Numerical Modelling of Fully Grouted Rock Bolts using a 2D Finite Element Method

ABSTRACT: Rock bolts are one of the primary underground support systems utilized to stabilize the rock mass surrounding the opening of an excavation by transferring the load from the surrounding rock to the more stable rock mass further from the excavation. Modelling fully grouted rock bolts has been the focus of many researchers due to the difficulties associated with capturing the interaction mechanism(s) concerning the interface between the rebar and the grout as well as the grout and the rock at the micro-scale. In this paper, two-dimensional (2D) numerical simulations have been conducted in order to model the behaviour of fully grouted rock bolts (FGRBs) during axial pullout tests. Joint parameters of the rebar-grout interface (i.e. shear stiffness, normal stiffness and cohesion) are investigated as well as grout parameters (i.e. Poisson’s ratio and Young’s modulus) in terms of the influence on the rock bolt behaviour. The results indicate that the Young’s modulus of the grout and joint shear stiffness have significant influences on the overall behaviour and performance of the FGRB system. On the basis of these results, the upper and lower limit of strain distribution along with the rock bolt is determined. These results are also compared to the nominally identical axial pullout tests of rock bolts that have been conducted in the laboratory as part of the physical testing components of the overall research program.