Experimental Study on Mechanical Properties of Fully Bonded Bolts with Varied Bond Length

The fully bonded bolting method is widely applied in geotechnical engineering areas and is considered as an efficient approach due to its better loading capacity compared with end-anchored methods. However, the mechanical property of fully bonded bolt under various bond lengths is still unclear. This study comprises a mixed methodology of laboratorial experiments and theoretical analysis to discuss the mechanical law of fully bonded bolts under different bond lengths. Results show that the plastic debonding at the interface tends to expand as the bond length increases. Moreover, the undergoing time of the yield stage, which is between the initial and peak force stages, shows an increasing trend that is also applicable to the corresponding pull-out displacement. We have also identified that AE capturing indicated that intense energy events/values are easy to identify when the bond length increases, a phenomenon; that is closely related to the longer frictional process of the specimens with longer bond length. This study provides a reference for the design of fully bonded bolts, that is, the bond length should be carefully considered to avoid the premature failure of bolting systems due to progressive debonding.