Investigation of impact dynamics of roof bolting with passive friction control

• Developed a non-linear model for modeling yieldable rock bolt (Roofex).
• Established a conceptual mechanism of bolt yielding and validated it by laboratory data.
• Investigated the effects of ground vibrating frequency and velocity on bolt behavior.
• Identified a potential problem due to a gap between the rock surface and bolt plate.

In this paper, the impact dynamics of rock bolt with passive friction control is modeled. Numerical investigations are performed for the bolts with frictional energy absorber under various dynamic loads. The results are compared with those from fully grouted rigid bolts. The studies indicate that without the frictional energy absorber, the bolts are highly susceptible to failure under dynamic impact loads, while the bolts with the fictional energy absorber significantly reduce this risk. The studies also reveal that the bolt sliding may occur at the combined effect of vibration frequency and velocity magnitude. Sliding will only initiate above certain threshold value defined by vibration frequency and velocity magnitude. Furthermore, the simulation results show that under certain impact forces when rock mass subject to only elastic deformation, bolt sliding may occur causing the detachment of bolt head and rock face, which may incapacitate the rock bolt in supporting the rock excavation. The investigation signifies that further development and appropriate design of the rock bolt system with a frictional energy absorber are critical in maintaining stability under dynamic loading.