<p>The slotted pipe wrapped by steel wire mesh, as a common type of drainage facilities in tailing dam, not only reduce the phreatic line effectually, but also can reinforce the dam, like friction piles protecting slope. In this study, the interfacial shearing properties of tailing-steel wire mesh interface are investigated by a direct shear test first, as well as the influence of aperture size. Moreover, the evolution law of interface microscopic behaviour is studied by a discrete element method (DEM) simulation. The results indicate that the shear strength experience three changing processes with increasing the shear displacement, i.e. linear increasing stage, nonlinear hardening stage and stable stage. The interface shear strength under different aperture size can be regarded as following Mohr–Coulomb shear failure criterion. The interfacial cohesion increase and interfacial friction coefficient increase first and then decrease with the aperture size. The interface initial shear stiffness increases first and then decreases with aperture sizes. The vertical shear deformation suffers three development stages with increasing the shear displacement, i.e. slight shear shrinkage stage, significant shear expansion stage, and stable stage. The shear expansion increases first and then decreases with aperture sizes under a given normal stress.</p>