Abstract
To investigate the impact pressure of snow avalanches, it is necessary to study the collisions of individual snow blocks, because snow avalanches include many small snow masses. The author therefore made measurements of the impact pressures of snow blocks onto a small plate and investigated the difference in wave form of impact pressure caused by the difference of properties of snow and the condition of collisions. Cubical or Cylindrical snow blocks were dropped from a height of about 7 m onto a small circular iron plate 10 cm in diameter. Time sequence of impact pressures was measured with a strain-gauge-type load cell and a data recorder. To examine how the snow block breaks, it was photographed by a strobocamera at the instant of collision with the plate. Peak values of impact pressure were analysed in terms of the initial density of snow samples, the value of hardness obtained from Kinosita's hardness gauge and the velocity at the initiation of impact. Assuming that the peak value of impact pressure P is given by P=K · ρ · V2, where ρ is the density and V is the velocity, then the constant K ranges from 1.0 to 5.0, with a mean value of 3.0. The impact pressure of harder snow blocks depended considerably on the value of hardness obtained from Kinosita's hardness gauge.
