Method for determining anchor sleeve thickness considering radial stiffness damage

The impact and static mechanical properties of a bolt are usually tested by pull-out tests. Sleeves of metal or other materials are often used to replace the surrounding rock when bolt anchoring performance tests are performed in the laboratory. In this article, it is proposed that, when the thicknesses of anchor sleeves are determined, the damage to the diameter directional stiffness of the rock surrounding the anchoring borehole should be fully considered. By analyzing the plastic zone radius and modulus of the damage to the rock surrounding the anchoring borehole, formulas for calculating the radial stiffness of the anchoring borehole and determining the thickness of the sleeves are derived, which include the radial stiffness damage variable of the anchoring borehole. For several anchoring boreholes with different diameters, using steel sleeves as an example, the quantitative relationship between the thicknesses of steel sleeves and the mechanical parameters of the surrounding rock is provided. In addition, a method flow for determining the thickness parameters of the anchor sleeves is proposed. The conclusions of this study provide a theoretical reference for determining the thicknesses of anchor sleeves for bolt pull-out tests and the interface stiffness parameters of numerical simulations.