OCR Text |
Show terrain that falls away steeply, downward acting thrust and frictional forces can occur, depending upon the possibilities for the compression and flowing off of the snow. The total dynamic thrust on a horizontal roof overrun by an avalanche is, per meter of width: ( X) P = Yh' ( h'/ 2 + v2/ g) tan( tu/ 2) The pressure distribution is such that the specific damming pressure Ytimes v2 sin ^ u/ 2g is not exceeded. In addition the specific static pressure Yh'u and the specific frictional force H • Y • h'< u are acting. 2. Calculation of Individual Situations A. Blons and Sonntag ( see Section I, 2A) a) Powder avalanche, without whirling up the lower snow layer h = 1.6 m, Y0 = 150 kg/ m3, + m ~ 30° From Eq. ( Ill, 10) ( III, 9) ( III, 11) ( VI ) ( VIII ) Y = 15.6 kg/ m3 h' = 15.4 m v = 62 m/ sec H = 205 m p = 3800 kg/ m2 ( local determination: p = 3000 to 5000 kg/ m2) ( n ): Ymax = 330 kg/ m3 H' = 11 m pv = 570 kg/ m2 Average for the facade up to a height of 6.5 m above ground pv = 800 kg/ m2 ( local determination: pv = 650 to 800 kg/ m2) b) Esch Gulch avalanche ( Bodenlawine) h = 1.6 m, y0 = 150 kg/ m3, ^ fm ~ 30 , p, = y 0/ 1000, P = 60° ( VI ( IX 50 |