Figure 5. (a) Effect of permeability on friction coefficient of loess.
(b) Effect of fluid viscosity on friction coefficient of loess.
The above results elucidate that the macroscopic contact and friction
behavior of the geomaterials depend on the creep accumulation process of
microscopic asperities in the normal and tangential directions. This is
closely related to temperature and creep activation energy. However,
temperature-induced changes in normal and tangential stresses and phase
transitions significantly affect the changes in its frictional force.
The relative creep difference in the normal and tangential directions of
the asperities can cause velocity strengthening or weakening effects. It
is due to the different amounts of stress reduction in the tangential
and normal directions corresponding to different activation energies.
In addition, the water content
also significantly affects its friction coefficient, which can attribute
to the lubrication effect and the role of sharing part of the pore
pressure. Thus, the permeability and fluid viscosity coefficients, which
affect the water flow and distribution characteristics, affect the
coefficient of friction.