[S-SS05] Fault Rheology and Earthquake Physics

[SSS05-13] Relationship between evolution of slip-surface structure and mechanical behavior of frictional sliding at Indian sandstone

*Hatanaka Mamoru¹, Tetsuro Hirono¹, Kiyokazu Oohashi², Akihiro Ito³ (1.Osaka Metropolitan University, 2.Yamaguchi University, 3.Osaka University)

Keywords:Friction, Indian sandstone, Slip-weakening

For understanding the mechanisms and processes of landslide and earthquake, evaluation of frictional property of sandstone is fundamentally important. Although many laboratory experiments using sandstones have been performed over the last half-century, the relationship between evolution of slip-surface structure and mechanical behavior under various environmental conditions have not fully investigated. Here we showed the results of rock-on-rock rotary-shear experiments using Indian sandstone at 1 mm/s slip rate at the range of 0.5-20 m slip distance under humid air and N₂ gas conditions. Frictional coefficient under humid air showed a peak at 0.5 m distance and decrease after 5 m, whereas the coefficient under N₂ gas exhibited drastic decrease just after reaching a peak at 0.5 m. Our microscopic observation by using electron microscope on the specimens before and after experiments revealed that generation of ultrafine particles and development of flat structure under N₂ gas experiments occurred at shorter slip distance than those under humid air conditions. Therefore, change in frictional coefficients and evolution of slip surface structure strongly depend on the environmental conditions (that is, humid air vs. N₂ gas), which may be essentially causing from the amount of absorbed water molecule on mineral surfaces and their low friction coefficient.