The study of rock joint behavior is an important research topic in various fields. A mechanical simulation model has been developed in order to simulate normal and shear tests on rock joints. The model is applied to the study of scale effects with respect to normal and shear stiffness and contact area. Scale effects are first analyzed in terms of the level of discretization of the joint surfaces. Because an increase of the step size in the discretization results in a smoothing of the surfaces, it leads to a decrease in the calculated tangential stiffness. Secondly, the scale effect is studied by performing simulations with joints of various sizes. Normal and shear stiffnesses and contact area decrease when the joint size increases. By linking mechanical results with morphological observations, we can conclude that the scale effect for rock joint behavior is not a mechanical effect, but a morphological scale effect. Furthermore, mechanical results are directly linked to the variograms of joint surface elevations.
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