OCR Text |
Show often the case with heavy gliding - which remained vertical, while other columns on horizontal ground ( terraces) were tipped downhill. Surfaces of discontinuity within the snow cover were never observed to conform to column deformation. As one began to measure the glide motion of the snow cover within the defense structures " Schilt" ( Stein) on an east slope at 1400- 1550 m above sea level, it was possible readily to detect a partially favorable influence of the retention structures and glide anchors ( path terraces, stakes, small structures). Nevertheless, doubts soon arose about the adequacy of their effects. We repeat here some commentaries from the Winter Reports which presented results of the measurements. The winter of 1950/ 51 brought very deep snow. In the four previous winters, the measurement sites were largely or completely outside the defended area. " in 1950/ 51 all of the measurements sites lay within the defense structure area, which led to the expectation of reduced glide motion. The deep snow, the relatively high temperature and the persistently unfrozen ground all led to the opposite effect. Striking among the research results is the obviously small damming effect of the rakes on the snow cover lying above them. The lowermost glide shoes, which were installed about 3 m above Rakes 33 and 20, still moved downhill k0 to 50 cm. This was at least half of the glide shoe motion farther uphill in the so- called neutral zone. Observations in earlier winters indicated a stronger braking action exerted by the structures on snow glide." The average glide path of the 18 metal shoes |