This study presents a numerical framework for analytically modeling the discontinuity load transfer behavior of grouted rockbolt induced by a bond defect under axial loads, addressing the complex interplay of nonlinear interface slip and rockbolt plastic yielding. A bi-exponential shear–slip model captures the nonlinear bonding, softening, and debonding at the grout–bolt interface, while a bilinear strain-hardening model accounts for the rockbolt’s plastic yielding and rupture. A numerical procedure, employing a discretization method and displacement-controlled strategy, effectively simulates the snap-back phenomenon in long embedment rockbolt. Validated against experimental and numerical data, the model accurately predicts load transfer, failure modes, and the influence of bond defect on pull-out capacity. Parametric analysis reveals that bond defect and plastic yielding mitigate snap-back by reducing interfacial frictional effects during unloading. Plastic yielding, more pronounced with longer anchorage lengths, lowers ultimate pull-out load and increases axial displacement. Defect topology primarily reduces deformation capacity in the plastic yielding stage, with defect size exerting a greater impact than location on load-bearing capacity. Anchorage length, especially at the pull-out end, governs the load–displacement curve’s phase characteristics, transitioning from single-peak to multi-stage double-peak patterns as length increases. The plastic yielding behavior of rockbolt allows segments on both sides of the defect to alternate in bearing the load. The dynamic balance of load-bearing capacity across defective segment highlights the need for tailored rockbolt designs: high-ductility rockbolt for defect near the pull-out end and high-stiffness rockbolt for defect near the free end. These insights provide theoretical guidance for defect detection and prevention in engineering practice, enhancing the design and performance of grouted rockbolt in defective conditions.Highlights<UnorderedList Mark="Bullet"> <ItemContent> A numerical model for bond defect-induced load transfer in grouted rockbolt considering interface nonlinearity and rockbolt plasticity is established. </ItemContent> <ItemContent> Bond defect and rockbolt plastic yielding behavior mitigate snap-back phenomenon by reducing interfacial frictional effects during unloading. </ItemContent> <ItemContent> The load–displacement curve’s phase variation results from the dynamic load-bearing balance across segments on either side of the bond defect. </ItemContent> </UnorderedList>

A Numerical Model for Considering Discontinuity Load Transfer Effect on Grouted Rockbolt with Complex Interface and Rockbolt Behavior

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发表日期：

2026年3月17日

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Kai Guan,
Bowang Li,
Yuanjing Liu,
Wancheng Zhu,
Leandro R. Alejano,
Ye Yao

摘要

This study presents a numerical framework for analytically modeling the discontinuity load transfer behavior of grouted rockbolt induced by a bond defect under axial loads, addressing the complex interplay of nonlinear interface slip and rockbolt plastic yielding. A bi-exponential shear–slip model captures the nonlinear bonding, softening, and debonding at the grout–bolt interface, while a bilinear strain-hardening model accounts for the rockbolt’s plastic yielding and rupture. A numerical procedure, employing a discretization method and displacement-controlled strategy, effectively simulates the snap-back phenomenon in long embedment rockbolt. Validated against experimental and numerical data, the model accurately predicts load transfer, failure modes, and the influence of bond defect on pull-out capacity. Parametric analysis reveals that bond defect and plastic yielding mitigate snap-back by reducing interfacial frictional effects during unloading. Plastic yielding, more pronounced with longer anchorage lengths, lowers ultimate pull-out load and increases axial displacement. Defect topology primarily reduces deformation capacity in the plastic yielding stage, with defect size exerting a greater impact than location on load-bearing capacity. Anchorage length, especially at the pull-out end, governs the load–displacement curve’s phase characteristics, transitioning from single-peak to multi-stage double-peak patterns as length increases. The plastic yielding behavior of rockbolt allows segments on both sides of the defect to alternate in bearing the load. The dynamic balance of load-bearing capacity across defective segment highlights the need for tailored rockbolt designs: high-ductility rockbolt for defect near the pull-out end and high-stiffness rockbolt for defect near the free end. These insights provide theoretical guidance for defect detection and prevention in engineering practice, enhancing the design and performance of grouted rockbolt in defective conditions.

Highlights

A numerical model for bond defect-induced load transfer in grouted rockbolt considering interface nonlinearity and rockbolt plasticity is established.

Bond defect and rockbolt plastic yielding behavior mitigate snap-back phenomenon by reducing interfacial frictional effects during unloading.

The load–displacement curve’s phase variation results from the dynamic load-bearing balance across segments on either side of the bond defect.