On the base which the roughness profile is model as a series of irregular shaped

triangular asperities

the shear failure mechanism of tooth-shaped joints was studied. The shear strength equation was derived

in which the surface profile of joints were considered.The relationship between equivalent cohesion and joints cohesion was established. The equivalent coefficient was proposed and the rule of the coefficient was studied. By discussing the equation under low

medium

high normal stress

some conclusions were drawn.