山形県白川中流部におけるシーティング節理

概要

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The joints at the surveyed area develop nearly parallel to the ground surface, and their number decreases with the depth, so that these can be regarded as sheeting joints. The joint pattern and its rock control are investigated in detail at excavated tunnels, and conclusions are as follows. 1) The sheeting joints are caused by the expansion and buckling of rock mass, either due to stress release or chemical weathering. 2) The sheeting joints by chemical weathering are superimposed on the joints by stress release, and the former are steeper in gradient, closer in spacing and shallwer in depth than the latter. 3) The difference of rock expansion by stress release is also found at rock type boundary, so that the intensity and orientation of sheeting joints is complicated where the slope is composed of different type of rock mass. 4) The sheeting joints develope in the rock mass of which qu is more than 200 kg/cm2. 5) The rate of joint development is in the order of 1 meter deep per 1000 years. 6) The process of chemical weathering is accelerated by the water infiltration through the preexisting joints of sheeting. 7) Unconformity is found between joint pattern and estimated gravity induced stress field, so that no gravity contributes to sheeting joint development.
社団法人東京地学協会の論文