Study on Hydrogeologic Characteristics of Landslide Ground and Behavior of Melting Snow (I)
The Case Study of Yokone Landslide Area, Niigata Prefecture.
1982 Volume 18 Issue 3 Pages 54-62_1
Details
1982 Volume 18 Issue 3 Pages 54-62_1
This paper presents the results of detailed studies on the hydrogeologic characteristics and the behavior of melting snow in landslide ground. The investigated area, located in the Aburuma river basin, is well known as the concentrated zone of landslide.
The results of the investigation are summarized as follows.
Geology
1) Base Rocks-Tertiary-
Base Rocks concerned with the landslide phenomena of this area are Tertiary and are divided into two horizons. The lower one mainly consists of green rocks and the upper one consists of alternating perlitic tuff and mudstone. These strata trend east northeast and dip 20 to 30°northwest.
2) Ejecta of Sumon-dake-Quaternary-
Ejecta of Sumon-dake are divided into two horizons, The lower one is composed of weathered tuff and debris with volcanic ash, sand and weathered andesite breccia. The upper one, Sumondake Lavas, constitutes Sumon volcano. This is not related directly to the landslide of this area.
3) Landslide ground
Field evidence and boring data shows that the landslide ground exists at several horizons and they are divided into two groups. One is old land failure deposits and the other is recent landslide ground. The former is recognized in the both area of Tertiary and Ejecta of Sumon-dake. The latter ranges in thickness from a few meters to 6 meteres and its permeability is higher than the former.
Groundwater
Continuous observation of water level, temperature, flux and electric conductivity of groundwater are executed by using bore hole and collective well. The outline of the discussion about the behavior of the melting snow is as follows.
i. Infiltration of melting snow is occured within a period of May or April in natural condition.
ii. Infiltration speed is accelerated by the artificial agent (collective well).
iii. In early stage, groundwater is supplied from melting snow in the neighborhood area of landslide but in process of time and as a depth increases, the groundwater is changed place by the water which is supplied from distant area.
