Surface roughness effects on peak and residual shear strength of cohesive-frictional interfaces: an experimental study

Stone masonry buildings are vulnerable to a wide range of loadings, such as differential settlements and earthquakes. Damage to these buildings manifests itself mainly through cracks in the masonry walls, which often propagate along the interface between mortar and stone. In this study we investigate the role of the stone surface roughness on the interface shear strength, which is described through the Mohr-Coulomb failure criterion. To do so, we subject samples consisting of two units and one mortar joint to direct shear loading and a constant normal load. For the stone unit we used as proxy high-strength concrete that was cast against 3D printed surfaces with artificial surface roughness that contain one, two or three sinusoidal waves and vary the wavelength and the amplitude of these waves. We conducted 160 tests and analysed the influence of the wavelengths and amplitudes that characterise the surface roughness on the shear behaviour.