[SCG61-P18] Frictional properties of dolerite and granite at intermediate slip rates and controlled ambient temperatures
Keywords:friction, temperature dependence, dolerite, granite
Experiments were performed on dolerite (Belfast, Northern Ireland) and granite (Aji, Japan) using a rotary shear deformation apparatus at Chiba University. Samples were displaced up to 10 - 20 m at a normal stress of 1 MPa, slip rates of 1 to 300 mm/s, and ambient temperatures of 20 - 500oC in an argon atmosphere with an oxygen concentration of 0.2 %.
At 20oC and 100oC, dolerite showed velocity weakening at slip rates ranging from 1 to 30 mm/s with µ of 0.81 - 0.83 at 1 mm/s and of 0.73 at 30 mm/s. Whereas at high temperatures >300oC, friction is almost constant (µ = 0.81 - 0.85) at < 30 mm/s. At 100 mm/s, the behavior is slight velocity strengthening at 20oC and 100oC with µ = 0.75 - 0.79 and clear velocity-weakening at more than 300oC with µ = 0.67 - 0.76. At 300 mm/s, the dolerite showed strong velocity weakening at all temperatures investigated. The amount of weakening (i.e., the drop in friction, Δµ) increases with increasing temperature (Δµ = 0.1 - 0.38). Thus, the frictional properties of dolerite are affected not only by slip rate but also by ambient temperature.
Experiments using granite to decipher the effect of materials on temperature dependence are in progress. Our preliminary results are summarized as follows. At <30 mm/s, the behavior is slight velocity strengthening at room temperature and velocity-weakening at temperatures of 100-300oC. At >300oC, friction is almost constant. Friction coefficient decreases with increasing temperature of 20-300oC and increase again at >400oC. At >100 mm/s, clear velocity-weakening did not occur except at temperatures of 20oC. More results especially on granite will be reported at the meeting.