Abstract
The mode of freezing of soil was examined by digging in the frozen ground at eight spots. in Hokkaido. where the climatic condition and the soil nature are qui_??_e different from each other. The excavation was one always on railway tracks.
The frozen ballast was found to consist of gravels stuck together with hoar crystals; that is crystaline frost. Many beautiful hoar crystals in various forms were found on the bottom surface of gravels. showing that the ventilation of water vapour is quite well through the frozen ballast From the stan lpoint of m croscopic view. the thermal conduc_??_ivity of a ballast layer must be very large. as the latent heat of evaporation and condensation of ice conveys a considerable amount of heat by convection from the depth of the ballast ot the upper layer.
The freezing of soil, especially of the one mixed with clay is characterlsed by many ice layers, the ice being separated from the moistened soil by freezing. Two sors of ice layers w_??_re found. The ones are thick and few in number, two or three of them being usu_??_ly observel in a section of the ground. The others are very thin and an innumerable number of them are observed in the section of one frozen laryr. The ice in the former case s of the same nature as the frost pillar that is a common product in winter in some districts of our conntry. The ice in the latter case originates in the cracks in soil which are produced by contraction of soil. The frost heaving is found to be chiefly due to these ice layers separated from the soil by freezing.
