Impact of installation variations on axial performance of rock bolts: an experimental and numerical study

Abstract This study investigates the influence of installation variations, including eccentricity and inclination, on the axial load transfer capacity of fully resin-encapsulated rock bolting systems (FRERBS). The effect of the annulus area and the stiffness of the confinement were also examined. For this, experimental pullout tests were conducted on specimens with varying eccentricities, from 0 to 9 mm, within 43 and 48 mm diameter steel confinements. The pullout results showed that eccentricity reduced peak load capacity depending on the level of eccentricity, with up to 69.6% reductions observed for increasing eccentricities by 9 mm. FEM numerical simulations were also developed using ABAQUS and validated using the experimental findings. The numerical investigations provided valuable insights into stress distribution and damage patterns, revealing that damage initiation primarily occurred along the bolt-resin interface. The study further examined the impact of installation variations, demonstrating a decrease in load-carrying capacity with increasing inclination. Combined effects of eccentricity and inclination were also investigated, highlighting their detrimental influence on FRERBS’s performance. A parametric study explored the impact of the annulus area and the surrounding materials’ stiffness, revealing that a balanced combination of grout thickness and radial stiffness consideration is crucial for studying FRERB performance. The findings emphasise the critical role of proper design and implementation of the drill holes and installation practices considerations to ensure the long-term stability and effectiveness of FRERBS in rock engineering applications.