Abstract
The Izumigoshi tunnel was excavated in volcanic rocks belong to the Yugawara volcanic rocks group (pleistocene), Inamura andesite group (pleistocene). During the excavation of thil tunnel many accidents were encountered, were break down of fault zone at 92K 890m from Tokyo, deformation and failure of tunnel suports, tunnel lining due to swelling rocks extended about 360m total long, which from altered volcanic glass, tuff and tuff breccia by hydrothermal alternation.
The author analysed clay minerals in the rocks by X-ray diffraction method, concerned the relations between content of clay minerals and value of compressive strength, velosity of super sonic waves, and engineering difficulty occurred in the tunnel.
In the results its was found that this clay minerals composed mainly montmorillonite, deformation and failure in the tunnel connected with content of clay minerals.
The result of survey and analysis are shown in fig.2-5.
