Influence of fault surface characteristics on stress drop due to stick-slip events revealed by large-scale biaxial friction experiments

摘要

We investigated stick-slip events that occurred during large-scale biaxial friction experiments. Thernexperiments were carried out by using a large shaking table working at NIED. We used a pair of largernsquare prismatic rock samples, whose were 0.5 × 0.5 × 1.5 m~3 and 0.5 × 0.5 × 2.0 m~3. The shorter rockrnsample was overlaid on the longer one, which resulted in the nominal contact area of 1.5 × 0.5 m~2.rnThe experiments were carried out with a loading rate between 0.025 and 1 m/s under a constantrnnormal stress ranging between 0.13 and 1.3 MPa. The maximum displacement was 0.4 m. Slidingrnsurfaces were flattened within 24 μm undulation before the series of experiments. With thernexperiments proceeding, the sliding surfaces were evolved and generated wear materials. Thernexperiments were repeatedly carried out under various mechanical conditions, and the total amount ofrndisplacement attained to 77 m. To investigate the effect of wear materials on friction behavior, wernsometimes kept and sometimes removed the wear materials from the sliding surfaces. We found thatrnthe stress drop is negatively proportional to both the sliding surface roughness and the amount of wearrnmaterials independent of the loading rate, and the amount of stress drop could be expressed as arnmultivariate function of them. In particular, the correlation at loading rate of 100 mm/s is so high thatrnthe coefficient of determination attains to 0.87, which indicates that the stick-slip behavior isrndominantly controlled by the wear materials and the sliding surface roughness at this loading rate. Wernalso found positive correlation between the stress drop amplitude and the loading rate, which isrninconsistent with the previous studies. This discrepancy may come from velocity weakening featurernof rock friction at high loading rate.