Microscopic-NPR bolt slurry-anchor interface bonding performance

The excellent bonding performance between bolt and anchor materials is crucial for controlling the deformation of deep-buried surrounding rock and strengthening the rock and soil mass in the slope. This paper conducted an anchoring test and ABAQUS numerical simulation of an anchoring system comprising a micro-NPR (microscopic negative Poisson's ratio) bolt and cement mortar as the anchoring material. The failure mode of this system and the distribution of average bonding strength, axial force, and shear stress along the anchoring depth were studied. We also evaluated the bonding properties at the micro-NPR (microscopic negative Poisson's ratio) bolt-cement mortar interface. The findings indicate that the cement mortar is partially spalled from the micro-NPR bolt surface. The average bonding strength at the micro-NPR bolt-cement mortar interface is positively correlated with anchoring length and cement mortar strength. In contrast, it exhibits a negative correlation with bolt diameter. The axial force is generated at the starting point of the anchorage and decreases non-uniformly across the anchoring region. The axial force transfers or diffuses toward the deeper sections of the anchoring segment with increasing loads. The shear stress at the micro-NPR bolt-cement mortar interface exhibits a single-peak pattern, i.e., it climbs to a peak value and decreases along the anchoring depth. The peak position varies with changes in bolt diameter and anchoring length. By comparison, it is independent of cement mortar strength. The simulated bonding properties of the micro-NPR bolt-cement mortar interface are consistent with experimental results. The findings can provide a reference for engineering applications and anchoring design of micro-NPR.