| OCR Text |
Show In all the situations discussed above the action of a tensile force in the upper main beams of the obstruction supports was observed as evidenced by the lifting of the foundations on the side toward the mountains and their displacement. These upward directed forces are understandable as the results of the upward pressure from the impact of small snow slides ( Equation IX); however in the third situation they also occur for static reasons as a result of creep pressure. It was not possible to procure all the details with the desired completeness for the examples discussed; however the calculations show that the interrelations established are not to be doubted and may serve as a suggestion for additional evaluations of avalanche observations. 3. Conclusions for Protective Designs A. The research described enables the essential systematic compilation of additional experimental data, especially about flow and frictional resistance to avalanches under varying weather, snow, and ground conditions. The simplified Equations ( I) through ( X) allow, in view of the evidence furnished, a suitable assessment of the effects of avalanches to which structures are exposed under given conditions and thereby the construction of sufficiently avalanche- proof new structures and protective structures. Reinforcement of existing building structure, especially to absorb the forces directed upwards, can considerably improve safety in avalanche imperiled territory. Along with the impact effect of avalanches, as a rule important upward force components occur in accordance with Equation ( IX). Above all, for structures of any kind, the resistance to avalanche effects in each case is dependent upon their adequate resistance to tipping, which, in turn, depending upon the system of construction, requires anchorings at the building site on the side towards the mountain. For the permanence of any protective structures an adequate means of diverting the surface melt water and seepage is important. B. The construction elements of avalanche- proof protective and new structures must resist the impact load of the avalanche snow given by Equations ( VIII) and ( X). Data for the snow heights and densities to take as a basis for a calculation are to be found in the SLF Reports [ l] . As a rule for Formation of powder and surface avalanches: New snow depth > 1 m Dangerous powder and surface avalanches: New snow depth > 3/ 2 m Danger of ground avalanches ( Grundlawinen): Settled snow > 1/ 2 m Danger of a catastrophic avalanche: New snow depth > 5/ 2 m Settled snow > 1 m and for Powder avalanches: Yo UP to 200 kg/ m3 57 |
