3:30 PM - 3:45 PM
[SSS29-08] Verification of unstable frictional behavior for smectite as elevated temperature
Keywords:frictional experiments under rising temperature, the updip limit along subducting plate, smectite-illite transformation, frictional property for clays, the effect of temperature, the effect of interlayer water
Experimental methods: Frictional experiments were performed using a biaxial frictional testing ma-chine at Hiroshima University. The powder materials of clays were placed on the simulated fault surface and two side blocks were placed together to produce a double-direct shear configuration. Normal stress was ap-plied via a hydraulic ram on the side block with 60 MPa, and then, shear stress was applied by advancing the central block downward at a constant velocity. The sample assembly was heated by an external furnace up to 200oC that is monitored by thermocouples located close to the central block. Mechanical data were recorded continuously with a sampling rate of 10 Hz and the frictional coefficient was calculated from the shear force divided by the normal force assuming zero cohesion.
Results and Discussion: Our experiments showed three phase change as elevated temperature. 1. De-creasing frictional strength, 2. Increasing frictional strength, and 3. Appearance of persistent stick-slip behavior. At phase 1, expansion of interlayer water due to rising temperature may open interlayer of clays, weakening adhesion. At phase 2, dehydration leads to healing adhesion and frictional strength. At phase 3, we observed persistent stick-slip behavior. This frictional behavior implies to have a potential of velocity weakening behavior, and temperature has significant influence on frictional behavior of clay minerals.