Effect of rock bolt support mechanism on tunnel deformation in jointed rockmass: A numerical approach

Abstract

A parametric study was conducted to determine the influence of different bolt parameters (bolt length and diameter) on the maximum induced boundary displacements in jointed rockmass, using a numerical method based on finite element code. Three different types of jointed systems (Type A, Type B, and Type C) were considered and analyzed. Type A displays normal joint closure, Type B demonstrates a combination of normal and shear joint closure, and in Type C, the majority of the joint is loaded in shear condition. The ground surface settlement profiles for these three joint systems, under unsupported conditions, are presented in this work. For the same rockmass properties, the cases in Type A and Type B exhibit the maximum and minimum settlement, respectively. For each joint type, the effect of variable bolt parameters on the tunnel boundary is studied in terms of the total displacement. The simulation results confirm that an increase in the bolt length does not significantly reduce the boundary displacement, whereas an increase in the bolt diameter substantially reduces the tunnel boundary displacement.