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Show The Swiss use mortars. In this country we prefer artillery for the following reasons: equal shock power, greater range and accuracy and better crew safety factor. A 75 mm. cannon has been in use at Alta for three seasons, manned by the Utah National Guard ( Figure 23). It has done work that could not have been accomplished by any other means. The winters of both 1950- 51 and 1951- 52 developed abnormal avalanche hazard. In both cases, climax avalanche conditions in the area of concentrated use were eliminated by gunfire. The end product of a projectile fired into an avalanche path or a demolition charge carried there by hand is of course the same. Projectiles have marked advantages in speed, labor and safety, but cannot entirely replace the other methods of employing explosives. Artillery fire cannot be directed at targets close to fixed installations such as lifts and shelters. A conventional artillery piece also lacks portability in the snow country. This disadvantage will be eliminated when the 75 mm recoil-less cannon becomes available to avalanche busters. There is considerable misconception, even among professionals, of the objective of using explosives to control avalanche hazard. To most people who take part in or witness a blasting operation an avalanche has to occur or the expedition is a failure. Granted that an avalanche release makes a spectacular and satisfying conclusion to the show, the fact remains that an avalanche is merely the most violent form of snow stabilization. Stabilization is the objective and it can take place without an avalanche. When a blast is fired in a slidepath, there are several possible results: 1. Nothing at all happens except a crater in the snow. 2. Surface sluffing may occur. 3. There may be extensive fracturing of a slab with stabilization in place ( Figure 24). 4. A large loose snow, slab or combination avalanche may occur. Regardless of the outcome, the snow ranger has his answer. In a winter sports area it is actually more desirable for the snow to stabilize in place since an avalanche spoils the skiing on that particular run until wind action, thawing or new snowfall cover the rough surface. It is likely that some avalanches, artificially released, might stabilize in place if left to themselves. But where the safety of people and valuable installations is at stake, the snow ranger can hardly afford to guess. Observations over a period of years indicate that it is almost impossible to release an avalanche artificially that would not eventually come" by itself and in much greater volume. - 69 - |