LAUSR

Abstract The bond–slip relationship of fully grouted rockbolts with long encapsulation lengths is critical to the bolt axial performances. However, how to properly determine its profile still remains a challenge. It is proposed that the pullout tests of short encapsulated rockbolts could be used to estimate the bond–slip relationships of long rockbolts under the same conditions. This method is based on two assumptions: (1) The bond–slip relationship simply calculated from the load–displacement curve of a short rockbolt could represent its interfacial shear stress characteristics and (2) bolts with different embedment lengths have the same bond–slip relationship when subjected to the same conditions. Pullout tests were carried out on instrumented rockbolts with short embedment lengths to verify the first assumption, and pullout tests on rockbolts with various embedment lengths were numerically modeled to validate the second assumption. It was found that the shear stresses were not uniformly distributed along the bolt–grout interface; the load–displacement curve of a short rockbolt could still be used to derive the bond–slip relationship of a bolt. The bond–slip relationships computed from short grouted rockbolts tend to underestimate the interfacial shear bond stresses of longer bolts.