Bond Stress Distribution at the Joint Between Rock Bolts and Grout Under Different Grouting Conditions

In rock reinforcement systems, bond stress at the joint between rock bolts and grout exerts a crucial influence on determining the bonding capacity of rock bolts. However, much less research has been conducted to study the joint bond stress (JBS) distribution with analytical deduction. Therefore, this paper adopted an analytical model to evaluate JBS distribution. The novelty of this paper is that the JBS distribution under different grouting conditions can be quantitatively studied. Based on variable controlling techniques, the influence of different parameters on JBS distribution state was studied. These studied parameters included joint strength, joint remaining strength and relative slide at joint remaining strength. Results showed that after rock bolts were loaded, the loading process can be basically divided into five different stages. Joint strength exerts a crucial influence on determining the JBS distribution state before the joint fully disconnected. After the joint started disconnecting, larger joint strength led to a slower propagation speed of the maximum JBS. When the remaining strength of the joint increased, after the whole joint deformed plastically, the disconnected length became longer, and frictional resistance in the disconnected section became larger. This led to an increase in the bonding capacity of rock bolts. Compared with joint strength and joint remaining strength, relative slide at joint remaining strength had a slightly smaller influence on JBS distribution. Before the joint disconnected, increasing relative slide at joint remaining strength was likely to improve the propagation speed of the maximum JBS. This study is valuable for further understanding the stress-transferring mechanism in rock reinforcement systems.