Design and processing optimization of hollow grouted bolt for failure prevention

Abstract Hollow grouted bolt is an important component of slope reinforcement for structures like skyscrapers, tunnels, railways, highways, bridge foundations and dykes etc. The mechanical properties of it are significant for ensuring the safety and reliability of the structures reinforced, particularly the yield ratio, which must not exceed 0.8 according to the technical standard. For the purpose of alloy elements saving and production costs reduction, as well as for failure prevention, this paper endeavors to substitute the 45 carbon steel (equivalent to the ISO C45E4) for the Q345B low alloy steel (equivalent to the ISO E355DD) to produce the hollow grouted bolt, and focuses on the influencing factors in the processing technology to achieve the desirable properties. In detail, different designs in the chemical compositions, deformation extents and heat treatment processes were proposed and testified to figure out the optimum means for producing the 45 carbon steel hollow grouted bolts. Especially, a novel heat treatment process that applied the high-frequency rapid heating technology in hot rolling was also proposed for energy saving and efficiency improvement. On the finished bolts, the direct reading optical emission spectrometer, metallographic microscope and universal testing machine were utilized to evaluate the compositions, structures and properties. In addition, finite element analysis was performed on the hollow grouted bolts to evaluate the reliability in the application scenario of tunnel excavation. Achievement of this paper would have some reference values for failure prevention of the hollow grouted bolts serving under the similar engineering environments.