doi:10.16186/j.cnki.1673-9787.2023100051

Received:2023-10-23

Revised:2023-12-22

Online Date:2024-01-30

Study on bearing characteristics of variable-section anchor rods underpullout loads(Online)

LIU Xu, ZHU Changxing

School of Energy Science and Engineering， Henan Polytechnic University， Jiaozuo 454000， China

Abstract:  Objective  To solve the problem that the pull-out resistance of the tail steel cannot be fully developed when the resin anchor rod is loaded, a hollow variable-section anchor rods at the tail was proposed. Methods  Theoretical analysis was used to study the distribution law of internal forces in the anchorage segment, destruction mode, and elastic bearing capacity of variable-section anchor rods under pullout loads. The influence law of hollow segment on the bearing performance of anchor rods was revealed, and the theoretical results were verified through indoor pullout tests. Results  Research has found that compared to ordinary anchor rods, the appearance of a hollow segment will cause an increase in the nonlinearity of the axial force distribution curve of the anchor rods and an increase in the maximum shear stress at the anchorant-perimeter rock interface. The magnitude of the change increases with the increase of the size parameters of the hollow segment. The two destruction modes of the variable-section anchor rods are slip debonding at the anchorant-perimeter rock interface and anchor rods breakage at variable-section position. Based on the occurrence conditions of the two, the corresponding elastic bearing capacity calculation formula and critical state equation of the destruction mode were derived. On the basis of comparing the elastic bearing capacity and safety of the anchor rods under the two destruction modes, the slip debonding at the anchorant-perimeter rock interface was established as the primary destruction mode. When the variable-section anchor rods occurs slip debonding at the anchorant-perimeter rock interface, its elastic bearing capacity slowly decreases in the initial stage with the increase of the hollow segment size parameters, and then accelerates the decrease, showing a negative exponential decay. Conclusion This researches can provide some reference for improving the economic benefits of coal roadway support systems and solving the problem of low utilization of traditional anchor rods steel.

Key words:variable-section anchor rods;bearing characteristics;destruction mode;elastic bearing capacity

CLC：TD353.6