Modelling of Rock-Shotcrete Interfaces Using a Novel Bolted Cohesive Element

Rock-shotcrete interfaces are commonly encountered in mining and civil engineering infrastructures, which can trigger localised failure due to stress concentration. These interfaces are usually reinforced with support systems such as rock bolts and the behaviour of rock-shotcrete-bolt systems is often difficult to predict mechanically. In this study, we introduce a new technique to model rock-shotcrete interfaces embedding rock bolts using the finite element method. The proposed approach is implemented in the general purpose simulation package Abaqus via its user-defined element (UEL) subroutine. The proposed model takes into account the uneven interface roughness and the complex interaction between its components. The cohesive stiffness of the model degrades proportionally to the damage that occurs due to this interaction. The stiffness of the bolt connection and its location are also considered in the proposed mathematical formulation. The present bolted cohesive element has been validated experimentally; good agreement has been obtained between the measurement and numerical simulation under the conditions of direct shear test and bolt pull-out tests. Mesh independence has also been verified by examining the effect of mesh size on the overall force-displacement response of typical structures. With the model at hand, the effects of key installation parameters such as number of bolts, their inclinations and material properties have been investigated.