Frictional healing of quartz gouge under hydrothermal conditions: 2. Quantitative interpretation with a physical model

Abstract

[1] The companion paper by Nakatani and Scholz [2004] shows that a hydrothermal frictional healing mechanism results from local solution transfer. Here we evaluate this mechanism with the model of Brechet and Estrin [1994], which assumes that the healing occurs by stress-driven asperity creep. The absence of a clear temperature dependence of the healing parameter b in the narrow tested range of 100-200°C is consistent with the model's prediction. The analysis also indicates that the mechanism involves a high stress assist parameter Ws = 200 kJ/mol, which is consistent with the contact stress being the indentation hardness, s $ 10 GPa, and the activation volume W being the molar volume, both of which are reasonable. For this to be consistent with the observed temperature enhanced kinetics of healing also requires that the activation energy exceed 200 kJ/mol. This is much higher than the 20-70 kJ/mol known for low contact stress pressure solution. The analysis of several previously published studies of hydrothermal healing of hard silicates yielded the same results. Hence, if the underlying process is stress driven, it must have a different mechanism at high stress than at low stress. Alternatively, a solution transfer mechanism driven by something other than stress could be the underlying mechanism, but this is inconsistent with other aspects of our experimental results. On the other hand, the same analysis of phenomena that are independently inferred to proceed under relatively low contact stress yielded the parameter values consistent with low-stress pressure solution.

Fault instability on a finite and planar fault related to early phase of nucleation

“…In addition, both state evolution laws are used, as mentioned above. In all cases, the parameter range for which we perform the experiments is a/b ≥ 0.5, since a and b are considered to be comparable values in terms of the thermally activated rheology of the real contact area [Nakatani and Scholz, 2004].…”

Effects of Interfacial Bonding on Friction and Wear at Silica/Silica Interfaces

“…Frictional aging has been described by a phenomenological rate and state friction laws [24,25], which state that friction depends logarithmically on time. While this law has been validated and widely accepted, [26][27][28][29] the physical origin of frictional aging has remained a subject of debate. Two main hypotheses are plastic creep (which increases the contact area and therefore friction as a function of time) and chemical bonding (which increases adhesion as a function of time without necessarily increasing the contact area).…”

Application of rate‐and‐state friction laws to creep compaction of unconsolidated sand under hydrostatic loading conditions

“…[25] Mathematically, we are approximating exponential creep [Nakatani and Scholz, 2004] at asperity contacts with a power law creep in equation (7). For this to work we need the strain rate for both flow laws to be the same at the real stress s for the expansion…”

“…A natural choice for such a law is the rateand-state variable friction law, since it already contains the necessary terms and was empirically derived from laboratory observations in a concise mathematical form [e.g., Dieterich, 1978Dieterich, , 1979 and has a physical basis in thermally activated creep at high-stress asperity contacts [Nakatani, 2001;Rice et al, 2001;Beeler, 2004;Nakatani and Scholz, 2004]. In addition, rate-and-state friction laws have been shown to describe the shear deformation and normal compaction of a wide variety of materials.…”