Figure 7
μ ss plotted against smectite/clay-mineral content for the five samples tested in this study. Steady-state friction coefficient μss at an axial displacement rate (Vaxial) of 1µm/s is plotted against the content of smectite (squares) or clay minerals (circles). Values of μss are obtained by inputting the corresponding Vsliding value in the equations of the least-squares fitted lines shown in Figure 6.