Pseudo-discontinuum numerical models, where discontinuities such as joints are represented discretely in an otherwise intact rockmass (termed "explicit" models in this paper), can demonstrate spatially variable rockmass response with movement along discrete geological structures. Explicit models used for the design of tendon rock support can therefore produce localized axial and shear loading in rockbolts crossing discrete joints. With strain-based and displacement-based failure criteria becoming increasingly common for predicting the performance of tendon ground support in underground excavations, the interaction between the rockmass and rockbolts must be understood. This paper demonstrates that the selected numerical rockbolt model and rockbolt input parameters govern the interaction between the rockmass and the rockbolt, and the displacements that occur in both systems.
Pseudo-discontinuum numerical rockmass models, where discontinuities such as joints are represented discretely in an otherwise intact rockmass (termed "explicit" models in this paper), show spatial variability in predicted rockmass displacements. Explicit models enable localized axial loads, shear loads, and combinations of the two to occur in modelled rockbolts crossing discrete joints. Strain-based and displacement-based design are becoming increasingly common for assessing the performance of rockbolts. Observational design for large-scale cavern projects, where access to support is lost as excavation proceeds, requires an understanding of the impact of movement along geological structures on permanent ground support. To predict realistic rockbolt displacements and strains for comparison to failure criteria, the interaction between the rockmass and the rockbolt must be understood. This research investigates the impact of the selected numerical bolt model on rockmass and bolt behaviour, and highlights methods for analyzing axial displacement in numerically modelled rockbolts. The sensitivity of bolt response to interface stiffness is also examined. Grouted rockbolts (resin-grouted rebar and cement-grouted rebar) are the focus of this research due to their wide usage in civil engineering and mining engineering. Grouted rebar support is fully bonded to the rockmass using a grout material and generates shear resistance to movement through mechanical interlock between the bolt and the grout, and the grout and the rock. Resin-grouted rockbolts typically exhibit a stiffer bolt response, higher pull-out capacity, and lower axial strain limit compared to cement-grouted bolts. Both offer high tensile load resistance.