Comparison of methods for discontinuity roughness evaluation

Rock masses are natural media affected by the presence of discontinuities that influence significantly their stability conditions: blocks are detached by the discontinuity planes and can move along them; moreover, the possible kinematisms are ruled by the amount of shear strength offered by the discontinuities. Shear strength depends on mechanical properties but also on geometrical aspects of a discontinuity, such as its roughness. For this reason, the evaluation of this property is fundamental. In this paper the state of the art of the roughness descriptors is presented. The two surfaces of a joint, digitalized by means of a photogrammetric survey and already used to perform shear tests [FERRERO et al., 2010], are used to apply the geometrical descriptors and analyze the results in terms of correspondence with laboratory results. Moreover, the influence of anisotropy and sampling interval (SI) is discussed. The paper compares different roughness quantitative descriptors showing as Tatone and Grasselli’s approach [2011; 2013] is in good agreement with experimental shear tests data.