A unified experimental-numerical assessment of Cable, Pile, and Zone solid rockbolt models in FLAC3D: bond-slip, load transfer, and model selection

Cable, Pile, and Zone solid rockbolt models are widely used for rockbolt simulation in FLAC3D, but their differences under consistently calibrated interface conditions remain unclear. This study establishes an experimental–numerical framework for their comparative assessment. Short-embedment pull-out tests were used to calibrate bilinear and nonlinear bond-slip relationships, yielding a mean peak interfacial bond strength of 3.006 MPa, while independent 0.3 m tests were used to validate load–displacement response and load transfer without further parameter adjustment. The validated models were then extended to a 1.0 m embedment length and a three-dimensional tunnel-support problem. Under bilinear interface conditions, the Cable and Pile models produced similar global responses, whereas the Zone solid rockbolt model showed stronger spatial nonuniformity associated with explicit geometry and contact representation. The nonlinear relationship enabled the Pile and Zone solid models to reproduce progressive slip, stress redistribution, and post-peak degradation. For the 0.3 m validation, the experimental peak pull-out load was 71.66 kN, compared with 71.65 kN for the nonlinear Pile model and 75.67 kN for the nonlinear Zone solid model, corresponding to peak-load errors of less than 0.1 % and approximately 5.6 %, respectively. The Pile model provided a smoother overall response, while the Zone solid model offered a more explicit representation of local contact and three-dimensional stress redistribution, although with greater sensitivity to discretisation and Interface settings. The results provide a practical basis for selecting appropriate FLAC3D rockbolt representations according to the required balance between computational efficiency and local response resolution.