A large and gentle sloping land is often developed in and around the piedmont lowland or the remnant erosion surface. A large-scale landslide is sometimes found on this sloping land. This kind of landslide is generally regarded as the secondary sliding of the gentle inclined plane formed by the original landslide. In our country, however, boulders or block streams produced by earthquakes or volcanic activity or the climatic change have buried valleys in the mountainside to form the gentle slopes. Therefore, when rock is apt to slide by nature, a varied phenomenon takes place at the boundaries between the layer of gravel filling buried valleys and the rock, and new landslides often occur near these buried valleys. Since the buried valleys are usually stabilized, attention should be drawn to the soft rock surrounding them. Hence, the secondary sliding of the large sliding area formed in the past should be investigated over again for the landslide occurring on some gentle sliding area.

View full abstract

Niigata Prefecture is famous for having not only many landslides, but also much snow.
This report mentions the relationship between landslides and snow.
Landslides can be divided into two types: one is seasonal movement-type landslides, the other is irregular movement-type landslides. The former, such as Sarukuyoji landslide or Kamiya landslide moves mainly during the times from autumn to the next spring, and stops its movement during the spring and summer seasons. It was turned out that the movement of the landslides related much to rainfalls, snow-melting water and load of snows. And a model to interpret mechanism of the landslide movement is considered.
On the other hand, snow-melting water and rainfalls cause the latter type of landslides and it needs a period of time and decrease of the shear strength in slip surface for the landslides to occur again. The landslides of this type occur very often in the snow-melting periods.

View full abstract

The distributed pattern of underground temperature was controlled pretty strongly by the distributing condition of underground water vein-stream in shallow layer, accordingly the writer examined theoretically the possibility using a simple two-dimensional model. By the results, it was admitted theoretically too. And it was shown that the scale and existing depth of underground water vein-stream could be estimated from Tx=1-y figure obtained in-situe. Surveyable limit of underground water vein-stream could be known from Fig. 15a-d in this paper. Interval of measured points required 5-10 meters in order to survey the underground water vein-stream. The season of execution of underground temperature survey was favorable season that there was three degree difference between underground temperature in one meter depth and underground water temperature.

View full abstract