The effects of rock-infill interfacial properties on the compressive damage behaviour of flawed rocks: Results from a DEM study

Abstract: Infilled rock discontinuities is a general technique to enhance the strength and stability of natural rock mass. However, the effects of rock-infill interfaces on the fracture of rock remain ambiguous due to difficulties in controlling interfacial properties in both laboratory and practice. In this study, we investigate the effects of rock-infill interfacial contact properties on the fracture behaviour of rock under uniaxial compression loads from a multiscale perspective based on Discrete Element Method (DEM). Single-flawed rock specimens with various inclined angles and three common types of rock-infill interfacial contacts (i.e. smooth, weak-cohesive and cohesive) are considered in the investigation. The mesoscopic responses of rock and infill material, as well as the cohesive interface, are characterized in DEM by a cohesive damage-plasticity model, while their smooth interfacial response is described by the smooth joint model. To bridge the meso- and macro-behaviour of infilled rock specimens, a local strain calculation technique for large deformation issues is used to quantify continuum strain fields from discrete displacements of DEM particles. After calibration and verification, the proposed numerical model is demonstrated to be capable of capturing the mechanical behaviour of both unfilled and infilled rock specimens with various flaw inclined angles. Sensitivity analyses of infilled rock performance demonstrate that the cohesive interfacial contact is more effective than smooth interfacial contact in enhancing the mechanical responses of rocks, and flawed rocks with full-cohesive interfacial contacts can behave like an intact mass. In addition, the interfacial contact types show significant effects on the cracking process and crack patterns in rock specimens.