長野県南部の花崗岩類の崩壊  [in Japanese] On the Landslides of Granitic Rocks in Southern Nagano Prefecture, Central Japan  [in Japanese]

We find numerous landslides, mainly in surface slip type and in joint failure type, on the granitic zones in southern Nagano Prerecture. Sliding material in this process is weathered soil due to granitic rocks. The deeper deposits will be, the more hillsides may be destroyed, in the end to marked devastation. Average inclination of hillsides in this suffered area is about 39 degree. The major factor of landslides occurred in granitic rocks may be that these are intensively prone to decay into weathered sliding deposits. As a comparative study of weathering velocity of granitic rocks, we tried to follow time series tracks of effective porosity and compression strength of each specimen, by repeated freezing-thawing tests and with observation in exposed situation in open air. We could find a procedure for estimation of weathering velocity, which seems be varied in accordance with crystallization structures of granite.