Scaling phenomena due to fractal contact in concrete and rock fractures

Concrete-to-concrete friction contributes in many cases to the stability of a structure. At different scales, the slope stability of rock joints is de eply influenced by the surface morphology and shows a marked size-dependenc e. In this paper, the closure and sliding-dilatant behaviour of cracks in c oncrete and rocks is investigated by means of a coupled numerical/experimen tal approach. These natural interfaces show self-affine properties in the r elevant scale range. Attention has been focused on the stress transfer mech anism across the interfaces, showing that the sets of contact points posses s the self-similar character of lacunar fractal sets. Scaling laws come int o play and the size-effects on the shear strength of rough interfaces, and on their closure deformability, can be explained.