積雪の弾塑性分類となだれへの応用

抄録

A new classification of the snowcover is discussed, which is based upon the mechanical deformation of the natural snowcover beam. For example, a numerical factor e_A of the beam is calculated as the ratio between the deformations when the beam is assumed of elastic or plastic property; and the beam of e_A_??_1 is defined as an elastic one. Thereby the snowcover beam can be classified into three kinds: (1) elastic one, (2) plastic one for normal stress and rigid for shearing stress or (3) plastic one for shearing stress. Observed values of e_A was 6_??_10⁴ and the snowcover beams may be of the property (2). Now e_A's are bound by certain maximum value e_A^* characterized at the district under consideration, and therefore e_A^* can be used to classify the snowcover. The value of e_A^* at the beginning of March is found as 60 at Fukui district and 10⁴ at Hokkaido. It was obtained also that the elastic model of the snowslide in his previous report can be applicable only for the snowcover of the e_A^*'s less than 100, and that another type of the snowslide can be expected for the snowcover of e_A^*'s much greater than 100.