Numerical simulation of the interfacial behaviour of grouted rockbolts in tunnel support based on a tri-linear bond-slip model

Grouted rockbolts are widely used in tunneling excavation. However, the rockbolt design is still basically empirical, the mechanical behavior of grouted rockbolts, especially the interfacial behavior, has never been studied systematically. First of all, a tri-linear bond slip model is proposed for modeling the rockbolt interfacial behavior. Then analytical solutions to grouted rockbolt are presented on the basis of a tri-linear bond-slip model. Finally, a numerical model using Abaqus program to simulate the tunnel rockbolt is proposed. This model uses cohesive elements to simulate debonding along the anchorage interfaces, meanwhile, tabular damage variable is obtained on the basis of the damage evolution law in order to correspond with the tri-linear material model. The developed model was validated by monitored data. It was found that the model was capable of predicting accurately the interfacial shear stress distribution, load on the bolt as well as the rock movements. Therefore, this model can be used to optimize the control parameters of grouted rockbolts.