Influence of the Elastic Modulus and Spiral Rib Appearance on the Resin Bonding Performance Based on an NPR Prestressed Bolt

This paper proposes a high-strength prestressed bolt that experiences both high strength and high elongation. Its elastic modulus is larger, and spiral ribs appear, which is referred to as the NPR bolt. The influence of different elastic moduli and spiral appearances on the bonding performance of the resin was analyzed. Theoretical analysis and FEM are used to analyze the influence of different elastic moduli on the mechanical distribution of the resin–rock interface. The results of the two methods are consistent. The maximum values of the interface shear stress and the axial force appear at the loading end, the minimum values appear at the end of the bolt, and both decays exponentially. With the increase in the elastic modulus of the bolt, the attenuation rate decreases, and the distribution becomes more uniform. The greater the elastic modulus is, the more positive the bonding performance of the resin–rock interface. The load transfer mechanism of the bolt–resin interface of a spiral rib under axial force was studied. With the same diameter and rib height, the spiral ribs of the NPR bolt can be more fully combined with the bonding agent to bear a greater tension load. Taking the NPR spiral and T-1 bolt used in this paper as examples, the bonding performance of the former is 2.24 times that of the latter. The loads of the spiral bolt and the inclined rib bolt are mainly borne by the ribs, accounting for 98.4% and 96.9%, respectively. The resin bonding performance experiment was carried out on an NPR spiral and commonly used T-1\T-2 resin bolts. From the experimental results, the spiral rib structure of the NPR bolt has excellent bonding performance with the resin, which can fully guarantee the bonding performance between the bolt–resin interface. With a resin anchor length of 600 mm, the average peak axial force of the NPR spiral bolt reaches 207 kN, and those of the T1 and T2 bolts are 163 kN and 139 kN, respectively. The NPR spiral bolts did not fail at the bolt–resin interface. Failure of the 1/4T-1 bolt and 3/4T-2 bolt occurred at the bolt–resin interface. The research results of this paper can provide a reference basis for the anchorage design of similar high-strength bolts with a spiral appearance.