山地地形における岩盤規制の研究 : 山形県梵字川中流地域を例に
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概要
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A lot of geological information by means of ground survey, boring, test pitting and geophysical prospecting for the dam construction is available from the area in the middle course of the river Bonji, a tributary of the river Aka. The anther has made a study about the rock mass controls in geomorphology of the area promoted by this situation. The principle of the study is based on the mass-wasting relating to both geomorphology and rock mass conditions. As a landform reflecting masswasting, a landslide landform, a knick line, valley distribution density and a talus slope including aluvial cone are taken into consideraration. The relations between each landforms and rock mass conditions are summarized as follows; 1) The distribution density of landslide landforms is much higher in the Akagawa formation consisted of siltstone, than the Bonji formation consisted of tuff breccia interbedded by andesite lava. 2) The rock mass at landslide landforms has been loosely fractured to cause gapping fissures, although the appearance is as like as in-situ one. 3) The knick line has been formed by the integration of small scale landslides. This landform is possible to be classified into the following 4 types: Type 1: The upper and lower slope from this line has much difference in their inclination, although both slope merge gradually to each other. The line can be traced as if a plane intersecting a slope, and in fact, it coincides the boundary between Bonji formation and Akakawa formation. Type 2: The upper and lower slope contacts sharply at this line and both slopes have much differences not only in slope inclination but also texture, i,e. the gentle, smooth upper slope and the steep, rough lower slope. The line intersects the contour lines at steep angle as if the lower slope has been conspicuously denuded. The rock mass condition at this type knick line has been deeply weathered. Type 3: The upper and lower slope contacts sharply at this line and the difference in slope inclination is not so much as the other knick lines. The line intersects the contour lines at small angle as if the lower slope has been denuded a little. The rock mass at this line has been slighty weathered. Type 4: The feature of this line is as type 2 knick line, although it is just on the shoulder of the side-cutting slope to the river, and can be traced along countour line. The rock mass at this knick line has been slightly weathered. 4) The rock mass at the slope with dense distribution of valley has been slightly weathered. 5) The dimension of a talus slope is proportional to the productivity of rock fragements at the upper slope judged from the type of knick line.
- 地学団体研究会の論文
- 1980-03-25