4. Results
4.1 Effect of
temperature
The interface temperature of the geomaterial varies with the
accumulation of the creep process and the sliding velocity variation.
This further affects the frictional behavior of the geomaterial via
changing its state. Figures 3 (a) and (b) show
the friction coefficient as a function of contact temperature. The
friction coefficient gradually decreases with the increase in contact
temperature; meanwhile, it drops sharply when the geomaterial reaches
phase transition temperature. This is because temperature affects the
normal and tangential creep processes, and has a more significant impact
on the tangential direction once a tangential slip occurs. Particularly,
the tangential stress decreases with a faster speed than the normal
stress as contact temperature increases, causing a decrease in the
coefficient of friction. In addition, the geomaterials exhibit obvious
flow characteristics before the phase transition temperature.
Figures 3 (c) and (d) show the relationship
between the ambient temperature and friction coefficient of the loess
and fault geomaterials under different sliding velocities. The influence
of ambient temperature on the friction coefficient is smaller than that
of the contact temperature because the maximum temperature difference
between winter and summer is only tens of degrees Fahrenheit. The
ambient temperature change still affects the creep stress in the normal
and tangential directions of these geomaterials, thus, the friction
coefficient gradually decreases with the increase in temperature.