Fences – Driftage control
Reexamination Certificate
1999-12-22
2002-05-07
Browne, Lynne H. (Department: 3629)
Fences
Driftage control
C256S001000
Reexamination Certificate
active
06382597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device for preventing the development of avalanches and other snow slides.
2. Description of the Related Art
For simplicity, the invention will be described below only with reference to the prevention of avalanches although it is not limited thereto. Accordingly, the invention also relates to the prevention of other snow slides, such as preventing the development of windslabs, preventing loose snow avalanches, new snow slides, old snow slides, wet snow avalanches, ground avalanches, and any other form of known avalanches and other creeping and sliding snow movements.
Snow deposits on slope-like structures are not a stationary medium. It is a continuously downhill moving mass. Both natural causes and outside interference are able to change this moving process quite significantly. The force of an avalanche moving downhill can be described as an extreme variant of this change.
Before attempting to counteract the danger of such a force of nature the basic premise of a potential avalanche has to be defined, as follows:
Reduced adherence of a partial or global snow mass deposited on slopes and precipitous formations.
Reasons for reduced adherence:
a) extremely precipitous gradient;
b) air cushion effect resulting from cushion-like vegetation on the covered sections of the ground;
c) high degree of “creeping” and “sliding” in the affected snow mass;
d) different overlying layers of snow with varying physical properties;
e) above average snow accumulation as a result of precipitation or wind-related shifts;
f) structural weaknesses as a result of snow metamorphosis (change in the crystalline structure);
g) added mechanical stress due to outside interference (such as winter sports, game trails, sound waves).
Previously, the moving process of an avalanche was counteracted merely by a so-called passive correction of movement.
In accordance with prior art, such a correction of movement is achieved either by a solid obstruction transversely to the slope to prevent the snow mass from moving downhill or by specifically deflecting the global moving processes by means of solid obstacles. The latter is used primarily in areas close to a valley floor. On this subject, we are referring to EP 0 494 563, EP 0 346 326, DE 28 07 536 and EP 0 359 704, among others.
However, said known solid obstructions or said known specific deflections in areas close to a valley floor have the disadvantage of seriously intervening in the natural environment. Massive obstacles have to be built using expensive construction processes at high altitudes under difficult working conditions resulting in high production costs. The highest expense is the anchoring in the slope required for such obstructions because the downward driving force of the moving snow mass acting on the obstacles has to be channeled into the pertaining mounting devices approximately vertically to the slope. This requires extensive structural measures so as to control the forces acting on the obstacles like a tearing off force.
Patent CH 674 996 A shows an avalanche obstruction and a method to mount said obstruction where reinforcement elements are suspended from anchoring ropes. Said ropes are anchored in the mountain by means of anchoring devices interspaced from the reinforcement elements. The reinforcement elements substantially serve only to retain the snow and rest freely on the base, thereby intending to hold back the snow mass.
The drawback of this avalanche obstruction is that the reinforcement elements are designed axisymmetrical along a longitudinal center axis, for example as a pyramid, a cone or truncated cone, or as a cylinder, and consequently, the snow layers overflow the reinforcement element both on top and below causing the snow layers that flow over the top of the reinforcement element to be lifted up from the slope resulting in a certain detachment of the snow mass from the slope.
The result is that the snow mass detached from the slope and separated from the remaining snow begins to slide and thereby triggers avalanches comparatively easier than other snow masses, which are channeled toward the slope. Therefore, the snow layers above the reinforcement element are lifted above the reinforcement element when the snow begins to slide. They separate from the lower, slope-side snow layer and begin to slide very easily.
When new snow is added the new snow will build up on the surface of the upper snow mass and will also be channeled away from the slope together with the upper snow mass which was detached by the reinforcement element. This additionally increases the danger of triggering an avalanche.
Therefore, the disadvantages of the avalanche obstructions known in the art are the high production expenses, the high maintenance expenses and the serious intervention in the natural environment which is necessary to transfer the required forces to the existing ground and rock.
Accordingly, the object of the invention is to propose a method and a device for preventing the development of avalanches that prevent the formation of an avalanche as such at significantly lower production costs and whose production is significantly more cost-effective and requires a less serious intervention in the existing natural environment.
To solve the above problem the invention is characterized by the technical theory in accordance with the characteristic features of the method as per claim
1
.
SUMMARY OF THE INVENTION
According to the invention, the snow mass moving downhill is separated into individual layers, not simply retained as is known in the art, or an existing division is utilized and the layers are mixed together. Said separation and mixing can take place in horizontal and/or in vertical direction. At the same time, the snow mass can be compacted.
Consequently, according to the technical theory of the invention, unstable snow structures are converted into stable compacted structures. Instead of stopping an uncontrolled moving process such a process is prevented from developing.
“Creeping” and “sliding” snow fields and the combination of these continuous moving processes provide the power potential required to modify the basic structure of the affected snow mass. The forces generated thereby not only transport, they also correct (transform) the existing directions of flow.
At the same time, the lack of adherence in the original layers is eliminated in that these layers are mixed together.
A respective device achieves the mechanical conversion (transformation) by means of a so-called snow transformer.
Wedge-shaped basic elements or variably designed geometric hollow bodies, hereinafter also referred to as separation elements or lifting elements, are mounted to elastic retaining rods that are anchored in the ground. This does not mean that the end of the rod is vertically planted into the ground. It is mounted parallel to the particular gradient of the slope. The retaining rod itself, however, is designed to straighten into a vertical position in rounded form after approximately ⅓ of its length.
The advantage of this particular mounting method is that the forces of the snow mass moving downhill slide over the actual fastening device in the ground, the retaining rod cannot break as a result of laterally acting forces. Vertical tensile forces, such as are known in mounting conventional avalanche obstructions, are thereby converted into a horizontal stress.
In order to fasten such a retaining rod flat to the ground (rock) it is sufficient to mount a simple “ground anchor” or “rock anchor”. Any stress that may arise is deflected in rectangular form at its upper end, thereby providing maximum resistance.
The transformation itself, however, is provided by the separation elements mounted on the retaining rods. This has four very different effects:
1. Horizontal Compacting
A parallel sliding snow mass is forced to escape laterally. The affected snow mass compacts, thereby achieving a higher adherence potential, and comes to a standstill at the expected int
Baker & Daniels
Walsh John B.
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