Behaviour of Hollow Core Bolts Subjected to Shear Loading: An Experimental Study

Abstract The shear capacity of hollow core bolts is still unclear due to the lack of experimental data. Therefore, to address this limitation, in this paper, the shear strength of three different types of hollow core bolts, including “X”, “S”, and “E” grade bolts, were studied experimentally using the double shear testing method under competent rock conditions. The outcomes of this research revealed that the shear force depended on the bolt type. The “X” grade hollow bolt tolerated larger shear displacement and shear force. In addition, it was found that the shear load capacity of hollow core bolts is not necessarily around 70% of their ultimate tensile strength under general engineering principles and Von Mises relations. Another finding was that the shear load–displacement plots showed five distinct stages in the shear process: self-adjusting, high stiffness, non-linear, low stiffness, and failure. The shear profiles indicated that the average shear stiffness was reduced as the inner diameter of the bolt increased. The results also showed that the “X” and “S” grade bolts are more brittle due to their higher tensile strength and lower elongation capacity. Moreover, strong concrete with internal confinement significantly improved the host medium integrity, simulating, more closely, competent rock conditions. The study offered insights into the shear performance of hollow core bolts and suggested further research of different types of hollow core bolts for comparison. Future studies can examine the bolt’s behaviour in weaker rock and explore the effects of various levels of pre-tensioning on the bolt shear strength and stiffness.