2:45 PM - 3:00 PM
[SSS07-05] Investigation of relationship between frictional behavior and slip surface structure by friction experiment of sandstone
Keywords:friction, sandstone, fault mirror
Frictional properties of sandy sediments and sandstones has been investigated for half a century. However, the experiments under wide-ranged velocities range and their surface structures have not been reported. Here we conducted rock-to-rock rotary shear experiments of sandstone, and observed slip surface structures together with measurements of the surface roughness. We performed rotary shear experiments of India sandstone at wide-ranges of slip rates (1.0 m/s ~200 μm/s). The normal stress and slip distance were 1.0 MPa and 10 m, respectively. At the experiment of high-slip rate (1.0 m/s), friction coefficient oscillated unsteadily, and the slip surface was intensively worn. At the case of low-slip rate (< 0.1 m/s), friction coefficient decreased exponentially and fault mirror was observed on the slip surface.
As the results of observations by using electron microscope, the slip surface at high-slip rate showed large roughness and included many large fragments (~10μm) of sand. On the other hand, those at low-slip rate showed well-polished mirror and included rounded nanograins (diameter size 100 nm~). Roughness of the slip surface at high rate, measured by laser microscope, was about 80μm and the Sdr was 219%. However, at low slip rate, the roughness and Sdr were 4μm and 18%, respectively.
By taking into consideration our results, we would suggest that frictional mechanism of sandy fault is dependent on the slip rate. At high-slip rate, wear process is dominant, leading to unsteady slip. On the other hand, at low-slip rate, nanograin formation by wearing was dominant together with formation of mirror surface and low friction coefficient.
As the results of observations by using electron microscope, the slip surface at high-slip rate showed large roughness and included many large fragments (~10μm) of sand. On the other hand, those at low-slip rate showed well-polished mirror and included rounded nanograins (diameter size 100 nm~). Roughness of the slip surface at high rate, measured by laser microscope, was about 80μm and the Sdr was 219%. However, at low slip rate, the roughness and Sdr were 4μm and 18%, respectively.
By taking into consideration our results, we would suggest that frictional mechanism of sandy fault is dependent on the slip rate. At high-slip rate, wear process is dominant, leading to unsteady slip. On the other hand, at low-slip rate, nanograin formation by wearing was dominant together with formation of mirror surface and low friction coefficient.