisture may be used. Frequently used explosives in Austria and Switzerland are z. E.g .: Riomon T1 (formerly: Sytamit ) or Emulex . The previously used Lawinit of Austin Powder is no longer manufactured.
In contrast to rock mining by blasting, an exact calculation of the loading amount is not required for avalanche blasting. The load amount between 2 and 2.5 kg or 4 and 5 kg is suitable in practice for almost all areas of application. Under- or over-dimensioning of the cargo cannot cause any damage.
commitment
The use of the cable car to trigger an avalanche is possible in almost any weather. A special permit is required in Austria and Switzerland for the use of explosives to trigger an avalanche. Due to the varied training, accidents when avalanches are detonated by explosives are very rare.
In Austria, the use of the system requires an explosive authority with special training in avalanche blasting.
Authority to issue orders and liability
The order for the use of explosives to trigger an avalanche for a specific area is usually made by the avalanche commission or a similar institution. A person authorized to blast is generally not authorized to carry out avalanche explosions. However, after the authorization to carry out the blasting work has been granted, the person authorized to blast alone is responsible and authorized to issue orders. It determines how the explosives and detonators will be transported by whom, how much explosives will be used, from where the corresponding charge will be detonated, how the locking and security measures are to be implemented, who will accompany him and who will detonate the explosive charge, etc. The cable car employees are bound by instructions to those authorized to blast.
Detection
Whether the detonation and the success of the explosion occurred is recorded by means of a visual inspection and prior manual documentation of whether an avalanche has occurred or not.
Failure elimination
If failures can no longer be driven into the drive station, they must be recovered as quickly as possible. However, a minimum waiting time must be observed (in Austria e.g. 15 minutes after ignition until recovery).
See also
- List of avalanche accidents , list of avalanches and landslides, landslides and list of disasters
- Search for avalanche victims , avalanche shovel and avalanche cord
Web links
- Avalanche explosions at Nebelhorn , video BR-Mediathek 5:13
- Doppelmayr ABR avalanche blasting lane "Gorner" Kals-Matrei, Austria (2008) , Doppelmayr.
Individual proof
- ↑ Lukas Stoffel: P Artificial Avalanche Release , Tec 21, Volume 131, 9/2005, p. 5.
- ↑ Lukas Stoffel: P Artificial Avalanche Release , Tec 21, Volume 131, 9/2005, p. 6.
