Figure 4. (a) Effect of creep
activation energy difference on friction coefficient of loess. (b)
Effect of creep activation energy difference on friction coefficient of
fault geomaterial.
When the creep activation energy in the normal direction of the
asperities is smaller than that in the tangential direction, the
friction coefficient decreases gradually with the slow increase of the
sliding velocity (Figure 4). This is because
normal creep is more likely to occur, and
the normal stress reduction is
smaller than the tangential stress reduction. As a result, the friction
coefficient decreases. Similarly, when the creep activation energy in
the normal direction of the asperities is greater than that in the
tangential direction, the friction coefficient gradually increases with
the slow increase of the sliding velocity (Figure
4). This is because
tangential creep is more likely
to occur and the tangential stress reduction is smaller than the normal
stress reduction, causing an increase in the coefficient of friction.
The creep activation energy of geomaterials is closely related to the
properties, composition, and other factors of these geomaterials.
Therefore, different materials will show shear strengthening or
weakening, even constant shear strength with increasing slide velocity.