Effect Of Stress Perturbation On Frictional Behavior: An Experimental Study

The crustal movement shows obviously non-linear characteristics in time and space, and the tectonic deformation and related phenomena are undoubtedly affected by such non-linear mechanical process. Experimental study on frictional behavior under non-linear loading is helpful for understanding the effect of stress change on earthquake mechanism. In this paper, the frictional experiments on medium-scale granodiorite sample containing 45°precut surface have been conducted by using a servo-controlled biaxial rig, and the effect of stress perturbation on friction has been studied, in which the effect of perturbation ofσ2 has been emphasized. The main results obtained in this paper are summarized as follows.(1) The experimental results indicate that the displacement perturbation modulated on average loading rate inσ1 direction has no obvious effect on frictional behavior of the sample, and the correlation degree between the timing of stick-slip events and imposed perturbation is rather weak. However, the stress perturbation modulated on averageσ2 makes frictional behavior be greatly changed. The stress drop and period of stick-slip events are scattered and the correlation degree between the timing of stick-slip events and imposed perturbation is very strong, and the effect increases with increasing the amplitude of the perturbation. In statistics, the interval and stress drop of stick-slip events increase with increasing normal stress on sliding surface under constant loading velocity in the direction ofσ1 and constantσ2, but the relation is greatly changed when stress perturbation of sine wave with high frequency and small amplitude is added toσ2. The scatter degree of stress drop and interval of stick- slip events is obviously increased. This indicates that the effect of perturbation inσ2 is mainly contributed to the corresponding perturbation in normal stress along the sliding surface.(2) The mechanism of scatter in stress drop of stick-slip events has been analyzed by introducing stress coefficient CS and comparing it with friction coefficientμ. Stress perturbation causes perturbation of stress coefficient, which can affect the timing of stick-slip event thus to lead scatter in interval of stick-slip events. This can also explain why the effect of perturbation inσ2 is much bigger than that of perturbation inσ1. The mechanism of scatter in stress drop of stick-slip events has been discussed base on the analysis of strain field. The analysis indicates that the perturbation inσ2...