Effects of roughness on shear properties and acoustic emission characteristics of bonded Rock-Concrete interfaces

The shear properties of bonded rock-concrete interfaces play a crucial role in the analysis of engineering structures stability. In this paper, laboratory direct shear tests and acoustic emission (AE) tests are conducted on standard cylinder specimens with varying levels of rock surface roughness. The aim is to gain a better understanding of shear behavior and failure mechanisms of the bonded interface between rock and concrete. The results show that increasing of roughness enhances the brittleness and peak dilatancy characteristics of the specimens. However, the residual shear strength exhibits the opposite trend. In addition, the distribution of residual concrete on the rock surface changes gradually from localized spots to larger areas. The AE test results demonstrate the occurrence of peak AE peak energy and count generation during shear failure. The evolution of the AE-b value indicates that the macro-fracture surface of the bonded surface is the result of the repeated conversion between large and small-scale micro-cracks. Moreover, the fluctuation value of the AE-b value is not influenced by the roughness of the rock interface. Hence, in this experiment, the 90% fluctuation mean value is selected as the primary parameter for rupture warning. Furthermore, The distribution of RA-AF values reveals the generation of numerous tension-shear composite crack types during the fracture process. The number of shear cracks in the failure stage exhibits an increasing trend with increasing roughness.