On the rate of frictional healing and the constitutive law for time- and slip-dependent friction

Laboratory experiments were conducted to measure the healing rate in simulated fault gouge. Experiments consisted of both slide-hold-slide tests and velocity stepping steps. The study addressed two main issues, including variation in healing rate with loading velocity, and consistency of friction parameters and constitutive behavior. Experiments were performed in the double-direct shear geometry at room temperature and at a constant normal stress of 25 MPa. The data obtained from the study indicate that healing is not simply a frictional property, but rather is a system response that varies with loading velocity and properties of the elastic loading system. Constitutive modeling was also carried out on three aspects of the data: slide-hold-slide tests, velocity stepping tests, and the rate of frictional healing.