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Show ( Y h/ y h f ) 1 / 2 = 1/ 2 ( ( 5) 1 / 2 - 1) 1 o ' ( 16) Yh'= 2.6 Y oh During the descent the damming pressure in the avalanche front reaches the value: p = Yvw2/ 2g = ( Y 0h/ 2gh') v2 ( 1 - Y Qh/ Y h') 2 = 0.146Yv2/ 2g or, taking into consideration Equations ( 4') and ( 16): ps = ( 0.38/ 2g) ( Y0h £ sin*) = 0.02 Y Qh £ siitf It can be shown that the influence of the compressibility of snow ( compare the next section) on the flow height h* of the ground avalanche ( Grundlawine) is small, so that for the flow phenomenon one can set ( 161) h' = 2.6 h The maximal velocity is calculated by Equation ( 4), in which, for wet snow, jx is approximately zero. The fundamental correctness of the theory is proved by evaluation of the measurements compiled in Figures 24 and 25; the square of the velocity proves to be proportional to sin>| r and h. The use of Equation ( 4) with the average value of the measurements shows for the observed ground avalanches ( Grundlawinen) 5 = 500; H = 0.075 o and assuming the relation^: = Y 0/ 2000 it would be true that Y0= 150 kg/ m , possibly however, larger snow densities correspond to a smaller average value of p, as a result of the influence of moisture content. Ground avalanches ( Grundlawinen), because of their relatively small velocity, follow existing gullies or terrain depressions faithfully; the flow phenomenon is completely equivalent to that of torrents ( see the next section). In the zone where the snow is deposited, significant damming cones frequently are formed ( see the next section under C and Figure 28). 3. Damming and Pressure Effects A. Energy Equation The basis for the calculations is the equation of motion for compressible fluids of Euler- Bernoulli, in which the frictional resistance of the usually short damming distance is neglected: 33 |