Static and kinetic friction of granite at high normal stress

Frictional sliding on ground surfaces of granite, angle of sliding planes 30° and 45°, was investigated as a function of confining pressure. Over the normal stress range of 2–12 kb, the static frictional shear stress τ^s follows the relationship τ^s = 0·5 + 0· σ_n and the kinetic frictional shear stress τ^k was calculated to be τ^k = 0·25 + 0·47 σ_n.