A BASIC STUDY OF FREEZING-THAWING DISASTER AND ITS PREVENTION TECHNOLOGY

本研究项目旨在调查日本多雪和寒冷地区的冻结指数和与冻融现象相关的区域灾害的特征。为此，在公路现场安装了现场试验装置，观测地下温度的年变化，并对新建公路所用土样进行室内试验，以区分防止冻融现象的岩土材料。另一方面，收集和分析了各种冬季气象资料。通过对试验数据的分析，得到以下几点新的信息：（1）近年来，冻结指数呈下降趋势。这一现象与本研究在时间序列数据分析中所证实的近期冬季变暖趋势相对应。（2）近世纪来，冬季气温呈上升趋势，札幌上升3℃，秋田上升1.5℃，福井上升1.5℃。这样就可以清楚地认识到高纬度地区冬季变暖的趋势。(3)根据日最低气温的谱分析，发现札幌和本州岛盆地地区的上级周期分别为11年和9年。（4）制作了2000/2001年冬季东北地区冰冻指数分布图。我们发现了一个新的冻结指数之间的关系，海拔高度，和冻结深度。其中，每个地区都有一个独立的分布方程系数。然而，建议的冻结指数方程没有遵循，特别是在大雪覆盖地区，因为它的有效性，雪绝缘。

This research project aims to investigate the characteristics of freezing indices and regional disasters related to freezing-thawing phenomena in snowy and cold regions in Japan. For this purpose, field test apparatus was installed at the site of public road to observe the variations of underground temperature through the year, then the laboratory testings of the soil samples used for new building road were carried out to distinguish the geomaterials for preventing freezing-thawing henomena. On the other side, various kind of winter meteorological data were collected and analysed. From the data analyses, several new information were obtained as follows : (1) Freezing index is getting lower in recent years. This phenomenon corresponds to the recent warming winter tendency that was verified by this research in analyzing the time series data. (2)Winter temperature is getting higher within the recent half century, that is, 3℃ up in Sapporo, 1.5℃ up in Akita, and 1.5℃ up in Fukui. In this way, warming winter tendency was recognized clearly in high latitude. (3) According to the spectrum analysis of daily minimum air temperatures, superior periodicity was found as 11- year in Sapporo, and 9- year at the basin areas in Honshu island. (4)Freezing indices distribution map of Tohoku district was made for the winter of 2000/2001. We found a new relationship between the freezing index, elevation from the sea level, and freezing depth. In which, each prefecture has an independent coefficient of the distribution equation. However, proposed equation on freezing index was not followed well especially in the heavy snow cover areas because of its effectiveness of snow insulation.